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

Genetics ◽  
1991 ◽  
Vol 129 (3) ◽  
pp. 685-696 ◽  
Author(s):  
P Laurenson ◽  
J Rine
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Transcriptional Repression ◽  
Point Mutations ◽  
Histone H4 ◽  
Yeast Saccharomyces Cerevisiae ◽  
Type Locus ◽  
Sir Proteins ◽  
Silencer Elements ◽  
Was Gene

Abstract 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.

scholarly journals High-Resolution Structural Analysis of Chromatin at Specific Loci: Saccharomyces cerevisiae Silent Mating Type Locus HMLα

1998 ◽  
Vol 18 (9) ◽  
pp. 5392-5403 ◽  
Author(s):  
Kerstin Weiss ◽  
Robert T. Simpson
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Chromatin Structure ◽  
Transcriptional Repression ◽  
Order Structure ◽  
Histone H4 ◽  
Type Locus ◽  
Transcription Start Sites ◽  
Chromosome Iii ◽  
Nucleotide Resolution

ABSTRACT Genetic studies have suggested that chromatin structure is involved in repression of the silent mating type loci in Saccharomyces cerevisiae. Chromatin mapping at nucleotide resolution of the transcriptionally silent HMLα and the activeMATα shows that unique organized chromatin structure characterizes the silent state of HMLα. Precisely positioned nucleosomes abutting the silencers extend over the α1 and α2 coding regions. The HO endonuclease recognition site, nuclease hypersensitive at MATα, is protected atHMLα. Although two precisely positioned nucleosomes incorporate transcription start sites at HMLα, the promoter region of the α1 and α2 genes is nucleosome free and more nuclease sensitive in the repressed than in the transcribed locus. Mutations in genes essential for HML silencing disrupt the nucleosome array near HML-I but not in the vicinity of HML-E, which is closer to the telomere of chromosome III. At the promoter and the HO site, the structure of HMLα in Sir protein and histone H4 N-terminal deletion mutants is identical to that of the transcriptionally active MATα. The discontinuous chromatin structure of HMLα contrasts with the continuous array of nucleosomes found at repressed a-cell-specific genes and the recombination enhancer. Punctuation at HMLα may be necessary for higher-order structure or karyoskeleton interactions. The unique chromatin architecture of HMLα may relate to the combined requirements of transcriptional repression and recombinational competence.

INTERCONVERSION OF YEAST MATING TYPES II. RESTORATION OF MATING ABILITY TO STERILE MUTANTS IN HOMOTHALLIC AND HETEROTHALLIC STRAINS

Genetics ◽  
1977 ◽  
Vol 85 (3) ◽  
pp. 373A-393
Author(s):  
James B Hicks ◽  
Ira Herskowitz
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Yeast Cells ◽  
Mating Types ◽  
Yeast Saccharomyces Cerevisiae ◽  
Type Locus ◽  
Mating Ability ◽  
Mating Type Locus ◽  
Regulatory Information ◽  
Ho Gene

ABSTRACT The two mating types of the yeast Saccharomyces cerevisiae can be interconverted in both homothallic and heterothallic strains. Previous work indicates that all yeast cells contain the information to be both a and α and that the HO gene (in homothallic strains) promotes a change in mating type by causing a change at the mating type locus itself. In both heterothallic and homothallic strains, a defective α mating type locus can be converted to a functional a locus and subsequently to a functional α locus. In contrast, action of the HO gene does not restore mating ability to a strain defective in another gene for mating which is not at the mating type locus. These observations indicate that a yeast cell contains an additional copy (or copies) of α information, and lead to the "cassette" model for mating type interconversion. In this model, HM  a and hmα loci are blocs of unexpressed α regulatory information, and HMα and hm  a loci are blocs of unexpressed a regulatory information. These blocs are silent because they lack an essential site for expression, and become active upon insertion of this information (or a copy of the information) into the mating type locus by action of the HO gene.

Regulation of STA1 gene expression by MAT during the life cycle of Saccharomyces cerevisiae

1989 ◽  
Vol 9 (9) ◽  
pp. 3992-3998
Author(s):  
A M Dranginis
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Yeast Cells ◽  
Specific Gene ◽  
Activity Levels ◽  
Sporulation Medium ◽  
Mrna Levels ◽  
Yeast Saccharomyces Cerevisiae ◽  
Type Locus ◽  
Diploid Cells

