Dynamics of Rad9 Chromatin Binding and Checkpoint Function Are Mediated by Its Dimerization and Are Cell Cycle-Regulated by CDK1 Activity
Dynamics of Rad9 Chromatin Binding and Checkpoint Function Are Mediated by Its Dimerization and Are Cell Cycle-Regulated by CDK1 Activity
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DOI：
10.1371/journal.pgen.1001047
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发表时间：
2010-08-01
期刊：
影响因子：
4.5
通讯作者：
Muzi-Falconi, Marco
中科院分区：
文献类型：
--
作者：
Granata, Magda;Lazzaro, Federico;Muzi-Falconi, Marco
酿酒酵母Rad 9是整个细胞周期中有效的DNA损伤反应所必需的。DNA损伤后，组蛋白修饰促进了Rad 9在染色质上的组装，组蛋白修饰为Rad 9的募集创建了对接位点，从而允许检查点激活。Rad 53磷酸化也依赖于BRCT指导的Rad 9寡聚化;然而，这些分子决定簇之间的串扰及其功能意义知之甚少。在这里，我们报告说，在G1和M期的细胞周期，组成和DNA损伤依赖的Rad 9染色质协会需要其BRCT域。在G1细胞中，GST或FKBP二聚化基序可以取代BRCT结构域用于Rad 9染色质结合和检查点功能。相反，在M期强迫Rad 9二聚化不能促进其募集到DNA上，尽管它支持Rad 9检查点功能。事实上，独立于组蛋白修饰并受CDK 1活性支配的平行途径允许在不存在Rad 9染色质结合的情况下激活检查点。丝氨酸11上的Rad 9的CDK 1依赖性磷酸化导致与Dpb 11的特异性相互作用，允许Rad 53活化并绕过对组蛋白分支的需要。
Saccharomyces cerevisiae Rad9 is required for an effective DNA damage response throughout the cell cycle. Assembly of Rad9 on chromatin after DNA damage is promoted by histone modifications that create docking sites for Rad9 recruitment, allowing checkpoint activation. Rad53 phosphorylation is also dependent upon BRCT-directed Rad9 oligomerization; however, the crosstalk between these molecular determinants and their functional significance are poorly understood. Here we report that, in the G1 and M phases of the cell cycle, both constitutive and DNA damage-dependent Rad9 chromatin association require its BRCT domains. In G1 cells, GST or FKBP dimerization motifs can substitute to the BRCT domains for Rad9 chromatin binding and checkpoint function. Conversely, forced Rad9 dimerization in M phase fails to promote its recruitment onto DNA, although it supports Rad9 checkpoint function. In fact, a parallel pathway, independent on histone modifications and governed by CDK1 activity, allows checkpoint activation in the absence of Rad9 chromatin binding. CDK1-dependent phosphorylation of Rad9 on Ser11 leads to specific interaction with Dpb11, allowing Rad53 activation and bypassing the requirement for the histone branch.