The impact of heterochromatin on DSB repair
The impact of heterochromatin on DSB repair
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DOI：
10.1042/bst0370569
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发表时间：
2009-06-01
影响因子：
3.9
通讯作者：
Jeggo, Penny A.
中科院分区：
文献类型：
--
作者：
Goodarzi, Aaron A.;Noon, Angela T.;Jeggo, Penny A.
DNA NHEJ（非同源末端连接）是哺乳动物细胞中主要的 DNA DSB（双链断裂）修复途径。尽管 NHEJ 缺陷细胞系表现出明显的 DSB 修复缺陷，但 ATM（共济失调毛细血管扩张突变）缺陷细胞可以正常修复大多数 DSB。因此 NHEJ 的功能独立于 ATM 信号。然而，类似 15% 的辐射诱导 DSB 是通过缓慢的动力学进行修复的，并且需要 ATM 和核酸酶 Artemis。在 ATM 抑制剂 ATMi 存在下持续存在的 DSB 定位于异染色质，这表明 ATM 是修复异染色质内或附近产生的 DSB 所必需的。与此一致的是，我们发现关键异染色质蛋白的 siRNA（小干扰 RNA），包括 KAP-1 [KRAB（Kruppel 相关盒）结构域相关蛋白 1]、HP1（异染色质蛋白 1）和 HDAC（组蛋白脱乙酰酶）1/2，减轻了 DSB 修复对 ATM 的需求。此外，ATMi 除了具有对异染色质有影响的遗传改变的细胞系外，包括 Suv39H1/2（杂色 3-9 同源物 1/2 抑制因子）敲除、ICFa（免疫缺陷、着丝粒区域不稳定、a 型面部异常综合征）和 Hutchinson-Guilford 早衰细胞系，未能对 DSB 修复产生影响。 KAP-1 是一种高度剂量依赖性、瞬时性和 ATM 特异性底物，KAP-1 上 ATM 磷酸化位点的突变会影响 DSB 修复。总的来说，研究结果表明 ATM 可以克服异染色质造成的 DSB 修复障碍。然而，即使存在 ATM，γ-H2AX（磷酸化组蛋白 H2AX）焦点也会形成在外周而不是异染色质中心内。最后，我们发现，随着细胞进行有丝分裂，KAP-1 与异染色质的关联会减弱。我们认为KAP-1是一个关键的异染色质因子，它经过特定的修饰以促进DSB修复和有丝分裂进展，其方式允许局部和短暂的染色质松弛，但排除异染色质上层结构的显着拆除。
DNA NHEJ (non-homologous end-joining) is the major DNA DSB (double-strand break) repair pathway in mammalian cells. Although NHEJ-defective cell lines show marked DSB-repair defects, cells defective in ATM (ataxia telangiectasia mutated) repair most DSBs normally. Thus NHEJ functions independently of ATM signalling. However, similar to 15% of radiation-induced DSBs are repaired with slow kinetics and require ATM and the nuclease Artemis. DSBs persisting in the presence of an ATM inhibitor, ATMi, localize to heterochromatin, suggesting that ATM is required for repairing DSBs arising within or close to heterochromatin. Consistent with this, we show that siRNA (small interfering RNA) of key heterochromatic proteins, including KAP-1 [KRAB (Kruppel-associated box) domain-associated protein 1], HP1 (heterochromatin protein 1) and HDAC (histone deacetylase) 1/2, relieves the requirement for ATM for DSB repair. Furthermore, ATMi addition to cell lines with genetic alterations that have an impact on heterochromatin, including Suv39H1/2 (suppressor of variegation 3-9 homologue 1/2)-knockout, ICFa (immunodeficiency, centromeric region instability, facial anomalies syndrome type a) and Hutchinson-Guilford progeria cell lines, fails to have an impact on DSB repair. KAP-1 is a highly dose-dependent, transient and ATM-specific substrate, and mutation of the ATM phosphorylation site on KAP-1 influences DSB repair. Collectively, the findings show that ATM functions to overcome the barrier to DSB repair posed by heterochromatin. However, even in the presence of ATM, gamma-H2AX (phosphorylated histone H2AX) foci form on the periphery rather than within heterochromatic centres. Finally, we show that KAP-1's association with heterochromatin is diminished as cells progress through mitosis. We propose that KAP-1 is a critical heterochromatic factor that undergoes specific modifications to promote DSB repair and mitotic progression in a manner that allows localized and transient chromatin relaxation, but precludes significant dismantling of the heterochromatic superstructure.