scholarly journals swi6, a gene required for mating-type switching, prohibits meiotic recombination in the mat2-mat3 "cold spot" of fission yeast.

Genetics ◽  
1991 ◽  
Vol 129 (4) ◽  
pp. 1033-1042
Author(s):  
A J Klar ◽  
M J Bonaduce
Keyword(s):  
Fission Yeast ◽  
Mating Type ◽  
Meiotic Recombination ◽  
Hot Spot ◽  
Strand Break ◽  
Double Strand Break ◽  
Cold Spot ◽  
Additional Result ◽  
Type Locus ◽  
Mating Type Switching

Abstract Mitotic interconversion of the mating-type locus (mat1) of the fission yeast Schizosaccharomyces pombe is initiated by a double-strand break at mat1. The mat2 and mat3 loci act as nonrandom donors of genetic information for mat1 switching such that switches occur primarily (or only) to the opposite mat1 allele. Location of the mat1 "hot spot" for transposition should be contrasted with the "cold spot" of meiotic recombination located within the adjoining mat2-mat3 interval. That is, meiotic interchromosomal recombination in mat2, mat3 and the intervening 15-kilobase region does not occur at all. swi2 and swi6 switching-deficient mutants possess the normal level of double-strand break at mat1, yet they fail to switch efficiently. By testing for meiotic recombination in the cold spot, we found the usual lack of recombination in a swi2 mutant but a significant level of recombination in a swi6 mutant. Therefore, the swi6 gene function is required to keep the donor loci inert for interchromosomal recombination. This finding, combined with the additional result that switching primarily occurs intrachromosomally, suggests that the donor loci are made accessible for switching by folding them onto mat1, thus causing the cold spot of recombination.

Sap1, a protein that binds to sequences required for mating-type switching, is essential for viability in Schizosaccharomyces pombe

1994 ◽  
Vol 14 (3) ◽  
pp. 2058-2065
Author(s):  
B Arcangioli ◽  
T D Copeland ◽  
A J Klar
Keyword(s):  
Dna Binding ◽  
Schizosaccharomyces Pombe ◽  
Mating Type ◽  
Biochemical Characterization ◽  
Strand Break ◽  
Double Strand Break ◽  
Type Locus ◽  
Protein Motifs ◽  
Mating Type Switching

The pattern of mating-type switching in cell pedigrees of the fission yeast Schizosaccharomyces pombe is dictated by the inheritance of specific DNA chains at the mating-type locus (mat1). The recombination event essential for switching is initiated by a site-specific double-strand break at mat1. The switch-activating protein, Sap1, binds in vitro to a mat1 cis-acting site that was shown earlier to be essential for efficient mating-type switching. We isolated the sap1 gene by using oligonucleotides corresponding to the amino acid sequence of purified Sap1 protein. The sequence of that gene predicted a 30-kDa protein with no significant homology to other canonical DNA-binding protein motifs. To facilitate its biochemical characterization, Sap1 was expressed in Escherichia coli. The protein expressed in bacteria displayed the same DNA-binding specificities as the protein purified from S. pombe. Interestingly, analysis of a sap1 null mutation showed that the gene is essential for growth even in a strain in which mating-type switching is prohibited because of a defect in generation of the double-strand break. Thus, the sap1 gene product implicated in mating-type switching is shown to be essential for cell viability.

scholarly journals Sap1, a protein that binds to sequences required for mating-type switching, is essential for viability in Schizosaccharomyces pombe.

