Abstract
The export of mRNA from the nucleus to the cytoplasm involves interactions of proteins with mRNA and the nuclear pore complex. We isolated Crp79p, a novel mRNA export factor from the same synthetic lethal screen that led to the identification of spMex67p in Schizosaccharomyces pombe. Crp79p is a 710-amino-acid-long protein that contains three RNA recognition motif domains in tandem and a distinct C-terminus. Fused to green fluorescent protein (GFP), Crp79p localizes to the cytoplasm. Like Mex67p, Crp79-GFP binds poly(A)(+) RNA in vivo, shuttles between the nucleus and the cytoplasm, and contains a nuclear export activity at the C-terminus that is Crm1p-independent. All of these properties are essential for Crp79p to promote mRNA export. Crp79p import into the nucleus depends on the Ran system. A domain of spMex67p previously identified as having a nuclear export activity can functionally substitute for the nuclear export activity at the C-terminus of Crp79p. Although both Crp79p and spMex67p function to export mRNA, Crp79p does not substitute for all of spMex67p functions and probably is not a functional homologue of spMex67p. We propose that Crp79p is a nonessential mRNA export carrier in S. pombe.
MeSH terms
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Active Transport, Cell Nucleus / physiology*
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Amino Acid Sequence
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Genes, Reporter
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Green Fluorescent Proteins
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HeLa Cells
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Humans
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Indicators and Reagents / metabolism
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Luminescent Proteins / genetics
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Luminescent Proteins / metabolism
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Molecular Sequence Data
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Nuclear Proteins / chemistry
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Nuclear Proteins / genetics
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Nuclear Proteins / metabolism*
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Nucleocytoplasmic Transport Proteins / chemistry
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Nucleocytoplasmic Transport Proteins / genetics
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Nucleocytoplasmic Transport Proteins / metabolism*
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RNA, Messenger / metabolism*
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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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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Saccharomyces cerevisiae Proteins / metabolism*
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Schizosaccharomyces / metabolism*
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Schizosaccharomyces pombe Proteins / chemistry
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Schizosaccharomyces pombe Proteins / genetics
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Schizosaccharomyces pombe Proteins / metabolism*
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ran GTP-Binding Protein / metabolism
Substances
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Crp79 protein, S pombe
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Indicators and Reagents
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Luminescent Proteins
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MEX67 protein, S cerevisiae
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Nuclear Proteins
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Nucleocytoplasmic Transport Proteins
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RNA, Messenger
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RNA-Binding Proteins
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Recombinant Fusion Proteins
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Saccharomyces cerevisiae Proteins
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Schizosaccharomyces pombe Proteins
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Green Fluorescent Proteins
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ran GTP-Binding Protein