Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537007
Title: Functional identification and mapping of a gene that represses telomerase hTERT transcription in prostate cancer cells
Author: Hasan, Rana
Awarding Body: Brunel University
Current Institution: Brunel University
Date of Award: 2010
Availability of Full Text:
Access from EThOS:
Access from Institution:
Abstract:
Telomerase is present in over 90% of tumour tissues and immortalized cells and is tightly regulated in most normal somatic cells. This suggests the existence of regulatory mechanisms repressing telomerase in normal cells that somehow have become inactive during cancer development. In this project, I used genetic complementation in the form of microcell-mediated monochromosome transfer (MMCT) to search for chromosomes that repress telomerase activity in a prostate cancer cell line, PC-3. Microcell hybrids generated by introducing normal human chromosome 11 strongly inhibited telomerase. Telomerase is regulated primarily at the level of hTERT transcription, its catalytic subunit. Consequently, endogenous hTERT mRNA levels were measured by quantitative RT-PCR in microcell hybrids generated by transferring normal human chromosomes into a PC-3 sub-clone (PC- 3/hTERT) ectopically expressing hTERT cDNA to prevent senescence. Only hybrids constructed with transferred chromosome 11 showed strong transcriptional repression of hTERT. Next, hybrids were constructed by the MMCT transfer of chromosome 11 fragments (X-ray-induced). FISH analysis of clones with completely silenced endogenous hTERT transcription revealed in all cases a discrete chromosome 11 fragment with both the p-arm and q-arm material. A randomly selected hTERT-repressed clone was treated with ganciclovir to select against the HyTK marker and reverse the phenotype. hTERT expression in majority of GCV-resistant clones returned to levels comparable to the parent PC-3/hTERT cells. Collectively, these results provide strong functional evidence for the presence of a powerful telomerase repressor sequence on the fragment. Transfer of one repressive fragment back into mouse A9 cells was then carried out to facilitate fine-structure mapping of its sequence content. High density STS mapping of the fragment in each of the clones revealed a considerable DNA content heterogeneity across the panel. These content maps, together with a further round of MMCT to confirm hTERTrepressive activity, enabled me to identify three candidate regions on the q-arm of chromosome 11 where the repressor sequence may be located: the first region lies between map positions 64.70Mb to 65.42Mb and the other two regions each flank a single positive STS marker at 69.71Mb and 127.32Mb. KAT5, a histone modifying gene has been identified as a potential candidate for repressing hTERT.
Supervisor: Newbold, R. F. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.537007  DOI: Not available
Keywords: Microcell mediated chromosome transfer (MMCT) ; Senescence ; Telomerase activity ; Endogenous hTERT ; Chromosome 11
Share: