Abstract
In response to integrin receptor binding to the extracellular matrix, the multidomain docking protein p130(cas) (Crk-associated substrate) activates various signaling cascades modulating such cellular processes as proliferation, migration, and apoptosis. During apoptosis, caspase-mediated cleavage of p130(cas) generated a C-terminal 31-kDa fragment (31-kDa) and promoted morphological changes characteristic of apoptosis, including loss of focal adhesions, cell rounding, and nuclear condensation and fragmentation. By contrast, a p130(cas) D748E mutant, which was unable to produce 31-kDa, attenuated the disassembly of focal adhesions at the bottom of the cell. 31-kDa contains a helix-loop-helix (HLH) domain that shows greater sequence homology with Id proteins than with basic HLH proteins, which enabled heterodimerization with E2A. Once coupled to E2A, 31-kDa was translocated to the cell nucleus, where it inhibited E2A-mediated p21(Waf1/Cip1) transcription. Moreover, overexpression of 31-kDa led to cell death that could be inhibited by treatment with the caspase inhibitor ZVAD-fluoromethyl ketone or by ectopic expression of E2A or p21(Waf1/Cip1). These data suggest that during etoposide-induced apoptosis, 31-kDa promotes caspase-mediated cell death by inhibiting E2A-mediated activation of p21(Waf1/Cip1) transcription.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adaptor Proteins, Vesicular Transport / chemistry
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Adaptor Proteins, Vesicular Transport / metabolism*
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Adaptor Proteins, Vesicular Transport / pharmacology
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Amino Acid Sequence
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Apoptosis / drug effects*
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Basic Helix-Loop-Helix Transcription Factors
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Biological Transport
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Caspases / metabolism*
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Cell Line
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Cell Nucleus
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Crk-Associated Substrate Protein
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Cyclin-Dependent Kinase Inhibitor p21
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Cyclins / genetics
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Cytosol / metabolism
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DNA-Binding Proteins / antagonists & inhibitors*
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DNA-Binding Proteins / genetics
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DNA-Binding Proteins / physiology
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Dimerization
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Etoposide / pharmacology
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Gene Expression
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HeLa Cells
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Helix-Loop-Helix Motifs
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Humans
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Luciferases / genetics
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Molecular Sequence Data
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Peptide Fragments / chemistry
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Peptide Fragments / metabolism
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Peptide Fragments / pharmacology*
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Phosphoproteins / chemistry
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Phosphoproteins / metabolism*
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Phosphoproteins / pharmacology
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Proteins*
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Recombinant Fusion Proteins
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Retinoblastoma-Like Protein p130
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Sequence Homology
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TCF Transcription Factors
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Transcription Factor 7-Like 1 Protein
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Transcription Factors / antagonists & inhibitors*
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Transcription Factors / genetics
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Transcription Factors / physiology
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Transcription, Genetic / drug effects*
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Transfection
Substances
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Adaptor Proteins, Vesicular Transport
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BCAR1 protein, human
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Basic Helix-Loop-Helix Transcription Factors
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CDKN1A protein, human
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Crk-Associated Substrate Protein
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Cyclin-Dependent Kinase Inhibitor p21
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Cyclins
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DNA-Binding Proteins
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Peptide Fragments
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Phosphoproteins
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Proteins
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Recombinant Fusion Proteins
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Retinoblastoma-Like Protein p130
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TCF Transcription Factors
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TCF3 protein, human
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TCF7L1 protein, human
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Transcription Factor 7-Like 1 Protein
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Transcription Factors
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Etoposide
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Luciferases
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Caspases