Characterization of the human and mouse WRN 3′→5′ exonuclease
Characterization of the human and mouse WRN 3′→5′ exonuclease
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DOI：
10.1093/nar/28.12.2396
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发表时间：
2000-06-15
影响因子：
14.9
通讯作者：
Campisi, J
中科院分区：
文献类型：
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作者：
Huang, SR;Beresten, S;Campisi, J
Werner综合征(WS)是一种常染色体隐性遗传性疾病，其特征是一系列与年龄相关的疾病的早期发展。WRN是WS中的缺陷基因，编码1432个氨基酸的蛋白质(HWRN)，具有内在的3‘-->；5’DNA解旋酶活性。我们最近发现hWRN也是一种3‘-->；5’外切酶。在这里，我们进一步鉴定了hWRN外切酶，hWRN有效地降解了双链DNA或DNA-RNA异源双链的3‘凹进链，对钝端DNA、带有3’突出链的DNA或单链DNA几乎没有活性。HWRN核酸外切酶有效地去除了3‘端不匹配的核苷酸，并能够从12个核苷酸的缺口或缺口中启动DNA降解。我们进一步证明，小鼠WRN(MWRN)也是一个3‘-->；5’外切酶，其底物特异性与hWRN相似。最后，我们证明了hWRN在体外形成一个三聚体，并与增殖细胞核抗原相互作用。这些发现为WRN的生化活性提供了新的数据，可能有助于阐明其在DNA代谢中的作用(S)。
Werner's syndrome (WS) is an autosomal recessive disorder in humans characterized by the premature development of a partial array of age-associated pathologies. WRN, the gene defective in WS, encodes a 1432 amino acid protein (hWRN) with intrinsic 3'-->5' DNA helicase activity. We recently showed that hWRN is also a 3'-->5' exonuclease. Here, we further characterize the hWRN exonuclease, hWRN efficiently degraded the 3' recessed strands of double-stranded DNA or a DNA-RNA heteroduplex, It had little or no activity on blunt-ended DNA, DNA with a 3' protruding strand, or single-stranded DNA. The hWRN exonuclease efficiently removed a mismatched nucleotide at a 3' recessed terminus, and was capable of initiating DNA degradation from a 12-nt gap, or a nick. We further show that the mouse WRN (mWRN) is also a 3'-->5' exonuclease, with substrate specificity similar to that of hWRN. Finally, we show that hWRN forms a trimer and interacts with the proliferating cell nuclear antigen in vitro. These findings provide new data on the biochemical activities of WRN that may help elucidate its role(s) in DNA metabolism.