1994 ◽  
Vol 14 (3) ◽  
pp. 2058-2065 ◽  
Author(s):  
B Arcangioli ◽  
T D Copeland ◽  
A J Klar
Keyword(s):  
Dna Binding ◽  
Schizosaccharomyces Pombe ◽  
Mating Type ◽  
Biochemical Characterization ◽  
Strand Break ◽  
Double Strand Break ◽  
Type Locus ◽  
Protein Motifs ◽  
Mating Type Switching

The pattern of mating-type switching in cell pedigrees of the fission yeast Schizosaccharomyces pombe is dictated by the inheritance of specific DNA chains at the mating-type locus (mat1). The recombination event essential for switching is initiated by a site-specific double-strand break at mat1. The switch-activating protein, Sap1, binds in vitro to a mat1 cis-acting site that was shown earlier to be essential for efficient mating-type switching. We isolated the sap1 gene by using oligonucleotides corresponding to the amino acid sequence of purified Sap1 protein. The sequence of that gene predicted a 30-kDa protein with no significant homology to other canonical DNA-binding protein motifs. To facilitate its biochemical characterization, Sap1 was expressed in Escherichia coli. The protein expressed in bacteria displayed the same DNA-binding specificities as the protein purified from S. pombe. Interestingly, analysis of a sap1 null mutation showed that the gene is essential for growth even in a strain in which mating-type switching is prohibited because of a defect in generation of the double-strand break. Thus, the sap1 gene product implicated in mating-type switching is shown to be essential for cell viability.

The clr1 locus regulates the expression of the cryptic mating-type loci of fission yeast.

Genetics ◽  
1992 ◽  
Vol 131 (2) ◽  
pp. 287-296 ◽  
Author(s):  
G Thon ◽  
A J Klar
Keyword(s):  
Fission Yeast ◽  
Mating Type ◽  
Cold Spot ◽  
Type Region ◽  
Type Locus ◽  
Silent Genes ◽  
The Right ◽  
Chromosome Ii ◽  
Donor Locus ◽  
Type Information

Abstract The mat2-P and mat3-M loci of fission yeast contain respectively the plus (P) and minus (M) mating-type information in a transcriptionally silent state. That information is transposed from the mat2 or mat3 donor locus via recombination into the expressed mating-type locus (mat1) resulting in switching of the cellular mating type. We have identified a gene, named clr1 (for cryptic loci regulator), whose mutations allow expression of the mat2 and mat3 loci. clr1 mutants undergo aberrant haploid meiosis, indicative of transcription of the silent genes. Production of mRNA from mat3 is detectable in clr1 mutants. Furthermore, the ura4 gene inserted near mat3, weakly expressed in wild-type cells, is derepressed in clr1 mutants. The clr1 mutations also permit meiotic recombination in the 15-kb mat2-mat3 interval, where recombination is normally inhibited. The clr1 locus is in the right arm of chromosome II. We suggest that clr1 regulates silencing of the mat2 and mat3 loci, and participates in establishing the "cold spot" for recombination by organizing the chromatin structure of the mating-type region.

scholarly journals A single Ho-induced double-strand break at the MAT locus is lethal in Candida glabrata

2020 ◽  
Author(s):  
Laetitia Maroc ◽  
Youfang Zhou-Li ◽  
Stéphanie Boisnard ◽  
Cécile Fairhead
Keyword(s):  
Cell Death ◽  
Sexual Reproduction ◽  
Mating Type ◽  
Candida Glabrata ◽  
Strand Break ◽  
Double Strand Break ◽  
Switching System ◽  
Massive Cell Death ◽  
Mating Type Switching ◽  
Massive Cell

