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Conditions required for activation of the mouse albumin or alpha-fetoprotein gene in hybrids between mouse lymphoblastoma and rat hepatoma cells.

Activation of two previously silent mouse hepatic genes has been investigated in hybrid cells between pseudodiploid mouse lymphoblastoma cells and hyperdiploid or hypertetraploid rat hepatoma cells. In this material, activation of the mouse albumin gene is a frequent event, whereas activation of mouse alpha-fetoprotein (AFP) occurs only in those cells that produce large amounts of albumin. Quantitative tests of hybrid populations for the activated proteins and their mRNAs revealed the expected sizes and structures: moreover, as in hepatoma cells, the amount of both rat and mouse albumin produced was directly proportional to the intracellular concentration of the corresponding mRNA. The cellular environment required for activation of the liver-specific genes was investigated by cell-by-cell analysis of each hybrid clone. Immunostaining for the presence of rat and mouse albumin and mouse AFP revealed unexpected heterogeneity in the phenotypes of the hybrid populations, which were found to contain cells that: (a) failed to express either of the proteins; (b) produced all three; (c) produced both rat and mouse albumin; or (d) produced rat albumin only. Karyotypic analysis indicated that the hybrid-cell phenotype depended on parental chromosome ratios rather than absolute numbers of chromosomes. It was found for albumin and mouse AFP that the fraction of immunostained cells was equal to the fraction of metaphases that contained a minimal rat-to-mouse chromosome ratio of 2.5 and 9, respectively. It is concluded that in those hybrids, expression of liver-specific genes is regulated by extinguishers, but in a dose-dependent fashion, suggesting the intervention of antagonistic activators from the rat hepatoma chromosomes.

Albumins↗

Localization of the mouse Mcf-2 (Dbl) protooncogene within a conserved linkage group on the mouse X chromosome.

A mouse cDNA probe homologous to the human MCF2 transforming sequence has been identified and partially cloned, and is used here to localize the gene on the mouse X chromosome. The human gene has been physically mapped to within 60 kb of the gene for coagulation factor IX, within a large conserved linkage group between the mouse and human genomes which extends from HPRT to G6PD on the X chromosomes of both mammalian species. In situ hybridization of the mouse Mcf-2 probe onto mouse metaphase chromosomes indicates that this gene lies in the same region of the X chromosome as Cf-9, the mouse gene for coagulation factor IX. Moreover, segregation of species-specific genomic DNA polymorphisms for Mcf-2 and Cf-9 in a total of 203 individuals derived from two large interspecific mouse backcross populations (which are also segregating for 17 other X-linked molecular markers) demonstrates that the mouse genes are separated by only 0.5 +/- 0.5 cM. Despite this short distance we were able to order Mcf-2 and Cf-9 relative to one another and other genes in this region. The mouse gene order Hprt-Cf-9-Mcf-2-G6pd predicts a similar ordering of genes on the human X chromosome, a gene order which has only recently been demonstrated by physical mapping. Thus, the map location and linkage relationships of the Mcf-2 gene are similar in man and mouse, and this unique protooncogenic locus is part of a conserved linkage group on the mammalian X chromosome.

Animals↗

Lactogenic response of cultured mouse mammary epithelial cells to mouse placental lactogen.

