Abstract
The RNA-binding protein HuR affects cell fate by regulating the stability and/or the translation of messenger RNAs that encode cell stress response proteins. In this study, we delineate a novel regulatory mechanism by which HuR contributes to stress-induced cell death. Upon lethal stress, HuR translocates into the cytoplasm by a mechanism involving its association with the apoptosome activator pp32/PHAP-I. Depleting the expression of pp32/PHAP-I by RNA interference reduces both HuR cytoplasmic accumulation and the efficiency of caspase activation. In the cytoplasm, HuR undergoes caspase-mediated cleavage at aspartate 226. This cleavage activity is significantly reduced in the absence of pp32/PHAP-I. Substituting aspartate 226 with an alanine creates a noncleavable isoform of HuR that, when overexpressed, maintains its association with pp32/PHAP-I and delays the apoptotic response. Thus, we propose a model in which HuR association with pp32/PHAP-I and its caspase-mediated cleavage constitutes a regulatory step that contributes to an amplified apoptotic response.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Antigens, Surface / chemistry
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Antigens, Surface / genetics
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Antigens, Surface / metabolism*
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Apoptosis* / drug effects
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Apoptosomes / physiology
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Binding Sites
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Caspases / metabolism*
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ELAV Proteins
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ELAV-Like Protein 1
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Enzyme Activation
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HeLa Cells
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Humans
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Intracellular Signaling Peptides and Proteins / metabolism
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Intracellular Signaling Peptides and Proteins / physiology*
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Models, Biological
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Mutagenesis, Site-Directed
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Nuclear Proteins / metabolism
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Nuclear Proteins / physiology*
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Phosphoproteins / metabolism
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Phosphoproteins / physiology
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Protein Isoforms / metabolism
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Protein Structure, Tertiary
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RNA Interference
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RNA-Binding Proteins / chemistry
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RNA-Binding Proteins / genetics
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RNA-Binding Proteins / metabolism*
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Staurosporine / pharmacology
Substances
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ANP32A protein, human
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Antigens, Surface
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Apoptosomes
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ELAV Proteins
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ELAV-Like Protein 1
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ELAVL1 protein, human
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Intracellular Signaling Peptides and Proteins
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Nuclear Proteins
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Phosphoproteins
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Protein Isoforms
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RNA-Binding Proteins
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Caspases
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Staurosporine