title: The minimal deneddylase core of the COP9 signalosome excludes the Csn6 MPN- domain.
abstract: The COP9 signalosome (CSN) is a eukaryotic protein complex, which regulates a wide range of biological processes mainly through modulating the cullin ubiquitin E3 ligases in the ubiquitin-proteasome pathway. The CSN possesses a highly conserved deneddylase activity that centers at the JAMM motif of the Csn5 subunit but requires other subunits in a complex assembly. The classic CSN is composed of 8 subunits (Csn1-8), yet in several Ascomycota, the complex is smaller and lacks orthologs for a few CSN subunits, but nevertheless contains a conserved Csn5. This feature makes yeast a powerful model to determine the minimal assemblage required for deneddylation activity. Here we report, that Csi1, a diverged S. cerevisiae CSN subunit, displays significant homology with the carboxyl terminal domain of the canonical Csn6, but lacks the amino terminal MPN(-) domain. Through the comparative and experimental analyses of the budding yeast and the mammalian CSNs, we demonstrate that the MPN(-) domain of the canonical mouse Csn6 is not part of the CSN deneddylase core. We also show that the carboxyl domain of Csn6 has an indispensable role in maintaining the integrity of the CSN complex. The CSN complex assembled with the carboxyl fragment of Csn6, despite its lack of an MPN(-) domain, is fully active in deneddylation of cullins. We propose that the budding yeast Csi1 is a functional equivalent of the canonical Csn6, and thus the composition of the CSN across phyla is more conserved than hitherto appreciated.
authors.affiliation: Department of Biology, University of Haifa at Oranim, Tivon, Israel. elahpic@research.haifa.ac.il
authors.forename: Elah
authors.initials: E
authors.lastname: Pick
authors.forename: Amnon
authors.initials: A
authors.lastname: Golan
authors.forename: Jacob Z
authors.initials: JZ
authors.lastname: Zimbler
authors.forename: Liquan
authors.initials: L
authors.lastname: Guo
authors.forename: Yehonatan
authors.initials: Y
authors.lastname: Sharaby
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Tsuge
authors.forename: Kay
authors.initials: K
authors.lastname: Hofmann
authors.forename: Ning
authors.initials: N
authors.lastname: Wei
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000075686:COP9 Signalosome Complex; D017124:Conserved Sequence; D044842:Cullin Proteins / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000378:metabolism*; D016296:Mutagenesis; D010447:Peptide Hydrolases / Q000378:metabolism*; D011485:Protein Binding; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D059748:Proteolysis; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D020798:Two-Hybrid System Techniques
chemical_list: C577560:Csi1 protein, S cerevisiae; D044842:Cullin Proteins; D046912:Multiprotein Complexes; D029701:Saccharomyces cerevisiae Proteins; D010447:Peptide Hydrolases; D000075686:COP9 Signalosome Complex