Cytogenetics and cell genetics最新文献

The human UBE2L6 gene encodes UbcH8(Kumar), a ubiquitin-conjugating enzyme (E2) highly simliar in primary structure to UbcH7 which is encoded by UBE2L3. Like UBC4 and UBC5 in yeast, these proteins demonstrate functional redundancy. Herein we report the intron/exon structure of UBE2L6. Comparison of the genomic organization of UBE2L6 with UBE2L3 demonstrates that these genes remain highly conserved at the genomic as well as at the protein level. We also describe the chromosomal localization of UBE2L6, which maps to chromosome 11q12.

We have mapped and characterized the human homolog of Drm/Gremlin (CKTFS1B1), a member of a family of BMP antagonists that have been linked to both developmental and transformation-related functions. By screening a human cDNA library, we isolated a 3.3-kb cDNA containing the 552-bp region encoding the human DRM protein. CKTFS1B1 was localized on human chromosome 15q13--> q15 by somatic cell hybrid analysis and, more precisely, using radiation hybrids, to a region of markers linked to SGNE1, secretory granule neuroendocrine protein 1 and RYR3, the ryanodyne receptor 3. Northern blot analysis showed the presence of a single DRM-specific mRNA expressed in different human tissues, including brain, ovary, intestine and colon. In the brain, DRM expression is associated with the region localized around the internal capsule in the large subcortical nuclei. DRM appears to be predominantly expressed in normal cells and tissues, including normal neurons, astrocytes and fibroblasts. Interestingly, we detected DRM expression in normal cells obtained from several patients, but not in tumor cell lines established from the same patients. The data suggest that down-regulation of DRM is associated with tumor progression, and support the hypothesis that human DRM may play an important role during both neuroembryological development and carcinogenesis.

The complete porcine c-fos proto-oncogene (FOS) with flanking regions was cloned and sequenced. FOS consists of four exons at amino acids 1-47, 48-131, 132-167, and 168-380 and includes all the typical motifs of the fos proto-oncogene. The promoter contains consensus sequences for CRE, SRE, CaRE, and the E-Box, as well as an AP-1 site. Homologies between human and swine were between 89.7% and 96.3% in the exons. Based on somatic cell hybrid panel screening and known homologies between swine chromosome 7 and human chromosome 14, the porcine c-fos gene was assigned to chromosome 7q23.

Smoothelins are cytoskeleton-associated proteins that are found in contractile smooth muscle. Two isoforms have been identified: smoothelin-A, expressed in visceral tissues and smoothelin-B, found in vascular tissues. The mouse smoothelin gene (Smtn) was isolated and characterized. It was assigned to chromosome 11 band A2-A3 by fluorescence in situ hybridization. The gene consists of 20 exons and spans 23 kb. Its structure is conserved between mouse and human. The proximal promoter of both smoothelin-A and smoothelin-B contains several transcription factor-binding sites but lacks a consensus TATA box.

Members of the F-box protein (Fbp) family are characterized by an approximately 40 amino acid F-box motif. SCF complexes (formed by Skp1, cullin, and one of many Fbps) act as protein-ubiquitin ligases that control the G(1)/S transition of the eukaryotic cell cycle. The substrate specificity of SCF complexes is determined by the presence of different Fbp subunits that recruit specific substrates for ubiquitination. Unchecked degradation of cellular regulatory proteins has been observed in certain tumors and it is possible that deregulated ubiquitin ligases play a role in the altered degradation of cell cycle regulators. We have recently identified a family of human Fbps. As a first step aimed at determining if FBP genes could be involved in human neoplasia, we have mapped the chromosome positions of 5 FBP genes by fluorescence in situ hybridization (FISH) to 10q24 (BTRC alias beta-TRCP/FBW1a), 9q34 (FBXW2 alias FBW2), 13q22 (FBXL3A alias FBL3a), 5p12 (FBXO4 alias FBX4) and 6q25-->q26 (FBXO5 alias FBX5). Since most of these are chromosomal loci frequently altered in tumors, we have screened 42 human tumor cell lines and 48 human tumor samples by Southern hybridization and FISH. While no gross alterations of the genes encoding beta-Trcp/Fbw1a, Fbw2, Fbx4 and Fbx5 were found, heterozygous deletion of the FBXL3A gene was found in four of 13 small cell carcinoma cell lines. This is the first evaluation of genes encoding Fbps in human tumors.