Recruitment of Xenopus Scc2 and cohesin to chromatin requires the pre-replication complex
Recruitment of Xenopus Scc2 and cohesin to chromatin requires the pre-replication complex
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DOI：
10.1038/ncb1177
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发表时间：
2004-10-01
影响因子：
21.3
通讯作者：
Walter, JC
中科院分区：
文献类型：
--
作者：
Takahashi, TS;Yiu, PY;Walter, JC
粘附素是一种多亚单位的环状蛋白复合体，从姐妹染色单体的合成到后期的分离(1-7)，粘附素将姐妹染色单体连接在一起。在酵母中，将粘附素装载到染色体上需要Scc2蛋白(8-10)。在脊椎动物中，当细胞退出有丝分裂时，粘附素首先结合到染色体上，但机制尚不清楚(3，11，12)。在粘附素结合的同时，复制前复合体(Pre-RCs)通过顺序加载启动因子ORC、CDC6、CDT1和MCM2-7在DNA复制的起始处组装(‘许可’反应)(13)。在S期，蛋白激酶CDK2激活Pre-RCS，引起起源解离和DNA复制。在这里，我们使用非洲爪哇卵提取物来表明，粘附素的募集到染色体上需要完全许可的染色质，并依赖于ORC、CDC6、CDT1和MCM2-7，但不依赖于CDK2。我们进一步表明，Xenopus Scc2是粘附素负载所必需的，并且XScc2与染色质的结合依赖于MCM2-7。我们的结果为脊椎动物模型系统中粘附素重新募集到染色体上定义了一条新的依赖于前RC的途径。
Cohesin is a multi-subunit, ring-shaped protein complex that holds sister chromatids together from the time of their synthesis in S phase until they are segregated in anaphase(1-7). In yeast, the loading of cohesin onto chromosomes requires the Scc2 protein(8-10). In vertebrates, cohesins first bind to chromosomes as cells exit mitosis, but the mechanism is unknown(3,11,12). Concurrent with cohesin binding, pre-replication complexes (pre-RCs) are assembled at origins of DNA replication through the sequential loading of the initiation factors ORC, Cdc6, Cdt1 and MCM2-7 (the 'licensing' reaction)(13). In S phase, the protein kinase Cdk2 activates pre-RCs, causing origin unwinding and DNA replication. Here, we use Xenopus egg extracts to show that the recruitment of cohesins to chromosomes requires fully licensed chromatin and is dependent on ORC, Cdc6, Cdt1 and MCM2-7, but is independent of Cdk2. We further show that Xenopus Scc2 is required for cohesin loading and that binding of XScc2 to chromatin is MCM2-7 dependent. Our results define a novel pre-RC-dependent pathway for cohesin recruitment to chromosomes in a vertebrate model system.