The conserved C terminus of Claspin interacts with Rad9 and promotes rapid activation of Chk1.
Claspin is a key mediator of the ATR-Chk1 checkpoint pathway. In response to DNA damage, Claspin interacts with Rad17 and Chk1 in a phosphorylation-dependent manner, enabling ATR to phosphorylate Chk1 efficiently. Claspin also interacts with Rad9, but how they interact and whether the interaction is functional remains unknown. Unexpectedly, our analysis of two splicing isoforms of Claspin provided an answer to these questions. The Claspin(1339) isoform contains an evolutionarily conserved C terminus, but the Claspin(1332) isoform does not. Although the transcripts encoding both Claspin isoforms coexist in HCT116 cells, Claspin(1339) is the predominant form responsible for Chk1 activation. When expressed in cells depleted of endogenous Claspin, both Claspin(1339) and Claspin(1332) are able to mediate Chk1 activation. However, the activation of Chk1 is delayed in Claspin(1332)-expressing cells compared with Claspin(1339)-expressing cells. Furthermore, only Claspin(1339) but not Claspin(1332) interacts with Rad9 efficiently. Together, these results suggest that the conserved C terminus of Claspin interacts with Rad9 and ensures timely activation of the ATR-Chk1 pathway.
Massachusetts General Hospital Cancer Center, Harvard Medical School, Charlestown, MA, USA.
Shizhou
S
Liu
Na
N
Song
Lee
L
Zou
D048868:Adaptor Proteins, Signal Transducing / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002460:Cell Line; D000071877:Checkpoint Kinase 1; D002645:Chickens; D045325:HCT116 Cells; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D010766:Phosphorylation; D020033:Protein Isoforms / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D012326:RNA Splicing; D034741:RNA, Small Interfering / Q000378:metabolism; D014981:Xenopus; D029867:Xenopus Proteins
D048868:Adaptor Proteins, Signal Transducing; C488158:CLSPN protein, human; D018797:Cell Cycle Proteins; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D029867:Xenopus Proteins; C069930:rad9 protein; D011494:Protein Kinases; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C000605875:Chek1 protein, Xenopus; C000605869:Chek1 protein, mouse