Regulation of yeast mating-type interconversion: feedback control of HO gene expression by the mating-type locus

The ultimate product of yeast mating-type interconversion is a stable a/α diploid cell. A haploid cell carrying the HO gene gives rise to a diploid cell in a two-step process: first, the cell switches mating type as a result of genetic rearrangement (cassette substitution) catalyzed by HO; then, cel...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 1983-05, Vol.80 (10), p.3035-3039
Main Authors: Jensen, Robert, Sprague, George F., Herskowitz, Ira
Format: Article
Language:English
Subjects:
Cells
Diploidy
DNA
DNA probes
DNA, Fungal - genetics
Feedback
Gene Expression Regulation
Genetic loci
Genetic mutation
Haploidy
Heterozygote
Plasmids
Recombination, Genetic
Reproduction
RNA
RNA, Fungal - genetics
Saccharomyces cerevisiae
Saccharomyces cerevisiae - genetics
Yeasts
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Summary:The ultimate product of yeast mating-type interconversion is a stable a/α diploid cell. A haploid cell carrying the HO gene gives rise to a diploid cell in a two-step process: first, the cell switches mating type as a result of genetic rearrangement (cassette substitution) catalyzed by HO; then, cells of opposite type mate to form a/α diploids. Mating-type interconversion does not occur in a/α diploids despite the presence of the HO gene. We have identified a plasmid carrying the HO gene by screening a yeast clone bank (constructed in vector YEp13) for plasmids that allow mating-type switching by ho cells. The yeast segment responsible for mating-type interconversion integrates by homology at the ho locus, thus confirming that it carries HO. Using the HO gene as a probe, we find that strains with an active mating-type interconversion system produce HO RNA, whereas a/α HO/HO cells do not and that this inhibition requires products of both the MATa1 and MATa2 genes. Thus, mating-type interconversion does not occur in a/α HO/HO cells because the HO gene product is not synthesized. These results demonstrate the following: (i) The mating-type locus, proposed on genetic grounds to be a regulatory locus, controls expression of an unlinked gene (HO) at the level of RNA production. (ii) The HO gene is under negative feedback control: its expression is inhibited after successful completion of diploidization (formation of a/α diploids).
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.80.10.3035