Repeated phosphopeptide motifs in human claspin are phosphorylated by Chk1 and mediate claspin function
Repeated phosphopeptide motifs in human claspin are phosphorylated by Chk1 and mediate claspin function
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DOI：
10.1074/jbc.m604373200
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发表时间：
2006-11-03
影响因子：
4.8
通讯作者：
Chen, Junjie
中科院分区：
文献类型：
--
作者：
Chini, Claudia C. S.;Chen, Junjie
Claspin是一种检查点蛋白，参与非洲爪蟾和人类细胞中ATR（（a）在bar taxia下，（t）在bar血管扩张突变下，和（R）在bar ad 3相关下）依赖性Chk 1激活。在非洲爪蟾中，Claspin在DNA损伤后通过含有两个高度保守的重复序列的区域与Chk 1相互作用，该区域在检查点响应期间被磷酸化。由于该区域在人类Claspin中也是保守的，因此我们研究了人类Claspin中这些潜在磷酸化位点的调节和功能。我们发现Claspin在体内在Thr-916处磷酸化以响应复制应激和UV损伤。Claspin上这些磷酸化位点的突变抑制Claspin-Chk 1在体内的相互作用，损害Chk 1活化，并诱导细胞中的过早染色质凝聚，表明复制检查点的缺陷。此外，我们发现Claspin上的Thr-916被Chk 1磷酸化，这表明Chk 1在检查点反应期间调节Claspin。这些结果共同表明，人Claspin中Claspin重复序列的磷酸化对于Claspin功能和人细胞中Claspin-Chk 1相互作用的调节是重要的。
Claspin is a checkpoint protein involved in ATR ((a) under bar taxia (t) under bar elangiectasia mutated-and (R) under bar ad3-related)-dependent Chk1 activation in Xenopus and human cells. In Xenopus, Claspin interacts with Chk1 after DNA damage through a region containing two highly conserved repeats, which becomes phosphorylated during the checkpoint response. Because this region is also conserved in human Claspin, we investigated the regulation and function of these potential phosphorylation sites in human Claspin. We found that Claspin is phosphorylated in vivo at Thr-916 in response to replication stress and UV damage. Mutation of these phosphorylation sites on Claspin inhibited Claspin-Chk1 interaction in vivo, impaired Chk1 activation, and induced premature chromatin condensation in cells, indicating a defect in replication checkpoint. In addition, we found that Thr-916 on Claspin is phosphorylated by Chk1, suggesting that Chk1 regulates Claspin during checkpoint response. These results together indicate that phosphorylation of Claspin repeats in human Claspin is important for Claspin function and the regulation of Claspin-Chk1 interaction in human cells.