ADP-ribosylation is a protein post-translational modification catalyzed by ADP-ribose transferases (ARTs). ART activity is critical in mediating many cellular processes, and is required for DNA damage repair. All five histone proteins are extensively ADP-ribosylated by ARTs upon induction of DNA damage. However, how these modifications aid in repair processes is largely unknown, primarily due to lack of knowledge about where they site-specifically occur on histones. Here, we conduct a comprehensive analysis of histone Asp/Glu ADP-ribosylation sites upon DNA damage induced by dimethyl sulfate (DMS). We also demonstrate that incubation of cell nuclei with NAD⁺, as has been done previously in the literature, leads to spurious ADP-ribosylation levels of histone proteins. Altogether, we were able to identify 30 modification sites, 20 of which are novel. We also quantify the abundance of these modification sites during the course of DNA damage insult to identify which sites are critical for mediating repair. We found that every quantifiable site increases in abundance over time and that each identified ADP-ribosylation site is located on the surface of the nucleosome. Together, the data suggest specific Asp/Glu residues are unlikely to be critical for DNA damage repair and rather that this process is likely dependent on ADP-ribosylation of the nucleosomal surface in general.

中文翻译：

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核小体表面是响应DNA损伤的组蛋白ADP-核糖基化的主要目标

ADP-核糖基化是由ADP-核糖转移酶（ARTs）催化的蛋白质翻译后修饰。ART活性在介导许多细胞过程中至关重要，是DNA损伤修复所必需的。在诱导DNA损伤后，所有5种组蛋白都被ARTs广泛地ADP-核糖基化。然而，这些修饰如何在修复过程中发挥帮助还很未知，这主要是由于缺乏关于它们在组蛋白上特定于何处​​发生的知识。在这里，我们对硫酸二甲酯（DMS）诱导的DNA损伤对组蛋白Asp / Glu ADP-核糖基化位点进行全面分析。我们还证明了细胞核与NAD ^+的孵育如先前在文献中所做的那样，导致组蛋白的伪造ADP-核糖基化水平。总共，我们能够鉴定出30个修饰位点，其中20个是新颖的。我们还对DNA损伤过程中这些修饰位点的数量进行了定量，以确定哪些位点对于介导修复至关重要。我们发现，每个可量化的位点都随着时间的流逝而增加，并且每个已识别的ADP-核糖基化位点都位于核小体的表面上。总之，数据表明特定的Asp / Glu残基不太可能对DNA损伤修复起关键作用，而该过程通常可能取决于核小体表面的ADP-核糖基化。