title: Characterization of the last subunit of the Arabidopsis COP9 signalosome: implications for the overall structure and origin of the complex.
abstract: The COP9 signalosome (CSN) is an evolutionarily conserved protein complex that resembles the lid subcomplex of proteasomes. Through its ability to regulate specific proteasome-mediated protein degradation events, CSN controls multiple aspects of development. Here, we report the cloning and characterization of AtCSN2, the last uncharacterized CSN subunit from Arabidopsis. We show that the AtCSN2 gene corresponds to the previously identified FUS12 locus and that AtCSN2 copurifies with CSN, confirming that AtCSN2 is an integral component of CSN. AtCSN2 is not only able to interact with the SCF(TIR1) subunit AtCUL1, which is partially responsible for the regulatory interaction between CSN and SCF(TIR1), but also interacts with AtCUL3, suggesting that CSN is able to regulate the activity of other cullin-based E3 ligases through conserved interactions. Phylogenetic analysis indicated that the duplication and subsequent divergence events that led to the genes that encode CSN and lid subunits occurred before the divergence of unicellular and multicellular eukaryotic organisms and that the CSN subunits were more conserved than the lid subunits during evolution. Comparative analyses of the subunit interaction of CSN revealed a set of conserved subunit contacts and resulted in a model of CSN subunit topology, some aspects of which were substantiated by in vivo cross-link tests.
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104, USA.
authors.forename: Giovanna
authors.initials: G
authors.lastname: Serino
authors.forename: Hongwen
authors.initials: H
authors.lastname: Su
authors.forename: Zhaohua
authors.initials: Z
authors.lastname: Peng
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Tsuge
authors.forename: Ning
authors.initials: N
authors.lastname: Wei
authors.forename: Hongya
authors.initials: H
authors.lastname: Gu
authors.forename: Xing Wang
authors.initials: XW
authors.lastname: Deng
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D000075686:COP9 Signalosome Complex; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D044842:Cullin Proteins; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D019204:GTP-Binding Proteins; D018506:Gene Expression Regulation, Plant; D047908:Intracellular Signaling Peptides and Proteins; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D011485:Protein Binding; D025941:Protein Interaction Mapping; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000235:genetics*; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; C401415:COP8 protein, Arabidopsis; C086322:CSN1 protein, Arabidopsis; C474638:CSN2 protein, Arabidopsis; C445070:CSN6B protein, Arabidopsis; C503645:CUL3 protein, human; D018797:Cell Cycle Proteins; D044842:Cullin Proteins; D018076:DNA, Complementary; C103315:GPS1 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; D012097:Repressor Proteins; D000075686:COP9 Signalosome Complex; D019204:GTP-Binding Proteins