Poly-ADP-ribosylation (PARylation) is regarded as a protein-specific modification. However, some PARPs were recently shown to modify DNA termini in vitro. Here, we use ultrasensitive mass spectrometry (LC-MS/MS), anti-PAR antibodies, and anti-PAR reagents to show that mammalian DNA is physiologically PARylated and to different levels in primary tissues. Inhibition of PAR glycohydrolase (PARG) increases DNA PARylation, supporting that the modification is reversible. DNA PARylation requires PARP1 and in vitro PARP1 PARylates single-stranded DNA, while PARG reverts the modification. DNA PARylation occurs at the N1-position of adenosine residues to form N1-Poly(ADP-ribosyl)-deoxyadenosine. Through partial hydrolysis of mammalian gDNA we identify PAR-DNA via the diagnostic deamination product N1-ribosyl-deoxyinosine to occur in vivo. The discovery of N1-adenosine PARylation as a DNA modification establishes the conceptual and methodological framework to elucidate its biological relevance and extends the role of PARP enzymes.

聚-ADP-核糖基化（PARylation）被认为是一种蛋白质特异性修饰。然而，最近显示一些 PARP 可以在体外修饰 DNA 末端。在这里，我们使用超灵敏质谱法 (LC-MS/MS)、抗 PAR 抗体和抗 PAR 试剂来证明哺乳动物 DNA 是生理性 PAR 化的，并且在初级组织中达到不同水平。抑制 PAR 糖水解酶 (PARG) 会增加 DNA PARylation，支持修饰是可逆的。DNA PARylation 需要 PARP1 和体外 PARP1 PARylates 单链 DNA，而 PARG 恢复修饰。DNA PARylation 发生在腺苷残基的 N1 位，形成 N1-聚（ADP-核糖基）-脱氧腺苷。通过哺乳动物 gDNA 的部分水解，我们通过在体内发生的诊断性脱氨产物 N1-核糖基-脱氧肌苷鉴定 PAR-DNA。