title: A novel protein complex involved in signal transduction possessing similarities to 26S proteasome subunits.
abstract: A novel protein complex has been identified in human cells that has a molecular mass of approximately 450 kDa. It consists of at least eight different subunits including JAB1, the Jun activation-domain binding protein 1, and Trip15, the thyroid hormone receptor-interacting protein 15. The purified complex contains COP9 and COP11 protein homologs and is very similar, if not identical, to the plant COP9 complex involved in light-mediated signal transduction. The isolated JAB1-containing particle has kinase activity that phosphorylates IkappaBalpha, the carboxy terminus of p105, and Ser63 and/or Ser73 of the amino-terminal activation domain of c-Jun. The phosphorylation of c-Jun requires the carboxy terminus of the protein containing the DNA binding and dimerization domains. Three subunits of the new complex--Sgn3, Sgn5/JAB1, and Sgn6--exhibit sequence similarities to regulatory components of the 26S proteasome, which could indicate the existence of common substrate binding sites. Immunofluorescence staining reveals that the new complex shows a subcellular distribution similar to that of the 26S proteasome. The functional relationship of the two particles in regulating transcriptional activity is discussed. Considering the putative role of the complex in signal transduction and its widespread occurrence, we suggest the name JAB1-containing signalosome.
authors.affiliation: Institute of Biochemistry, Humboldt-University, Medical Faculty (Charité), Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Seeger
authors.forename: R
authors.initials: R
authors.lastname: Kraft
authors.forename: K
authors.initials: K
authors.lastname: Ferrell
authors.forename: D
authors.initials: D
authors.lastname: Bech-Otschir
authors.forename: R
authors.initials: R
authors.lastname: Dumdey
authors.forename: R
authors.initials: R
authors.lastname: Schade
authors.forename: C
authors.initials: C
authors.lastname: Gordon
authors.forename: M
authors.initials: M
authors.lastname: Naumann
authors.forename: W
authors.initials: W
authors.lastname: Dubiel
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D000075686:COP9 Signalosome Complex; D003001:Cloning, Molecular; D003546:Cysteine Endopeptidases / Q000737:chemistry / Q000378:metabolism*; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism*; D009687:Nuclear Proteins; D010447:Peptide Hydrolases; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013347:Subcellular Fractions / Q000201:enzymology / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D046911:Macromolecular Substances; D009097:Multienzyme Complexes; D009687:Nuclear Proteins; D011506:Proteins; D016755:Proto-Oncogene Proteins c-jun; D014157:Transcription Factors; D011494:Protein Kinases; D010447:Peptide Hydrolases; C501488:COPS5 protein, human; D000075686:COP9 Signalosome Complex; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex