IFOM, the FIRC Institute of Molecular Oncology, Milan, Italy.
Institute for Cancer Genetics, Department of Pathology and Cell Biology, College of Physicians & Surgeons, Columbia University, New York, NY, USA.
Nat Commun. 2021 Apr 8;12(1):2111. doi: 10.1038/s41467-021-22217-w.
Smc5/6 is essential for genome structural integrity by yet unknown mechanisms. Here we find that Smc5/6 co-localizes with the DNA crossed-strand processing complex Sgs1-Top3-Rmi1 (STR) at genomic regions known as natural pausing sites (NPSs) where it facilitates Top3 retention. Individual depletions of STR subunits and Smc5/6 cause similar accumulation of joint molecules (JMs) composed of reversed forks, double Holliday Junctions and hemicatenanes, indicative of Smc5/6 regulating Sgs1 and Top3 DNA processing activities. We isolate an intra-allelic suppressor of smc6-56 proficient in Top3 retention but affected in pathways that act complementarily with Sgs1 and Top3 to resolve JMs arising at replication termination. Upon replication stress, the smc6-56 suppressor requires STR and Mus81-Mms4 functions for recovery, but not Srs2 and Mph1 helicases that prevent maturation of recombination intermediates. Thus, Smc5/6 functions jointly with Top3 and STR to mediate replication completion and influences the function of other DNA crossed-strand processing enzymes at NPSs.
Smc5/6 通过未知机制对基因组结构完整性至关重要。在这里，我们发现 Smc5/6 与 DNA 交叉链处理复合物 Sgs1-Top3-Rmi1（STR）在称为自然暂停位点（NPS）的基因组区域共定位，在该区域它促进 Top3 的保留。STR 亚基和 Smc5/6 的单独缺失会导致由反转叉、双 Holliday 连接和半侧链组成的连接分子（JMs）的类似积累，表明 Smc5/6 调节 Sgs1 和 Top3 的 DNA 处理活性。我们分离了一个等位基因内的抑制子 smc6-56，它在保留 Top3 方面很有效，但在与 Sgs1 和 Top3 互补的途径中受到影响，以解决在复制终止时出现的 JMs。在复制应激下，smc6-56 抑制子需要 STR 和 Mus81-Mms4 功能才能恢复，但不需要 Srs2 和 Mph1 解旋酶来防止重组中间体的成熟。因此，Smc5/6 与 Top3 和 STR 共同作用以介导复制完成，并影响 NPS 处其他 DNA 交叉链处理酶的功能。
