U.S. patent application number 10/947905 was filed with the patent office on 2005-03-10 for human dnase.
This patent application is currently assigned to Genentech, Inc.. Invention is credited to Baker, Kevin P., Baron, Will F..
Application Number | 20050053994 10/947905 |
Document ID | / |
Family ID | 46278822 |
Filed Date | 2005-03-10 |
United States Patent
Application |
20050053994 |
Kind Code |
A1 |
Baker, Kevin P. ; et
al. |
March 10, 2005 |
Human DNase
Abstract
This invention relates to a novel human deoxyribonuclease,
referred to as LS-DNase, that is relatively resistant to inhibition
by actin, as compared to human DNase I. The invention provides
nucleic acid sequences encoding LS-DNase, thereby enabling the
production of LS-DNase by recombinant DNA methods in quantities
sufficient for clinical use. The invention also relates to
pharmaceutical compositions and therapeutic uses of LS-DNase.
Inventors: |
Baker, Kevin P.; (San Mateo,
CA) ; Baron, Will F.; (Brisbane, CA) |
Correspondence
Address: |
GENENTECH, INC.
1 DNA WAY
SOUTH SAN FRANCISCO
CA
94080
US
|
Assignee: |
Genentech, Inc.
|
Family ID: |
46278822 |
Appl. No.: |
10/947905 |
Filed: |
September 22, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10947905 |
Sep 22, 2004 |
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10133065 |
Apr 26, 2002 |
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10133065 |
Apr 26, 2002 |
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09643520 |
Aug 22, 2000 |
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09643520 |
Aug 22, 2000 |
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08794827 |
Feb 4, 1997 |
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60109796 |
Feb 5, 1996 |
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Current U.S.
Class: |
435/6.11 ;
435/199; 435/320.1; 435/325; 435/6.1; 435/69.1; 536/23.2 |
Current CPC
Class: |
A61K 38/00 20130101;
C12N 9/22 20130101 |
Class at
Publication: |
435/006 ;
435/069.1; 435/199; 435/320.1; 435/325; 536/023.2 |
International
Class: |
C12Q 001/68; C07H
021/04; C12N 009/22 |
Claims
What is claimed is:
1. An isolated nucleic acid molecule comprising a nucleotide
sequence encoding the amino acid sequence shown in FIG. 1 for
mature LS-DNase.
2. An expression vector comprising a nucleotide sequence encoding
the amino acid sequence shown in FIG. 1 for mature LS-DNase
operably linked to a promoter recognized by a host cell transformed
with the vector.
3. An isolated nucleic acid molecule comprising a nucleotide
sequence that encodes an amino acid sequence having at least 95%
identity with the amino acid sequence shown in FIG. 1 for mature
LS-DNase.
4. An isolated nucleic acid molecule comprising a nucleotide
sequence that encodes an amino acid sequence that differs from the
amino acid sequence shown in FIG. 1 for mature LS-DNase by the
substitution of one amino acid for another at only a single
position within the FIG. 1 sequence.
5. An isolated nucleic acid molecule comprising a nucleotide
sequence that encodes an amino acid sequence that differs from the
amino acid sequence shown in FIG. 1 for mature LS-DNase by the
substitution of one amino acid for another at only two positions
within the FIG. 1 sequence.
6. A host cell transformed with an expression vector comprising a
nucleotide sequence encoding the amino acid sequence shown in FIG.
1 for mature LS-DNase.
7. A method of using a host cell transformed with an expression
vector comprising a nucleotide sequence encoding the amino acid
sequence shown in FIG. 1 for mature LS-DNase, which comprises
culturing the host cell under conditions such that expression
vector is replicated.
8. A process which comprises transforming a host cell with a
nucleic acid molecule that encodes a polypeptide comprising the
amino acid sequence shown in FIG. 1 for mature LS-DNase and
culturing the host cell under conditions such that the polypeptide
is produced in the host cell.
9. A method for producing LS-DNase comprising: (a) transforming a
cell containing an endogenous LS-DNase gene with a homologous DNA
comprising an amplifiable gene and a flanking sequence of at least
about 150 base pairs that is homologous with a DNA sequence within
or in proximity to the endogenous AL-1 gene, whereby the homologous
DNA integrates into the cell genome by recombination; (b) culturing
the cells under conditions that select for amplification of the
amplifiable gene, whereby the LS-DNase gene is also amplified; and
thereafter (c) recovering LS-DNase from the cells.
10. An isolated polypeptide comprising the amino acid sequence
shown in FIG. 1 for mature LS-DNase.
11. An isolated polypeptide comprising an amino acid sequence
having at least 95% identity with the amino acid sequence shown in
FIG. 1 for mature LS-DNase, which polypeptide has DNA-hydrolytic
activity.
12. An isolated polypeptide comprising an amino acid sequence that
differs from the amino acid sequence shown in FIG. 1 for mature
LS-DNase by the substitution of one amino acid for another at only
a single position within the FIG. 1 sequence.
13. A polypeptide of claim 12 wherein the amino acid substitution
creates a glycosylation site within the polypeptide that is not
present in human LS-DNase.
14. A pharmaceutical composition comprising a polypeptide
comprising the amino acid sequence shown in FIG. 1 for mature
LS-DNase and a physiologically acceptable excipient.
15. A composition of claim 14 that is sterile.
16. An antibody that is capable of binding to the amino acid
sequence shown in FIG. 1 for mature LS-DNase.
17. An antibody of claim 16 that is a monoclonal antibody.
18. A method for the treatment of a patient having a pulmonary
disease or disorder comprising administering to the patient a
therapeutically effective amount of LS-DNase.
19. The method of claim 18 wherein the disease or disorder is
cystic fibrosis.
20. A method for the treatment of a patient having systemic lupus
erythematosus comprising administering to the patient a
therapeutically effective amount of LS-DNase.
Description
RELATED APPLICATION
[0001] This is a non-provisional application filed under 37 CFR
1.53(b) (1), claiming priority to application Ser. Nos. 09/643,520,
filed 22 Aug. 2000 and 08/794,827, filed 04 Feb. 1997, under 35 USC
.sctn. 120, and claiming priority under USC Section 119(e) to
provisional Application Ser. No. 60/109,796 filed on Feb. 5,
1996.
FIELD OF THE INVENTION
[0002] The present invention relates to newly identified human
deoxyribonuclease (DNase) protein, nucleic acid encoding such
protein, the use of such protein and nucleic acid, as well as the
production of such protein and nucleic acid, for example, by
recombinant DNA methods.