AbstractMating-type switching is a complex mechanism that promotes sexual reproduction in Ascomycotina. In the model species Saccharomyces cerevisiae, mating-type switching is initiated by the Ho endonuclease that performs a site-specific double-strand break (DSB) at MAT, repaired by homologous recombination (HR) using one of the two silent mating type cassettes, HMLalpha and HMRa. The reasons why all the elements of the mating-type switching system have been conserved in some Ascomycotina, that do not show a sexual cycle nor mating-type switching, remain unknown. To gain insight on this phenomenon, we used the opportunistic pathogenic yeast Candida glabrata, phylogenetically close to S. cerevisiae, and for which no spontaneous and efficient mating-type switching has been observed. We have previously shown that expression of S. cerevisiae’s HO gene triggers mating-type switching in C. glabrata, but this leads to massive cell death. In addition, we unexpectedly found, that not only MAT but also HML was cut in this species, suggesting the formation of multiple chromosomal DSBs upon HO induction.We now report that HMR is also cut by S. cerevisiae’s Ho in wild-type strains of C. glabrata. To understand the link between mating-type switching and cell death in C. glabrata, we constructed strains mutated precisely at the Ho recognition sites. By mimicking S. cerevisiae’s situation, in which HML and HMR are protected from the cut, we unexpectedly find that one DSB at MAT is sufficient to induce cell death. We demonstrate that mating-type switching in C. glabrata can be triggered using CRISPR-Cas9, without high lethality. We also show that switching is Rad51-dependent, as in S. cerevisiae but that donor preference is not conserved in C. glabrata. Altogether, these results suggest that a DSB at MAT can be repaired by HR in C. glabrata, but that it is prevented by S. cerevisiae’s Ho.Author summaryMating-type switching is one of the strategies developed by fungi to promote crossing, sexual reproduction and propagation. This mechanism enables one haploid cell to give rise to a cell of the opposite mating-type so that they can mate together. It has been extensively studied in the model yeast S. cerevisiae in which it relies on a programmed double-strand break performed by the Ho endonuclease at the MAT locus which encodes the key regulators of sexual identity. Little is known about why the mating-type switching components have been conserved in species like C.glabrata, in which neither sexual reproduction nor mating-type switching is observed. We have previously shown that mating-type switching can be triggered, in C. glabrata, by expression of the HO gene from S. cerevisiae but this leads to massive cell death. We report here evidence toward a degeneration of the mating-type switching system in C. glabrata. We demonstrate that the DSB at MAT is only lethal when the Ho endonuclease performs the break, a situation unique to C. glabrata. Finally, we show that mating-type switching in C. glabrata can be triggered by CRISPR-Cas9 and without any high lethality.

scholarly journals Analysis of chromatin remodeling during formation of a DNA double-strand break at the yeast mating type locus

Methods ◽  
2009 ◽  
Vol 48 (1) ◽  
pp. 40-45 ◽  
Author(s):  
Toyoko Tsukuda ◽  
Kelly M. Trujillo ◽  
Emmanuelle Martini ◽  
Mary Ann Osley
Keyword(s):  
Chromatin Remodeling ◽  
Mating Type ◽  
Strand Break ◽  
Double Strand Break ◽  
Type Locus ◽  
Mating Type Locus ◽  
Yeast Mating ◽  
Dna Double Strand Break

A Test of the Double-Strand Break Repair Model for Meiotic Recombination in Saccharomyces cerevisiae

Genetics ◽  
1996 ◽  
Vol 144 (1) ◽  
pp. 27-41 ◽  
Author(s):  
Larry A Gilbertson ◽  
Franklin W Stahl
Keyword(s):  
Meiotic Recombination ◽  
Strand Break ◽  
Double Strand Break ◽  
Double Strand Break Repair ◽  
Holliday Junction ◽  
Single Event ◽  
Heteroduplex Dna ◽  
Holliday Junction Resolvase ◽  
Break Repair ◽  
Two Sides

Abstract We tested predictions of the double-strand break repair (DSBR) model for meiotic recombination by examining the segregation patterns of small palindromic insertions, which frequently escape mismatch repair when in heteroduplex DNA. The palindromes flanked a well characterized DSB site at the ARC4 locus. The “canonical” DSBR model, in which only 5′ ends are degraded and resolution of the four-stranded intermediate is by Holliday junction resolvase, predicts that hDNA will frequently occur on both participating chromatids in a single event. Tetrads reflecting this configuration of hDNA were rare. In addition, a class of tetrads not predicted by the canonical DSBR model was identified. This class represented events that produced hDNA in a “trans” configuration, on opposite strands of the same duplex on the two sides of the DSB site. Whereas most classes of convertant tetrads had typical frequencies of associated crossovers, tetrads with trans hDNA were parental for flanking markers. Modified versions of the DSBR model, including one that uses a topoisomerase to resolve the canonical DSBR intermediate, are supported by these data.

