Directionality of yeast mating-type interconversion

Klar, A. J. S., Hicks, J. B., Strathern, J. N. (1982) Directionality of yeast mating-type interconversion. Cell, 28 (3). pp. 551-561. ISSN 00928674 (ISSN)



The mating-type a and α alleles of the yeast Saccharomyces cerevisiae interconvert by a transposition-substitution reaction where replicas of the silent mating loci, at HML and HMR, are transmitted to the expressed mating-type locus (MAT). HML is on the left arm and HMR on the right arm, while MAT is in the middle of chromosome III. Cells with the genotype HMLα HMRa switch mating type efficiently at a frequency of about 86%. Since well over 50% of the cells switch, it is thought that switches do not occur randomly, but are directed to occur to the opposite mating-type allele. In contrast, we report that strains possessing the reverse HMLa HMRα arrangement switch (phenotype) inefficiently at a maximum of about 6%. The basis for this apparent reduced frequency of switching is that these strains preferentially yield futile homologous MAT locus switches-that is, MATa to MATa and MATα to MATα-and consequently, most of these events are undetected. We used genetically marked HM loci to demonstrate that a cells preferentially choose HMR as donor and a cells preferentially choose HML as donor, irrespective of the genetic content of the silent loci. Because of this feature, HMLα HMRa strains generate predominantly heterologous while HMLa HMRα strains produce predominantly homologous MAT switches. The control for directionality of switching therefore is not at the level of transposing heterologous mating-type information, but only at the level of choosing HML versus HMR as the donor. In strains where the preferred donor locus is deleted, the Inefficient donor becomes capable of donating efficiently. Thus the preference seems to be mediated by competition between the HM loci for donating information to MAT. © 1982.

Item Type: Paper
Uncontrolled Keywords: allele article biological model cell division fungus spore gene expression regulation genetic recombination genetics genotype pedigree reproduction Saccharomyces cerevisiae Alleles Models, Genetic Recombination, Genetic Spores, Fungal Support, U.S. Gov't, P.H.S.
Subjects: organism description > yeast
CSHL Authors:
Communities: CSHL labs > Hicks lab
Depositing User: Matt Covey
Date: 1982
Date Deposited: 09 Aug 2013 20:56
Last Modified: 12 Aug 2013 14:25
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