BACKGROUND OF THE INVENTION
[0003] Deoxyribonuclease (DNase) is a phosphodiesterase capable of
hydrolyzing polydeoxyribonucleic acid, and is known to occur in
several molecular forms. Based on their biochemical properties and
enzymatic activities, DNase proteins have been classified as two
types, DNase I and DNase II. DNase I proteins have a pH optimum
near neutrality, an obligatory requirement for divalent cations,
and produce 5'-phosphate nucleotides on hydrolysis of DNA. DNase II
proteins exhibit an acid pH optimum, can be activated by divalent
cations, and produce 3'-phosphate nucleotides on hydrolysis of
DNA.
[0004] DNase from various species have been purified to a varying
degree. For example, various forms of bovine DNase I have been
purified and completely sequenced (Liao, et al., J. Biol. Chem.
248:1489-1495 (1973); Oefner, et al., J. Mol. Biol. 192:605-632
(1986); Lahm, et al., J. Mol. Biol. 221:645-667 (1991)), and DNA
encoding bovine DNase I has been cloned and expressed (Worrall, et
al., J. Biol. Chem 265:21889-21895 (1990)). Porcine and orcine
DNase I proteins also have been purified and completely sequenced
(Paudel, et al., J. Biol. Chem. 261:16006-16011 (1986); Paudel, et
al., J. Biol. Chem. 261:16012-16017 (1986)).
[0005] DNA encoding a human DNase I has been isolated and sequenced
and the DNA has been expressed in recombinant host cells, thereby
enabling the production of human DNase I in commercially useful
quantities. Shak, et al., Proc. Natl. Acad. Sci. 87:9188-9192
(1990). The term "human DNase I" will be used hereafter to refer to
the mature polypeptide disclosed in Shak, et al.
[0006] DNA encoding other polypeptides having homology to human
DNase I also have been identified. Rosen, et al., PCT Patent
Publication No. WO 95/30428, published Nov. 16, 1995; Parrish, et
al., Hum. Mol. Genet. 4:1557-1564 (1995).
[0007] DNase I has a number of known utilities and has been used
for therapeutic purposes. Its principal therapeutic use has been to
reduce the viscoelasticity of pulmonary secretions (mucus) in such
diseases as pneumonia and cystic fibrosis (CF), thereby aiding in
the clearing of respiratory airways. See e.g., Lourenco, et al.,
Arch. Intern. Med. 142:2299-2308 (1982); Shak, et al., Proc. Natl.
Acad. Sci. 87:9188-9192 (1990); Hubbard, et al., New Engl. J. Med.
326:812-815 (1992); Fuchs, et al., New Engl. J. Med. 331:637-642
(1994); Bryson, et al., Drugs 48:894-906 (1994). Mucus also
contributes to the morbidity of chronic bronchitis, asthmatic
bronchitis, bronchiectasis, emphysema, acute and chronic sinusitis,
and even the common cold.
[0008] The pulmonary secretions of persons having such diseases are
complex materials, that include mucus glycoproteins,
mucopolysaccharides, proteases, actin, and DNA. DNase I is
effective in reducing the viscoelasticity of pulmonary secretions
by hydrolyzing, or degrading, high-molecular-weight DNA that is
present in such secretions. Shak, et al., Proc. Natl. Acad. Sci.
87:9188-9192 (1990); Aitken, et al., J. Am. Med. Assoc.
267:1947-1951 (1992). The DNA-hydrolytic activity of DNase I in
pulmonary secretions may be reduced, however, as a result of the
interaction of the DNase I with actin. Lazarides, et al., Proc.
Natl. Acad. Sci. 71:4742-4746 (1974); Mannherz, et al., Eur. J.
Biochem. 104:367-379 (1980). Accordingly, forms of DNase I that
bind actin with lower affinity than human native DNase I, but that
still possess DNA-hydrolytic activity should be useful therapeutic
agents, especially in the treatment of patients having pulmonary
secretions that comprise relatively large amounts of actin.
Variants of human DNase I having reduced affinity for actin have
been prepared synthetically and shown to be more potent than the
native enzyme in reducing the viscosity of sputum of cystic
fibrosis patients. Lazarus, et al., U.S. patent application Ser.
No. 08/540,527 (filed Oct. 9, 1995).
SUMMARY OF THE INVENTION
[0009] The present invention provides a novel DNase, as well as
analogs and variants thereof, that have DNA-hydrolytic activity but
that are resistant to inhibition by actin. This novel polypeptide,
referred to as LS-DNase, is of human origin.
[0010] The invention also provides nucleic acids encoding LS-DNase,
recombinant vectors comprising such nucleic acids, recombinant host
cells transformed with those nucleic acids or vectors, and
processes for producing LS-DNase by means of recombinant DNA
technology. The invention includes the use of such nucleic acids
and vectors for in vivo or ex vivo gene therapy.
[0011] The invention also provides pharmaceutical compositions
comprising LS-DNase, optionally together with a pharmaceutically
acceptable excipient, as well as substantially purified antibodies
that are capable of binding to LS-DNase.
[0012] The invention also provides methods for reducing the
viscoelasticity or viscous consistency of DNA-containing material
in a patient, comprising administering a therapeutically effective
dose of LS-DNase to the patient. The invention is particularly
directed to a method of treating a patient having a disease such as
cystic fibrosis, chronic bronchitis, pneumonia, bronchiectasis,
emphysema, asthma, or systemic lupus erythematosus, that comprises
administering a therapeutically effective amount of LS-DNase to the
patient. The invention also is directed to the use of LS-DNase in
in vitro diagnostic assays of a viscous material (e.g., sputum)
from a patient.
[0013] These and other aspects of the invention will be apparent to
the ordinary skilled artisan upon consideration of the following
detailed description.
BRIEF DESCRIPTION OF THE FIGURES
[0014] FIG. 1 shows the nucleotide sequence (SEQ. ID. NO: 1) and
deduced amino acid sequence (SEQ. ID. NO: 2) of LS-DNase. The
predicted leader (signal) amino acid sequence is underlined and the
start of the mature protein is indicated by the arrowhead.
[0015] FIG. 2 shows an alignment of the amino acid sequences of
human LS-DNase (SEQ. ID. NO: 3) and human DNase I (SEQ. ID. NO: 4).
