Functional interaction between the Bloom's syndrome helicase and the RAD51 paralog, RAD51L3 (RAD51D)
Functional interaction between the Bloom's syndrome helicase and the RAD51 paralog, RAD51L3 (RAD51D)
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DOI：
10.1074/jbc.m308838200
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发表时间：
2003-11-28
影响因子：
4.8
通讯作者：
Hickson, ID
中科院分区：
文献类型：
--
作者：
Braybrooke, JP;Li, JL;Hickson, ID
布鲁姆综合症（BS）是一种遗传性疾病，与身材矮小、生育缺陷和易患癌症有关。BS细胞的特点是基因组不稳定；特别是，姐妹染色单体和同源染色体之间的相互交换率很高。BS基因产物BLM是一种解旋酶，属于高度保守的RecQ家族。已知BLM与RAD51重组酶形成复合物，并作用于同源重组过程中形成的DNA中间体，包括d环和Holliday连接。在这里，我们表明BLM也与RAD51L3蛋白（也称为RAD51D）产生直接的物理关联，这是一个所谓的RAD51平行序列，与RAD51本身显示有限的序列相似性。这种相互作用是通过BLM的n端结构域介导的。为了分析BLM和RAD51L3之间的功能相互作用，我们纯化了一个由RAD51L3和第二个RAD51平行物XRCC2组成的异质复合物。我们发现RAD51L3-XRCC2复合物刺激BLM破坏模拟Holliday结的合成四向结。我们还表明，截断形式的BLM保留解旋酶活性，但不能结合RAD51L3，不受RAD51L3- xrcc2复合物的刺激。我们的数据表明，BLM的活性是通过与RAD51L3- xrcc2复合物的相互作用来调节的，并且这种对BLM的刺激作用依赖于BLM和RAD51L3蛋白之间的直接物理关联。我们认为，在同源重组过程的后期阶段，BLM与RAD51相似物合作，有助于在受损或停滞的复制分叉处恢复有效的DNA复制。
Bloom's syndrome (BS) is a genetic disorder associated with short stature, fertility defects, and a predisposition to the development of cancer. BS cells are characterized by genomic instability; in particular, a high rate of reciprocal exchanges between sister-chromatids and homologous chromosomes. The BS gene product, BLM, is a helicase belonging to the highly conserved RecQ family. BLM is known to form a complex with the RAD51 recombinase, and to act upon DNA intermediates that form during homologous recombination, including D-loops and Holliday junctions. Here, we show that BLM also makes a direct physical association with the RAD51L3 protein ( also known as RAD51D), a so-called RAD51 paralog that shows limited sequence similarity to RAD51 itself. This interaction is mediated through the N-terminal domain of BLM. To analyze functional interactions between BLM and RAD51L3, we have purified a heteromeric complex comprising RAD51L3 and a second RAD51 paralog, XRCC2. We show that the RAD51L3-XRCC2 complex stimulates BLM to disrupt synthetic 4-way junctions that model the Holliday junction. We also show that a truncated form of BLM, which retains helicase activity but is unable to bind RAD51L3, is not stimulated by the RAD51L3-XRCC2 complex. Our data indicate that the activity of BLM is modulated through an interaction with the RAD51L3-XRCC2 complex, and that this stimulatory effect on BLM is dependent upon a direct physical association between the BLM and RAD51L3 proteins. We propose that BLM co-operates with RAD51 paralogs during the late stages of homologous recombination processes that serve to restore productive DNA replication at sites of damaged or stalled replication forks.