Bridging of DNA breaks activates PARP2-HPF1 to modify chromatin.
Bridging of DNA breaks activates PARP2-HPF1 to modify chromatin.
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DOI：
10.1038/s41586-020-2725-7
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发表时间：
2020-09
期刊：
影响因子：
64.8
通讯作者：
Halic M
中科院分区：
文献类型：
--
作者：
Bilokapic S;Suskiewicz MJ;Ahel I;Halic M
DNA链断裂募集PARP 1及其parasitic PARP 2，以修饰组蛋白和许多其他底物与单和聚（ADP-核糖）（PAR）。在DNA损伤反应中，PAR翻译后修饰主要发生在丝氨酸氨基酸上，这需要HPF 1，其是将PARP 1/2的氨基酸特异性从天冬氨酸/谷氨酸转换为丝氨酸残基的辅助因子。聚（ADP）核糖基化（PAR化）对于随后的染色质解压缩是重要的，并且充当锚以将多种下游信号传导和修复因子募集到DNA断裂位点。为了了解DNA断裂识别的分子机制，PARP酶的背景下，染色质，我们确定了冷冻电镜结构的PARP 2/HPF 1结合到核小体。结构显示PARP 2/HPF 1桥接两个核小体，断裂的DNA在可连接的位置对齐，揭示了双链DNA断裂修复的初始步骤。桥接诱导PARP 2的结构变化，其信号DNA断裂识别到催化结构域，其许可HPF 1结合和PARP 2活化。我们的数据表明，活性PARP 2通过不同的构象状态循环以交换NAD+和底物，这可能使PARP酶在与染色质结合时具有进行性。我们描述的PARP激活和催化循环的机制可以解释PARP抑制剂的耐药机制，并将有助于开发更好的癌症治疗抑制剂。
DNA strand breaks recruit PARP1 and its paralogue PARP2 to modify histones and many other substrates with mono- and poly(ADP-ribose) (PAR). In DNA damage response, the PAR post-translational modification occurs predominantly on serine amino acids, which requires HPF1, an accessory factor that switches the amino-acid specificity of PARP1/2 from aspartate/glutamate to serine residues. Poly(ADP) ribosylation (PARylation) is important for subsequent chromatin decompaction and serves as an anchor to recruit a variety of downstream signaling and repair factors to the sites of DNA breaks. To understand the molecular mechanism of DNA break recognition by PARP enzymes in the context of chromatin, we determined cryo-EM structure of PARP2/HPF1 bound to a nucleosome. The structure shows that PARP2/HPF1 bridges two nucleosomes, with the broken DNA aligned in a ligation-competent position, revealing the initial step in double-strand DNA break repair. The bridging induces structural changes in PARP2 that signal DNA break recognition to the catalytic domain, which licenses HPF1 binding and PARP2 activation. Our data suggest that active PARP2 cycles through different conformational states to exchange NAD+ and substrate, which may enable PARP enzymes to be processive while bound to chromatin. The mechanisms of PARP activation and catalytic cycle we describe can explain resistance mechanisms to PARP inhibitors, and will aid development of better inhibitors for cancer treatments.
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影响因子：
14.8
作者：
Leidecker O;Bonfiglio JJ;Colby T;Zhang Q;Atanassov I;Zaja R;Palazzo L;Stockum A;Ahel I;Matic I
通讯作者：
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Halic M
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作者：
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通讯作者：
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