Identical amino acid residues are boxed, conservative amino acid
substitutions are indicated by a dot (.multidot.), and conserved
cysteine residues are indicated by arrowheads. Two potential
glycosylations sites in human DNase I are indicated by asterisks
(*). Amino acid residues of human DNase I that are involved in
actin binding are shaded. Conserved catalytic residues are in
inverted text (white on black).
[0016] FIG. 3 shows the nucleotide sequence (SEQ. ID. NO: 11) of
murine LS-DNase. The ATG start codon for the predicted protein is
indicated by the arrowhead, and the nucleotide sequence encoding
the predicted leader (signal) amino acid sequence of the protein is
underlined.
DETAILED DESCRIPTION
[0017] The various aspects of the present invention are
accomplished by first providing isolated DNA comprising the
nucleotide coding sequence for LS-DNase. By providing the full
nucleotide coding sequence for LS-DNase, the invention enables the
production of LS-DNase by means of recombinant DNA technology,
thereby making available for the first time sufficient quantities
of substantially pure LS-DNase protein for diagnostic and
therapeutic uses.
[0018] As used herein, the term "LS-DNase" refers to the
polypeptide having the amino acid sequence of the mature protein
set forth in FIG. 1, as well as modified and variant forms thereof
as described herein. The term "human LS-DNase" refers to the
polypeptide having the amino acid sequence of the mature protein
set forth in FIG. 1.
[0019] Modified and variant forms of LS-DNase are produced in vitro
by means of chemical or enzymatic treatment or in vivo by means of
recombinant DNA technology. Such polypeptides differ from human
LS-DNase, for example, by virtue of one or more amino acid
substitutions, insertions, and/or deletions, or in the extent or
pattern of glycosylation, but substantially retain a biological
activity of LS-DNase. Preferably, the modified and variant forms of
LS-DNase have DNA-hydrolytic activity that is substantially the
same as that of human LS-DNase.
[0020] A "variant" or "amino acid sequence variant" of LS-DNase is
a polypeptide that comprises an amino acid sequence different from
that of human LS-DNase. Generally, a variant will possess at least
80% sequence identity (homology), preferably at least 90% sequence
identity, more preferably at least 95% sequence identity, and most
preferably at least 98% sequence identity with human LS-DNase.
Percentage sequence identity is determined, for example, by the
Fitch, et al., Proc. Natl. Acad. Sci. USA 80:1382-1386 (1983),
version of the algorithm described by Needleman, et al., J. Mol.
Biol. 48:443-453 (1970), after aligning the sequences to provide
for maximum homology. Such variants include naturally occurring
allelic forms of human LS-DNase that are of human origin as well as
natuarlly occurring homologs of human LS-DNase that are found in
other animal species.
[0021] "DNA-hydrolytic activity" refers to the enzymatic activity
of a DNase in hydrolyzing (cleaving) substrate DNA to yield
5'-phosphorylated oligonucleotide end products. DNA-hydrolytic
activity is readily determined by any of several different methods
known in the art, including analytical polyacrylamide and agarose
gel electrophoresis, hyperchromicity assay (Kunitz, J. Gen.
Physiol. 33:349-362 (1950); Kunitz, J. Gen. Physiol. 33:363-377
(1950)), or methyl green assay (Kurnick, Arch. Biochem. 29:41-53
(1950); Sinicropi, et al., Anal. Biochem. 222:351-358 (1994)).
[0022] For convenience, substitutions, insertions, and/or deletions
in the amino acid sequence of human LS-DNase are usually made by
introducing mutations into the corresponding nucleotide sequence of
the DNA encoding human LS-DNase, for example by site-directed
mutagenesis. Expression of the mutated DNA then results in
production of the variant LS-DNase, having the desired amino acid
sequence.
[0023] Whereas any technique known in the art can be used to
perform site-directed mutagenesis, e.g. as disclosed in Sambrook,
et al., Molecular Cloning: A Laboratory Manual, Second Edition
(Cold Spring Harbor Laboratory Press, New York (1989)),
oligonucleotide-directed mutagenesis is the preferred method for
preparing the LS-DNase variants of this invention. This method,
which is well known in the art (Zoller, et al., Meth. Enzymol.
100:4668-500 (1983); Zoller, et al., Meth. Enzymol. 154:329-350
(1987); Carter, Meth. Enzymol. 154:382-403 (1987); Kunkel, et al.,
Meth. Enzymol. 154:367-382 (1987); Horwitz, et al., Meth. Enzymol.
185:599-611 (1990)), is particularly suitable for making
substitution variants, although it may also be used to conveniently
prepare deletion and insertion variants, as well as variants having
multiple substitution, insertion, and/or deletion mutations.
[0024] Briefly, in carrying out site-directed mutagenesis of DNA
encoding human LS-DNase (or a variant thereof), the DNA is altered
by first hybridizing an oligonucleotide encoding the desired
mutation to a single strand of the DNA. After hybridization, a DNA
polymerase is used to synthesize an entire second strand, using the
hybridized oligonucleotide as a primer, and using the single strand
of the DNA as a template. Thus, the oligonucleotide encoding the
desired mutation is incorporated in the resulting double-stranded
DNA.
[0025] Oligonucleotides may be prepared by any suitable method,
such as by purification of a naturally occurring DNA or by in vitro
synthesis. For example, oligonucleotides are readily synthesized
using various techniques in organic chemistry, such as described by
Narang, et al., Meth. Enzymol. 68:90-98 (1979); Brown, et al.,
Meth. Enzymol. 68:109-151 (1979); Caruthers, et al., Meth. Enzymol.
154:287-313 (1985). The general approach to selecting a suitable
oligonucleotide for use in site-directed mutagenesis is well known.
Typically, the oligonucleotide will contain 10-25 or more
nucleotides, and will include at least 5 nucleotides on either side
of the sequence encoding the desired mutation so as to ensure that
the oligonucleotide will hybridize preferentially at the desired
location to the single-stranded DNA template molecule.
[0026] "Polymerase chain reaction," or "PCR," generally refers to a
method for amplification of a desired nucleotide sequence in vitro,
as described, for example, in U.S. Pat. No. 4,683,195. In general,
the PCR method involves repeated cycles of primer extension
synthesis, using oligonucleotide primers capable of hybridizing
preferentially to a template nucleic acid.
[0027] PCR mutagenesis (Higuchi, in PCR Protocols, pp.177-183
(Academic Press, 1990); Vallette, et al., Nuc. Acids Res.
