Isolation and characterization of a gene amplified in human sarcomas.

A subset of human sarcomas including malignant fibrous histiocytoma and liposarcoma have been found to contain amplification of 12q13-14, a chromosomal region previously reported to include a number of growth-related genes including the GLI proto-oncogene, CDK4, a cyclin-dependent kinase gene, and the gene for the p53-associated protein, MDM2. This dissertation is based on the characterization of SAS (sarcoma amplified sequence), a novel gene found in this region, including an investigation of the hypothesis that SAS amplification may contribute to the transformed phenotype of cells in which it is amplified. Sequence analysis demonstrates that SAS encodes a new member of a transmembrane protein family (transmembrane 4 superfamily or TM4SF) thought to be involved in growth-related cellular processes. SAS also appears to be one of the more divergent members of this family based on amino acid identity and concensus alignment. The SAS gene, which contains an open reading frame encoding a 210 amino acid polypeptide, is the smallest member of this family at the genomic level. The position of three of its introns is perfectly conserved among characterized members of the TM4SF confirming its classification as a gene encoding a TM4SF protein. Two putative transcription start sites, two CCAAT consensus sequences, and potential binding sites for both Sp1 and ATF transcription factors were identified 5$\sp\prime$ to the translation start site. The theory that the TM4SF genes arose through duplication and divergent evolution was found to be supported by the map position of a number of these genes, and by similarities in flanking sequences. SAS transcription in sarcomas and cell lines with amplification of the SAS gene appears increased in comparison to those without amplification. Indirect immunofluorescence using polyclonal antiserum raised against a SAS peptide provided preliminary evidence that SAS is located within an intracellular organelle. However, further studies are necessary to confirm these observations. While it is still not clear whether SAS is the target of the amplification event, characterization of the SAS gene as a new member of the TM4SF suggests that this gene may be found to have an important role in cellular function.PhDHuman GeneticsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/103965/1/9423219.pdfDescription of 9423219.pdf : Restricted to UM users only