A Shld1-controlled POT1a provides support for repression of ATR signaling at telomeres through RPA exclusion.
We previously proposed that POT1 prevents ATR signaling at telomeres by excluding RPA from the single-stranded TTAGGG repeats. Here, we use a Shld1-stabilized degron-POT1a fusion (DD-POT1a) to study the telomeric ATR kinase response. In the absence of Shld1, DD-POT1a degradation resulted in rapid and reversible activation of the ATR pathway in G1 and S/G2. ATR signaling was abrogated by shRNAs to ATR and TopBP1, but shRNAs to the ATM kinase or DNA-PKcs did not affect the telomere damage response. Importantly, ATR signaling in G1 and S/G2 was reduced by shRNAs to RPA. In S/G2, RPA was readily detectable at dysfunctional telomeres, and both POT1a and POT1b were required to exclude RPA and prevent ATR activation. In G1, the accumulation of RPA at dysfunctional telomeres was strikingly less, and POT1a was sufficient to repress ATR signaling. These results support an RPA exclusion model for the repression of ATR signaling at telomeres.
Laboratory for Cell Biology and Genetics, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
Yi
Y
Gong
Titia
T
de Lange
D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism*; D019610:Cytoprotection / Q000187:drug effects; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D007399:Interphase / Q000187:drug effects; D051379:Mice; D009025:Morpholines / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D051716:Replication Protein A / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D000089804:Shelterin Complex; D015398:Signal Transduction / Q000187:drug effects*; D016615:Telomere / Q000378:metabolism*; D034501:Telomere-Binding Proteins
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009025:Morpholines; C507326:POT1 protein, mouse; D034741:RNA, Small Interfering; D051716:Replication Protein A; D012097:Repressor Proteins; D000089804:Shelterin Complex; C540198:Shield-1 compound; D034501:Telomere-Binding Proteins; C576897:Atr protein, mouse; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases