A new lymphocyte-specific gene which encodes a putative Ca2+-binding protein is not expressed in transformed T lymphocyte lines

The LSP1 gene is a new lymphocyte-specific gene which is expressed in normal mouse B and T lymphocytes and in transformed B cells but not (or in much smaller amounts) in nine T lymphoma lines tested. No LSP1 mRNA is found in myeloid cells or in liver, kidney, or heart tissue. Inspection of the predicted LSP1 protein sequence reveals the presence of two putative Ca2+-binding domains in the LSP1 protein. Southern blotting analysis of genomic DNA from mouse liver suggests that the LSP1 gene is present as one copy per haploid genome. Similar analysis of genomic DNA extracted from three transformed B cell lines and five transformed T cell lines shows that the absence of LSP1 mRNA in T cell lines is not due to deletion or gross rearrangements of the LSP1 locus. With the use of the mouse LSP1 cDNA as a probe we can detect a cross-hybridizing RNA species in four normal human functional T cell lines but not in three transformed human T cell lines. This suggests that at least part of the DNA sequence and the expression pattern of the LSP1 gene is conserved between mouse and man. These conserved features, together with the particular expression pattern and the protein sequence homologies, suggest that the LSP1 protein is involved in a Ca2+-dependent aspect of normal T cell growth.     

Genomic organization and chromosomal localization of the TAPA-1 gene.

TAPA-1 is a 26-kDa integral membrane protein expressed on many human cell types. Antibodies against TAPA-1 induce homotypic aggregation of cells and can inhibit their growth. The murine homologue of TAPA-1 was cloned from both cDNA and genomic DNA libraries. A very high level of homology was found between human and mouse TAPA-1. The 5' untranslated region of the TAPA-1 gene resembles housekeeping gene promoters with respect to G + C content and the presence of potential Sp1 binding sites. The chromosomal localization of human and murine TAPA-1 genes was determined by Southern blot experiments using DNA from somatic cell hybrids. The genes were found to be part of a conserved syntenic group in mouse chromosome 7 and the short arm of human chromosome 11. The organization of the TAPA-1 gene and the projection of the exon boundaries on the proposed protein structure are presented.     

A human homologue of the yeast GST1 gene codes for a GTP-binding protein and is expressed in a proliferation-dependent manner in mammalian cells.

A human homologue (GST1-Hs) of the yeast GST1 gene that encodes a new GTP-binding protein essential for the G1-to-S phase transition of the cell cycle was cloned from the cDNA library of human KB cells. The GST1-Hs cDNA contained a 1497 bp open reading frame coding for a 499 amino acid protein with mol. wt 55,754 and with the amino acid sequence homologies of 52.3 and 37.8% to the GST1 protein and polypeptide chain elongation factor EF1 alpha respectively. The regions potentially responsible for GTP binding and GTP hydrolysis were conserved in the GST1-Hs protein as well. When expressed in yeast cell, the GST1-Hs gene could complement the ts phenotype of yeast gst1 mutant. GST1-Hs and its mouse homologue were expressed in human fibroblasts and in various mouse cell types respectively, at relatively low levels in their quiescent states, and the level of those expressions increased rapidly, prior to the onset of DNA replication and the total RNA synthesis, when human or mouse fibroblasts were progressed out of the growth-arrested state by the addition of serum. A possible role of GST1-Hs in mammalian cell growth is discussed.     

The gene encoding TBC1D1 with homology to the tre-2/USP6 oncogene, BUB2, and cdc16 maps to mouse chromosome 5 and human chromosome 4

TBC1D1 is the founding member of a family of related proteins with homology to tre-2/UPS6, BUB2, and cdc16 and containing the tbc box motif of 180-220 amino acids. This protein family is thought to have a role in differentiation and in regulating cell growth. We set out to map the TBC1D1 gene in mouse and human. Segregation analysis of a TBC1D1 RFLP in two independent mouse RI (recombinant inbred) lines reveals that mouse Tbc1d1 is closely linked to Pgm1 on chromosome 5. The human TBC1D1 gene was assigned to human chromosome 4p15.1-->4q21 using Southern blot analyses of genomic DNAs from rodent-human somatic cell lines. A human-specific genomic fragment was observed in the somatic cell lines containing human chromosome 4 or the 4p15.1-->4q21 region of the chromosome. TBC1D1 maps to the region containing the ortholog of mouse Pgm1 adding another locus to this long region of conserved synteny between mouse and man.     