The ability of mouse placental lactogen (mPL), mouse prolactin (mPRL), mouse GH (mGH) and ovine prolactin (oPRL) to stimulate synthesis of alpha-lactalbumin was tested in a primary culture of mouse mammary gland epithelial cells. Mammary tissue was obtained from 10-day pregnant Swiss Webster mice, enzymatically dissociated and the cells were cultured on floating collagen gels for 5 days. The basic culture medium consisted of Nutrient Mixture F12/Dulbecco's Modified Eagle's Medium (1:1, v/v), containing 10 mg insulin/1, 5 mg cortisol/l, 10 micrograms epidermal growth factor/l, 5 g bovine serum albumin/l and 50 mg gentamycin/l. Mouse PL, mPRL, mGH and oPRL were added to the basic medium in concentrations from 1 microgram/l to 1 mg/l. Accumulation of alpha-lactalbumin in the culture medium was measured. For that purpose, mouse alpha-lactalbumin was purified from mammary tissue obtained from lactating Swiss Webster mice and a radioimmunoassay was developed. Mouse PL, mPRL and oPRL stimulated a dose-dependent increase in alpha-lactalbumin secretion. Mouse GH also caused a significant, but dose-independent, increase in alpha-lactalbumin secretion. Mouse PL showed the greatest activity in stimulating alpha-lactalbumin secretion. It was concluded that mPL is an important lactogenic hormone in the latter half of pregnancy in the mouse, when circulating mPRL concentrations are low.

Animals↗

Action of anti-mouse IgE on mouse and rat mast cells.

The action of anti-mouse IgE on normal or sensitized mouse and rat peritoneal mast cells as well as on the reaginic activity of mouse and rat antisera was studied. Anti-mouse IgE induced histamine release from normal mouse peritoneal mast cells in vitro and this effect was greatly enhanced when mast cells were actively sensitized. The action of anti-mouse IgE on normal rat peritoneal mast cells was slight; it was enhanced after sensitization of these cells with mouse reaginic antibodies as well as after active sensitization. Moreover, anti-mouse IgE is able to neutralise the reaginic activity of mouse and rat antisera. The results suggest that there exist some functional and structural similarities between mouse and rat IgE.

Animals↗

Cloning of mouse type XV collagen sequences and mapping of the corresponding gene to 4B1-3. Comparison of mouse and human alpha 1 (XV) collagen sequences indicates divergence in the number of small collagenous domains.

We report on full-length mouse type XV collagen cDNAs that encode a 1367-residue alpha 1(XV) chain. The amino acid sequences of the mouse and previously characterized human alpha 1(XV) chains exhibit an overall identity of 72%. The highest homology between these chains and to the structurally related type XVIII collagen is observed in their C-terminal noncollagenous domains. Although the mouse and human alpha 1(XV) chains are highly homologous and similar in their overall domain structure, the mouse chain contains only seven collagenous domains, whereas the human chain contains nine. Northern analysis of several mouse tissues indicated strong hybridization in the case of heart and skeletal muscle RNAs and moderate signals with kidney, lung, and testis RNAs. Analysis of type XV collagen mRNA levels at different stages of mouse embryonic development indicated a marked increase in the level between 11 and 15 days of development, which coincides with pronounced development of the muscles, heart, and vascular system in the mouse embryo. The mouse gene for type XV collagen was mapped by fluorescence in situ hybridization to chromosome 4, band B1-3. This result indicates that the mouse type XV collagen gene and its human counterpart are located in the chromosomal segments with conserved syntenies.

Amino Acid Sequence↗

Characterization of mouse Eppin and a gene cluster of similar protease inhibitors on mouse chromosome 2.

We have recently described a novel gene on human chromosome 20q 12-13.2 called Eppin (Epididymal protease inhibitor) that expresses three mRNAs encoding two isoforms of a cysteine-rich protein containing both Kunitz-type and WAP-type (four disulfide core) consensus sequences (Richardson et al., 2001). To further our studies on Eppin, we have cloned, sequenced and characterized mouse Eppin and report that it lies within a 200 Kb cluster of putative Eppin-like genes on mouse chromosome 2. Analysis of the homologies between the genes in the human and mouse Eppin clusters indicates that the first part of the cluster immediately surrounding Eppin represents a conserved linkage because the order of homologous genes is conserved. Sequencing of reverse transcription polymerase chain reaction (RT-PCR) products confirmed the expression of five of these novel Eppin-like genes in the mouse, which include the mouse homologue of HE-4. These genes are characterized by having either one or both of the Kunitz-type and WAP-type consensus sequences. Additional RT-PCR experiments revealed that expression of some of the Eppin-like genes is restricted to epididymis and testis while others are expressed in several somatic tissues. Northern blot analysis of 22 different mouse tissues identified Eppin transcripts only in the epididymis and testis. Immunostaining of Eppin with anti-recombinant mouse Eppin demonstrated Eppin predominantly on the postacrosomal region of mouse spermatozoa, in Sertoli cells, Leydig cells, and round spermatids in the testis, and in the principal cells of the cauda epididymidis epithelium. Eppin is first expressed by Sertoli cells of 12-day-old mice and subsequently in round spermatids, which is consistent with androgen regulation. Our results demonstrate that mouse chromosome 2 contains a conserved linkage of Eppin-like protease inhibitor genes that are expressed in the epididymis.

