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Genetics of a-agglutunin function in Saccharomyces cerevisiae
H de Nobel1, J Pike, P N Lipke
1Department of Microbiology and Molecular Genetics, University of Vermont, College of Medicine 05405-0068, USA.
Molecular & General Genetics : MGG
|May 20, 1995
Summary
Investigating Saccharomyces cerevisiae cell adhesion, this study identifies a new mutation affecting a-agglutinin function. The La199 mutant reveals a complex genetic interaction impacting Aga2p secretion and cell agglutination.
Area of Science:
- Molecular and Cellular Biology
- Yeast Genetics
- Protein Interactions
Background:
- The Saccharomyces cerevisiae cell adhesion protein, a-agglutinin, is crucial for mating and is composed of anchorage (Aga1p) and adhesion (Aga2p) subunits.
- Functional a-agglutinin is typically expressed in 'a' cells, but AGA1 RNA is found in both 'a' and 'alpha' cells post-pheromone induction.
- Alpha cells express the anchorage subunit (Aga1p), enabling agglutination, though Aga1p's role in alpha cells remains unclear.
Purpose of the Study:
- To investigate the genetic basis of cell adhesion defects in Saccharomyces cerevisiae.
- To characterize a novel mutant (La199) exhibiting an agglutination defect.
- To elucidate the function of the AGA2 gene and its role in a-agglutinin assembly and secretion.
Main Methods:
- Genetic analysis of Saccharomyces cerevisiae mutants, including complementation tests and linkage analysis.
- Gene cloning and sequencing to identify mutations.
- Plasmid-based expression of AGA2 under the control of the PGK promoter.
- Phenotypic analysis of cell agglutination and Aga2p secretion.
Main Results:
- A single mutant, La199, was initially considered a candidate for an aga2 mutant but failed to complement known aga2 mutations.
- Expression of AGA2 from a plasmid complemented defects in control strains but not in La199, suggesting additional mutations.
- The La199 mutation was tightly linked to aga2::URA3, and the cloned AGA2 gene from La199 contained an ochre mutation.
- Further analysis revealed additional mutations in La199 that reduced the expression of plasmid-borne genes, explaining the lack of complementation.
Conclusions:
- The La199 mutant harbors multiple mutations, including a non-functional allele of AGA2 and other mutations affecting gene expression.
- These findings highlight the complex genetic regulation of a-agglutinin function and secretion in Saccharomyces cerevisiae.
- The study refines our understanding of the AGA2 gene and its requirement for cell adhesion.