Substrate specificity of the p53-associated 3′-5′ exonuclease
Substrate specificity of the p53-associated 3′-5′ exonuclease
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DOI：
10.1038/sj.onc.1203649
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发表时间：
2000-07-06
期刊：
影响因子：
8
通讯作者：
Brown, KR
中科院分区：
文献类型：
--
作者：
Skalski, V;Lin, ZY;Brown, KR
p53表现出3 ′-5 ′核酸外切酶活性，这种生物化学功能的重要性目前还没有确定。为了获得有关这种外切核酸酶活性的潜在作用的信息，检查了重组和野生型人p53从定义的合成DNA底物中切除核苷酸的情况。p53从单链DNA中去除核苷酸的速度比从DNA双链体中快三倍，对含有单个核苷酸错配的DNA的3 '末端表现出1.5倍的偏好与正确配对的DNA相比，它可以有效地从平端和粘性DNA的3 '-末端切除核苷酸。（交错）DNA双链断裂，p53核酸外切酶主要在17个核苷酸长的DIVA上是非进行性的核苷酸切除的持续性在50 mM磷酸钾存在下降低，并且当全长p53被核心结构域取代时消除，所述核心结构域由氨基酸82-292组成，光亲和标记表明：（1）p53单体而不是二聚体与这些寡聚体的单链形式结合;（2）p53与30-mer之间的复合物比与17-mer形成的复合物更稳定。这些复合物的稳定性决定了核苷酸去除期间的持续合成能力，并调节p53的3 '-5'外切核酸酶活性。底物特异性的p53核酸外切酶DNA修复的相关性进行了讨论。
p53 exhibits 3'-5' exonuclease activity and the significance of this biochemical function is currently not defined. In order to gain information about the potential role(s) of this exonuclease activity, recombinant and wild-type human p53 was examined for excision of nucleotides from defined synthetic DNA substrates. p53 removes nucleotides threefold faster from single-strand DNA than from DNA duplexes, exhibits a 1.5-fold preference for 3'-terminals of DNA that contain a single nucleotide mispair (mismatch) as compared to correctly paired DNA and efficiently excises nucleotides from 3'-ends of blunt and cohesive (staggered) DNA double-strand breaks, The p53 exonuclease is predominantly non-processive on DIVA which is 17 nucleotides long (or shorter) and processive on the longer 30-mers, The processivity of nucleotide excision is decreased in the presence of 50 mM potassium phosphate and eliminated when full-length p53 is replaced with the core domain, comprised of amino acids 82-292, Photoaffinity labeling indicates that (1) p53 monomers, rather than dimers, bind to single-strand forms of these oligomers; (2) complexes between p53 and 30-mers are more stable than those formed with 17-mers, The stability of these complexes determines processivity during nucleotide removal and modulates the 3'-5' exonuclease activity of p53. The relevance of substrate specificity of the p53 exonuclease to DNA repair is discussed.