17:723-733 (1989)) is also suitable for making the variants of
LS-DNase. Briefly, when small amounts of template DNA are used as
starting material in a PCR, primers that differ slightly in
sequence from the corresponding region in the template DNA can be
used to generate relatively large quantities of a specific DNA
fragment that differs from the template sequence only at the
positions where the primers differ from the template. For
introduction of a mutation into a plasmid DNA, for example, the
sequence of one of the primers includes the desired mutation and is
designed to hybridize to one strand of the plasmid DNA at the
position of the mutation; the sequence of the other primer must be
identical to a nucleotide sequence within the opposite strand of
the plasmid DNA, but this sequence can be located anywhere along
the plasmid DNA. It is preferred, however, that the sequence of the
second primer is located within 200 nucleotides from that of the
first, such that in the end the entire amplified region of DNA
bounded by the primers can be easily sequenced. PCR amplification
using a primer pair like the one just described results in a
population of DNA fragments that differ at the position of the
mutation specified by the primer, and possibly at other positions,
as template copying is somewhat error-prone. Wagner, et al., in PCR
Topics, pp.69-71 (Springer-Verlag, 1991).
[0028] If the ratio of template to product amplified DNA is
extremely low, the majority of product DNA fragments incorporate
the desired mutation(s). This product DNA is used to replace the
corresponding region in the plasmid that served as PCR template
using standard recombinant DNA methods. Mutations at separate
positions can be introduced simultaneously by either using a mutant
second primer, or performing a second PCR with different mutant
primers and ligating the two resulting PCR fragments simultaneously
to the plasmid fragment in a three (or more)-part ligation.
[0029] Another method for preparing variants, cassette mutagenesis,
is based on the technique described by Wells et al., Gene,
34:315-323 (1985). The starting material is the plasmid (or other
vector) comprising the DNA sequence to be mutated. The codon(s) in
the starting DNA to be mutated are identified. There must be a
unique restriction endonuclease site on each side of the identified
mutation site(s). If no such restriction sites exist, they may be
generated using the above-described oligonucleotide-mediated
mutagenesis method to introduce them at appropriate locations in
the DNA. The plasmid DNA is cut at these sites to linearize it. A
double-stranded oligonucleotide encoding the sequence of the DNA
between the restriction sites but containing the desired
mutation(s) is synthesized using standard procedures, wherein the
two strands of the oligonucleotide are synthesized separately and
then hybridized together using standard techniques. This
double-stranded oligonucleotide is referred to as the cassette.
This cassette is designed to have 5' and 3' ends that are
compatible with the ends of the linearized plasmid, such that it
can be directly ligated to the plasmid. The resulting plasmid
contains the mutated DNA sequence.
[0030] The presence of mutation(s) in a DNA is determined by
methods well known in the art, including restriction mapping and/or
DNA sequencing. A preferred method for DNA sequencing is the
dideoxy chain termination method of Sanger, et al., Proc. Natl.
Acad. Sci. USA 72:3918-3921 (1979).
[0031] DNA encoding LS-DNase is inserted into a replicable vector
for further cloning or expression. "Vectors" are plasmids and other
DNAs that are capable of replicating within a host cell, and as
such, are useful for performing two functions in conjunction with
compatible host cells (a vector-host system). One function is to
facilitate the cloning of nucleic acid that encodes LS-DNase, i.e.,
to produce usable quantities of the nucleic acid. The other
function is to direct the expression of LS-DNase. One or both of
these functions are performed by the vector in the particular host
cell used for cloning or expression. The vectors will contain
different components depending upon the function they are to
perform.
[0032] The LS-DNase of the present invention may be in the form of
a preprotein wherein the DNase includes a leader or signal
sequence, or may be in the form of a mature protein which lacks a
leader or signal sequence. The LS-DNase also may be in the form of
a fusion protein wherein additional amino acid residues are
covalently joined to the amino- or carboxy-terminus of the
preprotein or mature form of the DNase.
[0033] To produce LS-DNase, an expression vector will comprise DNA
encoding LS-DNase, as described above, operably linked to a
promoter and a ribosome binding site. The LS-DNase then is
expressed directly in recombinant cell culture, or as a fusion with
a heterologous polypeptide, preferably a signal sequence or other
polypeptide having a specific cleavage site at the junction between
the heterologous polypeptide and the LS-DNase amino acid
sequence.
[0034] "Operably linked" refers to the covalent joining of two or
more DNA sequences, by means of enzymatic ligation or otherwise, in
a configuration relative to one another such that the normal
function of the sequences can be performed. For example, DNA for a
presequence or secretory leader is operably linked to DNA for a
polypeptide if it is expressed as a preprotein that participates in
the secretion of the polypeptide; a promoter or enhancer is
operably linked to a coding sequence if it affects the
transcription of the sequence; or a ribosome binding site is
operably linked to a coding sequence if it is positioned so as to
facilitate translation. Generally, "operably linked" means that the
DNA sequences being linked are contiguous and, in the case of a
secretory leader, contiguous and in reading phase. Linking is
accomplished by ligation at convenient restriction sites. If such
sites do not exist, then synthetic oligonucleotide adaptors or
linkers are used, in conjunction with standard recombinant DNA
methods.
[0035] Prokaryotes (e.g., E. coli, strains of Bacillus,
Pseudomonas, and other bacteria) are the preferred host cells for
the initial cloning steps of this invention. They are particularly
useful for rapid production of large amounts of DNA, for production
of single-stranded DNA templates used for site-directed
mutagenesis, and for DNA sequencing of the variants generated.
Prokaryotic host cells also may be used for expression of DNA
encoding LS-DNase. Polypeptides that are produced in prokaryotic
cells typically will be non-glycosylated.
[0036] In addition, LS-DNase may be expressed in eukaryotic host
cells, including eukaryotic microbes (e.g., yeast) or cells derived
from an animal or other multicellular organism (e.g., Chinese
hamster ovary cells, and other mammalian cells), or in live animals
(e.g., cows, goats, sheep). Insect cells also may be used.
[0037] Cloning and expression methodologies are well known in the
art. Examples of prokaryotic and eukaryotic host cells, and
starting expression vectors, suitable for use in producing LS-DNase
are, for example, those disclosed in Shak, PCT Patent Publication
No. WO 90/07572, published Jul. 12, 1990. To obtain expression of
LS-DNase, an expression vector of the invention is introduced into
host cells by transformation or transfection, and the resulting
recombinant host cells are cultured in conventional nutrient media,
modified as appropriate for inducing promoters, selecting
recombinant cells, or amplifying LS-DNase DNA. The culture
conditions, such as temperature, pH, and the like, are those
previously used with the host cell, and as such will be apparent to
the ordinarily skilled artisan.
