HCLK2 is essential for the mammalian S-phase checkpoint and impacts on Chk1 stability
HCLK2 is essential for the mammalian S-phase checkpoint and impacts on Chk1 stability
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DOI：
10.1038/ncb1555
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发表时间：
2007-04-01
影响因子：
21.3
通讯作者：
Boulton, Simon J.
中科院分区：
文献类型：
--
作者：
Collis, Spencer J.;Barber, Louise J.;Boulton, Simon J.
在这里，我们表明，秀丽隐杆线虫生物钟蛋白CLK-2（HCLK 2）的人类同源物与S期检查点组件ATR，ATRIP，claspin和Chk 1。与S期检查点中的关键作用一致，HCLK 2耗尽的细胞在S期积累自发DNA损伤，表现出放射抗性DNA合成，受损的FANCD 2损伤诱导的单倍半胱氨酸化，并且不能将FANCD 2和Rad 51（分别为范可尼贫血和同源重组途径的关键组分）募集到复制应激位点。尽管在没有HCLK 2的情况下，检查点效应激酶Chk 2的Thr 68磷酸化保持完整，但由于Chk 1降解加速，在复制应激后，检查点磷酸酶Cdc 25 A的claspin磷酸化和降解受到损害。已知ATR磷酸化既激活Chk 1又靶向其进行蛋白水解降解，并且在HCLK 2耗尽的细胞中耗尽ATR或Chk 1在Ser 345处的突变恢复Chk 1蛋白水平。我们的结论是，HCLK 2促进激活的S期检查点和下游修复反应，防止计划外Chk 1降解的蛋白酶体。
Here, we show that the human homologue of the Caenorhabditis elegans biological clock protein CLK-2 (HCLK2) associates with the S-phase checkpoint components ATR, ATRIP, claspin and Chk1. Consistent with a critical role in the S-phase checkpoint, HCLK2-depleted cells accumulate spontaneous DNA damage in S-phase, exhibit radio-resistant DNA synthesis, are impaired for damage-induced monoubiquitination of FANCD2 and fail to recruit FANCD2 and Rad51 (critical components of the Fanconi anaemia and homologous recombination pathways, respectively) to sites of replication stress. Although Thr 68 phosphorylation of the checkpoint effector kinase Chk2 remains intact in the absence of HCLK2, claspin phosphorylation and degradation of the checkpoint phosphatase Cdc25A are compromised following replication stress as a result of accelerated Chk1 degradation. ATR phosphorylation is known to both activate Chk1 and target it for proteolytic degradation, and depleting ATR or mutation of Chk1 at Ser 345 restored Chk1 protein levels in HCLK2-depleted cells. We conclude that HCLK2 promotes activation of the S-phase checkpoint and downstream repair responses by preventing unscheduled Chk1 degradation by the proteasome.