Yunus Ali A, Lima Christopher D
Sloan-Kettering Institute, New York, NY 10065, USA.
Mol Cell. 2009 Sep 11;35(5):669-82. doi: 10.1016/j.molcel.2009.07.013.
Siz1 is a founding member of the Siz/PIAS RING family of SUMO E3 ligases. The X-ray structure of an active Siz1 ligase revealed an elongated tripartite architecture comprised of an N-terminal PINIT domain, a central zinc-containing RING-like SP-RING domain, and a C-terminal domain we term the SP-CTD. Structure-based mutational analysis and biochemical studies show that the SP-RING and SP-CTD are required for activation of the E2 approximately SUMO thioester, while the PINIT domain is essential for redirecting SUMO conjugation to the proliferating cell nuclear antigen (PCNA) at lysine 164, a nonconsensus lysine residue that is not modified by the SUMO E2 in the absence of Siz1. Mutational analysis of Siz1 and PCNA revealed surfaces on both proteins that are required for efficient SUMO modification of PCNA in vitro and in vivo.
Siz1是Siz/PIAS SUMO E3连接酶家族的创始成员。活性Siz1连接酶的X射线结构显示出一种细长的三方结构，由一个N端PINIT结构域、一个中央含锌的类RING结构域SP-RING和一个C端结构域（我们称之为SP-CTD）组成。基于结构的突变分析和生化研究表明，SP-RING和SP-CTD对于激活E2-大约SUMO硫酯是必需的，而PINIT结构域对于将SUMO缀合重定向到赖氨酸164处的增殖细胞核抗原（PCNA）至关重要，赖氨酸164是一个非共有赖氨酸残基，在没有Siz1的情况下不会被SUMO E2修饰。对Siz1和PCNA的突变分析揭示了两种蛋白质上的表面，这对于在体外和体内对PCNA进行有效的SUMO修饰是必需的。