STA1 encodes a secreted glucoamylase of the yeast Saccharomyces cerevisiae var. diastaticus. Glucoamylase secretion is controlled by the mating type locus MAT; a and alpha haploid yeast cells secrete high levels of the enzyme, but a/alpha diploid cells produce undetectable amounts. It has been suggested that STA1 is regulated by MATa2 (I. Yamashita, Y. Takano, and S. Fukui, J. Bacteriol. 164:769-773, 1985), which is a MAT transcript of previously unknown function. In contrast, this work shows that deletion of the entire MATa2 gene had no effect on STA1 regulation but that deletion of MATa1 sequences completely abolished mating-type control. In all cases, glucoamylase activity levels reflected STA1 mRNA levels. It appears that STA1 is a haploid-specific gene that is regulated by MATa1 and a product of the MAT alpha locus and that this regulation occurs at the level of RNA accumulation. STA1 expression was also shown to be glucose repressible. STA1 mRNA was induced in diploids during sporulation along with SGA, a closely linked gene that encodes an intracellular sporulation-specific glucoamylase of S. cerevisiae. A diploid strain with a MATa1 deletion showed normal induction of STA1 in sporulation medium, but SGA expression was abolished. Therefore, these two homologous and closely linked glucoamylase genes are induced by different mechanisms during sporulation. STA1 induction may be a response to the starvation conditions necessary for sporulation, while SGA induction is governed by the pathway by which MAT regulates sporulation. The strain containing a complete deletion of MATa2 grew, mated, and sporulated normally.

scholarly journals DEPENDENCE ON MATING TYPE FOR THE OVERPRODUCTION OF ISO-2-CYTOCHROME c IN THE YEAST MUTANT CYC7–H2

Genetics ◽  
1980 ◽  
Vol 94 (4) ◽  
pp. 891-898
Author(s):  
Rodney J Rothstein ◽  
Fred Sherman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cytochrome C ◽  
Mating Type ◽  
Regulatory Region ◽  
The Other ◽  
Yeast Mutant ◽  
Yeast Saccharomyces Cerevisiae ◽  
Type Locus ◽  
Active Expression ◽  
Structural Region

ABSTRACT The CYC7-H2 mutation causes an approximately 20-fold overproduction of iso-2-cytochromo c in a and α haploid strains of the yeast Saccharomyces cerevisiae due to an alteration in the nontranslated regulatory region that is presumably contiguous with the structural region. In this investigation, we demonstrated that heterozygosity at the mating type locus, a /α or a/a/α/α, prevents expression of the overproduction, while homozygosity, a/a and α/α and hemizygosity, a/O and α/O, allow full expression of the CYC7-H2 mutation, equivalent to the expression observed in a and α haploid strains. There is no decrease in the overproduction of iso-2-cytochrome c in a/α diploid strains containing either of the other two similar mutations, CYC7-H1 and CYC7-H3. It appears as if active expression of one or another of the mating-type alleles is required for the overproduction of iso-2-cytochrome c in CYC7-H2 mutants.

Transcriptional control of the sporulation-specific glucoamylase gene in the yeast Saccharomyces cerevisiae

1985 ◽  
Vol 5 (11) ◽  
pp. 3069-3073
Author(s):  
I Yamashita ◽  
S Fukui
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Transcriptional Control ◽  
Northern Blot Analysis ◽  
Insertion Mutation ◽  
Yeast Saccharomyces Cerevisiae ◽  
Type Locus ◽  
Mating Type Genes ◽  
Diploid Cells ◽  
Glucoamylase Gene

In the yeast Saccharomyces cerevisiae, glucoamylase activity appears specifically in sporulating cells heterozygous for the mating-type locus (MAT). We identified a sporulation-specific glucoamylase gene (SGA) and show that expression of SGA is positively regulated by the mating-type genes, both MATa1 and MAT alpha 2. Northern blot analysis revealed that control of SGA is exerted at the level of RNA production. Expression of SGA or the consequent degradation of glycogen to glucose in cells is not required for meiosis or sporulation, since MATa/MAT alpha diploid cells homozygous for an insertion mutation at SGA still formed four viable ascospores.

scholarly journals SUM1-1, a dominant suppressor of SIR mutations in Saccharomyces cerevisiae, increases transcriptional silencing at telomeres and HM mating-type loci and decreases chromosome stability.

1996 ◽  
Vol 16 (8) ◽  
pp. 4281-4294 ◽  
Author(s):  
M H Chi ◽  
D Shore
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Transcriptional Silencing ◽  
Chromosome Loss ◽  
Yeast Saccharomyces Cerevisiae ◽  
Sir Proteins ◽  
Telomere Binding Protein ◽  
Single Allele ◽  
Dominant Suppressor

Transcriptional silencing in the yeast Saccharomyces cerevisiae occurs at HML and HMR mating-type loci and telomeres and requires the products of the silent information regulator (SIR) genes. Recent evidence suggests that the silencer- and telomere-binding protein Rap1p initiates silencing by recruiting a complex of Sir proteins to the chromosome, where they act in some way to modify chromatin structure or accessibility. A single allele of the SUM1gene (SUM1-1) which restores silencing at HM loci in strains mutant for any of the four SIR genes was identified a number of years ago. However, conflicting genetic results and the lack of other alleles of SUM1 made it difficult to surmise the wild-type function of SUM1 or the manner in which the SUM1-1 mutation restores silencing in sir mutant strains. Here we report the cloning and characterization of the SUM1 gene and the SUM1-1 mutant allele. Our results indicate that SUM1-1 is an unusual altered-function mutation that can bypass the need for SIR function in HM silencing and increase repression at telomeres. A sum1 deletion mutation has only minor effects on silencing in SIR strains and does not restore silencing in sir mutants. In addition to its effect on transcriptional silencing, the SUM1-1 mutation (but not a sum1 deletion) increases the rate of chromosome loss and cell death. We suggest several speculative models for the action of SUM1-1 in silencing based on these and other data.

scholarly journals Regulation of STA1 gene expression by MAT during the life cycle of Saccharomyces cerevisiae.

