Department of Biology, Graduate School of Sciences, Kyushu University, Fukuoka 812-8581, Japan.
Mol Biol Cell. 2010 Mar 15;21(6):905-13. doi: 10.1091/mbc.e09-11-0974. Epub 2010 Jan 20.
Emi2 (also called Erp1) inhibits the anaphase-promoting complex/cyclosome (APC/C) and thereby causes metaphase II arrest in unfertilized vertebrate eggs. Both the D-box and the zinc-binding region (ZBR) of Emi2 have been implicated in APC/C inhibition. However, it is not well known how Emi2 interacts with and hence inhibits the APC/C. Here we show that Emi2 binds the APC/C via the C-terminal tail, termed here the RL tail. When expressed in Xenopus oocytes and egg extracts, Emi2 lacking the RL tail fails to interact with and inhibit the APC/C. The RL tail itself can directly bind to the APC/C, and, when added to egg extracts, either an excess of RL tail peptides or anti-RL tail peptide antibody can dissociate endogenous Emi2 from the APC/C, thus allowing APC/C activation. Furthermore, and importantly, the RL tail-mediated binding apparently promotes the inhibitory interactions of the D-box and the ZBR (of Emi2) with the APC/C. Finally, Emi1, a somatic paralog of Emi2, also has a functionally similar RL tail. We propose that the RL tail of Emi1/Emi2 serves as a docking site for the APC/C, thereby promoting the interaction and inhibition of the APC/C by the D-box and the ZBR.
Emi2（也称为 Erp1）抑制后期促进复合物/细胞周期蛋白（APC/C），从而导致未受精卵的中期 II 期阻滞。Emi2 的 D 盒和锌结合区（ZBR）都被认为参与 APC/C 抑制。然而，Emi2 如何与 APC/C 相互作用并抑制 APC/C 尚不清楚。在这里，我们显示 Emi2 通过称为 RL 尾巴的 C 末端尾巴与 APC/C 结合。当在非洲爪蟾卵母细胞和卵提取物中表达时，缺乏 RL 尾巴的 Emi2 无法与 APC/C 相互作用并抑制 APC/C。RL 尾巴本身可以直接与 APC/C 结合，并且当添加到卵提取物中时，过量的 RL 尾巴肽或抗 RL 尾巴肽抗体可以将内源性 Emi2 从 APC/C 上解离，从而允许 APC/C 激活。此外，重要的是，RL 尾巴介导的结合显然促进了 Emi2 的 D 盒和 ZBR（的）与 APC/C 的抑制相互作用。最后，Emi1，Emi2 的体细胞同源物，也具有功能上类似的 RL 尾巴。我们提出 Emi1/Emi2 的 RL 尾巴作为 APC/C 的 docking 位点，从而促进 D 盒和 ZBR 与 APC/C 的相互作用和抑制。
