Chromatin binding, nuclear localization and phosphorylation of Xenopus cdc21 are cell-cycle dependent and associated with the control of initiation of DNA replication
Chromatin binding, nuclear localization and phosphorylation of Xenopus cdc21 are cell-cycle dependent and associated with the control of initiation of DNA replication
复制标题
DOI：
10.1002/j.1460-2075.1996.tb00446.x
复制
发表时间：
1996-03-01
期刊：
影响因子：
11.4
通讯作者：
Mechali, M
中科院分区：
文献类型：
--
作者：
Coue, M;Kearsey, SE;Mechali, M
裂殖酵母cdc21的非洲爪哇同源物被鉴定为MCM家族的一个新成员。CDC21蛋白表现出依赖于细胞周期的染色质结合和磷酸化，并与S时相控制有关。在有丝分裂结束时，CDC21与去凝集的染色质结合，定位于核膜重建之前形成的许多病灶。CDC21与染色质的结合发生在无膜高速提取液中，并且对洗涤剂提取具有抵抗力。Cdc21焦点的空间组织类似于复制前中心，尽管没有观察到与RP-A的共同定位。在DNA复制的启动过程中，CDC21仍然与染色质结合，并随着DNA复制的进展而被取代。这些亚核定位的变化与细胞周期调节的磷酸化变化相关。CDC21与染色质的结合处于低磷酸化状态，但在S早期，细胞核定位的CDC21在从染色质移位之前被部分磷酸化。细胞质的cdc21仍然是低磷酸化的，但在有丝分裂开始时，整个cdc21池被过度磷酸化，可能是通过cdc2/cyclinB激酶。这些特性表明，非洲爪哇cdc21可能是DNA许可因子的一个组成部分。
A Xenopus homologue of Schizosaccharomyces pombe cdc21 has been characterized as a new member of the MCM family of proteins. The cdc21 protein exhibits cell-cycle dependent chromatin binding and phosphorylation in association with S-phase control. Cdc21 binds to decondensing chromatin at the end of mitosis, localizing to numerous foci which form prior to reconstitution of the nuclear membrane. The association of cdc21 with chromatin occurs in membrane-free high speed extracts and is resistant to detergent extraction. The spatial organization of the cdc21 foci resembles that of pre-replication centres though no co-localization with RP-A was observed. Cdc21 remains bound to chromatin during the initiation of DNA replication and is displaced as the DNA replication forks progress. These subnuclear changes in localization correlate with cell-cycle-regulated changes in phosphorylation. Cdc21 binds to chromatin in an underphosphorylated state, but in early S phase the nuclear localized cdc21 is partially phosphorylated before it is displaced from the chromatin. Cytoplasmic cdc21 remains underphosphorylated but at the beginning of mitosis the entire pool of cdc21 is hyperphosphorylated, possibly by the cdc2/cyclinB kinase. These properties identify Xenopus cdc21 as a possible component of the DNA licensing factor.