Saka Y, Fantes P, Sutani T, McInerny C, Creanor J, Yanagida M
Department of Biophysics, Faculty of Science, Kyoto University, Japan.
EMBO J. 1994 Nov 15;13(22):5319-29. doi: 10.1002/j.1460-2075.1994.tb06866.x.
Fission yeast temperature-sensitive cut5 (cell untimely torn) mutants are defective in initiation and/or elongation of DNA replication but allow mitosis and cell division at a restrictive temperature. We show that the cut5 protein (identical to rad4) (i) is an essential component of the replication checkpoint system but not the DNA damage checkpoint, and (ii) negatively regulates the activation of M phase kinase at mitotic entry. Even if the replication checkpoint has been activated previously, cut5 mutations allow mitosis and cell division after shift to 36 degrees C. Transcription of cut5+ is not under the control of the START gene cdc10+. The cut5 protein is enriched in the nucleus, consisting of repeating domains. An essential domain which resembles the proto-oncoprotein Ect2 has a strong negative effect on the entry into mitosis when overexpressed. Expression of the cut5 mutant phenotype requires the function of the M phase regulator genes cdc2+, cdc25+ and cdc13+. The cut5 protein forms a novel, essential link between DNA synthesis and M phase activation in the replication checkpoint control pathway.
裂殖酵母温度敏感型cut5（细胞过早分裂）突变体在DNA复制起始和/或延伸过程中存在缺陷，但在限制温度下允许有丝分裂和细胞分裂。我们发现，cut5蛋白（与rad4相同）（i）是复制检查点系统的重要组成部分，而非DNA损伤检查点的组成部分，并且（ii）在有丝分裂进入时负向调节M期激酶的激活。即使复制检查点先前已被激活，cut5突变体在转移至36℃后仍允许有丝分裂和细胞分裂。cut5+的转录不受起始基因cdc10+的控制。cut5蛋白在细胞核中富集，由重复结构域组成。一个类似于原癌蛋白Ect2的必需结构域在过表达时对进入有丝分裂有强烈的负向作用。cut5突变体表型的表达需要M期调节基因cdc2+、cdc25+和cdc13+的功能。在复制检查点控制途径中，cut5蛋白在DNA合成和M期激活之间形成了一种新的重要联系。
