Hsk1 kinase and Cdc45 regulate replication stress-induced checkpoint responses in fission yeast
Hsk1 kinase and Cdc45 regulate replication stress-induced checkpoint responses in fission yeast
复制标题
DOI：
10.4161/cc.9.23.13937
复制
发表时间：
2010-12-01
期刊：
影响因子：
4.3
通讯作者：
Masai, Hisao
中科院分区：
文献类型：
--
作者：
Matsumoto, Seiji;Shimmoto, Michie;Masai, Hisao
在裂殖酵母中，复制叉停滞通过Rad（3ATR/Mec 1）-Mrc 1（Claspin）途径激活复制检查点效应激酶Cds 1（Chk 2/Rad 53）。Hsk 1是分裂酵母的Cdc 7同源物，是有效启动DNA复制所必需的，也是Cds 1激活所必需的。Hsk 1激酶活性是诱导和维持Mrc 1过度磷酸化所必需的，Mrc 1过度磷酸化由复制叉阻断诱导并由Rad 3介导。Rad 3激酶活性在hsk 1温度敏感突变体中不发生变化，并且Hsk 1激酶活性不受rad 3突变的影响。Hsk 1激酶在体外强烈磷酸化Mrc 1，主要是在非SQ/TQ网站，但这种磷酸化似乎并不影响Rad 3对Mrc 1的作用。有趣的是，在cdc 45的启动缺陷突变体中，复制应激诱导的Cds 1激活和Mrc 1过度磷酸化几乎完全消失，但在mcm 2或pole突变体中并不显着。结果表明，Hsk 1介导的Cdc 45加载到复制起点上可能在复制应激诱导的检查点中起重要作用。
In fission yeast, replication fork arrest activates the replication checkpoint effector kinase Cds1(Chk2/Rad53) through the Rad(3ATR/Mec1)-Mrc1(Claspin) pathway. Hsk1, the Cdc7 homolog of fission yeast required for efficient initiation of DNA replication, is also required for Cds1 activation. Hsk1 kinase activity is required for induction and maintenance of Mrc1 hyperphosphorylation, which is induced by replication fork block and mediated by Rad3. Rad3 kinase activity does not change in an hsk1 temperature-sensitive mutant, and Hsk1 kinase activity is not affected by rad3 mutation. Hsk1 kinase vigorously phosphorylates Mrc1 in vitro, predominantly at non-SQ/TQ sites, but this phosphorylation does not seem to affect the Rad3 action on Mrc1. Interestingly, the replication stress-induced activation of Cds1 and hyperphosphorylation of Mrc1 is almost completely abrogated in an initiation-defective mutant of cdc45, but not significantly in an mcm2 or pole mutant. The results suggest that Hsk1-mediated loading of Cdc45 onto replication origins may play important roles in replication stress-induced checkpoint.