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

1999 ◽  
Vol 19 (12) ◽  
pp. 7944-7950 ◽  
Author(s):  
Anish Ravindra ◽  
Kerstin Weiss ◽  
Robert T. Simpson
Keyword(s):  
High Resolution ◽  
Mating Type ◽  
Chromatin Structure ◽  
Micrococcal Nuclease ◽  
Histone H4 ◽  
Type Locus ◽  
Amino Terminal ◽  
Regulator Protein ◽  
Chromosome Iii ◽  
Nuclease Mapping

ABSTRACT Genetic and biochemical evidence implicates chromatin structure in the silencing of the two quiescent mating-type loci near the telomeres of chromosome III in yeast. With high-resolution micrococcal nuclease mapping, we show that the HMRa locus has 12 precisely positioned nucleosomes spanning the distance between the E and I silencer elements. The nucleosomes are arranged in pairs with very short linkers; the pairs are separated from one another by longer linkers of ∼20 bp. Both the basic amino-terminal region of histone H4 and the silent information regulator protein Sir3p are necessary for the organized repressive chromatin structure of the silent locus. Compared to HMRa, only small differences in the availability of the TATA box are present for the promoter in the cassette at the active MATa locus. Features of the chromatin structure of this silent locus compared to the previously studied HMLα locus suggest differences in the mechanisms of silencing and may relate to donor selection during mating-type interconversion.

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.

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 Formation of stable chromatin structures on the histone H4 gene during differentiation in Tetrahymena thermophila.

1986 ◽  
Vol 6 (8) ◽  
pp. 3014-3017 ◽  
Author(s):  
D S Pederson ◽  
K Shupe ◽  
G A Bannon ◽  
M A Gorovsky
Keyword(s):  
Chromatin Structure ◽  
Transcriptional Control ◽  
Tetrahymena Thermophila ◽  
Micrococcal Nuclease ◽  
Histone H4 ◽  
Hypersensitive Sites ◽  
Nuclear Differentiation ◽  
Histone Gene Transcription ◽  
The Relationship ◽  
I Gene

The relationship between chromatin structure and the transcriptional activity of the histone H4-I gene of Tetrahymena thermophila was explored. Indirect end-labeling studies demonstrated that major DNase I- and micrococcal nuclease-hypersensitive sites flank the active macronuclear genes but not the inactive micronuclear genes. Runon transcription experiments with isolated macronuclei indicated that histone gene transcription rates decreased when cells were starved. However, macronuclear nuclease-hypersensitive sites persisted upon starvation. Thus, one level of transcriptional control of the H4-I gene results in altered chromatin structure and is established during nuclear differentiation. The rate of transcription is also controlled, but not through hypersensitive site-associated structures.

scholarly journals Specific repression of the yeast silent mating locus HMR by an adjacent telomere.

1994 ◽  
Vol 14 (1) ◽  
pp. 446-455 ◽  
Author(s):  
J S Thompson ◽  
L M Johnson ◽  
M Grunstein
Keyword(s):  
Mating Type ◽  
Chromosomal Location ◽  
Regulatory Genes ◽  
Histone H4 ◽  
Cis Acting ◽  
N Terminus ◽  
Silencer Elements ◽  
Chromosome Iii

The yeast silent mating loci HML and HMR are located at opposite ends of chromosome III adjacent to the telomeres. Mutations in the N terminus of histone H4 have been previously found to derepress the yeast silent mating locus HML to a much greater extent than HMR. Although differences in the a and alpha mating-type regulatory genes and in the cis-acting silencer elements do not appear to strongly influence the level of derepression at HMR, we have found that the differential between the two silent cassettes is largely due to the position of the HMR cassette relative to the telomere on chromosome III. While HML is derepressed to roughly the same extent by mutations in histone H4 regardless of its chromosomal location, HMR is affected to different extends depending upon its chromosomal positioning. We have found that HMR is more severely derepressed by histone H4 mutations when positioned far from the telomere (cdc14 locus on chromosome VI) but is only minimally affected by the same mutations when integrated immediately adjacent to another telomere (ADH4 locus on chromosome VII). These data indicate that the degree of silencing at HMR is regulated in part by its neighboring telomere over a distance of at least 23 kb and that this form of regulation is unique for HMR and not present at HML. These data also indicate that histone H4 plays an important role in regulating the silenced state at both HML and HMR.

