Upstream and downstream signals of Ubc9 sumoylation

小的泛素相关修饰物SUMO以共价和非共价的方式调节蛋白质的功能。相扑通路的解除调控与癌症或各种神经退行性疾病等疾病的发病机制有关。相扑(底物上的共价相扑)由一个能量依赖的酶级联反应和一组解偶联酶控制。我的实验室有兴趣了解相扑结合水平的调节，这是由一个E1激活酶，一个E2结合酶和几个E3连接酶之一催化的。到目前为止，已经鉴定了数百种相扑底物，但还不清楚底物专一性是如何与这些有限数量的酶一起执行的。虽然苏木酸化主要通过E3连接酶来调节，但我们最近的发现表明，E2酶Ubc9有助于调节靶标识别。我们已经证明，Ubc9本身被求和，导致目标识别的转换。生化和结构分析表明，这种修饰增强了转录调控因子Sp100的总和甲基化，达到了只有在存在E3连接酶的情况下才能实现的程度，而其他底物不会改变或甚至受损。这项提案的总体目标是从生物学的角度描述监管和这种特殊的Ubc9修饰的后果。

The small ubiquitin related modifier SUMO regulates protein function in a covalent and non-covalent manner. Deregulation of the SUMO pathway is implicated in the pathogenesis of diseases like cancer or diverse neurodegenerative disorders. Sumoylation (covalent SUMO attachment to the substrate) is controlled by an energy dependent enzyme cascade for conjugation and by a set of enzymes for de-conjugation. My laboratory is interested in understanding the regulation at the level of SUMO conjugation, which is catalysed by one E1 activating enzyme, one E2 conjugating enzyme and one of a few E3 ligases. To date, hundreds of SUMO substrates are identified but it is unclear how substrate specificity is performed with this limited number of enzymes. Although sumoylation is mainly modulated via E3 ligases, our recent findings indicate that the E2 enzyme Ubc9 contributes to regulate target discrimination. We have shown that Ubc9 itself gets sumoylated resulting in a switch in target discrimination. Biochemical and structural analysis indicate that this modification enhances sumoylation of the transcriptional regulator Sp100 to an extent that can otherwise only be achieved in the presence of E3 ligases whereas other substrates are not altered or even impaired. The overall aim of this proposal is to characterise regulation and the consequences of this particular Ubc9 modification in a biological context.