Neal Francisco E, Li Wenjing, Uhrig Mollie E, Katz Jeffrey N, Syed Shahrez, Sharma Neelam, Dutta Arijit, Burma Sandeep, Hromas Robert, Mazin Alexander V, Dray Eloise, Libich David S, Olsen Shaun K, Wasmuth Elizabeth V, Zhao Weixing, Sørensen Claus S, Wiese Claudia, Kwon Youngho, Sung Patrick
Department of Biochemistry and Structural Biology, University of Texas Health at San Antonio, San Antonio, TX 78229, USA; Greehey Children's Cancer Research Institute, University of Texas Health at San Antonio, San Antonio, TX 78229, USA.
Department of Biochemistry and Structural Biology, University of Texas Health at San Antonio, San Antonio, TX 78229, USA.
Cell Rep. 2025 May 27;44(5):115654. doi: 10.1016/j.celrep.2025.115654. Epub 2025 May 3.
Homologous recombination (HR) removes DNA double-strand breaks (DSBs) and preserves stressed DNA replication forks. Successful HR execution requires the tumor suppressor BRCA2, which harbors distinct DNA-binding domains (DBDs): one that possesses three oligonucleotide/oligosaccharide-binding (OB) folds (OB-DBD) and another residing in the C-terminal recombinase binding domain (CTRB-DBD). Here, we employ multi-faceted approaches to delineate the contributions of these domains toward HR and replication fork maintenance. We show that OB-DBD and CTRB-DBD confer single-strand DNA (ssDNA)- and dsDNA-binding capabilities, respectively, and that BRCA2 variants mutated in either domain are impaired in their ability to load the recombinase RAD51 onto ssDNA pre-occupied by RPA. While the CTRB-DBD mutant is modestly affected by DNA break repair, it exhibits a strong defect in the protection of stressed replication forks. In contrast, the OB-DBD is indispensable for both BRCA2 functions. Our study thus defines the unique contributions of the two BRCA2 DBDs in genome maintenance.
同源重组（HR）可修复DNA双链断裂（DSB）并维持处于应激状态的DNA复制叉。成功执行HR需要肿瘤抑制因子BRCA2，它具有不同的DNA结合结构域（DBD）：一个拥有三个寡核苷酸/寡糖结合（OB）折叠（OB-DBD），另一个位于C端重组酶结合结构域（CTRB-DBD）。在这里，我们采用多方面的方法来描述这些结构域对HR和复制叉维持的贡献。我们表明，OB-DBD和CTRB-DBD分别赋予单链DNA（ssDNA）和双链DNA（dsDNA）结合能力，并且在任一结构域中发生突变的BRCA2变体在将重组酶RAD51加载到被RPA预先占据的ssDNA上的能力方面受损。虽然CTRB-DBD突变体在DNA断裂修复方面受到适度影响，但它在保护处于应激状态的复制叉方面表现出强烈缺陷。相比之下，OB-DBD对BRCA2的两种功能都是不可或缺的。因此，我们的研究确定了BRCA2的两个DBD在基因组维持中的独特贡献。