[0038] "Transformation" and "transfection" are used interchangeably
to refer to the process of introducing DNA into a cell. Following
transformation or transfection, the DNA may integrate into the host
cell genome, or may exist as an extrachromosomal element. If
prokaryotic cells or cells that contain substantial cell wall
constructions are used as hosts, the preferred methods of
transfection of the cells with DNA is the calcium treatment method
described by Cohen et al., Proc. Natl. Acad. Sci. 69:2110-2114
(1972) or the polyethylene glycol method of Chung et al., Nuc.
Acids. Res. 16:3580 (1988). If yeast are used as the host,
transfection is generally accomplished using polyethylene glycol,
as taught by Hinnen, Proc. Natl. Acad. Sci. U.S.A., 75: 1929-1933
(1978). If mammalian cells are used as host cells, transfection
generally is carried out by the calcium phosphate precipitation
method, Graham, et al., Virology 52:546 (1978), Gorman, et al., DNA
and Protein Eng. Tech. 2:3-10 (1990). However, other known methods
for introducing DNA into prokaryotic and eukaryotic cells, such as
nuclear injection, electroporation, or protoplast fusion also are
suitable for use in this invention.
[0039] Particularly useful in this invention are expression vectors
that provide for the transient expression in mammalian cells of DNA
encoding LS-DNase. In general, transient expression involves the
use of an expression vector that is able to efficiently replicate
in a host cell, such that the host cell accumulates many copies of
the expression vector and, in turn, synthesizes high levels of a
desired polypeptide encoded by the expression vector. Transient
expression systems, comprising a suitable expression vector and a
host cell, allow for the convenient positive identification of
polypeptides encoded by cloned DNAs, as well as for the rapid
screening of such polypeptides for desired biological or
physiological properties. Wong, et al., Science 228:810-815 (1985);
Lee, et al., Proc. Nat Acad. Sci. USA 82:4360-4364 (1985); Yang, et
al., Cell 47:3-10 (1986). Thus, transient expression systems are
conveniently used for expressing the DNA encoding amino acid
sequence variants of LS-DNase, in conjunction with assays to
identify those variants that have such useful properties as
increased half-life or decreased immunogenicity in vivo, increased
DNA hydrolytic activity, or increased resistance to inhibition by
actin. The inhibition of DNase activity by actin is readily
determined using assays and methods known in the art and as
described herein.
[0040] LS-DNase preferably is secreted from the host cell in which
it is expressed, in which case the variant is recovered from the
culture medium in which the host cells are grown. In that case, it
may be desirable to grow the cells in a serum free culture medium,
since the absence of serum proteins and other serum components in
the medium may facilitate purification of the variant. If it is not
secreted, then the LS-DNase is recovered from lysates of the host
cells. When the LS-DNase is expressed in a host cell other than one
of human origin, the variant will be completely free of proteins of
human origin. In any event, it will be necessary to purify the
LS-DNase from recombinant cell proteins in order to obtain
substantially homogeneous preparations of the LS-DNase. For
therapeutic uses, the purified LS-DNase preferably will be greater
than 99% pure (i.e., any other proteins will comprise less than 1%
of the total protein in the purified composition).
[0041] It is further contemplated that LS-DNase may be produced by
a method involving homologous recombination and amplification, for
example, as described in PCT Patent Publication No. WO 91/06667,
published May 16, 1991. Briefly, this method involves transforming
cells containing an endogenous gene encoding LS-DNase with a
homologous DNA, which homologous DNA comprises (1) an amplifiable
gene (e.g., a gene encoding dihydrofolate reductase (DHFR)), and
(2) at least one flanking sequence, having a length of at least
about 150 base pairs, which is homologous with a nucleotide
sequence in the cell genome that is within or in proximity to the
gene encoding LS-DNase. The transformation is carried out under
conditions such that the homologous DNA integrates into the cell
genome by recombination. Cells having integrated the homologous DNA
then are subjected to conditions which select for amplification of
the amplifiable gene, whereby the LS-DNase gene amplified
concomitantly. The resulting cells then are screened for production
of desired amounts of LS-DNase. Flanking sequences that are in
proximity to a gene encoding LS-DNase are readily identified, for
example, by the method of genomic walking, using as a starting
point the nucleotide sequence of LS-DNase shown in FIG. 1. Spoerel,
et al., Meth. Enzymol. 152:598-603 (1987).
[0042] Generally, purification of LS-DNase is accomplished by
taking advantage of the differential physicochemical properties of
the LS-DNase as compared to the contaminants with which it may be
associated. For example, as a first step, the culture medium or
host cell lysate is centrifuged to remove particulate cell debris.
The LS-DNase thereafter is purified from contaminant soluble
proteins and polypeptides, for example, by ammonium sulfate or
ethanol precipitation, gel filtration (molecular exclusion
chromatography), ion-exchange chromatography, hydrophobic
chromatography, immunoaffinity chromatography (e.g., using a column
comprising anti-LS-DNase antibodies coupled to Sepharose), tentacle
cation exchange chromatography (Frenz, et al., U.S. Pat. No.
5,279,823, issued Jan. 18, 1994), reverse phase HPLC, and/or gel
electrophoresis.
[0043] In some host cells (especially bacterial host cells) the
LS-DNase may be expressed initially in an insoluble, aggregated
form (referred to in the art as "refractile bodies" or "inclusion
bodies") in which case it will be necessary to solubilize and
renature the LS-DNase in the course of its purification. Methods
for solubilizing and renaturing recombinant protein refractile
bodies are known in the art (see e.g., Builder, et al., U.S. Pat.
No. 4,511,502, issued Apr. 16, 1985).
[0044] In another embodiment of this invention, covalent
modifications are made directly to LS-DNase to give it a desired
property (for example, increased half-life or decreased
immunogenicity in vivo, increased DNA hydrolytic activity, or
increased resistance to inhibition by actin), and may be made
instead of or in addition to the amino acid sequence substitution,
insertion, and deletion mutations described above.
[0045] Covalent modifications are introduced by reacting targeted
amino acid residues of LS-DNase with an organic derivatizing agent
that is capable of reacting with selected amino acid side-chains or
N- or C-terminal residues. Suitable derivatizing agents and methods
are well known in the art. Covalent coupling of glycosides to amino
acid residues of the protein may be used to modify or increase the
number or profile of carbohydrate substituents.