Amino Acid Sequence↗

The codon 72 polymorphism-specific effects of human p53 are absent in mouse cells: implications on generation of mouse models.

Human p53, unlike mouse p53, contains a polymorphic site at codon 72 in exon 4 encoding either an arginine amino acid (72R) or a proline residue (72P). The 72R form was shown to induce apoptosis better than the 72P form, partly owing to its ability to efficiently bind to the nuclear-export protein CRM1 and localize to the mitochondria. This polymorphism has also been associated with cancer predisposition and chemo-sensitivity. Further understanding of the in vivo significance of this polymorphism in carcinogenesis requires the generation of mouse models. We have thus evaluated if the polymorphism-specific effects of human p53 are retained in mouse cells. Though being transcriptionally active, both the human polymorphs were found to have lost their ability to differentially suppress growth and bind to CRM1 or MDM2 in mouse cells. Moreover, chimaeric proteins containing mouse exons 2-3 and human exons 4-11 have also lost the polymorphism-specific effects in human cells, suggesting that human exons 2-3 are important in regulating the polymorphism-specific effects. Furthermore, human p53 and the various chimaeric proteins were generally less effective in inhibiting growth of mouse cells compared to mouse p53, suggesting that mouse p53 is more potent than human p53 in suppressing growth, partly due to enhanced binding of MDM2 to human p53. The data together suggest that mouse cells may not provide an appropriate environment for the manifestation of the polymorphism-specific functional differences of human p53, and hence, cautions against the expression of full-length or chimaeric p53 proteins in mice to study the effects of the polymorphism.

Animals↗

Cloning and characterization of a novel mouse Siglec, mSiglec-F: differential evolution of the mouse and human (CD33) Siglec-3-related gene clusters.

A novel mouse Siglec (mSiglec-F) belonging to the subfamily of Siglec-3-related Siglecs has been cloned and characterized. Unlike most human Siglec-3 (hSiglec-3)-related Siglecs with promiscuous linkage specificity, mSiglec-F shows a strong preference for alpha2-3-linked sialic acids. It is predominantly expressed in immature cells of the myelomonocytic lineage and in a subset of CD11b (Mac-1)-positive cells in some tissues. As with previously cloned Siglec-3-related mSiglecs, the lack of strong sequence similarity to a singular hSiglec made identification of the human ortholog difficult. We therefore conducted a comprehensive comparison of Siglecs between the human and mouse genomes. The mouse genome contains eight Siglec genes, whereas the human genome contains 11 Siglec genes and a Siglec-like gene. Although a one-to-one orthologous correspondence between human and mouse Siglecs 1, 2, and 4 is confirmed, the Siglec-3-related Siglecs showed marked differences between human and mouse. We found only four Siglec genes and two pseudogenes in the mouse chromosome 7 region syntenic to the Siglec-3-related gene cluster on human chromosome 19, which, in contrast, contains seven Siglec genes, a Siglec-like gene, and thirteen pseudogenes. Although analysis of gene maps and exon structures allows tentative assignments of mouse-human Siglec ortholog pairs, the possibility of unequal genetic recombination makes the assignments inconclusive. We therefore support a temporary lettered nomenclature for additional mouse Siglecs. Current information suggests that mSiglec-F is likely a hSiglec-5 ortholog. The previously reported mSiglec-3/CD33 and mSiglec-E/MIS are likely orthologs of hSiglec-3 and hSiglec-9, respectively. The other Siglec-3-like gene in the cluster (mSiglec-G) is probably a hSiglec-10 ortholog. Another mouse gene (mSiglec-H), without an apparent human ortholog, lies outside of the cluster. Thus, although some duplications of Siglec-3-related genes predated separation of the primate and rodent lineages (about 80-100 million years ago), this gene cluster underwent extensive duplications in the primate lineage thereafter.

