Proteasome assembly influences interaction with ubiquitinated proteins and shuttle factors.
A major fraction of intracellular protein degradation is mediated by the proteasome. Successful degradation of these substrates requires ubiquitination and delivery to the proteasome followed by protein unfolding and disassembly of the multiubiquitin chain. Enzymes, such as Rpn11, dismantle multiubiquitin chains, and mutations can affect proteasome assembly and activity. We report that different rpn11 mutations can affect proteasome interaction with ubiquitinated proteins. Moreover, proteasomes are unstable in rpn11-1 and do not form productive interactions with multiubiquitinated proteins despite high levels in cell extracts. However, increased levels of ubiquitinated proteins were found associated with shuttle factors. In contrast to rpn11-1, proteasomes expressing a catalytically inactive mutant (rpn11(AXA)) were more stable and bound very high amounts of ubiquitinated substrates. Expression of the carboxyl-terminal domain of Rpn11 partially suppressed the growth and proteasome stability defects of rpn11-1. These results indicate that ubiquitinated substrates are preferentially delivered to intact proteasome.
Chandra
Abhishek
A
Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey 08854, USA.
Chen
Li
L
Liang
Huiyan
H
Madura
Kiran
K
D000251:Adenosine Triphosphatases / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000378:metabolism; D004260:DNA Repair / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism; D010450:Endopeptidases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D018832:Molecular Chaperones / Q000378:metabolism; D016296:Mutagenesis; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*; D014452:Ubiquitins / Q000378:metabolism
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C100415:DSK2 protein, S cerevisiae; D018832:Molecular Chaperones; C490846:RAD23 protein, S cerevisiae; C115451:RPN11 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D014452:Ubiquitins; D010450:Endopeptidases; D046988:Proteasome Endopeptidase Complex; D000251:Adenosine Triphosphatases; C084493:RPT1 protein, S cerevisiae