Abstract
SMAD transcription factors are key intracellular transducers of TGFβ cytokines. SMADs are tightly regulated to ensure balanced cellular responses to TGFβ signals. Ubiquitylation has a key role in regulating SMAD stability and activity. Several E3 ubiquitin ligases that regulate the turnover of SMADs are known; however, proteins that prevent the ubiquitylation or cause deubiquitylation of active SMADs remain undefined. Here we demonstrate that OTUB1 is recruited to the active phospho-SMAD2/3 complex only on TGFβ induction. Further, OTUB1 has a crucial role in TGFβ-mediated gene transcription and cellular migration. OTUB1 inhibits the ubiquitylation of phospho-SMAD2/3 by binding to and inhibiting the E2 ubiquitin-conjugating enzymes independent of its catalytic activity. Consequently, depletion of OTUB1 in cells causes a rapid loss in levels of TGFβ-induced phospho-SMAD2/3, which is rescued by the proteasomal inhibitor bortezomib. Our findings uncover a signal-induced phosphorylation-dependent recruitment of OTUB1 to its target in the TGFβ pathway.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Boronic Acids / pharmacology
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Bortezomib
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Cell Line, Tumor
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Cysteine Endopeptidases / genetics*
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Cysteine Endopeptidases / metabolism
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Deubiquitinating Enzymes
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Gene Expression Regulation
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Genes, Reporter
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Green Fluorescent Proteins / genetics
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Green Fluorescent Proteins / metabolism
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Humans
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Mice
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Phosphoproteins / genetics*
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Phosphoproteins / metabolism
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Phosphorylation
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Primary Cell Culture
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Proteasome Endopeptidase Complex / metabolism
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Proteasome Inhibitors / pharmacology
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Protein Stability
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Pyrazines / pharmacology
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Signal Transduction
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Smad2 Protein / genetics*
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Smad2 Protein / metabolism
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Smad3 Protein / genetics*
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Smad3 Protein / metabolism
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Transforming Growth Factor beta / genetics*
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Transforming Growth Factor beta / metabolism
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Transforming Growth Factor beta / pharmacology
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Ubiquitin / genetics
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Ubiquitin / metabolism
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Ubiquitination
Substances
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Boronic Acids
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Phosphoproteins
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Proteasome Inhibitors
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Pyrazines
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SMAD2 protein, human
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SMAD3 protein, human
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Smad2 Protein
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Smad3 Protein
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Transforming Growth Factor beta
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Ubiquitin
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Green Fluorescent Proteins
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Bortezomib
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Deubiquitinating Enzymes
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OTUB1 protein, human
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Cysteine Endopeptidases
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Proteasome Endopeptidase Complex