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A functional dominant mutation in Schizosaccharomyces pombe RNase MRP RNA affects nuclear RNA processing and requires
1Department of Developmental Biology, Stanford University School of Medicine, CA 94305-5427, USA.
Abstract:
The essential gene for RNase MRP RNA, mrp1, was identified previously in Schizosaccharomyces pombe by homology to mammalian RNase MRP RNAs. Here we describe distinct site-specific mutations in RNase MRP RNA that support a conserved role for this ribonucleoprotein in nucleolar 5.8S rRNA processing. One characterized mutation, mrp1-ND90, displays dominance and results in accumulation of unspliced precursor RNAs of dimeric tRNA(Ser)-tRNA(Met)i, suggesting a novel nuclear role for RNase MRP in tRNA processing. Cells carrying the mrp1-ND90 mutation, in the absence of a wild-type copy of mrp1, additionally require the mitochondrially associated nuclear mutation ptp1-1 for viability. Analysis of this mrp1 mutation reinforces previous biochemical evidence suggesting a role for RNase MRP in mitochondrial DNA replication. Several mutations in mrp1 result in unusual cellular morphology, including alterated nuclear organization, and are consistent with a broader nuclear role for RNase MRP in regulating a nuclear signal for septation; these results are a further indication of the multifunctional nature of this ribonucleoprotein.
Insights
Mutations in the RNase MRP RNA gene (mrp1) reveal conserved roles in rRNA processing and suggest new functions in nuclear tRNA processing and mitochondrial DNA replication in Schizosaccharomyces pombe.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- The essential gene mrp1 for RNase MRP RNA was previously identified in Schizosaccharomyces pombe.
- RNase MRP RNA is a ribonucleoprotein complex with known roles in rRNA processing.
Purpose of the Study:
- To investigate conserved roles of RNase MRP RNA in nucleolar 5.8S rRNA processing.
- To explore novel nuclear and mitochondrial functions of RNase MRP.
Main Methods:
- Site-specific mutations were introduced into the RNase MRP RNA gene (mrp1).
- Phenotypic analysis of mutant strains, including RNA accumulation and cellular morphology.
- Genetic interactions were assessed, particularly with the ptp1-1 mutation.
Main Results:
- Specific mutations in RNase MRP RNA support conserved nucleolar 5.8S rRNA processing.
- The mrp1-ND90 mutation suggests a novel nuclear role in tRNA processing, causing accumulation of precursor RNAs.
- The mrp1-ND90 mutation, combined with ptp1-1, is essential for viability, reinforcing a role in mitochondrial DNA replication.
- Other mrp1 mutations indicate a broader nuclear function in regulating cell septation and nuclear organization.
Conclusions:
- RNase MRP RNA plays conserved roles in rRNA processing.
- RNase MRP has novel nuclear functions in tRNA processing and cell cycle regulation (septation).
- RNase MRP is implicated in mitochondrial DNA replication, highlighting its multifunctional nature.