Poly(ADP-ribose)-binding promotes Exo1 damage recruitment and suppresses its nuclease activities.
Poly(ADP-ribose)-binding promotes Exo1 damage recruitment and suppresses its nuclease activities.
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DOI：
10.1016/j.dnarep.2015.09.021
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发表时间：
2015-11
期刊：
影响因子：
3.8
通讯作者：
You Z
中科院分区：
文献类型：
--
作者：
Cheruiyot A;Paudyal SC;Kim IK;Sparks M;Ellenberger T;Piwnica-Worms H;You Z
外切酶1 （Exo1）在DNA代谢交易中发挥重要作用，对基因组维持、端粒调控和癌症抑制至关重要。然而，在这些过程中调节Exo1活性的机制仍然不完全清楚。在这里，我们报道了Exo1的活性是通过与poly(ADP-ribose) （PAR）的直接相互作用来调节的，PAR是DNA损伤部位的一种突出的翻译后修饰。这种par结合活性促进了Exo1的早期募集到DNA损伤位点，在那里它通过与PCNA的相互作用被保留，PCNA与Exo1的c端相互作用。PAR和PCNA对Exo1损伤关联的影响均被14-3-3接头蛋白拮抗，该接头蛋白与Exo1的中心结构域相互作用。尽管PAR结合抑制了纯化的Exo1的外切酶活性和5 '瓣内切酶活性，但在无细胞的爪蟾卵提取物中，药理阻断PAR合成并不明显影响DNA双链断裂端切除。因此，PAR对Exo1招募和酶活性的抵消作用可能使DNA末端的适当切除成为可能，同时防止细胞中DNA断裂的计划外或不当处理。
Exonuclease 1 (Exo1) has important roles in DNA metabolic transactions that are essential for genome maintenance, telomere regulation and cancer suppression. However, the mechanisms for regulating Exo1 activity in these processes remain incompletely understood. Here we report that Exo1 activity is regulated by a direct interaction with poly(ADP-ribose) (PAR), a prominent posttranslational modification at the sites of DNA damage. This PAR-binding activity promotes the early recruitment of Exo1 to sites of DNA damage, where it is retained through an interaction with PCNA, which interacts with the C-terminus of Exo1. The effects of both PAR and PCNA on Exo1 damage association are antagonized by the 14-3-3 adaptor proteins, which interact with the central domain of Exo1. Although PAR binding inhibits both the exonuclease activity and the 5’ flap endonuclease activity of purified Exo1, the pharmacological blockade of PAR synthesis does not overtly affect DNA double-strand break end resection in a cell free Xenopus egg extract. Thus, the counteracting effects of PAR on Exo1 recruitment and enzymatic activity may enable appropriate resection of DNA ends while preventing unscheduled or improper processing of DNA breaks in cells.