Homothallic mating type switching generates lethal chromosome breaks in rad52 strains of Saccharomyces cerevisiae

1981 ◽  
Vol 1 (6) ◽  
pp. 522-534
Author(s):  
B Weiffenbach ◽  
J E Haber
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Deoxyribonucleic Acid ◽  
Type Locus ◽  
Mating Type Switching ◽  
Lethal Event ◽  
Bona Fide ◽  
Chromosome Iii ◽  
Mat Locus ◽  
Type Information

In homothallic cells of Saccharomyces cerevisiae, a or alpha mating type information at the mating type locus (MAT) is replaced by the transposition of the opposite mating type allele from HML alpha or HMRa. The rad52-1 mutation, which reduces mitotic and abolishes meiotic recombination, also affects homothallic switching (Malone and Esposito, Proc. Natl. Acad. Sci. U.S.A. 77:503-507, 1980). We have found that both HO rad52 MATa and HO rad52 MAT alpha cells die. This lethality is suppressed by mutations that substantially reduce but do not eliminate homothallic conversions. These mutations map at or near the MAT locus (MAT alpha inc, MATa-inc, MATa stk1) or are unlinked to MAT (HO-1 and swi1). These results suggest that the switching event itself is involved in the lethality. With the exception of swi1, HO rad52 strains carrying one of the above mutations cannot convert mating type at all. MAT alpha rad52 HO swi1 strains apparently can switch MAT alpha to MATa. However, when we analyzed these a maters, we found that few, if any, of them were bona fide MATa cells. These a-like cells were instead either deleted for part of chromosome III distal to and including MAT or had lost the entire third chromosome. Approximately 30% of the time, an a-like cell could be repaired to a normal MATa genotype if the cell was mated to a RAD52 MAT alpha-inc strain. The effects of rad52 were also studied in mata/MAT alpha-inc rad52/rad52 ho/HO diploids. When this diploid attempted to switch mata to MATa, an unstable broken chromosome was generated in nearly every cell. These studies suggest that homothallic switching involves the formation of a double-stranded deoxyribonucleic acid break or a structure which is labile in rad52 cells and results in a broken chromosome. We propose that the production of a double-stranded deoxyribonucleic acid break is the lethal event in rad52 HO cells.

scholarly journals The fission yeast heterochromatin protein Rik1 is required for telomere clustering during meiosis

2004 ◽  
Vol 165 (6) ◽  
pp. 759-765 ◽  
Author(s):  
Creighton T. Tuzon ◽  
Britta Borgstrom ◽  
Dietmar Weilguny ◽  
Richard Egel ◽  
Julia Promisel Cooper ◽  
...  
Keyword(s):  
Fission Yeast ◽  
Mating Type ◽  
Sexual Differentiation ◽  
Histone H3 ◽  
Heterochromatin Protein ◽  
Type Locus ◽  
Heterochromatin Formation ◽  
Mating Type Locus ◽  
Telomere Protein ◽  
Chromosome Movements

Telomeres share the ability to silence nearby transcription with heterochromatin, but the requirement of heterochromatin proteins for most telomere functions is unknown. The fission yeast Rik1 protein is required for heterochromatin formation at centromeres and the mating-type locus, as it recruits the Clr4 histone methyltransferase, whose modification of histone H3 triggers binding by Swi6, a conserved protein involved in spreading of heterochromatin. Here, we demonstrate that Rik1 and Clr4, but not Swi6, are required along with the telomere protein Taz1 for crucial chromosome movements during meiosis. However, Rik1 is dispensable for the protective roles of telomeres in preventing chromosome end-fusion. Thus, a Swi6-independent heterochromatin function distinct from that at centromeres and the mating-type locus operates at telomeres during sexual differentiation.

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