scholarly journals 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.

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.

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.

scholarly journals 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.

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

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.

Functional domains of SIR4, a gene required for position effect regulation in Saccharomyces cerevisiae

1987 ◽  
Vol 7 (12) ◽  
pp. 4441-4452
Author(s):  
M Marshall ◽  
D Mahoney ◽  
A Rose ◽  
J B Hicks ◽  
J R Broach
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Position Effect ◽  
Protein Activity ◽  
Multicomponent Complex ◽  
Mating Type Genes ◽  
Chromosome Iii ◽  
Covalently Linked ◽  
High Level ◽  
Mat Locus

The product of the Saccharomyces cerevisiae SIR4 gene, in conjunction with at least three other gene products, prevents expression of mating-type genes resident at loci at either end of chromosome III, but not of the same genes resident at the MAT locus in the middle of the chromosome. To address the mechanism of this novel position effect regulation, we have conducted a structural and genetic analysis of the SIR4 gene. We have determined the nucleotide sequence of the gene and found that it encodes a lysine-rich, serine-rich protein of 152 kilodaltons. Expression of the carboxy half of the protein complements a chromosomal nonsense mutation of sir4 but not a complete deletion of the gene. These results suggest that SIR4 protein activity resides in two portions of the molecule, but that these domains need not be covalently linked to execute their biological function. We also found that high-level expression of the carboxy domain of the protein yields dominant derepression of the silent loci. This anti-Sir activity can be reversed by increased expression of the SIR3 gene, whose product is normally also required for maintaining repression of the silent loci. These results are consistent with the hypothesis that SIR3 and SIR4 proteins physically associate to form a multicomponent complex required for repression of the silent mating-type loci.

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

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.

scholarly journals Mechanism of MAT alpha donor preference during mating-type switching of Saccharomyces cerevisiae.

1996 ◽  
Vol 16 (2) ◽  
pp. 657-668 ◽  
Author(s):  
X Wu ◽  
J K Moore ◽  
J E Haber
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Strand Break ◽  
Normal Donor ◽  
Alpha Cells ◽  
Cis Acting ◽  
Mating Type Switching ◽  
Chromosome Iii ◽  
The Right ◽  
Donor Preference

During homothallic switching of the mating-type (MAT) gene in Saccharomyces cerevisiae, a- or alpha-specific sequences are replaced by opposite mating-type sequences copied from one of two silent donor loci, HML alpha or HMRa. The two donors lie at opposite ends of chromosome III, approximately 190 and 90 kb, respectively, from MAT. MAT alpha cells preferentially recombine with HMR, while MATa cells select HML. The mechanisms of donor selection are different for the two mating types. MATa cells, deleted for the preferred HML gene, efficiently use HMR as a donor. However, in MAT alpha cells, HML is not an efficient donor when HMR is deleted; consequently, approximately one-third of HO HML alpha MAT alpha hmr delta cells die because they fail to repair the HO endonuclease-induced double-strand break at MAT. MAT alpha donor preference depends not on the sequence differences between HML and HMR or their surrounding regions but on their chromosomal locations. Cloned HMR donors placed at three other locations to the left of MAT, on either side of the centromere, all fail to act as efficient donors. When the donor is placed 37 kb to the left of MAT, its proximity overcomes normal donor preference, but this position is again inefficiently used when additional DNA is inserted in between the donor and MAT to increase the distance to 62 kb. Donors placed to the right of MAT are efficiently recruited, and in fact a donor situated 16 kb proximal to HMR is used in preference to HMR. The cis-acting chromosomal determinants of MAT alpha preference are not influenced by the chromosomal orientation of MAT or by sequences as far as 6 kb from HMR. These data argue that there is an alpha-specific mechanism to inhibit the use of donors to the left of MAT alpha, causing the cell to recombine most often with donors to the right of MAT alpha.

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.

scholarly journals Detection of the DNA primary structure modifications induced by the base analog 6-n-hydroxylaminopurine in the alpha-test in yeast saccharomyces cerevisiae

2020 ◽  
Vol 18 (3) ◽  
pp. 357-366
Author(s):  
Anna S. Zhuk ◽  
Elena I. Stepchenkova ◽  
Sergey G. Inge-Vechtomov
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Dna Lesions ◽  
Genetic Toxicology ◽  
Yeast Saccharomyces Cerevisiae ◽  
Genetic Changes ◽  
Mating Type Switching ◽  
Base Modifications ◽  
Type Switch ◽  
Chromosome Iii

