Abstract：
Nucleosomes, the basic structural units of chromatin, hinder recruitment and activity of various DNA repair proteins, necessitating modifications that enhance DNA accessibility. Poly(ADP-ribosyl)ation (PARylation) of proteins near damage sites is an essential initiation step in several DNA-repair pathways; however, its effects on nucleosome structural dynamics and organization are unclear. Using NMR, cryoelectron microscopy (cryo-EM), and biochemical assays, we show that PARylation enhances motions of the histone H3 tail and DNA, leaving the configuration of the core intact while also stimulating nuclease digestion and ligation of nicked nucleosomal DNA by LIG3. PARylation disrupted interactions between nucleosomes, preventing self-association. Addition of LIG3 and XRCC1 to PARylated nucleosomes generated condensates that selectively partition DNA repair-associated proteins in a PAR- and phosphorylation-dependent manner in vitro. Our results establish that PARylation influences nucleosomes across different length scales, extending from the atom-level motions of histone tails to the mesoscale formation of condensates with selective compositions.
摘要：
核小体,染色质的基本结构单元，阻碍各种DNA修复蛋白的募集和活性，需要进行修饰以增强DNA的可及性。损伤位点附近蛋白质的聚（ADP-核糖）化（PARylation）是几种DNA修复途径中必不可少的起始步骤；然而，其对核小体结构动力学和组织的影响尚不清楚。使用NMR，低温电子显微镜（cryo-EM），和生化化验，我们显示PARylation增强了组蛋白H3尾和DNA的运动，保留完整的核心构型，同时还刺激核酸酶消化和LIG3连接有缺口的核小体DNA。PARylation破坏了核小体之间的相互作用，防止自我联想。将LIG3和XRCC1添加到PAR化的核小体中产生缩合物，该缩合物在体外以PAR和磷酸化依赖性方式选择性地分配DNA修复相关蛋白。我们的结果确定PARylation在不同长度尺度上影响核小体，从组蛋白尾巴的原子级运动延伸到具有选择性组成的冷凝物的中尺度形成。