Cell cycle regulatory functions of the human oncoprotein MDM2

The protein (MDM2) coded by the mouse double minute-2 (mdm2) gene or its human homologue is well known as an oncoprotein. Malignant human tumors particularly breast tumors and soft tissue sarcomas frequently overexpress MDM2. Artificial amplification of mdm2 gene derived from a transformed murine cell line enhances tumorigenic potential of murine cells. Consistent with its tumorigenic property, mouse or human MDM2 can inactivate several functions of the tumor suppressor p53 and can degrade p53. The protein also interacts with other tumor suppressors, and these interactions may contribute to its tumorigenic property. In spite of its oncogenic role, mouse or human MDM2 induces G(1) arrest in normal human or murine cells. Some cell lines bearing known genetic mutations are insensitive to MDM2-mediated growth arrest. This review is aimed to collect available information on the functions of MDM2 that could potentially regulate cell cycle and to discuss how this information may fit in one model that could explain the two apparently opposite G(1) arrest and oncogenic function of MDM2.     

Localization of the photoreceptor gene ROM1 to human chromosome 11 and mouse chromosome 19: sublocalization to human 11q13 between PGA and PYGM.

Rom-1 is a retinal integral membrane protein that, together with the product of the human retinal degeneration slow gene (RDS), defines a photoreceptor-specific protein family. The gene for rom-1 (HGM symbol: ROM1) has been assigned to human chromosome 11 and mouse chromosome 19 by Southern blot analysis of somatic cell hybrid DNAs. ROM1 was regionally sublocalized to human 11p13-11q13 by using three mouse-human somatic cell hybrids; in situ hybridization refined the sublocalization to human 11q13. Analysis of somatic cell hybrids suggested that the most likely localization of ROM1 is in the approximately 2-cM interval between human PGA (human pepsinogen A) and PYGM (muscle glycogen phosphorylase). ROM1 appears to be a new member of a conserved syntenic group whose members include such genes as CD5, CD20, and OSBP (oxysterol-binding protein), on human chromosome 11 and mouse chromosome 19. Localization of the ROM1 gene will permit the examination of its linkage to hereditary retinopathies in man and mouse.     

Assignment of the developmentally regulated gene NEDD1 to human chromosome 12q22 by fluorescence in situ hybridization

The developmentally regulated mouse gene Nedd 1 encodes a protein showing similarities with the -subunit of heterotrimeric GTP-binding proteins and has growth suppressing activity when overexpressed in various cultured cell types. We have mapped the human homolog (NEDD1) of the mouse gene to chromosome 12q22 by fluorescence in situ hybridization using R-banded human (pro)metaphase chromosomes.     

Identification,genomic organization and mRNA expression of CRELD1, the founding member of a unique family of matricellular proteins

We have isolated and characterized a unique gene that encodes a highly conserved membrane bound extracellular protein that defines a new epidermal growth factor-related gene family. The CRELD1 (Cysteine-Rich with EGF-Like Domains 1) gene (previously known as cirrin) was cloned from a human chromosome 3 BAC. Mapping of the gene confirmed its position at chromosome 3p25.3. The gene is ubiquitously expressed in early development and later becomes more markedly expressed in the developing heart, limb buds, mandible and central nervous system. Expression persists in adulthood in most tissues. Sequence analysis suggests that this is a cell adhesion protein. The mouse orthologue was cloned and mapped to the syntenic region of mouse chromosome 6. Orthologues or homologues have also been identified for cow, Chinese hamster, Drosophila and Caenorhabditis elegans. The CRELD1 gene is deleted in the human cytogenetic disorder 3p- syndrome and is in the region of loss of heterozygosity for several types of cancer. A potential role for this protein in these disorders is discussed.     

Identification and preliminary function study of Xenopus laevis DRR1 gene

Xenopus laevis has recently been determined as a novel study platform of gene function. In this study, we cloned Xenopus DRR1 (xDRR1), which is homologous to human down-regulated in renal carcinoma (DRR1) gene. Bioinformatics analysis for DRR1 indicated that xDRR1 shared 74% identity with human DRR1 and 66% with mouse DRR1, and the phlogenetic tree of DRR1 protein was summarized. The xDRR1 gene locates in nuclei determined by transfecting A549 cells with the recombinant plasmid pEGFP-N1/xDRR1. RT-PCR analysis revealed that xDRR1 gene was expressed in all stages of early embryo development and all kinds of detected tissues, and whole-mount in situ hybridization showed xDRR1 was mainly present along ectoderm and mesoderm. Furthermore, xDRR1 expression could suppress A549 cell growth by transfecting with plasmid pcDNA3.1(+)/xDRR1. xDRR1 probably plays important roles involving in cell growth regulation and Xenopus embryo development.     