Evidence suggesting that the ARS elements associated with silencers of the yeast mating-type locus HML do not function as chromosomal DNA replication origins

1991 ◽  
Vol 11 (10) ◽  
pp. 5346-5355
Author(s):  
D D Dubey ◽  
L R Davis ◽  
S A Greenfeder ◽  
L Y Ong ◽  
J G Zhu ◽  
...  
Keyword(s):  
Mating Type ◽  
Transcriptional Repression ◽  
Replication Origins ◽  
Chromosomal Dna ◽  
Chromosomal Replication ◽  
Type Locus ◽  
Ars Elements ◽  
Dna Fragment ◽  
Dna Replication Origins ◽  
Chromosome Iii

The silent mating-type loci of Saccharomyces cerevisiae, HML and HMR, are flanked by transcriptional silencers that have ARS activity (i.e., they function as replication origins when in plasmids). To test whether these ARS elements are chromosomal origins, we mapped origins near HML (close to the left telomere of chromosome III). Our results indicate that the HML-associated ARS elements either do not function as chromosomal replication origins or do so at a frequency below our detection level, suggesting that replication from a silencer-associated origin in each S phase is not essential for the maintenance of transcriptional repression at HML. Our results also imply that the ability of a DNA fragment to function as an ARS element in a plasmid does not ensure its ability to function as an efficient chromosomal replication origin. Telomere proximity is not responsible for inactivating these ARS elements, because they are not detectably functional as chromosomal origins even in genetically modified strains in which they are far from the telomere.

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.

scholarly journals BISEXUAL MATING BEHAVIOR IN A DIPLOID OF SACCHAROMYCES CEREVISIAE: EVIDENCE FOR GENETICALLY CONTROLLED NON-RANDOM CHROMOSOME LOSS DURING VEGETATIVE GROWTH

Genetics ◽  
1974 ◽  
Vol 78 (3) ◽  
pp. 843-858
Author(s):  
James E Haber
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Behavior ◽  
Mating Type ◽  
Vegetative Growth ◽  
Nuclear Gene ◽  
Chromosome Loss ◽  
Type Locus ◽  
Mating Efficiency ◽  
Single Mating ◽  
Chromosome Iii

ABSTRACT A diploid strain of Saccharomyces cerevisiae has been isolated which exhabits bisexual mating behavior. The strain mates with either a or α strains with a relative mating efficiency of 1 to 2%. The efficiency of mating is correlated with the frequency with which subclones of this strain revert to a single mating type. Crosses of the bisexual diploid with a/a or α/α diploids yield bisexual segregants with a frequency of approximately 3%. Analysis of the segregation of the mating type alleles and other markers on chromosome III indicates that the primary event which leads to the bisexual phenotype is the loss of one homolog of chromosome III during vegetative growth to produce a monosomic (2n-1) diploid. Evidence is presented that the loss of chromosome I11 and possibly of other chromosomes during vegetative growth is affected by a recessive nuclear gene-her (hermaphrodite)—which is not closely linked to the mating type locus.

