title: Cdk-dependent phosphorylation regulates TRF1 recruitment to PML bodies and promotes C-circle production in ALT cells.
abstract: TRF1, a duplex telomeric DNA binding protein, is implicated in homologous-recombination-based alternative lengthening of telomeres, known as ALT. However, how TRF1 promotes ALT activity has yet to be fully characterized. Here we report that Cdk-dependent TRF1 phosphorylation on T371 acts as a switch to create a pool of TRF1, referred to as (pT371)TRF1, which is recruited to ALT-associated PML bodies (APBs) in S and G2 phases independently of its binding to telomeric DNA. We find that phosphorylation of T371 is essential for APB formation and C-circle production, both of which are hallmarks of ALT. We show that the interaction of (pT371)TRF1 with APBs is dependent upon ATM and homologous-recombination-promoting factors Mre11 and BRCA1. In addition, (pT371)TRF1 interaction with APBs is sensitive to transcription inhibition, which also reduces DNA damage at telomeres. Furthermore, overexpression of RNaseH1 impairs (pT371)TRF1 recruitment to APBs in the presence of campothecin, an inhibitor that prevents topoisomerase I from resolving RNA-DNA hybrids. These results suggest that transcription-associated DNA damage, perhaps arising from processing RNA-DNA hybrids at telomeres, triggers (pT371)TRF1 recruitment to APBs to facilitate ALT activity.
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1 zhuxu@mcmaster.ca.
authors.forename: Florence R
authors.initials: FR
authors.lastname: Wilson
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1.
authors.forename: Angus
authors.initials: A
authors.lastname: Ho
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1.
authors.forename: John R
authors.initials: JR
authors.lastname: Walker
authors.affiliation: Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1 zhuxu@mcmaster.ca.
authors.forename: Xu-Dong
authors.identifier: 0000-0003-1859-3134
authors.initials: XD
authors.lastname: Zhu
mesh_terms: D019313:BRCA1 Protein / Q000235:genetics*; D016203:CDC2 Protein Kinase / Q000235:genetics*; D002460:Cell Line; D004249:DNA Damage / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D005786:Gene Expression Regulation; D059765:Homologous Recombination / Q000235:genetics; D006801:Humans; D045586:Intranuclear Inclusion Bodies / Q000235:genetics; D000076228:MRE11 Homologue Protein; D010766:Phosphorylation; D016914:Ribonuclease H / Q000235:genetics; D016615:Telomere / Q000235:genetics; D059505:Telomere Homeostasis / Q000235:genetics*; D035321:Telomeric Repeat Binding Protein 1 / Q000235:genetics*
chemical_list: D019313:BRCA1 Protein; D004268:DNA-Binding Proteins; C121766:MRE11 protein, human; D035321:Telomeric Repeat Binding Protein 1; D016203:CDC2 Protein Kinase; D000076228:MRE11 Homologue Protein; D016914:Ribonuclease H; C078856:ribonuclease HI
keywords: ALT; Cdk; PML bodies; TRF1