Background. The alpha-test allows to detect inherited genetic changes of different types, as well as phenotypic expression of primary DNA lesions before the lesions are fixed by repair. Here we investigate ability of the alpha-test to detect base modifications induced by 6-N-hydroxylaminopurine (HAP) and determine frequency of inherited and non-inherited genetic changes in yeast strains treated with HAP. Materials and methods. The alpha-test is based on mating type regulation and detects cell type switch from to a in heterothallic yeast Saccharomyces cerevisiae. The frequency of mating type switching reflects level of both spontaneous and induced by a mutagen DNA instability. The alpha-test may be performed in two variants: illegitimate hybridization and cytoduction. Conducting both complementary tests and analysis of phenotypes of the illegitimate hybrids and cytoductants allows to detect the full spectrum of genetic events that lead to mating type switching, such as chromosome III loss and chromosome III arm loss, mutations and temporary lesions, recombination and conversion. Results. HAP increases the frequency of illegitimate hybridization by 5-fold, and illegitimate cytoduction by 10-fold. A large proportion of the primary lesions induced by HAP causes temporary mating type switch and the remainder parts are converted into inherited point mutations. Conclusion. The alpha-test can detect HAP-induced base modifications and may be used to investigate the ratio between correct and error-prone processing of such primary DNA lesions. Like other genetic toxicology tests the alpha-test has limitations, which are discussed.

scholarly journals A Sir2-regulated locus control region in the recombination enhancer of Saccharomyces cerevisiae specifies chromosome III structure

2019 ◽  
Author(s):  
Mingguang Li ◽  
Ryan D. Fine ◽  
Manikarna Dinda ◽  
Stefan Bekiranov ◽  
Jeffrey S. Smith
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Control Region ◽  
Mating Type ◽  
Locus Control Region ◽  
A Cells ◽  
Mating Type Switching ◽  
Chromosome Iii ◽  
The Right ◽  
Donor Preference ◽  
Recombination Enhancer

AbstractThe NAD+-dependent histone deacetylase Sir2 was originally identified in Saccharomyces cerevisiae as a silencing factor for HML and HMR, the heterochromatic cassettes utilized as donor templates during mating-type switching. MATa cells preferentially switch to MATα using HML as the donor, which is driven by an adjacent cis-acting element called the recombination enhancer (RE). In this study we demonstrate that Sir2 and the condensin complex are recruited to the RE exclusively in MATa cells, specifically to the promoter of a small gene within the right half of the RE known as RDT1. We go on to demonstrate that the RDT1 promoter functions as a locus control region (LCR) that regulates both transcription and long-range chromatin interactions. Sir2 represses the transcription of RDT1 until it is redistributed to a dsDNA break at the MAT locus induced by the HO endonuclease during mating-type switching. Condensin is also recruited to the RDT1 promoter and is displaced upon HO induction, but does not significantly repress RDT1 transcription. Instead condensin appears to promote mating-type switching efficiency and donor preference by maintaining proper chromosome III architecture, which is defined by the interaction of HML with the right arm of chromosome III, including MATa and HMR. Remarkably, eliminating Sir2 and condensin recruitment to the RDT1 promoter disrupts this structure and reveals an aberrant interaction between MATa and HMR, consistent with the partially defective donor preference for this mutant. Global condensin subunit depletion also impairs mating type switching efficiency and donor preference, suggesting that modulation of chromosome architecture plays a significant role in controlling mating type switching, thus providing a novel model for dissecting condensin function in vivo.Author summarySir2 is a highly conserved NAD+-dependent protein deacetylase and defining member of the sirtuin protein family. It was identified about 40 years ago in the budding yeast, Saccharomyces cerevisiae, as a gene required for silencing of the cryptic mating-type loci, HML and HMR. These heterochromatic cassettes are utilized as templates for mating-type switching, whereby a programmed DNA double-strand break at the MATa or MATα locus is repaired by gene conversion to the opposite mating type. The preference for switching to the opposite mating type is called donor preference, and in MATa cells, is driven by a cis-acting DNA element called the recombination enhancer (RE). It was believed that the only role for Sir2 in mating-type switching was silencing HML and HMR. However, in this study we show that Sir2 also regulates expression of a small gene (RDT1) in the RE that is activated during mating-type switching. The promoter of this gene is also bound by the condensin complex, and deleting this region of the RE drastically changes chromosome III structure and alters donor preference. The RE therefore appears to function as a complex locus control region (LCR) that links transcriptional control to chromatin architecture, and thus provides a new model for investigating the underlying mechanistic principles of programmed chromosome architectural dynamics.

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