Molecular basis for Nse5-6 mediated regulation of Smc5/6 functions.
Molecular basis for Nse5-6 mediated regulation of Smc5/6 functions.
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Nse5-6 介导的 Smc5/6 功能调节的分子基础。
DOI：
10.1073/pnas.2310924120
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发表时间：
2023
影响因子：
11.1
通讯作者：
Zhao,Xiaolan
中科院分区：
文献类型：
--
作者：
Li,Shibai;Yu,You;Zheng,Jian;Miller-Browne,Victoria;Ser,Zheng;Kuang,Huihui;Patel,DinshawJ;Zhao,Xiaolan
Smc 5/6复合物（Smc 5/6）对于真核生物中的基因组复制和修复是重要的。其细胞功能与Smc 5和Smc 6亚基的ATP酶活性密切相关。这种活性需要两个SMC亚基的马达结构域的二聚化，并且由六个非SMC亚基（Nse 1至Nse 6）调节。在NSE中，Nse 5和Nse 6形成稳定的亚复合物（Nse 5 -6），其抑制复合物的ATP酶活性。然而，这种调节的潜在机制和生物学意义仍不清楚。在这里，我们使用结构和功能研究来解决这些问题。我们确定了冷冻EM结构的酵母Smc 5/6来自复合物组成的所有八个亚基或一个子集的五个亚基。这两种结构都表明Nse 5 -6与Smc 6的运动域和邻近的卷曲螺旋段（称为颈部区域）相关。我们的结构分析表明，这种结合是兼容的电机域二聚化，但在驱逐Smc 6颈部的Nse 4亚基的结果。由于Nse 4-Smc 6颈相互作用有利于运动域接合，因此有利于ATP酶活性，Nse 6与Nse 4的竞争可以解释Nse 5 -6如何不利于ATP酶活性。这种调节原则上可以根据它们对复合物的ATP酶活性的需要而不同地影响Smc 5/6介导的过程。事实上，在细胞中的诱变数据提供的证据表明，Nse 6-Smc 6颈相互作用是重要的DNA修复中间体的分辨率，但不是复制终止。我们的研究结果为Nse 5 -6如何调节Smc 5 - 6的ATP酶活性和细胞功能提供了分子基础。
The Smc5/6 complex (Smc5/6) is important for genome replication and repair in eukaryotes. Its cellular functions are closely linked to the ATPase activity of the Smc5 and Smc6 subunits. This activity requires the dimerization of the motor domains of the two SMC subunits and is regulated by the six non-SMC subunits (Nse1 to Nse6). Among the NSEs, Nse5 and Nse6 form a stable subcomplex (Nse5-6) that dampens the ATPase activity of the complex. However, the underlying mechanisms and biological significance of this regulation remain unclear. Here, we address these issues using structural and functional studies. We determined cryo-EM structures of the yeast Smc5/6 derived from complexes consisting of either all eight subunits or a subset of five subunits. Both structures reveal that Nse5-6 associates with Smc6’s motor domain and the adjacent coiled-coil segment, termed the neck region. Our structural analyses reveal that this binding is compatible with motor domain dimerization but results in dislodging the Nse4 subunit from the Smc6 neck. As the Nse4-Smc6 neck interaction favors motor domain engagement and thus ATPase activity, Nse6’s competition with Nse4 can explain how Nse5-6 disfavors ATPase activity. Such regulation could in principle differentially affect Smc5/6-mediated processes depending on their needs of the complex’s ATPase activity. Indeed, mutagenesis data in cells provide evidence that the Nse6-Smc6 neck interaction is important for the resolution of DNA repair intermediates but not for replication termination. Our results thus provide a molecular basis for how Nse5-6 modulates the ATPase activity and cellular functions of Smc5/6.