1989 ◽  
Vol 9 (9) ◽  
pp. 3992-3998 ◽  
Author(s):  
A M Dranginis
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Yeast Cells ◽  
Specific Gene ◽  
Activity Levels ◽  
Sporulation Medium ◽  
Mrna Levels ◽  
Yeast Saccharomyces Cerevisiae ◽  
Type Locus ◽  
Diploid Cells

STA1 encodes a secreted glucoamylase of the yeast Saccharomyces cerevisiae var. diastaticus. Glucoamylase secretion is controlled by the mating type locus MAT; a and alpha haploid yeast cells secrete high levels of the enzyme, but a/alpha diploid cells produce undetectable amounts. It has been suggested that STA1 is regulated by MATa2 (I. Yamashita, Y. Takano, and S. Fukui, J. Bacteriol. 164:769-773, 1985), which is a MAT transcript of previously unknown function. In contrast, this work shows that deletion of the entire MATa2 gene had no effect on STA1 regulation but that deletion of MATa1 sequences completely abolished mating-type control. In all cases, glucoamylase activity levels reflected STA1 mRNA levels. It appears that STA1 is a haploid-specific gene that is regulated by MATa1 and a product of the MAT alpha locus and that this regulation occurs at the level of RNA accumulation. STA1 expression was also shown to be glucose repressible. STA1 mRNA was induced in diploids during sporulation along with SGA, a closely linked gene that encodes an intracellular sporulation-specific glucoamylase of S. cerevisiae. A diploid strain with a MATa1 deletion showed normal induction of STA1 in sporulation medium, but SGA expression was abolished. Therefore, these two homologous and closely linked glucoamylase genes are induced by different mechanisms during sporulation. STA1 induction may be a response to the starvation conditions necessary for sporulation, while SGA induction is governed by the pathway by which MAT regulates sporulation. The strain containing a complete deletion of MATa2 grew, mated, and sporulated normally.

scholarly journals Transcriptional control of the sporulation-specific glucoamylase gene in the yeast Saccharomyces cerevisiae.

1985 ◽  
Vol 5 (11) ◽  
pp. 3069-3073 ◽  
Author(s):  
I Yamashita ◽  
S Fukui
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Transcriptional Control ◽  
Northern Blot Analysis ◽  
Insertion Mutation ◽  
Yeast Saccharomyces Cerevisiae ◽  
Type Locus ◽  
Mating Type Genes ◽  
Diploid Cells ◽  
Glucoamylase Gene

In the yeast Saccharomyces cerevisiae, glucoamylase activity appears specifically in sporulating cells heterozygous for the mating-type locus (MAT). We identified a sporulation-specific glucoamylase gene (SGA) and show that expression of SGA is positively regulated by the mating-type genes, both MATa1 and MAT alpha 2. Northern blot analysis revealed that control of SGA is exerted at the level of RNA production. Expression of SGA or the consequent degradation of glycogen to glucose in cells is not required for meiosis or sporulation, since MATa/MAT alpha diploid cells homozygous for an insertion mutation at SGA still formed four viable ascospores.

Efficient production of a ring derivative of chromosome III by the mating-type switching mechanism in Saccharomyces cerevisiae

1983 ◽  
Vol 3 (5) ◽  
pp. 803-810
Author(s):  
A J Klar ◽  
J N Strathern ◽  
J B Hicks ◽  
D Prudente
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Genetic Information ◽  
Recombination Event ◽  
Ring Chromosome ◽  
Efficient Production ◽  
Yeast Saccharomyces Cerevisiae ◽  
Type Locus ◽  
Mating Type Switching ◽  
Chromosome Iii

The mating-type switches in the yeast Saccharomyces cerevisiae occur by unidirectional transposition of replicas of unexpressed genetic information, residing at HML or HMR, into the mating-type locus (MAT). The source loci, HML and HMR, remain unchanged. Interestingly, when the HM cassettes are expressed, as in marl strains, the HML and HMR cassettes can also efficiently switch, apparently by obtaining genetic information from either of the other two cassettes (Klar et al., Cell 25:517-524, 1981). We have isolated a novel chromosome III rearrangement in heterothallic (marl ho) strains, which is also produced efficiently in marl HO cells, presumably the consequence of a recombination event between HML and HMR. The fusion results in the loss of sequences which are located distal to HML and to HMR and produces a ring derivative of chromosome III. Cells containing such a ring chromosome are viable as haploids; apparently, no essential loci are located distal to the HM loci. The fusion cassette behaves as a standard HM locus with respect to both regulation by the MAR/SIR control and its role in switching MAT.

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