title: Targeting of NEDD8 and its conjugates for proteasomal degradation by NUB1.
abstract: NEDD8 is a ubiquitin-like protein that controls vital biological events through its conjugation to cullin family members. Recently, we identified a negative regulator of the NEDD8 conjugation system, NUB1, which interacts with NEDD8 and down-regulates NEDD8 expression post-transcriptionally (Kito, K., Yeh, E. T. H., and Kamitani, T. (2001) J. Biol. Chem. 276, 20603-20609). Here, we show that NUB1 possesses a ubiquitin-like domain at the N-terminal region and binds to S5a of the 19 S proteasome activator (PA700). A GST pull-down assay revealed that the overexpression of NUB1 leads to a greater precipitation of NEDD8 conjugates with GST-S5a, suggesting that NUB1 might have an adaptor function between S5a and NEDD8. Furthermore, proteasome inhibitors completely block NUB1-mediated down-regulation of NEDD8 expression. These results suggest that NUB1 recruits NEDD8 and its conjugates to the proteasome for degradation, providing a direct functional link between the NEDD8 conjugation system and the proteasomal degradation pathway.
authors.affiliation: Department of Cardiology, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030, USA. tkamitani@mdanderson.org
authors.forename: T
authors.initials: T
authors.lastname: Kamitani
authors.forename: K
authors.initials: K
authors.lastname: Kito
authors.forename: T
authors.initials: T
authors.lastname: Fukuda-Kamitani
authors.forename: E T
authors.initials: ET
authors.lastname: Yeh
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D009097:Multienzyme Complexes / Q000378:metabolism*; D000075687:NEDD8 Protein; D046988:Proteasome Endopeptidase Complex; D011485:Protein Binding; D014157:Transcription Factors / Q000302:isolation & purification / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014452:Ubiquitins / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D009097:Multienzyme Complexes; D000075687:NEDD8 Protein; C082860:NEDD8 protein, human; C430242:NUB1 protein, human; D014157:Transcription Factors; D014452:Ubiquitins; D005982:Glutathione Transferase; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex