The chromatin remodeler ALC1 is recruited to and activated by DNA damage-induced poly(ADP-ribose) (PAR) chains deposited by PARP1/PARP2/HPF1 upon detection of DNA lesions. ALC1 has emerged as a candidate drug target for cancer therapy as its loss confers synthetic lethality in homologous recombination-deficient cells. However, structure-based drug design and molecular analysis of ALC1 have been hindered by the requirement for PARylation and the highly heterogeneous nature of this post-translational modification. Here, we reconstituted an ALC1 and PARylated nucleosome complex modified in vitro using PARP2 and HPF1. This complex was amenable to cryo-EM structure determination without cross-linking, which enabled visualization of several intermediate states of ALC1 from the recognition of the PARylated nucleosome to the tight binding and activation of the remodeler. Functional biochemical assays with PARylated nucleosomes highlight the importance of nucleosomal epitopes for productive remodeling and reveal that ALC1 preferentially slides nucleosomes away from DNA breaks.

中文翻译：

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染色质重塑剂 ALC1 与 PARylated 核小体结合的结构和动力学

在检测到 DNA 损伤时，染色质重塑剂 ALC1 被 PARP1/PARP2/HPF1 沉积的 DNA 损伤诱导的聚（ADP-核糖）（PAR）链募集并激活。ALC1 已成为癌症治疗的候选药物靶点，因为它的缺失赋予同源重组缺陷细胞的合成致死性。然而，基于结构的 ALC1 药物设计和分子分析受到 PARylation 的要求和这种翻译后修饰的高度异质性的阻碍。在这里，我们使用 PARP2 和 HPF1 在体外重组了 ALC1 和 PARylated 核小体复合物。这种复合物可以在没有交联的情况下进行冷冻电镜结构测定，这使得 ALC1 的几种中间状态的可视化，从 PARylated 核小体的识别到重塑物的紧密结合和激活。使用 PARylated 核小体的功能性生化分析强调了核小体表位对生产性重塑的重要性，并揭示 ALC1 优先使核小体远离 DNA 断裂。