Amino Acid Sequence↗

Characterization of NO and cytokine production in immune-activated microglia and peritoneal macrophages derived from a mouse model expressing the human NOS2 gene on a mouse NOS2 knockout background.

Significant differences exist in the production and release of nitric oxide (NO) from human macrophages versus macrophages of mouse origin. Human macrophages have been shown to respond poorly to stimuli that provoke strong inflammatory reactions from mouse macrophages. To address the differences in macrophage function in an animal model, a transgenic mouse was created that contained the entire human NOS2 gene, including the human promoter and all of its exons and introns. The huNOS2 transgenic mouse was then mated to mice lacking a functional NOS2 gene (muNOS2(/) or NOS2 knockout mice) to generate a double transgenic mouse (huNOS2(+/0)/muNOS2(/)) that expresses a functional human NOS2 gene in place of the mouse NOS2 gene. These double transgenic mice were found to express only human NOS2 mRNA and human iNOS proteins in response to immune stimulation. The production and release of nitric oxide from isolated macrophages from the doubly transgenic mouse also more closely paralleled human responses rather than mouse. Peritoneal macrophages from double transgenic mice generated nanomolar levels of nitrite in response to inflammatory stimuli, while peritoneal macrophages from wild-type mice generated micromolar levels of nitrite in response to the same inflammatory stimuli. Similarly, microglia from the huNOS2(+/0)/muNOS2(/) mice accumulated nanomolar levels of nitrite following inflammatory stimulation. Reduced nitrite release persisted in spite of normal responsiveness to inflammatory stimulation as measured by tumor necrosis factor alpha and interleukin-6 production and release. These data suggest that the human-specific release of nanomolar levels of nitrite may largely result from differences between the human and mouse NOS2 genes, which may program different degrees of nitric oxide responses to inflammatory signals in humans than in mice.

Animals↗

Mouse U14 snRNA is encoded in an intron of the mouse cognate hsc70 heat shock gene.

Mouse U14 snRNA (previously designated mouse 4.5S hybRNA) is an evolutionarily conserved eukaryotic low molecular weight RNA capable of intermolecular hybridization with both homologous and heterologous 18S rRNA (1). A single genomic fragment of mouse DNA containing the U14 snRNA gene(s) has been isolated from a Charon 4A lambda phage mouse genomic library and sequenced. Results have surprisingly revealed the presence of three U14 snRNA-homologous regions positioned within introns 5, 6, and 8 of the mouse cognate hsc70 heat shock gene. Comparative analysis with the previously reported rat and human cognate hsc70 genes revealed a similar positioning of U14 snRNA-homologous sequences within introns 5, 6 and 8 of the respective rat and human genes. The U14 sequences contained in all three introns of all three organisms are highly homologous to each other and well conserved with respect to the diverging intron sequences flanking each U14-homologous sequence. Comparison of the mouse U14 snRNA sequence with the U14 DNA sequences contained in the three mouse hsc70 introns indicates that intron 5 is utilized for U14 snRNA synthesis in normally growing mouse ascites cells. Analysis of the determined mouse, rat, and human U14-homologous sequences and the upstream and downstream flanking regions did not reveal the presence of any previously defined RNA polymerase I, II, or III binding sites. This suggests that either higher eukaryotic U14 snRNA is transcribed from a unique transcriptional promoter sequence, or alternatively, is generated by intron processing of the hsc70 pre-mRNA transcript.

