Zhang Shicheng, Wang Linlin, Tao Ye, Bai Tuya, Lu Rong, Zhang Tianlong, Chen Jiangye, Ding Jianping
State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Science Research Center, CAS Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, University of Chinese Academy of Sciences, Chinese Academy of Sciences; 333 Haike Road, Shanghai 201210, China.
School of Life Sciences, Shanghai University, 333 Nanchen Road, Shanghai 200444, China.
Nucleic Acids Res. 2017 Dec 15;45(22):13068-13079. doi: 10.1093/nar/gkx992.
The Shu complex, a conserved regulator consisting of Csm2, Psy3, Shu1 and Shu2 in budding yeast, plays an important role in the assembly of the Rad51-ssDNA filament in homologous recombination. However, the molecular basis for the assembly of the Shu complex and its functional role in DNA repair is still elusive. Here, we report the crystal structure of the yeast Shu complex, revealing that Csm2, Psy3, Shu1 and Shu2 interact with each other in sequence to form a V-shape overall structure. Shu1 adopts a structure resembling the ATPase core domain of Rad51 and represents a new Rad51 paralog. Shu2 assumes a novel structural fold consisting of a conserved zinc-finger containing SWIM domain and a small insertion domain. The functional roles of the key residues are validated using mutagenesis and in vitro pull-down and in vivo yeast growth studies. Structural analysis together with available biological data identifies two potential DNA-binding sites, one of which might be responsible for binding the ssDNA region of the 3'-overhang DNA and the other for the dsDNA region. Collectively, these findings reveal the molecular basis for the assembly of the Shu complex and shed new insight on its functional role in homologous recombination.
Shu复合体是一种在芽殖酵母中由Csm2、Psy3、Shu1和Shu2组成的保守调节因子，在同源重组中Rad51-ssDNA细丝的组装过程中发挥重要作用。然而，Shu复合体组装的分子基础及其在DNA修复中的功能作用仍不清楚。在此，我们报道了酵母Shu复合体的晶体结构，揭示Csm2、Psy3、Shu1和Shu2依次相互作用形成一个V形整体结构。Shu1采用类似于Rad51的ATP酶核心结构域的结构，代表一种新的Rad51旁系同源物。Shu2呈现出一种新的结构折叠，由一个含有保守锌指的SWIM结构域和一个小的插入结构域组成。使用诱变、体外下拉实验和体内酵母生长研究验证了关键残基的功能作用。结构分析结合现有生物学数据确定了两个潜在的DNA结合位点，其中一个可能负责结合3'-突出端DNA的ssDNA区域，另一个负责结合dsDNA区域。总体而言，这些发现揭示了Shu复合体组装的分子基础，并为其在同源重组中的功能作用提供了新的见解。
