title: Emi2 inhibition of the anaphase-promoting complex/cyclosome absolutely requires Emi2 binding via the C-terminal RL tail.
abstract: 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.
authors.affiliation: Department of Biology, Graduate School of Sciences, Kyushu University, Fukuoka 812-8581, Japan.
authors.forename: Munemichi
authors.initials: M
authors.lastname: Ohe
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Kawamura
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ueno
authors.forename: Daigo
authors.initials: D
authors.lastname: Inoue
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Kanemori
authors.forename: Chiharu
authors.initials: C
authors.lastname: Senoo
authors.forename: Michitaka
authors.initials: M
authors.lastname: Isoda
authors.forename: Nobushige
authors.initials: N
authors.lastname: Nakajo
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Sagata
mesh_terms: D000595:Amino Acid Sequence; D064173:Anaphase-Promoting Complex-Cyclosome; D000818:Animals; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D044783:F-Box Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008540:Meiosis / Q000502:physiology; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D043743:Ubiquitin-Protein Ligase Complexes / Q000037:antagonists & inhibitors*; D029867:Xenopus Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D044783:F-Box Proteins; C498166:FBXO43 protein, Xenopus; C429107:FBXO5 protein, Xenopus; D029867:Xenopus Proteins; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome