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

Dranginis, Anne M.

doi:10.1128/mcb.9.9.3992

Cited by 37 publications

(27 citation statements)

References 42 publications

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“…We have previously demonstrated that STA1 is expressed in haploids but not in diploids growing vegetatively in rich media (8). Diploid-specific repression of STA1 is dependent on the a1/␣2 repressor (8). Since the 5Ј flanking sequences of FLO11 have a high degree of homology to STA1, one might expect the two genes to be regulated in similar ways.…”

Section: Resultsmentioning

confidence: 99%

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FLO11, a yeast gene related to the STA genes, encodes a novel cell surface flocculin

1996

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We report the characterization of a gene encoding a novel flocculin related to the STA genes of yeast, which encode secreted glucoamylase. The STA genes comprise sequences that are homologous to the sporulationspecific glucoamylase SGA and to two other sequences, S2 and S1. We find that S2 and S1 are part of a single gene which we have named FLO11. The sequence of FLO11 reveals a 4,104-bp open reading frame on chromosome IX whose predicted product is similar in overall structure to the class of yeast serine/threoninerich GPI-anchored cell wall proteins. An amino-terminal domain containing a signal sequence and a carboxyterminal domain with homology to GPI (glycosyl-phosphatidyl-inositol) anchor-containing proteins are separated by a central domain containing a highly repeated threonine-and serine-rich sequence. Yeast cells that express FLO11 aggregate in the calcium-dependent process of flocculation. Flocculation is abolished when FLO11 is disrupted. The product of STA1 also is shown to have flocculating activity. When a green fluorescent protein fusion of FLO11 was expressed from the FLO11 promoter on a single-copy plasmid, fluorescence was observed in vivo at the periphery of cells. We propose that FLO11 encodes a flocculin because of its demonstrated role in flocculation, its structural similarity to other members of the FLO gene family, and the cell surface location of its product. FLO11 gene sequences are present in all yeast strains tested, including all standard laboratory strains, unlike the STA genes which are present only in the variant strain Saccharomyces cerevisiae var. diastaticus. FLO11 differs from all other yeast flocculins in that it is located near a centromere rather than a telomere, and its expression is regulated by mating type. Repression of FLO11-dependent flocculation in diploids is conferred by the mating-type repressor a1/␣2.

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Section: Resultsmentioning

confidence: 99%

“…4 reveals. FLO11 expression is regulated by mating type. We have previously demonstrated that STA1 is expressed in haploids but not in diploids growing vegetatively in rich media (8). Diploid-specific repression of STA1 is dependent on the a1/␣2 repressor (8).…”

Section: Resultsmentioning

confidence: 99%

FLO11, a yeast gene related to the STA genes, encodes a novel cell surface flocculin

1996

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“…These differences may be related in part to inherent properties of the loci. The level of expression may be modulated, since the functionality of the MATa gene products is limited compared to that of the ␣ gene products (3,14,21,45). Subtle differences in the chromatin structure of the promoters at HMRa and MATa may reflect lower levels of transcriptional activity of MATa.…”

Section: Discussionmentioning

confidence: 99%

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

Ravindra

Weiß

Simpson

1999

Molecular and Cellular Biology

113

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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 ϳ20 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 HML␣ locus suggest differences in the mechanisms of silencing and may relate to donor selection during mating-type interconversion.The silencing of the haploid mating-type loci is a critical requirement for the yeast life cycle (10). Mating types in the yeast Saccharomyces cerevisiae are defined by a set of genes expressed at the active MAT locus near the center of chromosome III. MATa and MAT␣ differ by approximately 750-bp regions, designated Ya and Y␣, respectively, which contain the promoters for genes encoding the master regulatory proteins that define the unique mating type of the cell. Strains with the MATa allele express the a1 and a2 genes, while strains with the MAT␣ allele express the ␣1 and ␣2 genes. In addition to the active MAT locus, two almost identical HM loci are located near the telomeres of chromosome III. HML␣ is near the left telomere, while HMRa resides near the right telomere. These loci are transcriptionally silent and make no direct contribution to mating type. Rather, they serve as donors during yeast mating-type interconversion, or switching (7).The switching event is initiated by expression of the HO endonuclease. This enzyme recognizes and cleaves doublestranded DNA at a site at MAT. The break is repaired by replacing it with the Y region of one of the HM loci, usually that with information of the opposite mating type (18,22,27,41). Interestingly, identical HO sites present at the silent loci are not recognized by the endonuclease. Thus, DNA at the silent mating-type loci is present in a unique state, in which it is invisible to the endonuclease and transcription machinery but completely competent to participate in a recombinational event.Extensive genetic studies (20) led to a model in which proteins binding to cis-acting DNA elements flanking the loci, a number of interacting, non-DNA binding proteins, and histones cooperate to form a repressive, heterochromatin-like structure that packages DNA in a presumably inaccessible format. Heterochromatic condensation has been implicated in position effect variegation in Drosophila melanogaster (9) and X-chromosome inactivation (13) and gene imprinting...

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“…Expression of the STA genes is regulated by complex interactions between positive and negative factors and their cognate elements (1,19,21,33,41). The negative regulation occurs at three different levels: (i) carbon catabolite repression by glucose (6,34); (ii) repression by STA10, which is known as a repressor gene in S. cerevisiae (33); and (iii) diploid cell-specific repression (6,34). The mechanisms underlying repression of the STA genes, however, are not yet understood.…”

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Nrg1 Is a Transcriptional Repressor for Glucose Repression ofSTA1Gene Expression inSaccharomyces cerevisiae

Park

Koh

Chun

et al. 1999

Molecular and Cellular Biology

108

119

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Expression of genes encoding starch-degrading enzymes is regulated by glucose repression in the yeast Saccharomyces cerevisiae. We have identified a transcriptional repressor, Nrg1, in a genetic screen designed to reveal negative factors involved in the expression of STA1, which encodes a glucoamylase. The NRG1 gene encodes a 25-kDa C 2 H 2 zinc finger protein which specifically binds to two regions in the upstream activation sequence of the STA1 gene, as judged by gel retardation and DNase I footprinting analyses. Disruption of the NRG1 gene causes a fivefold increase in the level of the STA1 transcript in the presence of glucose. The expression of NRG1 itself is inhibited in the absence of glucose. DNA-bound LexA-Nrg1 represses transcription of a target gene 10.7-fold in a glucose-dependent manner, and this repression is abolished in both ssn6 and tup1 mutants. Two-hybrid and glutathione S-transferase pull-down experiments show an interaction of Nrg1 with Ssn6 both in vivo and in vitro. These findings indicate that Nrg1 acts as a DNA-binding repressor and mediates glucose repression of the STA1 gene expression by recruiting the Ssn6-Tup1 complex.In yeast, a large number of genes are turned off during growth on glucose (9, 37, 49). These glucose-repressible genes can be divided into three groups: (i) genes for metabolizing other carbon sources; (ii) genes encoding enzymes unique to gluconeogenesis; and (iii) genes involved in the Krebs cycle and in respiration. The Mig1 glucose repressor is a zinc finger protein and binds to the GC-rich motif identified in the promoters of several glucose-repressed genes, including the GAL1, GAL4, SUC2, and MAL genes (10,13,28,29). In the absence of glucose, the Snf1 kinase inhibits the function of Mig1 protein directly or indirectly, leading to derepression of glucose-repressed genes (3, 4). Nuclear translocation of Mig1 is regulated by differential phosphorylation of the protein in response to glucose availability, and recruitment of the general repression complex Ssn6-Tup1 to the DNA-bound Mig1 is required for the repression (5,17,48). Disruption of the MIG1 gene, however, only partially relieves glucose repression of SUC2 and has little or no effect on glucose repression of other genes whose promoters contain the Mig1-binding sites (27,31,37,50), indicating the involvement of other repressors in glucose repression. For instance, Mig2 was recently identified as a second repressor responsible for the remaining glucose repression of SUC2 and contains zinc fingers very similar to those of Mig1 (24).In Saccharomyces cerevisiae var. diastaticus, three unlinked homologous STA genes (STA1, STA2, and STA3) encode glucoamylase isozymes (GAI, GAII, and GAIII), which are responsible for enzymatic degradation of starch to glucose (16,22,25,32,35,47,52). Expression of the STA genes is regulated by complex interactions between positive and negative factors and their cognate elements (1,19,21,33,41). The negative regulation occurs at three different levels: (i) carbon catabolite repression...

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

Cited by 37 publications

References 42 publications

FLO11, a yeast gene related to the STA genes, encodes a novel cell surface flocculin

FLO11, a yeast gene related to the STA genes, encodes a novel cell surface flocculin

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

Nrg1 Is a Transcriptional Repressor for Glucose Repression ofSTA1Gene Expression inSaccharomyces cerevisiae

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