Amino Acid Sequence↗

Significant differences between mouse and human trophinins are revealed by their expression patterns and targeted disruption of mouse trophinin gene.

Trophinin has been identified as a membrane protein mediating apical cell adhesion between two human cell lines: trophoblastic HT-H cells, and endometrial epithelial SNG-M cells. Expression patterns of trophinin in humans suggested its involvement in embryo implantation and early placental development. The mouse trophinin gene maps to the distal part of the X chromosome and corresponds to human chromosome Xp11.21-22, the locus where the human trophinin gene maps. Western blot analysis indicates that the molecular weight of mouse trophinin is 110 kDa, which is consistent with the calculated value of 107 kDa. Positive signals for trophinin proteins were detected in preimplantation mouse embryos at the morula and blastocyst stages. Implanting blastocysts do not show detectable levels of trophinin protein, demonstrating that trophinin is not involved in blastocyst adhesion to the uterus in the mouse. Mouse embryo strongly expressed trophinin in the epiblast 1 day after implantation. Trophinin protein was not found in the mouse uteri and placenta after 5.5 days postcoitus (dpc). Targeted disruption of the trophinin gene in the mouse showed a partial embryonic lethality in a 129/SvJ background, but the cause of this lethality remains undetermined. The present study indicates significant differences between mouse and human trophinins in their expression patterns, and it suggests that trophinin is not involved in embryo implantation and placental development in the mouse.

Amino Acid Sequence↗

Classification of proliferative pulmonary lesions of the mouse: recommendations of the mouse models of human cancers consortium.

Rapid advances in generating new mouse genetic models for lung neoplasia provide a continuous challenge for pathologists and investigators. Frequently, phenotypes of new models either have no precedents or are arbitrarily attributed according to incongruent human and mouse classifications. Thus, comparative characterization and validation of novel models can be difficult. To address these issues, a series of discussions was initiated by a panel of human, veterinary, and experimental pathologists during the Mouse Models of Human Cancers Consortium (NIH/National Cancer Institute) workshop on mouse models of lung cancer held in Boston on June 20-22, 2001. The panel performed a comparative evaluation of 78 cases of mouse and human lung proliferative lesions, and recommended development of a new practical classification scheme that would (a) allow easier comparison between human and mouse lung neoplasms, (b) accommodate newly emerging mouse neoplasms, and (c) address the interpretation of benign and preinvasive lesions of the mouse lung. Subsequent discussions with additional experts in pulmonary pathology resulted in the current proposal of a new classification. It is anticipated that this classification, as well as the complementary digital atlas of virtual histological slides, will help investigators and pathologists in their characterization of new mouse models, as well as stimulate further research aimed at a better understanding of proliferative lesions of the lung.

Animals↗

In silico cloning of mouse Muc5b gene and upregulation of its expression in mouse asthma model.

Using a BLAST-searching approach, we identified a mouse expressed sequence tag (EST) clone (AA038672) showing great similarity to the 3' end of the human MUC5B gene. The clone was named "3pmmuc5b-1" after complete nucleotide sequencing (Genbank Accession, AF369933). A subsequent search of the mouse genome database with the 3pmmuc5b-1 sequence identified two overlapping genomic clones (AC020817 and AC020794) that contained the sequence of both 3pmmuc5b-1 and the mouse Muc5ac gene. Like their human homologs, the genomic order of the mouse Muc genes is 5'-Muc5ac-Muc5b-3'. These results suggest that the newly identified EST clone, 3pmmuc5b-1, is part of the 3' portion of the mouse Muc5b gene. In situ hybridization demonstrated that this putative mouse Muc5b message was expressed in a restricted manner in the sublingual gland region of the tongue and the submucosal gland region of the mouse trachea in a normal animal. However, the gene expression was greatly enhanced in airway surface epithelium and the submucosal gland region in ovalbumin-induced asthmatic mice. These results were consistent with previous studies of human airway tissues. We therefore conclude that this newly cloned mouse Muc5b gene could be used as a marker for studying aberrant mucin gene expression in mouse models of various airway diseases.