[0046] The covalent attachment of agents such as polyethylene
glycol (PEG) or human serum albumin to LS-DNase may reduce
immunogenicity and/or toxicity of the LS-DNase and/or prolong its
half-life, as has been observed with other proteins. Abuchowski, et
al., J. Biol. Chem. 252:3582-3586 (1977); Poznansky, et al., FEBS
Letters 239:18-22 (1988); Goodson, et al., Biotechnology 8:343-346
(1990); Katre, J. Immunol. 144:209-213 (1990); Harris, Polyethylene
Glycol Chemistry (Plenum Press, 1992). In addition, modification of
LS-DNase by these agents at or adjacent to (i.e., within about five
amino acid residues of) an amino acid residue that affects actin
binding may produce a variant having increased resistance to
inhibition by actin. As another example, the variant or modified
form of LS-DNase may comprise an amino acid sequence mutation or
other covalent modification that reduces the susceptibility of the
variant to degradation by proteases (e.g., neutrophil elastase)
that may be present in sputum and other biological materials, as
compared to human LS-DNase.
[0047] Antibodies to LS-DNase are produced by immunizing an animal
with LS-DNase or a fragment thereof, optionally in conjunction with
an immunogenic polypeptide, and thereafter recovering antibodies
from the serum of the immunized animals. Alternatively, monoclonal
antibodies are prepared from cells of the immunized animal in
conventional fashion. The antibodies also can be made in the form
of chimeric (e.g., humanized) or single chain antibodies or Fab
fragments, using methods well known in the art. Preferably, the
antibodies will bind to LS-DNase but will not substantially bind to
(i.e., cross react with) other DNase proteins (such as human and
bovine DNase I). The antibodies can be used in methods relating to
the localization and activity of LS-DNase, for example, for
detecting LS-DNase and measuring its levels in tissues or clinical
samples. Immobilized anti-LS-DNase antibodies are particularly
useful in the detection of LS-DNase in clinical samples for
diagnostic purposes, and in the purification of LS-DNase.
[0048] Purified LS-DNase is used to reduce the viscoelasticity of
DNA-containing material, such as sputum, mucus, or other pulmonary
secretions. LS-DNase is particularly useful for the treatment of
patients with pulmonary disease who have abnormal viscous or
inspissated secretions and conditions such as acute or chronic
bronchial pulmonary disease, including infectious pneumonia,
bronchitis or tracheobronchitis, bronchiectasis, cystic fibrosis,
asthma, tuberculosis, and fungal infections. For such therapies, a
solution or finely divided dry preparation of the LS-DNase is
instilled in conventional fashion into the airways (e.g., bronchi)
or lungs of a patient, for example by aerosolization.
[0049] LS-DNase also is useful for adjunctive treatment of
abscesses or severe closed-space infections in conditions such as
empyema, meningitis, abscess, peritonitis, sinusitis, otitis,
periodontitis, pericarditis, pancreatitis, cholelithiasis,
endocarditis and septic arthritis, as well as in topical treatments
in a variety of inflammatory and infected lesions such as infected
lesions of the skin and/or mucosal membranes, surgical wounds,
ulcerative lesions and burns. LS-DNase may improve the efficacy of
antibiotics used in the treatment of such infections (e.g.,
gentamicin activity is markedly reduced by reversible binding to
intact DNA).
[0050] LS-DNase also is useful for preventing the new development
and/or exacerbation of respiratory infections, such as may occur in
patients having cystic fibrosis, chronic bronchitis, asthma,
pneumonia, or other pulmonary disease, or patients whose breathing
is assisted by ventilator or other mechanical device, or other
patients at risk of developing respiratory infections, for example
post-surgical patients.
[0051] LS-DNase also is useful for the treatment for systemic lupus
erythematosus (SLE), a life-threatening autoimmune disease
characterized by the production of diverse autoantibodies. DNA is a
major antigenic component of the immune complexes. In this
instance, the LS-DNase may be given systemically, for example by
intravenous, subcutaneous, intrathecal, or intramuscular
administration to the affected patient.
[0052] Finally, LS-DNase is useful for the treatment of other
non-infected conditions in which there is an accumulation of
cellular debris that includes cellular DNA, such as pyelonephritis
and tubulo-interstitial kidney disease.
[0053] LS-DNase can be formulated according to known methods to
prepare therapeutically useful compositions. Typically, the
LS-DNase is formulated with a physiologically acceptable excipient
(or carrier) for therapeutic use. Such excipients are used, for
example, to provide liquid formulations and sustained-release
formulations of LS-DNase. A preferred therapeutic composition is a
solution of LS-DNase in a buffered or unbuffered aqueous solution,
and preferably is an isotonic salt solution such as 150 mM sodium
chloride containing 1.0 mM calcium chloride at pH 7. These
solutions are particularly adaptable for use in
commercially-available nebulizers including jet nebulizers and
ultrasonic nebulizers useful for administration directly into the
airways or lungs of an affected patient. Another preferred
therapeutic composition is a dry powder of LS-DNase, preferably
prepared by spray-drying of a solution of the LS-DNase, essentially
as described in co-pending U.S. patent application Ser. No.
08/206,020 (filed Mar. 4, 1994). In all cases, it is desirable that
the therapeutic compositions be sterile. Preferably, the
therapeutic compositions are disposed in a container fabricated of
plastic or other non-glass material.
[0054] In a further embodiment, the therapeutic composition
comprises cells actively producing LS-DNase. Such cells may be
directly introduced into the tissue of a patient, or may be
encapsulated within porous membranes which are then implanted in a
patient (see e.g., Aebischer, et al., U.S. Pat. No. 4,892,538,
issued Jan. 9, 1990; Aebischer, et al., U.S. Pat. No. 5,283,187,
issued Feb. 1, 1994), in either case providing for the delivery of
the LS-DNase into areas within the body of the patient in need of
increased concentrations of DNA-hydrolytic activity. For example,
the patient's own cells could be transformed, either in vivo or ex
vivo, with DNA encoding LS-DNase, and then used to produce the
LS-DNase directly within the patient. This latter method is
commonly referred to as gene therapy.
