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The MBR1 gene from Saccharomyces cerevisiae is activated by and required for growth under sub-optimal conditions
P Reisdorf1, E Boy-Marcotte, M Bolotin-Fukuhara
1Institut de Génétique et Microbiologie, URA CNRS D1354, Université Paris-Sud, Orsay, France.
Abstract:
The MBR1 gene was isolated as a multicopy suppressor of the phenotype on glycerol medium of a Saccharomyces cerevisiae strain mutant for the Hap2/3/4/5 transactivator complex. In this paper, we show that Mbr1p is a limiting factor for growth on glycerol medium under the following sub-optimal culture conditions: in late growth phase, at low temperature, at high external pH or in the presence of 1,10-phenanthroline. Moreover, deletion of MBR1 protects cells against stress, whilst overexpression of this gene has the opposite effect. MBR1 expression is induced in the late growth phase and is negatively controlled by the cAMP-dependent protein kinase A (PKA). Both activation of PKA or overexpression of SOK1 or SCH9-two genes isolated as multicopy suppressors of a PKA null mutant-suppress the mbr1 growth defect. Our results indicate that Mbr1p is not an essential element of any one of these pathways. Deletion of SAC1, a gene implicated in vesicular transport, in association with MBR1 deletion, causes synthetic lethality. A possible role of Mbr1p in intracellular trafficking is discussed.
Insights
The MBR1 gene is crucial for yeast growth under stress. Deleting MBR1 enhances stress protection, while its overexpression is detrimental, suggesting a role in cellular stress response.
Area of Science:
- Molecular biology
- Yeast genetics
Background:
- The MBR1 gene was identified as a suppressor of growth defects in Saccharomyces cerevisiae lacking the Hap2/3/4/5 transactivator complex.
- Understanding MBR1's function is key to comprehending yeast's adaptation to various environmental conditions.
Purpose of the Study:
- To investigate the role of the MBR1 gene in Saccharomyces cerevisiae growth and stress response.
- To elucidate the regulatory mechanisms controlling MBR1 expression and its interaction with other cellular pathways.
Main Methods:
- Genetic analysis of MBR1 deletion and overexpression mutants.
- Phenotypic analysis under various sub-optimal growth conditions (glycerol medium, late growth phase, low temperature, high pH, 1,10-phenanthroline).
- Investigating the relationship between MBR1, protein kinase A (PKA), SOK1, SCH9, and SAC1.
Main Results:
- Mbr1p is a limiting factor for yeast growth on glycerol under stress conditions.
- MBR1 deletion confers stress protection, whereas MBR1 overexpression sensitizes cells to stress.
- MBR1 expression is induced during late growth and negatively regulated by PKA.
- MBR1 deletion exhibits synthetic lethality with SAC1 deletion, suggesting a role in intracellular trafficking.
Conclusions:
- Mbr1p plays a significant role in yeast stress response and adaptation.
- The MBR1 gene is regulated by PKA and involved in pathways beyond the Hap2/3/4/5 complex.
- Mbr1p may be implicated in intracellular trafficking pathways, as suggested by its interaction with SAC1.