Tsabar Michael, Waterman David P, Aguilar Fiona, Katsnelson Lizabeth, Eapen Vinay V, Memisoglu Gonen, Haber James E
Department of Biology, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02454, USA.
Genes Dev. 2016 May 15;30(10):1211-24. doi: 10.1101/gad.280685.116.
To allow for sufficient time to repair DNA double-stranded breaks (DSBs), eukaryotic cells activate the DNA damage checkpoint. In budding yeast, Rad53 (mammalian Chk2) phosphorylation parallels the persistence of the unrepaired DSB and is extinguished when repair is complete in a process termed recovery or when the cells adapt to the DNA damage checkpoint. A strain containing a slowly repaired DSB does not require the histone chaperone Asf1 to resume cell cycle progression after DSB repair. When a second, rapidly repairable DSB is added to this strain, Asf1 becomes required for recovery. Recovery from two repairable DSBs also depends on the histone acetyltransferase Rtt109 and the cullin subunit Rtt101, both of which modify histone H3 that is associated with Asf1. We show that dissociation of histone H3 from Asf1 is required for efficient recovery and that Asf1 is required for complete dephosphorylation of Rad53 when the upstream DNA damage checkpoint signaling is turned off. Our data suggest that the requirements for recovery from the DNA damage checkpoint become more stringent with increased levels of damage and that Asf1 plays a histone chaperone-independent role in facilitating complete Rad53 dephosphorylation following repair.
为了留出足够的时间来修复DNA双链断裂(DSB),真核细胞会激活DNA损伤检查点。在芽殖酵母中,Rad53(哺乳动物的Chk2)的磷酸化与未修复的DSB的持续存在平行,并且在修复完成时(在一个称为恢复的过程中)或当细胞适应DNA损伤检查点时会消失。含有缓慢修复的DSB的菌株在DSB修复后恢复细胞周期进程不需要组蛋白伴侣Asf1。当向该菌株中添加第二个可快速修复的DSB时,恢复就需要Asf1。从两个可修复的DSB中恢复也取决于组蛋白乙酰转移酶Rtt109和cullin亚基Rtt101,这两者都会修饰与Asf1相关的组蛋白H3。我们表明,组蛋白H3与Asf1解离是有效恢复所必需的,并且当上游DNA损伤检查点信号关闭时,Asf1是Rad53完全去磷酸化所必需的。我们的数据表明,随着损伤水平的增加,从DNA损伤检查点恢复的要求变得更加严格,并且Asf1在促进修复后Rad53的完全去磷酸化中发挥着不依赖于组蛋白伴侣的作用。