Ulrich H D, Jentsch S
Department of Molecular Cell Biology, Max Planck Institute for Biochemistry, Am Klopferspitz 18a, 82152 Martinsried, Germany.
EMBO J. 2000 Jul 3;19(13):3388-97. doi: 10.1093/emboj/19.13.3388.
Two ubiquitin-conjugating enzymes, RAD6 and the heteromeric UBC13-MMS2 complex, have been implicated in post-replicative DNA damage repair in yeast. Here we provide a mechanistic basis for cooperation between the two enzymes. We show that two chromatin-associated RING finger proteins, RAD18 and RAD5, play a central role in mediating physical contacts between the members of the RAD6 pathway. RAD5 recruits the UBC13-MMS2 complex to DNA by means of its RING finger domain. Moreover, RAD5 association with RAD18 brings UBC13-MMS2 into contact with the RAD6-RAD18 complex. Interaction between the two RING finger proteins thus promotes the formation of a heteromeric complex in which the two distinct ubiquitin-conjugating activities of RAD6 and UBC13-MMS2 can be closely coordinated. Surprisingly, UBC13 and MMS2 are largely cytosolic proteins, but DNA damage triggers their redistribution to the nucleus. These findings suggest a mechanism by which the activity of this DNA repair pathway could be regulated.
两种泛素结合酶，RAD6和异源二聚体UBC13-MMS2复合物，已被证明参与酵母中的复制后DNA损伤修复。在此，我们为这两种酶之间的协作提供了一个机制基础。我们表明，两种与染色质相关的环指蛋白，RAD18和RAD5，在介导RAD6途径成员之间的物理接触中起核心作用。RAD5通过其环指结构域将UBC13-MMS2复合物招募到DNA上。此外，RAD5与RAD18的结合使UBC13-MMS2与RAD6-RAD18复合物接触。因此，这两种环指蛋白之间的相互作用促进了异源复合物的形成，其中RAD6和UBC13-MMS2的两种不同泛素结合活性可以紧密协调。令人惊讶的是，UBC13和MMS2主要是胞质蛋白，但DNA损伤会触发它们重新分布到细胞核中。这些发现提示了一种可调节该DNA修复途径活性的机制。