[0055] The therapeutically effective amount of LS-DNase will
depend, for example, upon the amount of DNA and actin in the
material to be treated, the therapeutic objectives, the route of
administration, and the condition of the patient. Accordingly, it
will be necessary for the therapist to titer the dosage and modify
the route of administration as required to obtain the optimal
therapeutic effect. In view of its reduced inhibition by actin and
consequential increased DNA-hydrolytic activity in the presence of
actin relative to human DNase I, the amount of LS-DNase required to
achieve a therapeutic effect may be less than the amount of human
DNase I necessary to achieve the same effect under the same
conditions. Generally, the therapeutically effective amount of
LS-DNase will be a dosage of from about 0.1 .mu.g to about 5 mg of
the variant per kilogram of body weight of the patient,
administered within pharmaceutical compositions, as described
herein.
[0056] LS-DNase optionally is combined with or administered in
concert with one or more other pharmacologic agents used to treat
the conditions listed above, such as antibiotics, bronchodilators,
anti-inflammatory agents, mucolytics (e.g. n-acetyl-cysteine),
actin binding or actin severing proteins (e.g., gelsolin;
Matsudaira et al., Cell 54:139-140 (1988); Stossel, et al., PCT
Patent Publication No. WO 94/22465, published Oct. 13, 1994;
protease inhibitors; or gene therapy product (e.g., comprising the
cystic fibrosis transmembrane conductance regulator (CFTR) gene);
Riordan, et al., Science 245:1066-1073 (1989)).
[0057] This invention also provides methods for determining the
presence of a nucleic acid molecule encoding LS-DNase in test
samples prepared from cells, tissues, or biological fluids,
comprising contacting the test sample with isolated DNA comprising
all or a portion of the nucleotide coding sequence for LS-DNase and
determining whether the isolated DNA hybridizes to a nucleic acid
molecule in the test sample. DNA comprising all or a portion of the
nucleotide coding sequence for LS-DNase is also used in
hybridization assays to identify and to isolate nucleic acids
sharing substantial sequence identity to the coding sequence for
LS-DNase, such as nucleic acids that encode naturally-occurring
allelic variants of LS-DNase.
[0058] Also provided is a method for amplifying a nucleic acid
molecule encoding LS-DNase that is present in a test sample,
comprising the use of an oligonucleotide having a portion of the
nucleotide coding sequence for LS-DNase as a primer in a polymerase
chain reaction.
[0059] The following examples are offered by way of illustration
only and are not intended to limit the invention in any manner. All
patent and literature references cited herein are expressly
incorporated.
EXAMPLE 1
Cloning LS-DNase cDNA
[0060] Full-length cDNA encoding LS-DNase was identified by
screening a human liver cDNA library (in .lambda.-UniZAP XR,
Stratagene, La Jolla, Calif.) with a mixture of the following
oligonucleotide probes, each of which had been end-labeled with T4
polynucleotide kinase and .gamma.-.sup.32P-adenosine triphosphate
to a high specific radioactivity:
1 5'-ACTGTAGTTTAAATTCAACTGGAAAGTGGTCGCTGACATCCAGGG-3' (SEQ. ID. NO:
5) 5'-GATGTCATTGTGAAGGTCATCAAACGCTGTGACATCATACTCGTG-3' (SEQ. ID.
NO: 6) 5'-GTGTTTTCCAGGGGAGCCCTTTGTGGTCTGGTTCCAA- TCTCCCCA-3' (SEQ.
ID. NO: 7) 5'-CTGGAGGTCTCCCAGCACTGGCAGAG- CAAGGACGTGATCCTGCTT-3'
(SEQ. ID. NO: 8)
5'-GCCCAGCATCATCGCGAAGTTCCTGGCTGGCTATCACCTCGCGCT-3' (SEQ. ID. NO:
9) 5'-CCAGTACAAGGAGATGTACCTCTTCGTTTACAGGAAAGACGCCGT-3' (SEQ. ID.
NO: 10)
[0061] The first three of the oligonucleotide probes listed above
(SEQ. ID. NOS: 5-7) comprise portions of the EST sequences having
accession codes T68985, T69063, HSAAACIFW, T73558, T61400, T73653,
and T61368 in the Genbank database. The other two oligonucleotide
probes listed above (SEQ. ID. NOS: 9-10) comprise portions of the
EST sequences having accession codes R78020 and H42990 in the
Genbank database.
[0062] Hybridization of the probes to the cDNA library was carried
out under low stringency conditions (in 20% vol/vol formamide,
5.times.SSPE, 5.times.Denhardt's solution, 0.1% sodium dodecyl
sulfate (SDS), and 100 .mu.g/ml sonicated salmon sperm DNA), at
42.degree. C. Post hybridization washes were carried out in
2.times.SSC, 0.1% SDS, at 42.degree. C. 1.times.SSPE is 150 mM
NaCl, 10 mM sodium phosphate, 1 mM EDTA, pH 7.4. 1.times.Denhardt's
solution is 0.02% Ficoll, 0.02% bovine serum albumin, and 0.02%
polyvinyl-pyrrolidone. 1.times.SSC is 0.15 M NaCl, 0.015 M sodium
citrate, pH 7.0.
[0063] Hybridization-positive clones were found only with the first
three of the oligonucleotide probes listed above (SEQ. ID. NOS:
5-7). Those clones were converted into phagemid-based sequences
following standard procedures (Stratagene, La Jolla, Calif., USA)
and were sequenced. The largest inserted nucleotide sequence found
amongst the hybridization-positive clones was 1079 base-pairs in
length, including an open reading frame of 915 base-pairs that
encodes a predicted protein that is 305 amino acid residues in
length. The nucleotide sequence of the 1079 base-pair insert (SEQ.
ID. NO: 1) and the amino acid sequence of predicted protein (SEQ.
ID. NO: 2) are shown in FIG. 1.
[0064] The predicted protein includes a signal sequence that is 20
amino acid residues in length. Cleavage of the signal sequence
releases the mature protein (LS-DNase), which has a predicted
molecular weight of 33,400 Daltons and a predicted pI of 9.7. The
amino acid sequence of LS-DNase is 46% identical to the amino acid
sequence of human DNase I (FIG. 2).
[0065] LS-DNase contains five cysteine residues, two of which
(Cys-174 and Cys-211) coincide with a pair of cysteine residues in
human DNase I that are disulfide bonded, suggesting that LS-DNase
and human DNase I may have similar tertiary structures. Amino acid
residues known to be important for the DNA-hydrolytic activity of
human DNase I are conserved in LS-DNase, including the active site
histidine residues His-135 and His-254. Conversely, several amino
acid residues known to comprise the actin-binding site of human
DNase I are not conserved in LS-DNase. In particular, Val-67 and
Ala-114 of human DNase I are replaced by Ile-69 and Phe-115,
respectively, at the homologous positions in LS-DNase. An analogous
replacement of Val-67 by Ile occurs in rat DNase I, which has
approximately 1000-fold lower affinity for actin as compared to
human DNase I.
