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Delayed rRNA processing results in significant ribosome biogenesis and functional defects
Arturas Meskauskas1, Jennifer L Baxter, Edward A Carr
1Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, Maryland 20742, USA.
Abstract:
mof6-1 was originally isolated as a recessive mutation in Saccharomyces cerevisiae which promoted increased efficiencies of programmed -1 ribosomal frameshifting and rendered cells unable to maintain the killer virus. Here, we demonstrate that mof6-1 is a unique allele of the histone deacetylase RPD3, that the deacetylase function of Rpd3p is required for controlling wild-type levels of frameshifting and virus maintenance, and that the closest human homolog can fully complement these defects. Loss of the Rpd3p-associated histone deacetylase function, either by mutants of rpd3 or loss of the associated gene product Sin3p or Sap30p, results in a delay in rRNA processing rather than in an rRNA transcriptional defect. This results in production of ribosomes having lower affinities for aminoacyl-tRNA and diminished peptidyltransferase activities. We hypothesize that decreased rates of peptidyl transfer allow ribosomes with both A and P sites occupied by tRNAs to pause for longer periods of time at -1 frameshift signals, promoting increased programmed -1 ribosomal frameshifting efficiencies and subsequent loss of the killer virus. The frameshifting defect is accentuated when the demand for ribosomes is highest, suggesting that rRNA posttranscriptional modification is the bottleneck in ribosome biogenesis.
Insights
The histone deacetylase RPD3 controls ribosomal frameshifting and virus stability in yeast. Its loss causes ribosome defects, increasing frameshifting and impacting virus maintenance.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- The mof6-1 mutation in Saccharomyces cerevisiae affects programmed -1 ribosomal frameshifting and killer virus maintenance.
- Histone deacetylases play crucial roles in gene regulation and cellular processes.
Purpose of the Study:
- To identify the gene responsible for the mof6-1 mutation.
- To elucidate the role of histone deacetylase RPD3 in ribosomal frameshifting and virus maintenance.
- To investigate the mechanism by which RPD3 influences ribosome function.
Main Methods:
- Genetic analysis of the mof6-1 mutation in yeast.
- Complementation studies using the human homolog of RPD3.
- Analysis of rRNA processing and ribosome activity in wild-type and mutant strains.
Main Results:
- The mof6-1 mutation is an allele of the histone deacetylase gene RPD3.
- RPD3's deacetylase function is essential for normal ribosomal frameshifting and killer virus stability.
- Loss of RPD3 function leads to delayed rRNA processing, producing ribosomes with altered tRNA affinities and reduced peptidyltransferase activity.
- The human homolog of RPD3 can rescue these yeast defects.
Conclusions:
- RPD3-mediated histone deacetylation is critical for proper ribosome biogenesis and function.
- Defects in rRNA processing and ribosome activity underlie the increased frameshifting efficiencies observed in rpd3 mutants.
- These findings highlight a conserved role for histone deacetylases in regulating translation fidelity and viral stability.