Characterization of two subunits of Arabidopsis 19S proteasome regulatory complex and its possible interaction with the COP9 complex

• Published in: Journal of molecular biology 1999-01, Vol.285 (1), p.85-95
• Main Authors: Kwok, S.F, Staub, J.M, Deng, X.W
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphatases - genetics; Amino Acid Sequence; amino acid sequences; Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis Proteins; Arabidopsis thaliana; binding proteins; binding sites; Cell Nucleus; Chromosome Mapping; complementary DNA; COP9 Signalosome Complex; Cysteine Endopeptidases - metabolism; genbank/af083890; Gene Dosage; GTP-Binding Proteins; Humans; immunocytochemistry; interactions; Intracellular Signaling Peptides and Proteins; Molecular Sequence Data; Multienzyme Complexes - metabolism; Multiprotein Complexes; nuclei; Nucleic Acid Hybridization; nucleotide sequences; open reading frames; Peptide Hydrolases; Plant Proteins - metabolism; polypeptides; Precipitin Tests; Proteasome Endopeptidase Complex; proteinases; Proteins - metabolism; Repressor Proteins; Sequence Homology, Amino Acid; Yeasts
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1006/jmbi.1998.2315

The nuclear localized, multi-subunit COP9 complex (or COP9 signalosome) is a key developmental modulator involved in repression of photomorphogenesis. In an effort to further define the molecular actions of the COP9 complex, a yeast two hybrid interactive screen was undertaken to identify proteins that could directly interact with one subunit of this complex, namely FUS6/COP11. This screen identified one specific interactive protein, AtS9, that is likely the Arabidopsis non-ATPase S9 (subunit 9) of the 19S regulatory complex from the 26S proteasome. AtS9 specifically interacts with FUS6/COP11 via the C-terminal domain of FUS6/COP11, which is distinct from the N-terminal domain necessary for FUS6/COP11 to interact with itself. As anticipated, AtS9 is not a member of the COP9 complex, but tightly associates with an ATPase subunit of the Arabidopsis 19S proteasome regulatory complex, AtS6A. Since all three proteins, FUS6/COP11, AtS9, and AtS6A, are present as complexed forms in vivo, the observed interaction implies that the COP9 complex may directly interact with the 19S regulatory complex of the 26S proteasome or other potential AtS9-containing complex. This notion is consistent with the parallel tissue-specific expression patterns and the similar, predominantly nuclear localization of both the COP9 complex and the AtS9 protein.