PDF(Pubmed)
Abstract：
The chromatin remodeler ALC1 is activated by DNA damage-induced poly(ADP-ribose) deposited by PARP1/PARP2 and their co-factor HPF1. ALC1 has emerged as a cancer drug target, but how it is recruited to ADP-ribosylated nucleosomes to affect their positioning near DNA breaks is unknown. Here we find that PARP1/HPF1 preferentially initiates ADP-ribosylation on the histone H2B tail closest to the DNA break. To dissect the consequences of such asymmetry, we generate nucleosomes with a defined ADP-ribosylated H2B tail on one side only. The cryo-electron microscopy structure of ALC1 bound to such an asymmetric nucleosome indicates preferential engagement on one side. Using single-molecule FRET, we demonstrate that this asymmetric recruitment gives rise to directed sliding away from the DNA linker closest to the ADP-ribosylation site. Our data suggest a mechanism by which ALC1 slides nucleosomes away from a DNA break to render it more accessible to repair factors.
摘要：
染色质重塑剂ALC1被PARP1/PARP2及其辅因子HPFl沉积的DNA损伤诱导的聚(ADP-核糖)激活。ALC1已经成为癌症药物的靶点，但它是如何被招募到ADP-核糖基化核小体来影响它们在DNA断裂附近的定位的，目前尚不清楚。在这里，我们发现PARP1/HPF1优先在最接近DNA断裂的组蛋白H2B尾巴上启动ADP-核糖基化。为了剖析这种不对称的后果，我们仅在一侧产生具有确定的ADP-核糖基化H2B尾的核小体。与这种不对称核小体结合的ALC1的低温电子显微镜结构表明在一侧优先接合。使用单分子FRET，我们证明了这种不对称募集导致从最接近ADP-核糖基化位点的DNA接头的定向滑动。我们的数据表明，ALC1将核小体从DNA断裂中滑出，使其更易于修复因子的机制。
