Bhaskar Varun, Basquin Jérôme, Conti Elena
Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Munich, Germany.
Department of Structural Cell Biology, Max-Planck-Institute of Biochemistry, Am Klopferspitz 18, 82152 Munich, Germany.
Structure. 2015 May 5;23(5):921-928. doi: 10.1016/j.str.2015.03.011. Epub 2015 Apr 23.
The Ccr4-Not complex regulates eukaryotic gene expression at multiple levels, including mRNA turnover, translational repression, and transcription. We have studied the ubiquitylation module of the yeast Ccr4-Not complex and addressed how E3 ligase binds cognate E2 and how it is tethered to the complex. The 2.8-Å resolution crystal structure of the N-terminal RING domain of Not4 in complex with Ubc4 shows the detailed interactions of this E3-E2 complex. The 3.6-Å resolution crystal structure of the C-terminal domain of the yeast Not4 in complex with the C-terminal domain of Not1 reveals how a largely extended region at the C-terminus of Not4 wraps around a HEAT-repeat region of Not1. This C-terminal region of Not4 is only partly conserved in metazoans, rationalizing its weaker Not1-binding properties. The structural and biochemical data show how Not1 can incorporate both the ubiquitylation module and the Not2-Not3/5 module concomitantly in the Ccr4-Not complex.
Ccr4-Not复合物在多个水平上调节真核基因表达，包括mRNA周转、翻译抑制和转录。我们研究了酵母Ccr4-Not复合物的泛素化模块，并探讨了E3连接酶如何结合同源E2以及它如何与复合物相连。Not4的N端RING结构域与Ubc4形成复合物的2.8 Å分辨率晶体结构展示了该E3-E2复合物的详细相互作用。酵母Not4的C端结构域与Not1的C端结构域形成复合物的3.6 Å分辨率晶体结构揭示了Not4 C端的一个很大的延伸区域如何围绕Not1的HEAT重复区域。Not4的这个C端区域在后生动物中仅部分保守，这解释了其与Not1结合较弱的特性。结构和生化数据表明Not1如何在Ccr4-Not复合物中同时整合泛素化模块和Not2-Not3/5模块。
