Ohashi Y, Ueda K, Kawaichi M, Hayaishi O
Proc Natl Acad Sci U S A. 1983 Jun;80(12):3604-7. doi: 10.1073/pnas.80.12.3604.
To elucidate the molecular mechanism by which poly(ADP-ribose) participates in DNA excision repair, we examined the effect of poly(ADP-ribose) on DNA ligase activity in DNA/histone and reconstituted chromatin systems. The ligase activity was markedly inhibited by histones; the inhibition varied depending on histone subfraction and DNA/histone ratio. Poly(ADP-ribose), either exogenous or synthesized in situ by poly(ADP-ribose) synthetase, reversed this inhibition by histone almost completely. This effect was specific for poly(ADP-ribose); polyanions such as mRNA, rRNAs, tRNA, and synthetic poly(A) were less effective or ineffective. The ligase activity with reconstituted chromatin as the substrate was about half of that with free DNA whereas the activities with these two substrates were almost the same in the presence of poly(ADP-ribose) synthesized in situ. The polymers synthesized under these conditions were exclusively bound to the synthetase. Together with our previous finding that the enzyme is the main acceptor of the polymer in DNA-damaged cells, these results suggest that poly(ADP-ribose) in the synthetase-bound form counteracts inhibition by histones and activates DNA ligase to rejoin DNA strands in polynucleosomal structures.
为阐明聚（ADP - 核糖）参与DNA切除修复的分子机制，我们研究了聚（ADP - 核糖）对DNA/组蛋白及重组染色质体系中DNA连接酶活性的影响。组蛋白可显著抑制连接酶活性；抑制程度因组蛋白亚组分及DNA/组蛋白比例而异。外源性聚（ADP - 核糖）或由聚（ADP - 核糖）合成酶原位合成的聚（ADP - 核糖）几乎可完全逆转组蛋白的这种抑制作用。这种作用对聚（ADP - 核糖）具有特异性；诸如mRNA、rRNA、tRNA及合成的聚（A）等多阴离子的效果较差或无效果。以重组染色质为底物时的连接酶活性约为以游离DNA为底物时的一半，而在原位合成聚（ADP - 核糖）存在的情况下，这两种底物的连接酶活性几乎相同。在这些条件下合成的聚合物仅与合成酶结合。结合我们之前的发现，即该酶是DNA损伤细胞中聚合物的主要受体，这些结果表明，以与合成酶结合形式存在的聚（ADP - 核糖）可抵消组蛋白的抑制作用，并激活DNA连接酶以重新连接多核小体结构中的DNA链。
