Yang Yuanyuan, Shi Li, Ding Yiluan, Shi Yanhong, Hu Hong-Yu, Wen Yi, Zhang Naixia
CAS Key Laboratory of Receptor Research, Department of Analytical Chemistry, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China; University of Chinese Academy of Sciences, Beijing, China.
CAS Key Laboratory of Receptor Research, Department of Analytical Chemistry, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, China.
Biophys J. 2017 May 23;112(10):2099-2108. doi: 10.1016/j.bpj.2017.04.022.
Ubiquitin-specific protease 25 (Usp25) is a deubiquitinase that is involved in multiple biological processes. The N-terminal ubiquitin-binding region (UBR) of Usp25 contains one ubiquitin-associated domain, one small ubiquitin-like modifier (SUMO)-interacting motif and two ubiquitin-interacting motifs. Previous studies suggest that the covalent sumoylation in the UBR of Usp25 impairs its enzymatic activity. Here, we raise the hypothesis that non-covalent binding of SUMO, a prerequisite for efficient sumoylation, will impair Usp25's catalytic activity as well. To test our hypothesis and elucidate the underlying molecular mechanism, we investigated the structure and function of the Usp25 N-terminal UBR. The solution structure of Usp25 is obtained, and the key residues responsible for recognition of ubiquitin and SUMO2 are identified. Our data suggest inhibition of Usp25's catalytic activity upon the non-covalent binding of SUMO2 to the Usp25 SUMO-interacting motif. We also find that SUMO2 can competitively block the interaction between the Usp25 UBR and its ubiquitin substrates. Based on our findings, we have proposed a working model to depict the regulatory role of the Usp25 UBR in the functional display of the enzyme.
泛素特异性蛋白酶25（Usp25）是一种去泛素化酶，参与多种生物学过程。Usp25的N端泛素结合区域（UBR）包含一个泛素相关结构域、一个小泛素样修饰物（SUMO）相互作用基序和两个泛素相互作用基序。先前的研究表明，Usp25的UBR中的共价SUMO化会损害其酶活性。在此，我们提出一个假说，即SUMO的非共价结合（高效SUMO化的先决条件）也会损害Usp25的催化活性。为了验证我们的假说并阐明潜在的分子机制，我们研究了Usp25 N端UBR的结构和功能。获得了Usp25的溶液结构，并鉴定了负责识别泛素和SUMO2的关键残基。我们的数据表明，SUMO2与Usp25的SUMO相互作用基序非共价结合后，Usp25的催化活性受到抑制。我们还发现SUMO2可以竞争性地阻断Usp25 UBR与其泛素底物之间的相互作用。基于我们的研究结果，我们提出了一个工作模型来描述Usp25 UBR在该酶功能展示中的调节作用。
