Holliday junction resolution in human cells: two junction endonucleases with distinct substrate specificities
Holliday junction resolution in human cells: two junction endonucleases with distinct substrate specificities
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DOI：
10.1093/emboj/cdf554
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发表时间：
2002-10-15
期刊：
影响因子：
11.4
通讯作者：
West, SC
中科院分区：
文献类型：
--
作者：
Constantinou, A;Chen, XB;West, SC
分裂假日连接的酶活性对于重组中间体的分解和停滞的复制分叉的重新启动是必需的。在这里，我们表明人类无细胞提取物具有两种不同的内切酶，可以切割假日连接。第一种以结构和序列特异性的方式切割假日连接，并与atp依赖的分支迁移活动相关。总之，这些活动促进分支迁移/分解反应类似于大肠杆菌RuvABC分解体催化的反应。就像ruvc介导的分辨率一样，产品也可以进行宗教化。第二种含有Mus8l蛋白，可以切断假日连接，但产物大多是不可连接的。每种核酸酶都有明确的底物特异性：分支迁移相关的分解酶对Holliday连接具有高度特异性，而mus81相关的内切酶对复制叉和3'-flap结构的活性要高一个数数式。因此，这两种核酸酶都能够切割在重组过程中或通过停止复制分叉的回归形成的假日连接。然而，mus81相关的内切酶可能通过催化停滞叉结构的分裂在复制叉崩溃中发挥更直接的作用。
Enzymatic activities that cleave Holliday junctions are required for the resolution of recombination intermediates and for the restart of stalled replication forks. Here we show that human cell-free extracts possess two distinct endonucleases that can cleave Holliday junctions. The first cleaves Holliday junctions in a structure- and sequence-specific manner, and associates with an ATP-dependent branch migration activity. Together, these activities promote branch migration/resolution reactions similar to those catalysed by the Escherichia coli RuvABC resolvasome. Like RuvC-mediated resolution, the products can be religated. The second, containing Mus8l protein, cuts Holliday junctions but the products are mostly non-ligatable. Each nuclease has a defined substrate specificity: the branch migration-associated resolvase is highly specific for Holliday junctions, whereas the Mus81-associated endonuclease is one order of magnitude more active upon replication fork and 3'-flap structures. Thus, both nucleases are capable of cutting Holliday junctions formed during recombination or through the regression of stalled replication forks. However, the Mus81-associated endonuclease may play a more direct role in replication fork collapse by catalysing the cleavage of stalled fork structures.