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Updated: Aug 16, 2026
A Deep-sequencing-assisted, Spontaneous Suppressor Screen in the Fission Yeast Schizosaccharomyces pombe
Published on: March 7, 2019
Suppressors of the ras2 mutation of Saccharomyces cerevisiae
Abstract:
Saccharomyces cerevisiae contains two members of the ras gene family. Strains with disruptions of the RAS2 gene fail to grow efficiently on nonfermentable carbon sources. This growth defect can be suppressed by extragenic mutations called sra. We have isolated 79 independent suppressor mutations, 68 of which have been assigned to one of five loci. Eleven additional dominant mutations have not been assigned to a specific locus. Some sra1 and SRA4 and all SRA3 mutations were RAS independent, allowing growth of yeast cells that lack a functional RAS gene. Mutations in sra1, SRA3, SRA4 and sra6 are linked to his6, ino1, met3 and ade6, respectively. Some sra mutants have pleiotropic phenotypes that affect glycogen accumulation, sporulation, viability, respiratory capacity and suppression of two cell-division-cycle mutations, cdc25 and cdc35. The proposed functions of many of the suppressor genes are consistent with the model in which RAS activates adenylate cyclase.
Insights
Disruptions in the RAS2 gene of Saccharomyces cerevisiae hinder growth on certain nutrients. Extragenic suppressor of RAS (sra) mutations were identified to restore this growth defect, revealing insights into RAS signaling.
Area of Science:
- * Molecular Biology
- * Yeast Genetics
- * Cellular Signaling
Background:
- * Saccharomyces cerevisiae possesses two RAS genes, RAS1 and RAS2.
- * Disruptions in the RAS2 gene lead to impaired growth on nonfermentable carbon sources.
- * Extragenic mutations, termed suppressors of RAS (sra), can rescue this growth defect.
Purpose of the Study:
- * To isolate and characterize extragenic suppressor mutations (sra) that restore growth in RAS2-deficient yeast.
- * To investigate the genetic loci and functional roles of these suppressor mutations.
- * To further elucidate the RAS signaling pathway in yeast.
Main Methods:
- * Isolation and characterization of 79 independent suppressor mutations in Saccharomyces cerevisiae.
- * Genetic mapping of mutations to identify suppressor loci.
- * Analysis of suppressor phenotypes, including RAS independence and pleiotropic effects.
Main Results:
- * 79 suppressor mutations were isolated, with 68 assigned to five loci (sra1-sra6) and 11 unassigned dominant mutations.
- * Certain mutations (in sra1, SRA3, SRA4) conferred RAS independence, enabling growth in the absence of functional RAS genes.
- * Mutations exhibited pleiotropic effects on glycogen accumulation, sporulation, viability, respiration, and cell-division-cycle gene suppression (cdc25, cdc35).
Conclusions:
- * The identified suppressor mutations provide valuable tools for studying RAS function in yeast.
- * The diverse phenotypes associated with sra mutants suggest complex roles for RAS signaling in cellular processes.
- * Findings support the model where RAS proteins activate adenylate cyclase, influencing downstream pathways.
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