Functional role of SETD2, BAP1, PARP-3 and PBRM1 candidate genes on the regulation of hTERT gene expression
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Hannah Linne1, Hemad Yasaei1,4, Alison Marriott1, Amanda Harvey1,2, Kefah Mokbel1,3, Robert Newbold1,2 and Terry Roberts1,2
1College of Health and Life Sciences, Department of Life Sciences, Biosciences, Brunel University London, Middlesex, UK
2Institute of Environment, Health and Societies, Brunel University London, Middlesex, UK
3London Breast Institute, The Princess Grace Hospital, London, UK
4Current address: Dubai Genetics Centre, Dubai Health Authority, Dubai, United Arab Emirates
Terry Roberts, email: firstname.lastname@example.org
Keywords: telomerase, breast cancer, epigenetic, chromosome 3, microcell-mediated chromosome transfer
Received: January 25, 2017 Accepted: May 15, 2017 Published: June 27, 2017
Narrowing the search for the critical hTERT repressor sequence(s) has identified three regions on chromosome 3p (3p12-p21.1, 3p21.2 and 3p21.3-p22). However, the precise location and identity of the sequence(s) responsible for hTERT transcriptional repression remains elusive. In order to identify critical hTERT repressor sequences located within human chromosome 3p12-p22, we investigated hTERT transcriptional activity within 21NT microcell hybrid clones containing chromosome 3 fragments. Mapping of chromosome 3 structure in a single hTERT-repressed 21NT-#3fragment hybrid clone, revealed a 490kb region of deletion localised to 3p21.3 and encompassing the histone H3, lysine 36 (H3K36) trimethyltransferase enzyme SETD2; a putative tumour suppressor gene in breast cancer. Three additional genes, BAP1, PARP-3 and PBRM1, were also selected for further investigation based on their location within the 3p21.1-p21.3 region, together with their documented role in the epigenetic regulation of target gene expression or hTERT regulation. All four genes (SETD2, BAP1, PARP-3 and PBRM1) were found to be expressed at low levels in 21NT. Gene copy number variation (CNV) analysis of SETD2, BAP1, PARP-3 and PBRM1 within a panel of nine breast cancer cell lines demonstrated single copy number loss of all candidate genes within five (56%) cell lines (including 21NT cells). Stable, forced overexpression of BAP1, but not PARP2, SETD2 or PBRM1, within 21NT cells was associated with a significant reduction in hTERT expression levels relative to wild-type controls. We propose that at least two sequences exist on human chromosome 3p, that function to regulate hTERT transcription within human breast cancer cells.
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