Abstract
The transcription factors p53 and E2F-1 play important roles in the control of cell cycle progression. In transient transfection experiments, expression of E2F-1, other E2F family members, or p53 squelched transcription from cotransfected plasmids in a dose-dependent manner. Although the proteasome inhibitors MG-132 and lactacystin markedly increased the level of expression of E2F-1 and p53, these inhibitors completely alleviated squelching by both proteins. Several observations indicate MG-132 alleviates squelching by influencing the conformation of newly synthesized p53 and E2F-1:MG-132 increased the fraction of wild type p53 bound by a monoclonal antibody which preferentially recognizes mutant conformers of p53, increased binding of hsp70 to p53 and inhibited nuclear accumulation of both p53 and E2F-1, but not the pocket protein p107. The protease inhibitors ALLN and ALLM did not influence expression of E2F-1 or p53, nor did they alleviate squelching by either transcription factor. Because MG-132 and lactacycstin are highly specific inhibitors of the proteasome protease, our results suggest that the proteasome influences post-translational processes involved in proper folding and cytoplasmic clearing of E2F-1 and p53.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Acetylcysteine / analogs & derivatives*
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Acetylcysteine / metabolism
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Animals
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Blotting, Northern
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CHO Cells
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Carrier Proteins*
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Cell Cycle Proteins / drug effects
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism*
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Cricetinae
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Cycloheximide / pharmacology
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Cysteine Proteinase Inhibitors / metabolism*
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Cysteine Proteinase Inhibitors / pharmacology
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DNA-Binding Proteins*
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E2F Transcription Factors
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E2F1 Transcription Factor
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Leupeptins / metabolism*
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Leupeptins / pharmacology
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Oligopeptides / pharmacology
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Protein Synthesis Inhibitors / pharmacology
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RNA, Messenger / metabolism
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Retinoblastoma-Binding Protein 1
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Transcription Factors / drug effects
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Transcription Factors / genetics
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Transcription Factors / metabolism*
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Transcription, Genetic / drug effects*
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Transcriptional Activation
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Transfection
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Tumor Suppressor Protein p53 / drug effects
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Tumor Suppressor Protein p53 / genetics
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Tumor Suppressor Protein p53 / metabolism*
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Ubiquitins / metabolism
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beta-Galactosidase / genetics
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beta-Galactosidase / metabolism
Substances
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Carrier Proteins
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Cell Cycle Proteins
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Cysteine Proteinase Inhibitors
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DNA-Binding Proteins
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E2F Transcription Factors
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E2F1 Transcription Factor
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Leupeptins
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Oligopeptides
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Protein Synthesis Inhibitors
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RNA, Messenger
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Retinoblastoma-Binding Protein 1
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Transcription Factors
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Tumor Suppressor Protein p53
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Ubiquitins
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acetylleucyl-leucyl-norleucinal
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calpain inhibitor 2
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lactacystin
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Cycloheximide
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beta-Galactosidase
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benzyloxycarbonylleucyl-leucyl-leucine aldehyde
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Acetylcysteine