Slx1-Slx4 is a second structure-specific endonuclease functionally redundant with Sgs1-Top3
Slx1-Slx4 is a second structure-specific endonuclease functionally redundant with Sgs1-Top3
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DOI：
10.1101/gad.1105203
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发表时间：
2003-07-15
影响因子：
10.5
通讯作者：
Brill, SJ
中科院分区：
文献类型：
--
作者：
Fricke, WM;Brill, SJ
RecQ DNA解旋酶人BLM和酵母Sgs 1与DNA拓扑异构酶III相互作用，并被认为作用于停滞的复制叉以维持基因组稳定性。为了深入了解这一机制，我们以前确定SLX 1和SLX 4为在缺乏SGS 1-TOP3的情况下生存力和完成rDNA复制所需的基因。在这里，我们表明，SLX 1和SLX 4编码异聚体结构特异性核酸内切酶。Slx 1-Slx 4核酸酶在分支DNA底物上有活性，特别是简单的Y、5 ′-瓣或复制叉结构。它在分支连接处切割带有5'非同源臂的链，并从5'-瓣或复制叉底物产生可连接的切口产物。Slx 1是具有预测的URI核酸酶结构域和PHD型锌指的蛋白质家族的创始成员。该亚基自身显示弱的结构特异性内切核酸酶活性，被Slx 4刺激500倍，并且需要PHD指用于体外和体内活性。这两种亚基在体内都是抵抗甲基甲烷磺酸盐（MMS）造成的DNA损伤所必需的。我们建议，Sgs 1-Top3的行为在终止rDNA复制decatenate失速叉，并在其缺席，Slx 1-Slx 4切割这些失速叉。
The RecQ DNA helicases human BLM and yeast Sgs1 interact with DNA topoisomerase III and are thought to act on stalled replication forks to maintain genome stability. To gain insight into this mechanism, we previously identified SLX1 and SLX4 as genes that are required for viability and for completion of rDNA replication in the absence of SGS1-TOP3. Here we show that SLX1 and SLX4 encode a heteromeric structure-specific endonuclease. The Slx1-Slx4 nuclease is active on branched DNA substrates, particularly simple-Y, 5'-flap, or replication fork structures. It cleaves the strand bearing the 5' nonhomologous arm at the branch junction and generates ligatable nicked products from 5'-flap or replication fork substrates. Slx1 is the founding member of a family of proteins with a predicted URI nuclease domain and PHD-type zinc finger. This subunit displays weak structure-specific endonuclease activity on its own, is stimulated 500-fold by Slx4, and requires the PHD finger for activity in vitro and in vivo. Both subunits are required in vivo for resistance to DNA damage by methylmethane sulfonate (MMS). We propose that Sgs1-Top3 acts at the termination of rDNA replication to decatenate stalled forks, and, in its absence, Slx1-Slx4 cleaves these stalled forks.