DNA对聚（ADP - 核糖）糖水解酶的影响以及来自HeLa细胞核的组蛋白H1 - 聚（ADP - 核糖）复合物的降解
Effect of DNA on poly (ADP-ribose) glycohydrolase and the degradation of histone H1-poly (ADP-ribose) complex from HeLa cell nuclei.
作者信息
Stone P R, Lorimer W S, Ranchalis J, Danley M, Kidwell W R
出版信息
Nucleic Acids Res. 1978 Jan;5(1):173-84. doi: 10.1093/nar/5.1.173.
A poly(ADP-ribose)-H1 histone complex has been isolated from HeLa cell nuclei incubated with NAD. The rate of poly(ADP-ribose) glycohydrolase catalyzed hydrolysis of the polymer in the complex is only 1/9 that of free poly(ADP-ribose), indicating that the polymer is in a protected environment within the complex. Comparison of the rate of hydrolysis of free poly(ADP-ribose) in the presence or absence of H1 to that in the complex synthesized de novo indicates a specific mode of packaging of the complex. This is further indicated by the fact that alkaline dissociation of the complex followed by neutralization markedly exposes the associated poly(ADP-ribose) to the glycohydrolase. The complex also partially unfolds when it binds to DNA as evidenced by a 2-fold increase in the rate of glycolytic cleavage of poly(ADP-ribose). This effect of DNA is not due to a stimulation of the glycohydrolase per se since hydrolysis of free polymer by the enzyme is strongly inhibited by DNA, especially single-stranded DNA. Inhibition of glycohydrolase by DNA results from the binding of the enzyme to DNA and conditions which decrease this binding (increased ionic strength or addition of histone H1 which competes for DNA binding) relieve the DNA inhibition.
已从用烟酰胺腺嘌呤二核苷酸（NAD）孵育的HeLa细胞核中分离出一种聚（ADP - 核糖）-H1组蛋白复合物。复合物中聚（ADP - 核糖）糖苷水解酶催化聚合物水解的速率仅为游离聚（ADP - 核糖）的1/9，这表明聚合物在复合物中处于受保护的环境。比较在有或没有H1存在下游离聚（ADP - 核糖）的水解速率与从头合成的复合物中的水解速率，表明复合物存在特定的包装模式。复合物经碱解离后再中和会使相关的聚（ADP - 核糖）显著暴露于糖苷水解酶，这一事实进一步证明了这一点。当复合物与DNA结合时也会部分展开，这可通过聚（ADP - 核糖）糖酵解切割速率增加2倍得到证明。DNA的这种作用并非由于其对糖苷水解酶本身的刺激，因为该酶对游离聚合物的水解受到DNA的强烈抑制，尤其是单链DNA。DNA对糖苷水解酶的抑制是由于酶与DNA的结合，而降低这种结合的条件（增加离子强度或添加竞争DNA结合的组蛋白H1）可解除DNA的抑制作用。
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