Abstract
NIPP1 is a ubiquitous regulator of protein phosphatase-1 (PP1) and is targeted to the splicing factor storage sites (speckles) in the nucleus by its forkhead-associated domain. We show here that NIPP1 is also a component of the spliceosomes in HeLa cell-splicing extracts and that the interaction with the spliceosomes requires a functional forkhead-associated domain. The in vitro splicing of beta-globin pre-mRNA was not affected by exogenous wild type NIPP1 but was blocked by mutants that lacked residues 225-329. The inhibition by these dominant negative mutants resulted from a block in a late phase of spliceosome assembly, i.e. at the transition between the B-complex and the C-complex. Site-directed mutagenesis furthermore showed that this spliceosomal function of NIPP1 was unrelated to its ability to bind PP1 or RNA. Our data suggest that NIPP1 can function independently as a splicing factor and a phosphatase regulator.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Alternative Splicing
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Carrier Proteins*
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Cell Nucleus / metabolism
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Dose-Response Relationship, Drug
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Endoribonucleases*
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Enzyme Inhibitors / pharmacology
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Globins / metabolism
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HeLa Cells
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Humans
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Intracellular Signaling Peptides and Proteins*
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Models, Biological
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Mutagenesis, Site-Directed
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Okadaic Acid / pharmacology
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Phosphoprotein Phosphatases
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Protein Binding
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Protein Phosphatase 1
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RNA Splicing*
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RNA, Messenger / metabolism
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RNA-Binding Proteins / metabolism*
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RNA-Binding Proteins / physiology*
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Recombinant Proteins / metabolism
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Spliceosomes / physiology*
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Temperature
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Time Factors
Substances
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Carrier Proteins
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Enzyme Inhibitors
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Intracellular Signaling Peptides and Proteins
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RNA, Messenger
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RNA-Binding Proteins
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Recombinant Proteins
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protein phosphatase inhibitor-1
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Okadaic Acid
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Globins
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Endoribonucleases
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Phosphoprotein Phosphatases
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Protein Phosphatase 1
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PPP1R8 protein, human