Bhaskara Venugopal, Dupré Aude, Lengsfeld Bettina, Hopkins Ben B, Chan Angela, Lee Ji-Hoon, Zhang Xiaoming, Gautier Jean, Zakian Virginia, Paull Tanya T
Department of Chemistry and Biochemistry, University of Texas at Austin, Austin, TX 78712, USA.
Mol Cell. 2007 Mar 9;25(5):647-61. doi: 10.1016/j.molcel.2007.01.028.
Mre11 and Rad50 are the catalytic components of a highly conserved DNA repair complex that functions in many aspects of DNA metabolism involving double-strand breaks. The ATPase domains in Rad50 are related to the ABC transporter family of ATPases, previously shown to share structural similarities with adenylate kinases. Here we demonstrate that Mre11/Rad50 complexes from three organisms catalyze the reversible adenylate kinase reaction in vitro. Mutation of the conserved signature motif reduces the adenylate kinase activity of Rad50 but does not reduce ATP hydrolysis. This mutant resembles a rad50 null strain with respect to meiosis and telomere maintenance in S. cerevisiae, correlating adenylate kinase activity with in vivo functions. An adenylate kinase inhibitor blocks Mre11/Rad50-dependent DNA tethering in vitro and in cell-free extracts, indicating that adenylate kinase activity by Mre11/Rad50 promotes DNA-DNA associations. We propose a model for Rad50 that incorporates both ATPase and adenylate kinase reactions as critical activities that regulate Rad50 functions.
Mre11和Rad50是一种高度保守的DNA修复复合物的催化成分，该复合物在涉及双链断裂的DNA代谢的许多方面发挥作用。Rad50中的ATP酶结构域与ATP酶的ABC转运蛋白家族相关，先前已证明其与腺苷酸激酶具有结构相似性。在这里，我们证明来自三种生物体的Mre11/Rad50复合物在体外催化可逆的腺苷酸激酶反应。保守特征基序的突变降低了Rad50的腺苷酸激酶活性，但不降低ATP水解。在酿酒酵母中，这种突变体在减数分裂和端粒维持方面类似于rad50缺失菌株，将腺苷酸激酶活性与体内功能相关联。一种腺苷酸激酶抑制剂在体外和无细胞提取物中阻断Mre11/Rad50依赖性的DNA连接，表明Mre11/Rad50的腺苷酸激酶活性促进DNA-DNA缔合。我们提出了一个Rad50模型，该模型将ATP酶和腺苷酸激酶反应都纳入作为调节Rad50功能的关键活性。
