ATRX as a Regulator of Telomerase Activity in Cancer Cells
AdvisorBeattie, Tara L.
Cairncross, Gregory J.
Committee MemberRiabowol, Karl T.
Grewal, Savraj S.
MetadataShow full item record
AbstractTelomere maintenance is the central process governing cellular immortality. The two distinct pathways – 1) telomerase activity and 2) the alternative lengthening of telomeres (ALT) – result in telomere elongation and allow cells to evade normal cellular ageing mechanisms. Both telomere maintenance pathways can become activated through gene mutations, leading to genetically unstable cells capable of unlimited proliferation. Expression of the chromatin remodeling protein ATRX is lost in almost all ALT+ cancers, suggesting a role for ATRX in ALT repression, however its exact role in telomere maintenance remains unclear. This thesis provides novel evidence suggesting ATRX acts to resolve telomeric G-quadruplexes (G4), thereby facilitating telomerase activity and indirectly repressing ALT. Using RNA interference in human cancer cell lines and a novel DNA ELISA-based technique, the data presented here establish that loss of ATRX expression results in increased G4 at the telomere. This G4 enrichment correlates with a reduction in telomerase activity in vitro which is exacerbated following treatment with the G4 stabilizing agent, Pyridostatin. Further, loss of the full-length ATRX isoform alone does not directly correlate with the ALT phenotype in the selected cell panel. However, a truncated ATRX isoform, ATRXt, was found to be expressed in all selected telomerase+ cells and shown to maintain key functions of the full-length protein. Therefore, alternative ATRX isoforms may act to facilitate telomerase activity through G4 resolution, even in the absence of full-length protein. Taken together, these data provide novel evidence identifying ATRX as an important factor facilitating telomerase-mediated telomere elongation through G4 resolution at the telomere.
CitationBriggs, S. (2020). ATRX as a Regulator of Telomerase Activity in Cancer Cells (Unpublished doctoral thesis). University of Calgary, Calgary, AB.
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