title: Role of individual subunits of the Neurospora crassa CSN complex in regulation of deneddylation and stability of cullin proteins.
abstract: The Cop9 signalosome (CSN) is an evolutionarily conserved multifunctional complex that controls ubiquitin-dependent protein degradation in eukaryotes. We found seven CSN subunits in Neurospora crassa in a previous study, but only one subunit, CSN-2, was functionally characterized. In this study, we created knockout mutants for the remaining individual CSN subunits in N. crassa. By phenotypic observation, we found that loss of CSN-1, CSN-2, CSN-4, CSN-5, CSN-6, or CSN-7 resulted in severe defects in growth, conidiation, and circadian rhythm; the defect severity was gene-dependent. Unexpectedly, CSN-3 knockout mutants displayed the same phenotype as wild-type N. crassa. Consistent with these phenotypic observations, deneddylation of cullin proteins in csn-1, csn-2, csn-4, csn-5, csn-6, or csn-7 mutants was dramatically impaired, while deletion of csn-3 did not cause any alteration in the neddylation/deneddylation state of cullins. We further demonstrated that CSN-1, CSN-2, CSN-4, CSN-5, CSN-6, and CSN-7, but not CSN-3, were essential for maintaining the stability of Cul1 in SCF complexes and Cul3 and BTB proteins in Cul3-BTB E3s, while five of the CSN subunits, but not CSN-3 and CSN-5, were also required for maintaining the stability of SKP-1 in SCF complexes. All seven CSN subunits were necessary for maintaining the stability of Cul4-DDB1 complexes. In addition, CSN-3 was also required for maintaining the stability of the CSN-2 subunit and FWD-1 in the SCF(FWD-1) complex. Together, these results not only provide functional insights into the different roles of individual subunits in the CSN complex, but also establish a functional framework for understanding the multiple functions of the CSN complex in biological processes.
authors.affiliation: State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, China.
authors.forename: Jiyong
authors.initials: J
authors.lastname: Wang
authors.forename: Qiwen
authors.initials: Q
authors.lastname: Hu
authors.forename: Huijie
authors.initials: H
authors.lastname: Chen
authors.forename: Zhipeng
authors.initials: Z
authors.lastname: Zhou
authors.forename: Weihua
authors.initials: W
authors.lastname: Li
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.forename: Shaojie
authors.initials: S
authors.lastname: Li
authors.forename: Qun
authors.initials: Q
authors.lastname: He
mesh_terms: D000075686:COP9 Signalosome Complex; D044842:Cullin Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009492:Neurospora crassa / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics; D010447:Peptide Hydrolases / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D055550:Protein Stability; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D044842:Cullin Proteins; D005656:Fungal Proteins; D046912:Multiprotein Complexes; D021122:Protein Subunits; D010447:Peptide Hydrolases; D000075686:COP9 Signalosome Complex