Functional Analysis of the Role of TRF1 Phosphorylation on Threonine 271 and Threonine 371 in Telomere Maintenance

Abstract

TRF1, telomeric-repeat binding factor 1, is a component of the six-subunit protein complex, referred to as shelterin, which is essential for not only regulating telomere length maintenance but also protecting mammalian telomeres from being recognized as damaged DNA. TRF1 acts as a negative mediator of telomerase-dependent telomere elongation in telomerase-expressing cells, whereas it promotes alternative lengthening of telomeres (ALT) activity by regulating ALT features including the production of extrachromosomal telomere-repeat (ECTR) DNA such as C-circles, and ALT-associated promyelocytic leukemia bodies, or APBs. The activity of TRF1 is tightly regulated by post-translational modification such as phosphorylation. This thesis sets out to investigate the function of TRF1 phosphorylation on threonine-271 (T271) and threonine-371 in telomere maintenance. The results presented in this thesis demonstrate that TRF1 phosphorylation on T271 positively regulates the association of TRF1 to telomeric DNA in telomerase expressing cells. In ALT cells, TRF1 phosphorylation on both T271 and T371 is shown to be important for the formation of APBs. Furthermore, the work presented here suggests that transcription-associated DNA damage mediates the association of phosphorylated (pT371)TRF1 with APBs.