EXAMPLE 2
Expression of LS-DNase cDNA
[0066] The cDNA encoding LS-DNase was subcloned into a mammalian
expression vector pRK5 (Gorman, et al., DNA and Protein Engineering
Techniques 2:1 (1990); European Patent Publication EP 307,247,
published Mar. 15, 1989). The resulting recombinant vector is
referred to as pRK5/LS-DNase. Human embryonic kidney 293 cells
(American Type Culture Collection, CRL 1573) were grown in
serum-containing Dulbecco Modified Eagle's medium (DMEM) to 70%
confluency and then transiently transfected with pRK5/LS-DNase, or
as a control, pRK5 alone. 24 hours post-transfection, the cells
were washed with phosphate buffered saline and transferred to
serum-free medium containing insulin. 72-96 hours later,
conditioned medium was collected from the cell cultures and
concentrated approximately 10-fold. Proteins expressed in the cell
cultures were analyzed by SDS-polyacrylamide gel electrophoresis
(SDS-PAGE).
[0067] Cells transfected with pRK-5/LS-DNase were found to produce
a unique, sharply resolving protein of about 32,000-34,000 Daltons,
that was not produced in cells transfected with pRK5 alone. The
molecular weight size of this protein is in good agreement with
that predicted for LS-DNase.
EXAMPLE 3
Biological Activity of LS-DNase
[0068] Concentrated cell culture supernatants, prepared as
described above, were tested for DNase activity in a
hyperchromicity assay (Kunitz, J. Gen. Physiol. 33:349-362 (1950);
Kunitz, J. Gen. Physiol. 33:363-377 (1950)), and a methyl green
assay (Kurnick, Arch. Biochem. 29:41-53 (1950); Sinicropi, et al.,
Anal. Biochem. 222:351-358 (1994)). In both assays, DNase activity
was detected in the supernatants from cells transfected with
pRK5/LS-DNase, but not in the supernatants from cells transfected
with pRK5 alone.
EXAMPLE 4
Resistance to Actin Inhibition
[0069] To determine whether the DNA-hydrolytic activity of LS-DNase
is inhibited by actin, a plasmid nicking assay was used. This assay
measures the conversion of supercoiled double-stranded pBR322
plasmid DNA to nicked, linear, and degraded forms. Specifically,
various DNase samples were added to 20 .mu.l of solution containing
25 .mu.g/ml supercoiled double-stranded pBR322 DNA in 25 mM HEPES
buffer, 1 mM MgCl.sub.2, 1 mM CaCl.sub.2, 100 .mu.g/ml bovine serum
albumin, and the samples were incubated for 10 minutes at
21.degree. C. To determine inhibition by actin, the DNase samples
were pre-incubated with actin for 15 minutes at 21.degree. C. prior
to being added to the solution of pBR322 DNA. Reactions were
stopped by the addition of EDTA to a final concentration of 10 mM,
together with xylene cyanol, bromphenol blue, and glycerol. The
integrity of the pBR322 DNA was analyzed by electrophoresis of the
reaction mixtures on 0.8% weight/vol. agarose gels. After
electrophoresis, the gels were stained with a solution of ethidium
bromide and the DNA in the gels was visualized by ultraviolet
light.
[0070] As expected, human DNase I converted the starting plasmid
DNA to degraded forms, and the DNA-hydrolytic activity of human
DNase I was inhibited by added actin in a concentration-dependent
manner. LS-DNase converted the starting plasmid DNA to nicked,
linear, and degraded forms, but the DNA-hydrolytic activity of
LS-DNase was not inhibited by concentrations of actin that fully
inhibited human DNase I.
EXAMPLE 5
Pattern of Expression of LS-DNase in Human Tissue
[0071] Northern blots of various human tissues were performed using
a radiolabeled probe comprising a portion of the coding sequence of
the cloned LS-DNase cDNA. Expression of LS-DNase messenger RNA
(mRNA) was found to be highest in liver and spleen. LS-DNase mRNA
either was poorly expressed or not expressed in other tissues
examined. No LS-DNase mRNA was detectable in pancreas tissue.
[0072] Northern blots of various human tissues also were performed
using a radiolabeled probe comprising a portion of the nucleotide
coding sequence for human DNase I. In contrast to LS-DNase mRNA,
human DNase I mRNA appeared to be exclusively expressed in pancreas
tissue.
EXAMPLE 6
Cloning of LS-DNase Variant
[0073] A 649 base-pair EcoRI-PstI fragment of the coding sequence
of the cloned LS-DNase cDNA was used to screen a murine liver cDNA
library (in .lambda.-gt10, Clontech, Palo Alto, Calif., USA). From
about two million clones screened, more than 60 hybridization
positive clones were identified. Partial sequencing of six random
positive clones showed that they all originated from the same gene.
The inserted nucleotide sequence of one of those positive clones
was completely sequenced. The insert was 1124 base-pairs in length,
including an open reading frame of 930 base-pairs that encodes a
predicted protein, referred to as murine LS-DNase, that is 310
amino acid residues in length.
[0074] The nucleotide sequence of the 1124 base-pair insert (SEQ.
ID. NO: 11) is shown in FIG. 3. The open reading frame begins with
the ATG codon at nucleotide 173 and continues to the stop codon at
nucleotide 1103. The first 75 nucleotides of the open reading frame
(the first 25 amino acid residues of the predicted protein) encode
a putative signal sequence. Accordingly, the predicted murine
mature LS-DNase protein is 285 amino acid residues in length, has a
molecular weight of 33,100 Daltons and a predicted pI of 9.4. The
amino acid sequence of the murine mature LS-DNase is 84% identical
to the amino acid sequence shown in FIG. 1 for human mature
LS-DNase.
[0075] Northern blots of various mouse tissues were performed using
a radiolabeled probe comprising a portion of the nucleotide coding
sequence for murine LS-DNase. Expression of murine LS-DNase
messenger RNA (mRNA) was found to be highest in liver and spleen.
LS-DNase mRNA either was poorly expressed or not expressed in other
tissues examined.
Sequence CWU 1
1
* * * * *