Centre de Recherche de Biochimie Macromoléculaire, CNRS UMR5237, University Montpellier I and II, 1919 route de Mende, 34293 Montpellier Cedex 05, France.
Nat Commun. 2013;4:1850. doi: 10.1038/ncomms2875.
The small ubiquitin-like modifier (SUMO) pathway is essential for the maintenance of genome stability. We investigated its possible involvement in the control of DNA replication during S phase by using the Xenopus cell-free system. Here we show that the SUMO pathway is critical to limit the number and, thus, the density of replication origins that are activated in early S phase. We identified cyclin E, which regulates cyclin-dependent kinase 2 (Cdk2) to trigger origin firing, as an S-phase substrate of this pathway. We show that cyclin E is dynamically and highly conjugated to SUMO2/3 on chromatin, independently of Cdk2 activity and origin activation. Moreover, cyclin E is the predominant SUMO2/3 target on chromatin in early S phase, as cyclin E depletion abolishes, while its readdition restores, the SUMO2/3 signal. Together, our data indicate that cyclin E SUMOylation is important for controlling origin firing once the cyclin E-Cdk2 complex is recruited onto replication origins.
小泛素样修饰物 (SUMO) 途径对于维持基因组稳定性至关重要。我们通过使用非洲爪蟾无细胞系统研究了其在 S 期 DNA 复制控制中的可能作用。在这里，我们表明 SUMO 途径对于限制在早期 S 期激活的复制起点的数量，从而限制其密度至关重要。我们鉴定出细胞周期蛋白 E，它调节细胞周期蛋白依赖性激酶 2 (Cdk2) 以触发起始，作为该途径的 S 期底物。我们表明，细胞周期蛋白 E 在染色质上动态地高度与 SUMO2/3 缀合，独立于 Cdk2 活性和起始激活。此外，细胞周期蛋白 E 是早期 S 期染色质上的主要 SUMO2/3 靶标，因为细胞周期蛋白 E 的消耗会消除，而其重新添加则会恢复 SUMO2/3 信号。总之，我们的数据表明，一旦细胞周期蛋白 E-Cdk2 复合物被招募到复制起点，细胞周期蛋白 E 的 SUMO 化对于控制起始至关重要。
