Small ubiquitin‐like modifier (SUMO) conjugation, or SUMOylation, is a reversible post‐translational modification that is important for regulation of many cellular processes including cell division cycle in the eukaryotic kingdom. However, only a portion of the components of the Chlamydomonas SUMOylation system are known and their functions and regulation investigated. The present studies are aimed at extending discovery and characterization of new components and improving the annotation and nomenclature of all known proteins and genes involved in the system. Even though only one copy of the heterodimerized SUMO‐activating enzyme, SAE1 and SAE2, was identified, the number of SUMO‐conjugating enzymes (SCEs) and SUMO proteases/isopeptidase was expanded in Chlamydomonas. Using the reconstituted SUMOylation system, we showed that SCE1, SCE2, and SCE3 have SUMO‐conjugating activity. In addition to SUMOylation, components required for other post‐translational modifications such as NEDDylation, URMylation, and UFMylation, were confirmed to be present in Chlamydomonas. Our data also showed that besides isopeptidase activity, the SUMO protease domain of SUPPRESSOR OF MAT3 7/SENTRIN‐SPECIFIC PROTEASE 1 (SMT7/SENP1) has endopeptidase activity that is capable of processing SUMO precursors. Moreover, the key cell cycle regulators of Chlamydomonas E2F1, DP1, CDKG1, CYCD2, and CYCD3 were SUMOylated in vitro, suggesting SUMOylation may be part of regulatory pathway modulating cell cycle regulators.

中文翻译：

---

莱茵衣藻 SUMOylation 系统组分的修订注释和扩展表征


小泛素样修饰剂 (SUMO) 缀合或 SUMOylation 是一种可逆的翻译后修饰，对于调节许多细胞过程（包括真核王国中的细胞分裂周期）非常重要。然而，仅了解衣藻 SUMO 化系统的一部分组件，并研究了它们的功能和调节。目前的研究旨在扩展新成分的发现和表征，并改进系统中涉及的所有已知蛋白质和基因的注释和命名法。尽管仅鉴定出异二聚化 SUMO 激活酶SAE1和SAE2的一个副本，但衣藻中 SUMO 结合酶 ( SCE ) 和 SUMO 蛋白酶/异肽酶的数量有所增加。使用重建的 SUMO 化系统，我们表明 SCE1、SCE2 和 SCE3 具有 SUMO 缀合活性。除了 SUMO 化之外，衣藻中还存在其他翻译后修饰（如 NEDDylation、URMylation 和 UFMylation）所需的成分。我们的数据还表明，除了肽酶活性外，SUPPRESSOR OF MAT3 7/SENTRIN-SPECIFIC PROTEASE 1 (SMT7/SENP1) 的 SUMO 蛋白酶结构域还具有内肽酶活性，能够处理 SUMO 前体。此外，衣藻E2F1、DP1、CDKG1、CYCD2和CYCD3的关键细胞周期调节因子在体外被SUMO化，表明SUMO化可能是调节细胞周期调节因子的调节途径的一部分。