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 Regulation of Nuclear Positioning and Dynamics of the Silent Mating Type Loci by the Yeast Ku70/Ku80 Complex

2008 ◽  
Vol 29 (3) ◽  
pp. 835-848 ◽  
Author(s):  
Kerstin Bystricky ◽  
Haico Van Attikum ◽  
Maria-Dolores Montiel ◽  
Vincent Dion ◽  
Lutz Gehlen ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Nuclear Envelope ◽  
Mating Type ◽  
Chromatin Structure ◽  
Specific Binding ◽  
Type Locus ◽  
Specific Manner ◽  
Donor Choice ◽  
Spatial Positioning ◽  
Donor Locus

ABSTRACT We have examined the hypothesis that the highly selective recombination of an active mating type locus (MAT) with either HMLα or HMR a is facilitated by the spatial positioning of relevant sequences within the budding yeast (Saccharomyces cerevisiae) nucleus. However, both position relative to the nuclear envelope (NE) and the subnuclear mobility of fluorescently tagged MAT, HML, or HMR loci are largely identical in haploid a and α cells. Irrespective of mating type, the expressed MAT locus is highly mobile within the nuclear lumen, while silent loci move less and are found preferentially near the NE. The perinuclear positions of HMR and HML are strongly compromised in strains lacking the Silent information regulator, Sir4. However, HMLα, unlike HMR a and most telomeres, shows increased NE association in a strain lacking yeast Ku70 (yKu70). Intriguingly, we find that the yKu complex is associated with HML and HMR sequences in a mating-type-specific manner. Its abundance decreases at the HMLα donor locus and increases transiently at MAT a following DSB induction. Our data suggest that mating-type-specific binding of yKu to HMLα creates a local chromatin structure competent for recombination, which cooperates with the recombination enhancer to direct donor choice for gene conversion of the MAT a locus.

scholarly journals PLEIOTROPIC MUTATIONS AT THE TUP1 LOCUS THAT AFFECT THE EXPRESSION OF MATING-TYPE-DEPENDENT FUNCTIONS IN SACCHAROMYCES CEREVISIAE

Genetics ◽  
1980 ◽  
Vol 94 (4) ◽  
pp. 899-920
Author(s):  
Jeffrey F Lemontt ◽  
Donna R Fugit ◽  
Vivian L Mackay
Keyword(s):  
Mating Type ◽  
Single Point ◽  
Mating Frequency ◽  
Single Point Mutation ◽  
Cellular Functions ◽  
Phenotypic Properties ◽  
Type Locus ◽  
Independent Functions ◽  
Induced Mutagenesis ◽  
Chromosome Iii

ABSTRACT The umr7-1 mutation, previously identified in a set of mutants that had been selected for defective UV-induced mutagenesis at CAN1, affects other cellular functions, including many of those regulated by the mating-type locus (MAT) in heterothallic Saccharomyces cereuisiae. The recessive umr7-1 allele, mapping approximately 20 cM distal to thr4 on chromosome III, causes clumpy growth in both a and α cells and has no apparent effect on a mating functions. However, α umr7 meiotic segregants fail to express several α-specific functions (e.g., high-frequency conjugation with a strains, secretion of the hormone α-factor and response to the hormone a-factor). In addition, α umr7 cells exhibit some a-specific characteristics, such as the barrier phenotype (Bar+) that prevents diffusion of α-factor and an increased mating frequency with α strains. The most striking property of α umr7 strains is their altered morphology, in which mitotic cells develop an asymmetric pear shape, like that of normal a cells induced to form "shmoos" by interaction with α-factor. Some a/α-specific diploid functions are also affected by umr7; instead ofpolar budding patterns, a/α umr7/umr7 diploids have medial budding like a/a,α/α and haploid strains. Moreover, a/α umr7/umr7 diploids have lost the ability to sporulate and are Bar+ like a or a/a strains. Revertant studies indicate that umr7-1 is a single point mutation. The umr7 mutant fails to complement mutants of both tup1 (selected for deoxythymidine monophosphate utilization) and cyc9 (selected for high iso-2-cytochrome c levels), and all three isolates have similar genetic and phenotypic properties. It is suggested that the product of this gene plays some common central role in the complex regulation of the expression of both MAT-dependent and MAT-independent functions.

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