The neurodegenerative disease protein aprataxin resolves abortive DNA ligation intermediates
The neurodegenerative disease protein aprataxin resolves abortive DNA ligation intermediates
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DOI：
10.1038/nature05164
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发表时间：
2006-10-12
期刊：
影响因子：
64.8
通讯作者：
West, Stephen C.
中科院分区：
文献类型：
--
作者：
Ahel, Ivan;Rass, Ulrich;West, Stephen C.
眼共济失调性失用症-1（AOA 1）是一种由编码aprataxin（1，2）的基因（APTX）突变引起的神经系统疾病。Aprataxin是核苷酸水解酶和转移酶的组氨酸三联体（HIT）家族的成员（3），失活突变主要限于该HIT结构域。Aprataxin与DNA修复蛋白XRCC 1和XRCC 4结合，它们分别是DNA连接酶III和连接酶IV的伴侣（4-7），提示在DNA修复中的作用。与此一致，APTX缺陷细胞系对导致单链断裂的药物敏感，并显示诱导染色体畸变的发生率增加（4，5，8）。然而，目前尚不清楚aprataxin是否在DNA修复中具有直接或间接的作用，或者aprataxin的生理底物可能是什么。在这里，我们表明，使用纯化的aprataxin蛋白和提取物来自APTX缺陷的鸡DT 40细胞或Aptx（-/-）小鼠原代神经细胞，aprataxin解决流产的DNA连接中间体。具体而言，aprataxin催化在单链切口和缺口处共价连接至5 '-磷酸末端的腺苷酸基团的亲核释放，导致产生可以有效重新连接的5'-磷酸末端。这些数据表明，与APTX突变相关的神经系统疾病可能是由失败的DNA连接事件导致的未修复的DNA链断裂的逐渐积累引起的。
Ataxia oculomotor apraxia-1 (AOA1) is a neurological disorder caused by mutations in the gene (APTX) encoding aprataxin(1,2). Aprataxin is a member of the histidine triad (HIT) family of nucleotide hydrolases and transferases(3), and inactivating mutations are largely confined to this HIT domain. Aprataxin associates with the DNA repair proteins XRCC1 and XRCC4, which are partners of DNA ligase III and ligase IV, respectively(4-7), suggestive of a role in DNA repair. Consistent with this, APTX-defective cell lines are sensitive to agents that cause single-strand breaks and exhibit an increased incidence of induced chromosomal aberrations(4,5,8). It is not, however, known whether aprataxin has a direct or indirect role in DNA repair, or what the physiological substrate of aprataxin might be. Here we show, using purified aprataxin protein and extracts derived from either APTX-defective chicken DT40 cells or Aptx(-/-) mouse primary neural cells, that aprataxin resolves abortive DNA ligation intermediates. Specifically, aprataxin catalyses the nucleophilic release of adenylate groups covalently linked to 5'-phosphate termini at single-strand nicks and gaps, resulting in the production of 5'-phosphate termini that can be efficiently rejoined. These data indicate that neurological disorders associated with APTX mutations may be caused by the gradual accumulation of unrepaired DNA strand breaks resulting from abortive DNA ligation events.