title: CSN1 N-terminal-dependent activity is required for Arabidopsis development but not for Rub1/Nedd8 deconjugation of cullins: a structure-function study of CSN1 subunit of COP9 signalosome.
abstract: The COP9 signalosome (CSN) is a multifunctional protein complex essential for arabidopsis development. One of its functions is to promote Rub1/Nedd8 deconjugation from the cullin subunit of the Skp1-cullin-F-box ubiquitin ligase. Little is known about the specific role of its eight subunits in deneddylation or any of the physiological functions of CSN. In the absence of CSN1 (the fus6 mutant), arabidopsis CSN complex cannot assemble, which destabilizes multiple CSN subunits and contributes, together with the loss of CSN1, to the phenotype of fus6. To distinguish CSN1-specific functions, we attempted to rescue the complex formation with deletion or point-mutation forms of CSN1 expressed as transgenes in fus6. We show that the central domain of CSN1 is critical for complex assembly, whereas the C-terminal domain has a supporting role. By expressing the C231 fragment, which contains the structural information but lacks the presumed functional domain located at the N terminus, we have rescued the complex formation and restored the Rub1/Nedd8 deconjugation activity on cullins (fus6/C231). Nonetheless, fus6/C231 exhibits pleiotropic phenotype, including photomorphogenic defects and growth arrest at seedling stage. We conclude that CSN1 N-terminal domain is not required for the Rub1/Nedd8 deconjugation activity of cullins, but contributes to a significant aspect of CSN functions that are essential for plant development.
authors.affiliation: Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520.
authors.forename: Xiping
authors.initials: X
authors.lastname: Wang
authors.forename: Dingming
authors.initials: D
authors.lastname: Kang
authors.forename: Suhua
authors.initials: S
authors.lastname: Feng
authors.forename: Giovanna
authors.initials: G
authors.lastname: Serino
authors.forename: Claus
authors.initials: C
authors.lastname: Schwechheimer
authors.forename: Ning
authors.initials: N
authors.lastname: Wei
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins; D000075686:COP9 Signalosome Complex; D005656:Fungal Proteins / Q000502:physiology*; D019204:GTP-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes; D009154:Mutation; D010447:Peptide Hydrolases; D030821:Plants, Genetically Modified / Q000254:growth & development; D011506:Proteins / Q000235:genetics / Q000502:physiology*; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D014452:Ubiquitins
chemical_list: D029681:Arabidopsis Proteins; C086322:CSN1 protein, Arabidopsis; D005656:Fungal Proteins; C103315:GPS1 protein, human; D047908:Intracellular Signaling Peptides and Proteins; D046911:Macromolecular Substances; D046912:Multiprotein Complexes; D011506:Proteins; C111706:RUB1 protein, S cerevisiae; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D014452:Ubiquitins; D010447:Peptide Hydrolases; D000075686:COP9 Signalosome Complex; D019204:GTP-Binding Proteins