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EMBO J. 2006 Dec 13;25(24):5742-53. Epub 2006 Nov 30.

hRpn13/ADRM1/GP110 is a novel proteasome subunit that binds the deubiquitinating enzyme, UCH37.

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  • 1National Laboratory of Medical Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Tsinghua University, 5 Dongdan Santiao, Beijing, China. xbqiu@yahoo.com

Abstract

The 26S proteasome catalyzes the degradation of most proteins in mammalian cells. To better define its composition and associated regulatory proteins, we developed affinity methods to rapidly purify 26S proteasomes from mammalian cells. By this approach, we discovered a novel 46-kDa (407 residues) subunit of its 19S regulatory complex (previously termed ADRM1 or GP110). As its N-terminal half can be incorporated into the 26S proteasome and is homologous to Rpn13, a 156-residue subunit of the 19S complex in budding yeast, we renamed it human Rpn13 (hRpn13). The C-terminal half of hRpn13 binds directly to the proteasome-associated deubiquitinating enzyme, UCH37, and enhances its isopeptidase activity. Knockdown of hRpn13 in 293T cells increases the cellular levels of ubiquitin conjugates and decreases the degradation of short-lived proteins. Surprisingly, an overproduction of hRpn13 also reduced their degradation. Furthermore, transfection of the C-terminal half of hRpn13 slows proteolysis and induces cell death, probably by acting as a dominant-negative form. Thus in human 26S proteasomes, hRpn13 appears to be important for the binding of UCH37 to the 19S complex and for efficient proteolysis.

PMID:
17139257
[PubMed - indexed for MEDLINE]
PMCID:
PMC1698896
Free PMC Article
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