The yeast Prp3 protein is a U4/U6 snRNP protein necessary for integrity of the U4/U6 snRNP and the U4/U6.U5 tri-snRNP.
Copyright policy )The yeast Prp3 protein is a U4/U6 snRNP protein necessary for integrity of the U4/U6 snRNP and the U4/U6.U5 tri-snRNP.
Previously, yeast prp3 mutants were found to be blocked prior to the first catalytic step of pre-mRNA splicing. No splicing intermediates or products are formed from pre-mRNA in heat-inactivated prp3 mutants or prp3 mutant extracts. Here we show that Prp3p is a component of the U4/U6 snRNP and is also present in the U4/U6.U5 tri-snRNP. Heat inactivation of prp3 extracts results in depletion of free U6 snRNPs and U4/U6.U5 tri-snRNPs, but not U4/U6 snRNPs or U5 snRNPs. Free U4 snRNP, normally not present in wild-type extracts, accumulates under these conditions. Assays of in vivo levels of snRNAs in a prp3 mutant revealed that amounts of free U6 snRNA decreased, free U4 snRNA increased, and U4/U6 hybrids decreased slightly. These results suggest that Prp3p is required for formation of stable U4/U6 snRNPs and for assembly of the U4/U6.U5 tri-snRNP from its component snRNPs. Upon inactivation of Prp3p, spliceosomes cannot assemble from prespliceosomes due to the absence of intact U4/U6.U5 tri-snRNPs. Prp3p is homologous to a human protein that is a component of U4/U6 snRNPs, exemplifying the conservation of splicing factors between yeast and metazoans.
- Carnegie Mellon University United States
Saccharomyces cerevisiae Proteins, Ribonucleoprotein, U4-U6 Small Nuclear, RNA Splicing, Nuclear Proteins, Saccharomyces cerevisiae, Sodium Chloride, Blotting, Northern, Ribonucleoproteins, Small Nuclear, Precipitin Tests, Fungal Proteins, Mutation, Centrifugation, Density Gradient, RNA Precursors, Spliceosomes, Nucleic Acid Conformation, Electrophoresis, Polyacrylamide Gel, RNA, Messenger, DNA Probes
Saccharomyces cerevisiae Proteins, Ribonucleoprotein, U4-U6 Small Nuclear, RNA Splicing, Nuclear Proteins, Saccharomyces cerevisiae, Sodium Chloride, Blotting, Northern, Ribonucleoproteins, Small Nuclear, Precipitin Tests, Fungal Proteins, Mutation, Centrifugation, Density Gradient, RNA Precursors, Spliceosomes, Nucleic Acid Conformation, Electrophoresis, Polyacrylamide Gel, RNA, Messenger, DNA Probes
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