title: TRF1 phosphorylation on T271 modulates telomerase-dependent telomere length maintenance as well as the formation of ALT-associated PML bodies.
abstract: TRF1, a component of the shelterin complex, plays a key role in both telomerase-dependent telomere maintenance and alternative lengthening of telomeres, the latter also known as ALT. Characteristics of ALT cells include C-circles and ALT-associated PML bodies, referred to as APBs. The function of TRF1 is tightly regulated by post-translational modification including phosphorylation, however TRF1 phosphorylation sites have yet to be fully characterized. Here we report a novel TRF1 phosphorylation site threonine 271. We show that a nonphosphorylatable mutation of T271A impairs TRF1 binding to telomeric DNA in vivo and renders TRF1 defective in inhibiting telomerase-dependent telomere elongation. On the other hand, TRF1 carrying a phosphomimic mutation of T271D is competent in not only binding to telomeric DNA but also inhibiting telomerase-mediated telomere lengthening. These results suggest that TRF1 phosphorylation on T271 negatively regulates telomerase-mediated telomere maintenance. We find that in telomerase-negative ALT cells, TRF1 carrying either a T271A or T271D mutation is able to promote C-circle production but fails to support APB formation. These results suggest that TRF1 phosphorylation on T271 is necessary for APB formation but dispensable for C-circle production. These results further imply that APB formation can be mechanistically separated from C-circle production.
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
authors.forename: Angus
authors.initials: A
authors.lastname: Ho
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
authors.forename: Florence R
authors.initials: FR
authors.lastname: Wilson
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
authors.forename: Stephanie L
authors.initials: SL
authors.lastname: Peragine
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
authors.forename: Kajaparan
authors.initials: K
authors.lastname: Jeyanthan
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
authors.forename: Taylor R H
authors.initials: TR
authors.lastname: Mitchell
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
authors.forename: Xu-Dong
authors.initials: XD
authors.lastname: Zhu
mesh_terms: D045744:Cell Line, Tumor; D006367:HeLa Cells; D006706:Homeostasis; D006801:Humans; D045586:Intranuclear Inclusion Bodies / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation; D000071156:Promyelocytic Leukemia Protein / Q000378:metabolism*; D011485:Protein Binding; D019098:Telomerase / Q000378:metabolism*; D016615:Telomere / Q000378:metabolism*; D059505:Telomere Homeostasis; D035321:Telomeric Repeat Binding Protein 1 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014443:Tyrosine / Q000737:chemistry*
chemical_list: D000071156:Promyelocytic Leukemia Protein; D035321:Telomeric Repeat Binding Protein 1; C070576:PML protein, human; D014443:Tyrosine; D019098:Telomerase