SUM1-1: a suppressor of silencing defects in Saccharomyces cerevisiae.

The repression of transcription of the silent mating-type locus HMRa in the yeast Saccharomyces cerevisiae requires the four SIR proteins, histone H4 and a flanking site designated HMR-E. The SUM1-1 mutation alleviated the need for many of these components in transcriptional repression. In the absence of each of the SIR proteins, SUM1-1 restored repression in MAT alpha strains; thus, SUM1-1 appeared to bypass the need for the SIR genes in repression of HMRa. Repression was not specific to the genes normally present at HMR, since the TRP1 gene placed at HMR was repressed by SUM1-1 in a sir3 strain. Therefore, like the mechanisms of silencing normally used at HMR, silencing by SUM1-1 was gene-nonspecific. SUM1-1 suppressed point mutations in histone H4, but failed to suppress strongly a deletion mutation in histone H4. Similarly, SUM1-1 suppressed mutations in the three known elements of HMR-E, but was unable to suppress a deletion of HMR-E. These epistasis analyses implied that the functions required for repression at HMR can be ordered, with the SIR genes and silencer elements acting upstream of SUM1-1. SUM1-1 itself may function at the level of chromatin in the assembly of inactive DNA at the silent mating-type loci.

[1]  J. Rine,et al.  A synthetic silencer mediates SIR-dependent functions in Saccharomyces cerevisiae , 1991, Molecular and cellular biology.

[2]  S. Elgin,et al.  Mutation in a heterochromatin-specific chromosomal protein is associated with suppression of position-effect variegation in Drosophila melanogaster. , 1990, Proceedings of the National Academy of Sciences of the United States of America.

[3]  Barbara L. Billington,et al.  Position effect at S. cerevisiae telomeres: Reversible repression of Pol II transcription , 1990, Cell.

[4]  J. Szostak,et al.  Point mutations in the yeast histone H4 gene prevent silencing of the silent mating type locus HML. , 1990, Molecular and cellular biology.

[5]  P. Spierer,et al.  Dependence of position-effect variegation in Drosophila on dose of a gene encoding an unusual zinc-finger protein , 1990, Nature.

[6]  J. Broach,et al.  The HML mating-type cassette of Saccharomyces cerevisiae is regulated by two separate but functionally equivalent silencers , 1989, Molecular and cellular biology.

[7]  J. Smith,et al.  N alpha acetylation is required for normal growth and mating of Saccharomyces cerevisiae , 1989, Journal of bacteriology.

[8]  J. C. Eissenberg.  Position effect variegation in Drosophila: Towards a genetics of chromatin assembly , 1989, BioEssays : news and reviews in molecular, cellular and developmental biology.

[9]  I. Herskowitz,et al.  Life cycle of the budding yeast Saccharomyces cerevisiae. , 1988, Microbiological reviews.

[10]  M. Grunstein,et al.  Extremely conserved histone H4 N terminus is dispensable for growth but essential for repressing the silent mating loci in yeast , 1988, Cell.

[11]  J. Diffley,et al.  Purification of a yeast protein that binds to origins of DNA replication and a transcriptional silencer. , 1988, Proceedings of the National Academy of Sciences of the United States of America.

[12]  I. Herskowitz,et al.  Four genes responsible for a position effect on expression from HML and HMR in Saccharomyces cerevisiae. , 1987, Genetics.

[13]  J. Broach,et al.  Identification of sites required for repression of a silent mating type locus in yeast. , 1984, Journal of molecular biology.

[14]  J. Strathern,et al.  Regulation of mating-type information in yeast. Negative control requiring sequences both 5' and 3' to the regulated region. , 1984, Journal of molecular biology.

[15]  I. Herskowitz,et al.  A suppressor of mating-type locus mutations in Saccharomyces cerevisiae: evidence for and identification of cryptic mating-type loci. , 1979, Genetics.

[16]  I. Herskowitz,et al.  Putting the HO gene to work: practical uses for mating-type switching. , 1991, Methods in enzymology.

[17]  S. Henikoff.  Position-effect variegation after 60 years. , 1990, Trends in genetics : TIG.

[18]  J. Strathern,et al.  Involvement of double-strand chromosomal breaks for mating-type switching in Saccharomyces cerevisiae. , 1984, Cold Spring Harbor symposia on quantitative biology.