Extragenic suppressors of mar2(sir3) mutations in Saccharomyces cerevisiae

Lin, C. I., Livi, G. P., Ivy, J. M., Klar, A. J. (June 1990) Extragenic suppressors of mar2(sir3) mutations in Saccharomyces cerevisiae. Genetics, 125 (2). pp. 321-31. ISSN 0016-6731 (Print)0016-6731 (Linking)

URL: http://www.ncbi.nlm.nih.gov/pubmed/2199314

Abstract

The silent mating-type genes (HML and HMR) of Saccharomyces cerevisiae are kept under negative transcriptional control by four trans-acting MAR (or SIR) loci. We have isolated extragenic suppressors of the mar2-1 mutation which, based on genetic complementation tests, define two additional loci involved in regulating the expression of HML and HMR. A strain with the genotype HMLa MAT alpha HMRa mar2-1 is sterile due to the simultaneous expression of a and alpha information. Two mutants exhibiting an alpha phenotype (which may result from the restoration of MAR/SIR repression) were isolated and genetically characterized. The mutations in these strains: (1) are recessive, (2) are capable of suppressing a mar2-deletion mutation, (3) are unlinked to MAT, (4) complement one another as well as the previously identified sum1-1 mutation, and (5) are not new alleles of the known MAR/SIR loci. We designate these new regulatory loci SUM2 and SUM3 (suppressor of mar). Unlike the sum1-1 mutation, suppression by sum2-1 and sum3-1 is mar2-locus specific. Both sum2-1 and sum3-1 affect the expression of a information at the HM loci. Transcript analysis shows a significant reduction in HMLa and HMRa gene transcription in mar2-1 sum2-1 and mar2-1 sum3-1 cells. Furthermore, we have found genetic evidence to suggest that mar2-1 sum2-1 cells exhibit only partial expression of silent alpha information. We conclude that the SUM2 and SUM3 gene products are required for expression of the HM loci and act downstream of the MAR2 (SIR3) gene function. Possible mechanisms for the action of the SUM gene products are discussed.

Item Type: Paper
Uncontrolled Keywords: Alleles Genes, Fungal Genes, Mating Type, Fungal Genes, Recessive Genetic Complementation Test Phenotype Saccharomyces cerevisiae/*genetics *Suppression, Genetic
Subjects: bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > genes, structure and function > gene expression
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > genes, structure and function > gene regulation
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > genes, structure and function > gene regulation

organism description > yeast
CSHL Authors:
Communities: CSHL labs
Depositing User: Matt Covey
Date: June 1990
Date Deposited: 30 Mar 2016 20:53
Last Modified: 30 Mar 2016 20:53
PMCID: PMC1204022
Related URLs:
URI: http://repository.cshl.edu/id/eprint/32283

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