Separable roles for Exonuclease I in meiotic DNA double-strand break repair
Separable roles for Exonuclease I in meiotic DNA double-strand break repair
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DOI：
10.1016/j.dnarep.2010.09.024
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发表时间：
2011-02-07
期刊：
影响因子：
3.8
通讯作者：
Borts, Rhona H.
中科院分区：
文献类型：
--
作者：
Keelagher, Rebecca E.;Cotton, Victoria E.;Borts, Rhona H.
Exo 1是Rad 2蛋白家族的成员，具有5 '-3'核酸外切酶和5'侧翼核酸内切酶活性。除了在有丝分裂生长期间执行各种功能外，Exo 1对于减数分裂期间的交叉产生也很重要。然而，其精确的分子作用仍不明确，已经提出了几种模型来解释在其不存在的情况下观察到的交叉缺陷。在这里，我们提供了物理证据，表明Exo 1的核酸酶活性对于在其他野生型细胞中Spoil依赖性HIS 4热点处的正常5 '-3'切除是必需的。同样的活性也是该位点正常水平的基因转换所必需的。然而，基因转换经常观察到的距离超出切除是很容易检测到的，认为这不是限制异源双链体形成的初始DNA末端切除的程度。除了这些核酸酶依赖的功能，我们发现，一个exo 1-D173 A突变体的核酸酶活性缺陷是能够保持在野生型水平的交叉在一些遗传间隔，这表明exo 1也发挥了核酸酶独立的作用，在交叉促进。(C)2010 Elsevier B. V.保留所有权利。
Exo1 is a member of the Rad2 protein family and possesses both 5'-3' exonuclease and 5' flap endonuclease activities. In addition to performing a variety of functions during mitotic growth, Exo1 is also important for the production of crossovers during meiosis. However, its precise molecular role has remained ambiguous and several models have been proposed to account for the crossover deficit observed in its absence. Here, we present physical evidence that the nuclease activity of Exo1 is essential for normal 5'-3' resection at the Spoil-dependent HIS4 hotspot in otherwise wild-type cells. This same activity was also required for normal levels of gene conversion at the locus. However, gene conversions were frequently observed at a distance beyond that at which resection was readily detectable arguing that it is not the extent of the initial DNA end resection that limits heteroduplex formation. In addition to these nuclease-dependent functions, we found that an exo1-D173A mutant defective in nuclease activity is able to maintain crossing-over at wild-type levels in a number of genetic intervals, suggesting that Exo1 also plays a nuclease-independent role in crossover promotion. (C) 2010 Elsevier B.V. All rights reserved.