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Interactions between chromosomal omnipotent suppressors and extrachromosomal effectors in Saccharomyces cerevisiae
B Ono1, Y O Chernoff, Y Ishino-Arao
1Laboratory of Environmental Hygiene Chemistry, Faculty of Pharmaceutical Sciences, Okayama University, Japan.
Abstract:
Chromosomal omnipotent suppressor mutations recovered in psi+ strains of Saccharomyces cerevisiae were brought into psi- cytoplasm. SUP46, SUP138 and SUP139 acted as dominant omnipotent suppressors in the psi- cytoplasm though their suppressor activity was substantially reduced. SUP46 and SUP138 conferred recessive thermosensitivity and antibiotic sensitivity in psi- cytoplasm as in psi+ cytoplasm. On the other hand, sup111 through sup115, which acted as recessive omnipotent suppressors in the psi+ cytoplasm, manifested no, or very low, suppressor activity in the psi- cytoplasm. They, however, still enhanced the efficiency of the SUP29 tRNA suppressor in psi- cytoplasm. A multicopy plasmid carrying the wild-type SUP35 gene enhanced the efficiency of sup111 in psi- cytoplasm.
Insights
Omnipotent suppressor mutations in Saccharomyces cerevisiae show varied activity in different cytoplasmic states. Some mutations retain function in psi- cytoplasm, while others require psi+ for full suppressor activity.
Area of Science:
- Genetics
- Molecular Biology
- Yeast Genetics
Background:
- The psi+ factor in Saccharomyces cerevisiae is a prion influencing translation fidelity.
- Omnipotent suppressors are mutations that can suppress a wide range of nonsense mutations.
- Understanding suppressor mutations' behavior in different cytoplasmic states (psi+ vs. psi-) is crucial for genetic analysis.
Purpose of the Study:
- To investigate the behavior and activity of previously identified omnipotent suppressor mutations when transferred from psi+ to psi- cytoplasm in Saccharomyces cerevisiae.
- To determine if suppressor activity is dependent on the presence of the psi+ factor.
Main Methods:
- Introduction of chromosomal omnipotent suppressor mutations (SUP46, SUP138, SUP139, sup111-sup115) into psi- Saccharomyces cerevisiae strains.
- Assessment of suppressor activity in the psi- cytoplasm.
- Evaluation of associated phenotypes like thermosensitivity and antibiotic sensitivity.
- Complementation studies using a multicopy plasmid with the wild-type SUP35 gene.
Main Results:
- SUP46, SUP138, and SUP139 exhibited reduced but still present dominant suppressor activity in psi- cytoplasm.
- SUP46 and SUP138 retained recessive thermosensitivity and antibiotic sensitivity in psi- cytoplasm.
- Recessive omnipotent suppressors (sup111-sup115) showed little to no activity in psi- cytoplasm.
- sup111-sup115 enhanced the efficiency of the SUP29 tRNA suppressor in psi- cytoplasm.
- Wild-type SUP35 gene on a multicopy plasmid enhanced sup111 efficiency in psi- cytoplasm.
Conclusions:
- The activity of omnipotent suppressors in Saccharomyces cerevisiae is influenced by the cytoplasmic psi state.
- Dominant suppressors show partial function in psi- cytoplasm, while recessive suppressors are largely dependent on psi+.
- The SUP35 gene plays a role in mediating the function of certain recessive suppressors, even in the absence of the psi+ prion.