A DNA-Damage Selective Role for BRCA1 E3 Ligase in Claspin Ubiquitylation, CHK1 Activation, and DNA Repair
A DNA-Damage Selective Role for BRCA1 E3 Ligase in Claspin Ubiquitylation, CHK1 Activation, and DNA Repair
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DOI：
10.1016/j.cub.2012.07.034
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发表时间：
2012-09-25
期刊：
影响因子：
9.2
通讯作者：
Venkitaraman, Ashok R.
中科院分区：
文献类型：
--
作者：
Sato, Ko;Sundaramoorthy, Elayanambi;Venkitaraman, Ashok R.
背景：乳腺癌和卵巢癌抑制因子BRCA1对于细胞对DNA损伤的反应至关重要[1]。它与BARD 1异源二聚化以获得E3泛素（Ub）连接酶活性，该活性通常受到癌症相关突变的影响[2]。无论是这种活动的损伤反应的意义，也没有相关的体内substrate，是clear.Results：我们已经分离的DNA损伤反应需要BRCA1 E3连接酶从那些独立的，使用基因靶向的点突变在脊椎动物DT40细胞，废除BRCA1的催化活性，而不干扰BARD 1结合。我们发现，BRCA1泛素化claspin，一个重要的辅激活CHK1检查点激酶，拓扑异构酶抑制后，但不是DNA交联丝裂霉素C。BRCA 1 E3失活降低了染色质结合的claspin水平，并通过中断从损伤激活的ATR激酶到其效应物CHK 1的信号转导来损害同源定向的DNA修复。结论：我们的研究结果确定claspin是BRCA 1 E3连接酶的体内底物，并表明其修饰选择性地触发CHK 1激活，用于同源定向修复一部分遗传毒性损伤。这种机制出乎意料地定义了BRCA1 E3连接酶活性在细胞对DNA损伤的反应中的基本但选择性的功能。
Background: The breast and ovarian cancer suppressor BRCA1 is essential for cellular responses to DNA damage [1]. It heterodimerizes with BARD1 to acquire an E3 ubiquitin (Ub) ligase activity that is often compromised by cancer-associated mutations [2]. Neither the significance of this activity to damage responses, nor a relevant in vivo substrate, is clear.Results: We have separated DNA-damage responses requiring the BRCA1 E3 ligase from those independent of it, using a gene-targeted point mutation in vertebrate DT40 cells that abrogates BRCA1's catalytic activity without perturbing BARD1 binding. We show that BRCA1 ubiquitylates claspin, an essential coactivator of the CHK1 checkpoint kinase, after topoisomerase inhibition, but not DNA crosslinking by mitomycin C. BRCA1 E3 inactivation decreases chromatin-bound claspin levels and impairs homology-directed DNA repair by interrupting signal transduction from the damage-activated ATR kinase to its effector, CHK1.Conclusions: Our findings identify claspin as an in vivo substrate for the BRCA1 E3 ligase and suggest that its modification selectively triggers CHK1 activation for the homologydirected repair of a subset of genotoxic lesions. This mechanism unexpectedly defines an essential but selective function for BRCA1 E3 ligase activity in cellular responses to DNA damage.