Formation of deletions during double-strand break repair in Drosophila DmBlm mutants occurs after strand invasion
Formation of deletions during double-strand break repair in Drosophila DmBlm mutants occurs after strand invasion
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DOI：
10.1073/pnas.0406157101
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发表时间：
2004-11-02
影响因子：
11.1
通讯作者：
Sekelsky, JJ
中科院分区：
文献类型：
--
作者：
McVey, M;LaRocque, JR;Sekelsky, JJ
布卢姆综合征是一种与癌症易感性和基因组不稳定相关的罕见疾病，由 RecQ 解旋酶 BLM 缺失引起。通过同源重组精确修复 DNA 双链缺口需要果蝇 BLM 直向同源物 (DmBlm)。与野生型相比，DmBlm 突变体的修复产物具有更短的修复合成道长度，并且经常与断裂位点侧翼的缺失相关。为了确定在缺乏 DmBlm 的情况下导致缺失形成的机制，我们对各种遗传背景下 P{w(a)} 元件切除后的修复进行了表征。缺乏 DmRad51 的果蝇缺失频率并不升高。此外，DmRad51 的缺失会抑制 DmBlm 突变体中缺失的形成。这些数据支持一个模型，其中 DmBlm 在链入侵下游发挥作用，解开 D 环中间体，从而释放新合成的链。在缺乏 DmBlm 的情况下，D 环分解的替代途径会导致修复合成束短或侧翼缺失。该模型解释了 RecQ 解旋酶如何促进同源重组，同时防止非法重组。
Bloom syndrome is a rare disorder associated with cancer predisposition and genomic instability and is caused by loss of the RecQ helicase BLM. The Drosophila ortholog of BLM (DmBlm) is required for accurate repair of DNA double-strand gaps by homologous recombination. Repair products from DmBlm mutants have shorter repair synthesis tract lengths compared to wild type and are frequently associated with deletions flanking the break site. To determine the mechanisms responsible for deletion formation in the absence of DmBlm, we characterized repair after excision of the P{w(a)} element in various genetic backgrounds. Flies lacking DmRad51 do not have an elevated deletion frequency. Moreover, loss of DmRad51 suppresses deletion formation in DmBlm mutants. These data support a model in which DmBlm acts downstream of strand invasion to unwind a D-loop intermediate to free the newly synthesized strand. In the absence of DmBlm, alternative pathways of D-loop disassembly result in short repair synthesis tracts or flanking deletions. This model explains how RecQ helicases can promote homologous recombination while preventing illegitimate recombination.