Animals↗

Homozygous deletion of mouse homolog of p16/CDKN2 gene on chromosome 4 in mouse liver epithelial cells in culture.

The culture of hepatocytes isolated from C3H mouse liver results in the spontaneous development of colonies of liver epithelial cells that possess some features of the hepatocytes. These liver epithelial cells frequently have a loss of chromosome 4, and become neoplasms which are hepatocellular carcinomas by transfection with the activated c-Ha-ras gene. The suppression of malignant phenotypes by mouse chromosome 4 has already been shown by fusion between normal and malignant mouse cells. We established a total of six liver epithelial cell lines from C3H mice in order to investigate the presence of a tumor suppressor gene(s) on chromosome 4 in mouse hepatocarcinogenesis, and performed an allelotype analysis in seven microsatellites on chromosome 4 by the comparative multiplex PCR method. The result of analysis revealed that three of the six liver epithelial cells had allelic imbalances in four microsatellite loci, especially, two liver epithelial cell lines showed homozygous deletion in the D4MIT77 locus. Then, we investigated the status of the mouse homolog of p16/CDKN2 gene (mouse p16) on chromosome 4 by the comparative multiplex PCR method, and detected the homozygous deletion in two liver epithelial cell lines. Our result thus supports the theory that alterations of tumor suppressor gene(s) located on chromosome 4 may play a role in mouse hepatocarcinogenesis. Mouse p16, which is an inhibitor of cyclin dependent kinase 4, may suppress the cancer development in mouse hepatocarcinogenesis, or suppress liver cell immortalization.

Animals↗

Targeting rat anti-mouse transferrin receptor monoclonal antibodies through blood-brain barrier in mouse.

Drug targeting through the brain capillary endothelium, which forms the blood-brain barrier (BBB) in vivo, may be achieved with peptidomimetic monoclonal antibodies that target peptide transcytosis systems on the BBB in vivo. Murine monoclonal antibodies to the rat transferrin receptor, such as the OX26 monoclonal antibody, are targeted through the BBB on the transferrin receptor in the rat. However, the present studies show the OX26 monoclonal antibody is not an effective brain delivery vector in mice. The emergence of transgenic mouse models creates a need for brain drug-targeting vectors for this species. Two rat monoclonal antibodies, 8D3 and RI7-217, to the mouse transferrin receptor were evaluated in the present studies. Both the RI7-217 and the 8D3 antibody had comparable permeability-surface area products at the mouse BBB in vivo. However, owing to a higher plasma area under the concentration curve, the mouse brain uptake of the 8D3 antibody was higher, 3.1 +/- 0.4% of injected dose [(ID)/g] compared with the brain uptake of the RI7 antibody, 1.6 +/- 0.2% ID/g, at 60 min after i.v. injection. Conversely, the mouse brain uptake of the OX26 antibody, which does not recognize the mouse transferrin receptor, was negligible, 0.06 +/- 0.01% ID/g. The RI7-127 antibody was more selective for brain because this antibody was not measureably taken up by liver. The capillary depletion technique demonstrated transcytosis of the RI7-217 antibody through the mouse BBB in vivo. The brain uptake of the 8D3 antibody was saturable, consistent with a receptor-mediated transport process. In conclusion, these studies indicate rat monoclonal antibodies to the mouse transferrin receptor may be used for brain drug-targeting studies in mice such as transgenic mouse models.

Animals↗

Effect of transgenic expression of human alpha 1-acid glycoprotein (AGP) on the glycosylation of human and mouse AGP in various transgenic mouse sera.