Constitutive activation of the Saccharomyces cerevislae mating response pathway by a MAP kinase kinase from Candida albicans

The HST7 gene of Candida albicans encodes a protein with structural similarity to MAP kinase kinases. Expression of this gene in Saccharomyces cerevisiae complements disruption of the Ste7 MAP kinase kinase required for both mating in haploid cells and pseudohyphal growth in diploids. However, Hst7 expression does not complement loss of either the Pbs2 (Hog4) MAP kinase kinase required for response to high osmolarity, or loss of the Mkk1 and Mkk2 MAP kinase kinases required for proper cell wall biosynthesis. Intriguingly, HST7 acts as a hyperactive allele of STE7; expression of Hst7 activates the mating pathway even in the absence of upstream signaling components including the Ste7 regulator Ste11, elevates the basal level of the pheromone-inducible FUS1 gene, and amplifies the pseudohyphal growth response in diploid cells. Thus Hst7 appears to be at least partially independent of upstream activators or regulators, but selective in its activity on downstream target MAP kinases. Creation of Hst7/Ste7 hybrid proteins revealed that the C-terminal two-thirds of Hst7, which contains the protein kinase domain, is sufficient to confer this partial independence of upstream activators.     

The ras-related ypt protein is an ubiquitous eukaryotic protein: isolation and sequence analysis of mouse cDNA clones highly homologous to the yeast YPT1 gene.

The YPT1 gene of the yeast Saccharomyces cerevisiae codes for a guanine nucleotide-binding protein which is essential for cell viability. Using as hybridization probe cloned yeast YPT1 gene sequences, we have isolated from cDNA libraries prepared from RNA of mouse F9 and C3H10T1/2 cells several overlapping cDNA clones with identical sequence in the regions of overlap. The cDNAs were derived from a gene, designated ypt1, which codes for a protein of 205 amino acids with 71% homology to the yeast YPT1 gene product. Amino acid sequences typical for guanine nucleotide-binding proteins and characteristic for ypt proteins are perfectly conserved in the mouse ypt1 protein. Two mRNAs of 1600 and 3200 nucleotides, originating from the mouse ypt1 gene and differing in the length of their 3'-non-translated region, were identified in mouse F9 cells and in all mouse tissues examined. A monoclonal antibody specifically recognizing the 23.5-kd yeast YPT1 protein cross-reacted with a protein of identical size on protein blots of mouse, rat, pig, bovine and human cell lines.     

cDNA cloning of human muskelin and localisation of the muskelin (MKLN1) gene to human chromosome 7q32 and mouse chromosome 6 B1/B2 by physical mapping and FISH

Muskelin is a novel intracellular protein, identified in mouse cells, that acts as a mediator of cell spreading and cytoskeletal responses to the extracellular matrix component thrombospondin-1. We report that human muskelin is 98% identical with mouse muskelin at the amino acid level. The human muskelin gene is located at 7q32. The mouse muskelin gene maps syntenically at chromosome 6 B1/B2.     

Constitutive activation of the Saccharomyces cerevislae mating response pathway by a MAP kinase kinase from Candida albicans

The HST7 gene of Candida albicans encodes a protein with structural similarity to MAP kinase kinases. Expression of this gene in Saccharomyces cerevisiae complements disruption of the Ste7 MAP kinase kinase required for both mating in haploid cells and pseudohyphal growth in diploids. However, Hst7 expression does not complement loss of either the Pbs2 (Hog4) MAP kinase kinase required for response to high osmolarity, or loss of the Mkk1 and Mkk2 MAP kinase kinases required for proper cell wall biosynthesis. Intriguingly, HST7 acts as a hyperactive allele of STE7; expression of Hst7 activates the mating pathway even in the absence of upstream signaling components including the Ste7 regulator Ste11, elevates the basal level of the pheromone-inducible FUS1 gene, and amplifies the pseudohyphal growth response in diploid cells. Thus Hst7 appears to be at least partially independent of upstream activators or regulators, but selective in its activity on downstream target MAP kinases. Creation of Hst7/Ste7 hybrid proteins revealed that the C-terminal two-thirds of Hst7, which contains the protein kinase domain, is sufficient to confer this partial independence of upstream activators.Communicated by C. P. Hollenberg     

The WFDC1 gene encoding ps20 localizes to 16q24, a region of LOH in multiple cancers

We previously identified ps20 protein as a secreted growth inhibitor and purified the protein from fetal rat prostate urogenital sinus mesenchymal cell conditioned medium. The rat cDNA was subsequently cloned, and ps20 was found to contain a WAP-type four-disulfide core motif, indicating it may function as a protease inhibitor. We now report cloning and characterization of the mouse ps20 gene (designated Wfdc1), the human homolog cDNA, and the human gene (designated WFDC1). Both the mouse and human WFDC1 genes consist of seven exons and encode respective ps20 proteins sharing 79.1% identity and nearly identical WAP motifs in exon 2. The WFDC1 gene was mapped by FISH analysis to human Chromosome (Chr) 16q24, an area of frequent loss of heterozygosity (LOH) previously identified in multiple cancers including prostate, breast, hepatocellular, and Wilms' tumor. Identification and characterization of the WFDC1 gene may aid in better understanding the potential role of this gene and ps20 in prostate biology and carcinogenesis.