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MAR1-a Regulator of the HMa and HMalpha Loci in SACCHAROMYCES CEREVISIAE

A J Klar1, S Fogel, K Macleod

  • 1Department of Genetics, University of California Berkeley, California 94720.

Genetics
|September 1, 1979
PubMed

Insights

A mutation in the MAR1 locus of Saccharomyces cerevisiae causes sterility by preventing mating-type switching. This finding supports the cassette model of yeast mating-type determination.

Area of Science:

  • Molecular Biology
  • Genetics
  • Yeast Biology

Background:

  • The regulation of mating-type determination in Saccharomyces cerevisiae is complex, involving multiple loci.
  • The MAR1 locus is implicated in controlling mating-type expression.

Purpose of the Study:

  • To investigate the role of the MAR1 locus in yeast mating-type regulation.
  • To characterize a specific mutation, mar1-1, and its effect on sterility.

Main Methods:

  • Genetic mapping of the mar1-1 mutation on linkage group IV.
  • Analysis of haploid yeast strains with various genotypes including MAT, HMalpha, and HMa.
  • Phenotypic analysis of mating capabilities in mutant strains.

Main Results:

  • The mar1-1 mutation was mapped to linkage group IV, between trp1 and cdc2.
  • Haploid strains carrying mar1-1 exhibited sterility, but could regain mating ability with secondary mutations.
  • The MAR1 locus appears to regulate the expression of MATalpha and MATa information at the HMa and HMalpha loci.

Conclusions:

  • The MAR1 locus acts as a negative regulator of mating-type gene expression.
  • The results support the cassette model, where HM loci contain silent mating-type information.
  • The mar1-1 mutation leads to a non-mating phenotype by allowing expression of both MATa and MATalpha information simultaneously.

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