The occurrence and the glycosylation of human alpha 1-acid glycoprotein (AGP) was studied in two classes of transgenic mice expressing either the A, B and B' genes (ABB'-mice) or only the A gene of human AGP (A-mice). The glycosylation of the human AGP molecules in the transgenic mouse sera was compared with the glycosylation of mouse AGP in the same animal and with human AGP in normal human serum by studying their heterogeneity in binding to concanavalin A (Con A), using crossed affino immunoelectrophoresis (CAIE) with Con A as the affinocomponent in the first dimension gel. Three to four different glycosylated fractions of human as well as mouse AGP were revealed by this method in all the transgenic mouse sera. A close relationship was apparent between the heterogeneities in Con A binding of human and mouse AGP in the same transgenic mouse. The magnitude of this so-called Con A reactivity was, however, strongly dependent on the transgenic mouse studied. Especially within the group of ABB'-mice dramatic changes in Con A reactivity were found when the human AGP genes were expressed. This indicates in the first place that the oligosaccharide chains of the human AGP molecules expressed also mouse-specific features. Secondly, and more importantly, these findings indicate that the expression of the human AGP genes affected the glycosylation process of the transgenic mouse liver. This organ is the source of the AGP forms occurring in serum. We do not know whether this effect has been caused by the introduction or the expression of the human gene(s) or by the presence of human AGP in the Golgi system or in serum.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute-Phase Proteins↗

Activation of mouse complement by different classes of mouse antibody.

The capacity of mouse IgM, IgGl, IgG2 and IgA anti-dinitrophenyl (DNP) antibodies to activate mouse or guinea-pig complement was studied, using a sensitive haemolytic assay and two-dimensional immunoelectrophoresis to detect cleavage of mouse C3. Three monoclonal IgM antibodies, and a heterogeneous IgM fraction, lysed trinitrophenylated erythrocytes in the presence of guinea-pig C, but failed to produce lysis in the presence of mouse C. and only activated mouse C3 very inefficiently. A monoclonal IgGl antibody did not produce haemolysis in the presence of guinea-pig or mouse C, but cleaved mouse C3 via the alternative pathway. Two IgA myeloma proteins (M315 and M460) had similar properties. A heterogeneous IgG2 antibody fraction produced haemolysis in the presence of both mouse and guinea-pig C, and was shown to activate both the classical and alternative pathways of mouse C.

Animals↗

2 cloning and expression of mouse deoxycytidine kinase. Pure recombinant mouse and human enzymes show differences in substrate specificity.

A cDNA encoding mouse deoxycytidine kinase (dCK) (EC 2.7.1.74) was cloned from a mouse T-cell lambda ZAP cDNA library. An insert of 2.8 kilobases (kb) contained the entire coding sequence of 780 base pairs. The protein coding sequence was 88% homologous at the nucleotide level with human dCK cDNA (Chottiner, E. G., Shewach, D. S., Datta, N. S., Ashcraft, E., Gribbin, D., Ginsburg, D., Fox, I. H., and Mitchell, B. S. (1991) Proc. Natl. Acad. Sci. U. S. A. 88, 1531-1535). At the amino acid level the homology was greater with only 16 of the 260 amino acids being different. Northern blot analyses revealed a size of 3.4 kb for mouse dCK mRNA as compared with 2.8 kb for human dCK. Part of the 3'-untranslated region was conserved between human and mouse dCK cDNA in contrast to the remainder of the 3'-sequence which was unrelated and about 500 nucleotides longer in mouse dCK cDNA. Mouse dCK cDNA showed cross-hybridization with several bands in EcoRI-digested genomic DNA from seven different mammalian species and chicken but not with yeast DNA. Both mouse and human dCK were cloned into the T5 promotor pQE30 vector system, expressed in Escherichia coli and purified to homogeneity. The kinetic constants for dCyd phosphorylation were similar for the human and mouse enzymes and also similar to what previously has been observed for dCK purified from human tissues. Mouse dCK was less efficient with regard to dAdo, dGuo, and ddCyd phosphorylation as compared with human dCK when using ATP as phosphate donor in a phosphoryl transfer assay.

Amino Acid Sequence↗