Pleiotropic effects of heterozygosity at the mating-type locus of the yeast Saccharomyces cerevisiae on repair, recombination and transformation

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.

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SWITCHING OF A MATING-TYPE a MUTANT ALLELE IN BUDDING YEAST SACCHAROMYCES CEREVISIAE

Genetics ◽

10.1093/genetics/92.3.759 ◽

1979 ◽

Vol 92 (3) ◽

pp. 759-776

Author(s):

Amar J S Klar ◽

Seymour Fogel ◽

David N Radin

Keyword(s):

Saccharomyces Cerevisiae ◽

Mating Type ◽

Mutant Allele ◽

Budding Yeast ◽

High Capacity ◽

Tetrad Analysis ◽

Yeast Saccharomyces Cerevisiae ◽

Type Locus ◽

Mating Type Locus ◽

Parental Allele

ABSTRACT Aimed at investigating the recovery of a specific mutant allele of the mating type locus (MAT) by switching a defective MAT allele, these experiments provide information bearing on several models proposed for MAT interconversion in bakers yeast, Saccharomyces cerevisiae. Hybrids between heterothallic (ho) cells carrying a mutant MAT a allele, designated mata-2, and MATα ho strains show a high capacity for mating with MAT a strains. The MATα/mata-2 diploids do not sporulate. However, zygotic clones obtained by mating MATa homothallic (HO) cells with mata-2 ho cells are unable to mate and can sporulate. Tetrad analysis of such clones revealed two diploid (MATa/MATa) :two haploid segregants. Therefore, MAT switches occw in MATα/mata-2 HO/ho cells to produce MATα/MAT a cells capable of sporulation. In heterothallic strains, the mata-2 allele can be switched to a functional MATα and subsequently to a functional MATa. Among 32 MATα to MATa switches tested, where the MATα was previously derived from the mata-2 mutant, only one mata-2 like isolate was observed. However, the recovered allele, unlike the parental allele, conplements the matα stel-5 mutant, suggesting that these alleles are not identical and that the recovered allele presumably arose as a mutation of the MATα locus. No mata-2 was recovered by HO-mediated switching of MATα (previously obtained from mata-2 by HO) in 217 switches analyzed. We conclude that in homothallic and heterothallic strains, the mata-2 allele can be readily switched to a functional MATα and subsequently to a functional MATa locus. Overall, the results are in accord with the cassette model (HICKS, STRATKERN and HERSKO-WITZ 1977b) proposed to explain MAT interconversions.

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rme1 Mutation of Saccharomyces cerevisiae: map position and bypass of mating type locus control of sporulation.

Molecular and Cellular Biology ◽

10.1128/mcb.1.10.958 ◽

1981 ◽

Vol 1 (10) ◽

pp. 958-960 ◽

Cited By ~ 35

Author(s):

J Rine ◽

G F Sprague ◽

I Herskowitz

Keyword(s):

Saccharomyces Cerevisiae ◽

Mating Type ◽

Type Locus ◽

Mating Type Locus ◽

Type Information

Sporulation in Saccharomyces cerevisiae normally occurs only in MATa/MAT alpha diploids. We show that mutations in RME1 bypassed the requirements for both a and alpha mating type information in sporulation and therefore allowed MATa/MATa and MAT alpha/MAT alpha diploids to sporulate. RME1 was located on chromosome VII, between LEU1 and ADE6.

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

Molecular and Cellular Biology ◽

10.1128/mcb.9.9.3992-3998.1989 ◽

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.

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Identification of sequence elements that confer cell-type-specific control of MF alpha 1 expression in Saccharomyces cerevisiae

Molecular and Cellular Biology ◽

10.1128/mcb.7.9.3185-3193.1987 ◽

1987 ◽

Vol 7 (9) ◽

pp. 3185-3193

Author(s):

K Inokuchi ◽

A Nakayama ◽

F Hishinuma

Keyword(s):

Saccharomyces Cerevisiae ◽

Mating Type ◽

Specific Gene ◽

Cell Type ◽

Coding Region ◽

Transcription Start ◽

Specific Expression ◽

Type Locus ◽

Mating Type Locus ◽

Cell Type Specific

The MF alpha 1 gene of Saccharomyces cerevisiae, a major structural gene for mating pheromone alpha factor, is an alpha-specific gene whose expression is regulated by the mating-type locus. To study the role of sequences upstream of MF alpha 1 in its expression and regulation, we generated two sets of promoter deletions: upstream deletions and internal deletions. By analyzing these deletions, we have identified a TATA box and two closely related, tandemly arranged upstream activation sites as necessary elements for MF alpha 1 expression. Two upstream activation sites were located ca. 300 and 250 base pairs upstream of the MF alpha 1 transcription start points, which were also determined in this study. Each site contained a homologous 22-base-pair sequence, and both sites were required for maximum transcription level. The distance between the upstream activation sites and the transcription start points could be altered without causing loss of transcription efficiency, and the sites were active in either orientation with respect to the coding region. These elements conferred cell type-specific expression on a heterologous promoter. Analysis with host mating-type locus mutants indicates that these sequences are the sites through which the MAT alpha 1 product exerts its action to activate the MF alpha 1 gene. Homologous sequences with these elements were found in other alpha-specific genes, MF alpha 2 and STE3, and may mediate activation of this set of genes by MAT alpha 1.

