Dissociation of cohesin from chromosome arms and loss of arm cohesion during early mitosis depends on phosphorylation of SA2.
Dissociation of cohesin from chromosome arms and loss of arm cohesion during early mitosis depends on phosphorylation of SA2.
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DOI：
10.1371/journal.pbio.0030069
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发表时间：
2005-03
期刊：
影响因子：
9.8
通讯作者：
Peters JM
中科院分区：
文献类型：
--
作者：
Hauf S;Roitinger E;Koch B;Dittrich CM;Mechtler K;Peters JM
凝聚素是一种蛋白质复合物，需要将姐妹染色单体保持在一起。蛋白酶分离酶切割粘着蛋白的Scc 1亚基，从染色体上释放复合物，从而使分裂后期的姐妹染色单体分离成为可能。在脊椎动物细胞中，大量的粘着蛋白已经在前期和前中期从染色体臂上解离，而没有Scc 1的裂解。Polo样激酶1（Plk 1）和Aurora-B是这个解离过程所必需的，Plk 1可以在体外磷酸化粘着蛋白亚基Scc 1和SA 2，这与Plk 1引起的粘着蛋白磷酸化触发粘着蛋白从染色体臂解离的可能性一致。然而，这一假设尚未得到验证，在芽殖酵母中，已经发现Polo样激酶Cdc 5对Scc 1的磷酸化增强了粘着蛋白的可切割性，但不会导致粘着蛋白与染色体的分离酶无关的解离。为了解决在人类细胞中的粘附蛋白磷酸化的功能意义，我们已经搜索了所有四个亚基的粘附蛋白的质谱磷酸化位点。我们已经确定了许多有丝分裂特异性位点Scc 1和SA 2，突变它们，并在人体细胞中稳定地表达两种蛋白质的非磷酸化形式。这些细胞系的分析，结合体外生化实验，表明Scc 1磷酸化是cohesin解离从染色体在早期有丝分裂，但增强Scc 1的裂解分离酶。与此相反，我们的数据显示，磷酸化的SA 2是必不可少的粘附蛋白解离在前期和前中期，但不需要粘附蛋白裂解分离酶。在人细胞中表达不可磷酸化的SA 2后获得的表型与Plk 1耗竭后所见的表型的相似性表明，SA 2是Plk 1在粘附素解离途径中的关键靶点。黏连蛋白将新复制的染色体固定在一起，直到细胞准备好分裂。这些作者展示了磷酸化是如何调节粘附素功能的
Cohesin is a protein complex that is required to hold sister chromatids together. Cleavage of the Scc1 subunit of cohesin by the protease separase releases the complex from chromosomes and thereby enables the separation of sister chromatids in anaphase. In vertebrate cells, the bulk of cohesin dissociates from chromosome arms already during prophase and prometaphase without cleavage of Scc1. Polo-like kinase 1 (Plk1) and Aurora-B are required for this dissociation process, and Plk1 can phosphorylate the cohesin subunits Scc1 and SA2 in vitro, consistent with the possibility that cohesin phosphorylation by Plk1 triggers the dissociation of cohesin from chromosome arms. However, this hypothesis has not been tested yet, and in budding yeast it has been found that phosphorylation of Scc1 by the Polo-like kinase Cdc5 enhances the cleavability of cohesin, but does not lead to separase-independent dissociation of cohesin from chromosomes. To address the functional significance of cohesin phosphorylation in human cells, we have searched for phosphorylation sites on all four subunits of cohesin by mass spectrometry. We have identified numerous mitosis-specific sites on Scc1 and SA2, mutated them, and expressed nonphosphorylatable forms of both proteins stably at physiological levels in human cells. The analysis of these cells lines, in conjunction with biochemical experiments in vitro, indicate that Scc1 phosphorylation is dispensable for cohesin dissociation from chromosomes in early mitosis but enhances the cleavability of Scc1 by separase. In contrast, our data reveal that phosphorylation of SA2 is essential for cohesin dissociation during prophase and prometaphase, but is not required for cohesin cleavage by separase. The similarity of the phenotype obtained after expression of nonphosphorylatable SA2 in human cells to that seen after the depletion of Plk1 suggests that SA2 is the critical target of Plk1 in the cohesin dissociation pathway. Cohesin holds newly replicated chromosomes together until a cell is ready to divide. These authors show how phosphorylation regulates cohesin function
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影响因子：
9.8
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McGuinness BE;Hirota T;Kudo NR;Peters JM;Nasmyth K
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