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Methyl-deficient transfer ribonucleic acid in Saccharomyces cerevisiae
Abstract:
Methyl-deficient transfer ribonucleic acid (tRNA) is found in certain methionine auxotrophs of Saccharomyces cerevisiae during logarithmic growth (at one generation time before the late growth phase) and during residual growth in the absence of exogenous methionine. The former effect seems to be accounted for by the general increase in RNA synthesis that occurs at the time; there is no specific synthesis of tRNA in the absence of ribosomal RNA synthesis, nor is the methyl group deficiency limited to a single tRNA species. During methionine starvation, all species of tRNA are methyl-deficient, but this occurs only in strains with certain blocks in the methionine pathway. The kinetics of disappearance of the methyl group donor, S-adenosylmethionine, during starvation of D73 (which accumulates methyl-deficient tRNA), do not differ from other strains, but D73 loses the methylase inhibitor, S-adenosylhomocysteine, much more slowly.
Insights
Methyl-deficient transfer RNA (tRNA) occurs in yeast under specific growth conditions and methionine starvation. This deficiency is linked to blocks in the methionine pathway and altered S-adenosylhomocysteine metabolism.
Area of Science:
- Molecular Biology
- Yeast Genetics
- Nucleic Acid Chemistry
Background:
- Methylation is crucial for transfer RNA (tRNA) function.
- Methionine auxotrophs in Saccharomyces cerevisiae exhibit altered metabolic states.
- S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) are key metabolites in methylation pathways.
Purpose of the Study:
- To investigate the occurrence and characteristics of methyl-deficient tRNA in Saccharomyces cerevisiae.
- To explore the relationship between methionine metabolism and tRNA methylation.
- To analyze the kinetics of methyl group donors and inhibitors during methionine starvation.
Main Methods:
- Analysis of tRNA methylation status in various yeast strains under different growth conditions.
- Monitoring of S-adenosylmethionine and S-adenosylhomocysteine levels during methionine starvation.
- Characterization of tRNA methyl-deficiency across different tRNA species.
Main Results:
- Methyl-deficient tRNA was observed during logarithmic growth and residual growth in methionine-starved yeast.
- The deficiency was widespread across all tRNA species during starvation in specific methionine pathway mutants.
- Strain D73, accumulating methyl-deficient tRNA, showed slower clearance of the methylase inhibitor S-adenosylhomocysteine.
Conclusions:
- Methionine metabolism and tRNA methylation are interconnected in Saccharomyces cerevisiae.
- Specific blocks in the methionine pathway contribute to widespread tRNA methyl-deficiency.
- Altered regulation of S-adenosylhomocysteine may play a role in methyl-deficient tRNA accumulation.