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MUTATIONS AFFECTING SEXUAL CONJUGATION AND RELATED PROCESSES IN SACCHAROMYCES CEREVISIAE. II. GENETIC ANALYSIS OF NONMATING MUTANTS

Genetics ◽

10.1093/genetics/76.2.273 ◽

1974 ◽

Vol 76 (2) ◽

pp. 273-288

Author(s):

Vivian Mackay ◽

Thomas R Manney

Keyword(s):

Saccharomyces Cerevisiae ◽

Genetic Analysis ◽

Mating Type ◽

Tetrad Analysis ◽

Genetic Loci ◽

Type Locus ◽

Mating Type Locus

ABSTRACT Rare diploids formed by sterile mutants have been studied by tetrad analysis. Sixteen classes of mutants representing at least five distinct genetic loci have been defined. One group of mutations, isolated only in α, maps at the mating-type locus, while none of the others shows any linkage to mating type. Some of the mutations are nonspecific for mating type, while others act only on a or α. In addition, mutations were found that prevent sporulation when heterozygous in diploids. These appear to be mutations of the mating-type alleles.

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

Genetics ◽

10.1093/genetics/94.4.891 ◽

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.

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GENE CONVERSION OF THE MATING-TYPE LOCUS IN SACCHAROMYCES CEREVISIAE

Genetics ◽

10.1093/genetics/92.3.777 ◽

1979 ◽

Vol 92 (3) ◽

pp. 777-782

Author(s):

Amar J S Klar ◽

Seymour Fogel ◽

Karin Lusnak

Keyword(s):

Saccharomyces Cerevisiae ◽

Gene Conversion ◽

Mating Type ◽

Tetrad Analysis ◽

Type Locus ◽

Mating Type Locus ◽

Gene Conversions

ABSTRACT Tetrad analysis of MAT a/MATα diploids of Saccharomyces cerevisiae generally yields 2 MATa:2MATα meiotic products. About 1 to 1.8% of the tetrads yield aberrant segregations for this marker. Described here are experiments that determine whether the aberrant meiotic segregations at the mating-type locus are ascribable to gene conversions or to MAT switches, that is, to mating-type interconversions. Diploid strains incapable of switching MAT a to MATα, or the converse, nevertheless display changes of MAT a to MATα, or the reverse. These events must be attributed to gene conversion. Further, we suggest that MAT a and MATα alleles may represent nonhomologous sequences of DNA since they fail to display postmeiotic segregations.

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A SUPPRESSOR OF MATING-TYPE LOCUS MUTATIONS IN SACCHAROMYCES CEREVISIAE: EVIDENCE FOR AND IDENTIFICATION OF CRYPTIC MATING-TYPE LOCI

Genetics ◽

10.1093/genetics/93.4.877 ◽

1979 ◽

Vol 93 (4) ◽

pp. 877-901 ◽

Cited By ~ 6

Author(s):

Jasper Rine ◽

Jeffrey N Strathern ◽

James B Hicks ◽

Ira Herskowitz

Keyword(s):

Saccharomyces Cerevisiae ◽

Mating Type ◽

Mating Types ◽

Type Locus ◽

Mating Ability ◽

Mating Type Locus ◽

A Cells

ABSTRACT A mutation has been identified that suppresses the mating and sporulation defects of all mutations in the mating-type loci of S. cereuisiae. This suppressor, sir1-1, restores mating ability to matαl and matα2 mutants and restores sporulation ability to matα2 and mata1 mutants. MATa sir1-1 strains exhibit a polar budding pattern and have reduced sensitivity to α-factor, both properties of a/α diploids. Furthermore, sir1-1 allows MATa/MATa, matα1/matα1, and MATα/MATα strains to sporulate efficiently. All actions of sir1-1 are recessive to SIR1. The ability of sir1-1 to supply all functions necessary for mating and sporulation and its effects in a cells are explained by proposing that sir1-1 allows expression of mating type loci which are ordinarily not expressed. The ability of sir1-1 to suppress the matαl-5 mutation is dependent on the HMa gene, previously identified as required for switching of mating types from a to α. Thus, as predicted by the cassette model, HMa is functionally equivalent to MATα since it supplies functions of MATα. We propose that sir1-1 is defective in a function, Sir ("Silent-information regulator"), whose role may be to regulate expression of HMa and HMα.

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rme1 Mutation of Saccharomyces cerevisiae: map position and bypass of mating type locus control of sporulation

Molecular and Cellular Biology ◽

10.1128/mcb.1.10.958-960.1981 ◽

1981 ◽

Vol 1 (10) ◽

pp. 958-960

Author(s):

J Rine ◽

G F Sprague ◽

I Herskowitz

Keyword(s):

Saccharomyces Cerevisiae ◽

Mating Type ◽

Type Locus ◽

Mating Type Locus ◽

Type Information

Sporulation in Saccharomyces cerevisiae normally occurs only in MATa/MAT alpha diploids. We show that mutations in RME1 bypassed the requirements for both a and alpha mating type information in sporulation and therefore allowed MATa/MATa and MAT alpha/MAT alpha diploids to sporulate. RME1 was located on chromosome VII, between LEU1 and ADE6.

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