A 700-kb physical and transcription map of the cervical cancer tumor suppressor gene locus on chromosome 11q13.
Academic Article
Overview
abstract
Nonrandom deletion of chromosome 11q13 sequences is a significant event in a number of human tumors. We have recently identified a 300-kb minimal area of deletion in primary cervical tumors that overlaps with deletions observed in endocrine and nasopharyngeal tumors. We have also observed a 5.7-kb homozygous deletion within this interval in HeLa cells (a cervical cancer cell line), HeLa cell-derived tumorigenic hybrids, and a primary cervical tumor, suggesting the presence of a tumor suppressor gene in this region. In the present investigation, we have constructed a 700-kb contig map encompassing the 300-kb deletion using the human genome sequence database and confirmed the map using various STS markers from the region. Our map also shows the overlap of a previously published rare, heritable fragile site, FRA11A, with the cervical cancer deletion locus. The mapped region contains highly repetitive GC-poor sequences. We have identified and characterized eight different polymorphic microsatellite markers from the sequences within and surrounding the deletion. Further, expression studies performed with 18 different ESTs localized adjacent to the homozygous deletion showed the presence of a transcript for only one of the ESTs, AA282789. This EST mapping within the homozygous deletion is also expressed in HeLa cells, thereby excluding the EST as the putative tumor suppressor gene. Additionally, analysis of four candidate genes (SF3B2, BRMS1, RIN1, and RAB1B) from the region showed expression of the expected size message in both the nontumorigenic and the tumorigenic HeLa cell hybrids, thereby excluding them as the putative tumor suppressor gene(s). However, Northern blot analysis with a fifth candidate gene, PACS1 (phosphofurin acidic cluster sorting protein), mapped to the deletion/FRA11A overlap region showed the expression of an 8-kb transcript in HeLa and five other tumor cell lines in addition to the expected 4.5-kb transcript. Since the gene shows abundant expression in normal tissues and an altered transcript is observed in tumor cell lines, we hypothesize that this gene could represent sequences of the putative tumor suppressor gene. Finally, we have observed a perfect 48-bp CAG/CCG repeat 99 kb proximal to D11S913, the marker linked to the neurodegenerative disorder spinocerebellar ataxia 5. The physical and transcription maps and the microsatellite markers of the 700-kb region of chromosome 11q13 should be helpful in the cloning of the cervical cancer tumor suppressor gene.
