Regulation of nucleocytoplasmic transports by sumoylation

泛素样蛋白SUMO通过改变靶蛋白的稳定性、构象、结合活性或定位来调节许多细胞内过程。相扑被翻译后转移到目标蛋白的赖氨酸残基上。糖基化反应是由一个激活酶E1、一个结合酶E2和各种底物特异性的E3连接酶组成的酶级联反应。这是一个可逆的过程，这是由于特定的蛋白酶的活性，它将相扑从其目标中分离出来。我们最近发现酿酒酵母的Kap114是一种导入蛋白β家族的受体，介导蛋白质进入细胞核，它被相扑修饰和调节。我们将SUMO描述为一种核内货物释放因子，它是Kap114介导的进口途径所需的RAN GTP酶的补充。因此，相扑在核质转运中扮演了一个迄今未知的角色，我们打算详细研究这一点。我们将特别关注相扑诱导的货物释放的分子机制以及相扑调控的核运输中的其他因素的参与。此外，我们计划阐明苏莫化循环组件本身通过核孔复合体的运输机制。另一个目标是找出Importinβ家族的其他运输受体是否以及如何受到SUMO化的调节。我们的方法包括将适当的蛋白质相互作用研究与纯化因子相结合，以及使用野生型和突变菌株对货物和受体分子进行定位研究。在我们未来的研究中，我们的目标是进一步深入了解相扑修饰对细胞核和细胞质之间通讯的功能意义。

The ubiquitin-like protein SUMO regulates a number of intracellular processes by altering the stability, conformation, binding activity, or localization of target proteins. SUMO is transferred posttranslationally to a lysine residue of the target protein. The SUMOylation reaction is mediated by an enzymatic cascade consisting of an activating enzyme E1, a conjugating enzyme E2, and various substrate-specific E3 ligases. This is a reversible process due to the activity of specific proteases, which cleave SUMO off its targets. We recently showed that Kap114 from Saccharomyces cerevisiae, a receptor of the importin beta family mediating protein import into the cell nucleus, is modified and regulated by SUMO. We characterized SUMO as an intranuclear cargo release factor that is in addition to the Ran GTPase required for the Kap114-mediated import pathway. Thus SUMO plays a hitherto unknown role in nucleocytoplasmic transport, which we aim to study in detail. We will particularly focus on the examination of the molecular mechanism of SUMO-induced cargo release and the involvement of additional factors in SUMO-regulated nuclear transport. Furthermore, we plan to elucidate the mechanisms of transport across the nuclear pore complexes of the SUMOylation cycle components themselves. A further goal is to find out if and how other transport receptors of the importin beta family are regulated by SUMOylation. Our methods include a combination of appropriate protein interaction studies with purified factors and localization studies of cargo and receptor molecules using wildtype and mutant strains. In our future studies, we aim to gain further insight into the functional significance of the SUMO modification for communication between the cell nucleus and the cytoplasm.