PDF(Pubmed)
Abstract：
Poly(ADP-ribosyl)ation (PARylation), catalyzed mainly by poly(ADP-ribose) polymerase (PARP)1, is a key posttranslational modification involved in DNA replication and repair. Here, we report that TIMELESS (TIM), an essential scaffold of the replisome, is PARylated, which is linked to its proteolysis. TIM PARylation requires recognition of auto-modified PARP1 via two poly(ADP-ribose)-binding motifs, which primes TIM for proteasome-dependent degradation. Cells expressing the PARylation-refractory TIM mutant or under PARP inhibition accumulate TIM at DNA replication forks, causing replication stress and hyper-resection of stalled forks. Mechanistically, aberrant engagement of TIM with the replicative helicase impedes RAD51 loading and protection of reversed forks. Accordingly, defective TIM degradation hypersensitizes BRCA2-deficient cells to replication damage. Our study defines TIM as a substrate of PARP1 and elucidates how the control of replisome remodeling by PARylation is linked to stalled fork protection. Therefore, we propose a mechanism of PARP inhibition that impinges on the DNA replication fork instability caused by defective TIM turnover.
摘要：
聚(ADP-核糖基)化(PARylation),主要由聚（ADP-核糖）聚合酶（PARP）1催化，是参与DNA复制和修复的关键翻译后修饰。这里,我们报告说，没有时间(TIM)，复制体的基本支架，是PARylated的，这与它的蛋白水解有关。TIMPARylation需要通过两个聚（ADP-核糖）结合基序识别自修饰的PARP1，启动TIM的蛋白酶体依赖性降解。表达PARylation难治性TIM突变体或受到PARP抑制的细胞在DNA复制叉上积累TIM，导致复制压力和停滞叉的过度切除。机械上,TIM与复制性解旋酶的异常接合阻碍了RAD51的加载和反向叉的保护。因此，缺陷性TIM降解使BRCA2缺陷细胞对复制损伤过敏。我们的研究将TIM定义为PARP1的底物，并阐明了如何通过PARylation控制复制体重塑与停滞的叉保护相关联。因此,我们提出了一种PARP抑制机制，该机制会影响由TIM转换缺陷引起的DNA复制叉不稳定性。
