Furnari B, Blasina A, Boddy M N, McGowan C H, Russell P
Departments of Molecular Biology and Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Mol Biol Cell. 1999 Apr;10(4):833-45. doi: 10.1091/mbc.10.4.833.
In the fission yeast Schizosaccharomyces pombe, the protein kinase Cds1 is activated by the S-M replication checkpoint that prevents mitosis when DNA is incompletely replicated. Cds1 is proposed to regulate Wee1 and Mik1, two tyrosine kinases that inhibit the mitotic kinase Cdc2. Here, we present evidence from in vivo and in vitro studies, which indicates that Cds1 also inhibits Cdc25, the phosphatase that activates Cdc2. In an in vivo assay that measures the rate at which Cdc25 catalyzes mitosis, Cds1 contributed to a mitotic delay imposed by the S-M replication checkpoint. Cds1 also inhibited Cdc25-dependent activation of Cdc2 in vitro. Chk1, a protein kinase that is required for the G2-M damage checkpoint that prevents mitosis while DNA is being repaired, also inhibited Cdc25 in the in vitro assay. In vitro, Cds1 and Chk1 phosphorylated Cdc25 predominantly on serine-99. The Cdc25 alanine-99 mutation partially impaired the S-M replication and G2-M damage checkpoints in vivo. Thus, Cds1 and Chk1 seem to act in different checkpoint responses to regulate Cdc25 by similar mechanisms.
在裂殖酵母粟酒裂殖酵母中，蛋白激酶Cds1由S-M复制检查点激活，该检查点在DNA未完全复制时阻止有丝分裂。有人提出Cds1调节Wee1和Mik1，这两种酪氨酸激酶可抑制有丝分裂激酶Cdc2。在此，我们展示了来自体内和体外研究的证据，表明Cds1还抑制Cdc25，即激活Cdc2的磷酸酶。在一项测量Cdc25催化有丝分裂速率的体内试验中，Cds1导致了S-M复制检查点引起的有丝分裂延迟。Cds1在体外也抑制Cdc25依赖的Cdc2激活。Chk1是一种蛋白激酶，在DNA修复时阻止有丝分裂的G2-M损伤检查点中是必需的，在体外试验中也抑制Cdc25。在体外，Cds1和Chk1主要在丝氨酸-99处使Cdc25磷酸化。Cdc25丙氨酸-99突变在体内部分损害了S-M复制和G2-M损伤检查点。因此，Cds1和Chk1似乎通过类似机制在不同的检查点反应中调节Cdc25。
