Mutations that suppress the deletion of an upstream activating sequence in yeast: Involvement of a protein kinase and histone H3 in repressing transcription in vivo

Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115.
Genetics (Impact Factor: 4.87). 12/1993; 135(3):665-76.
Source: PubMed

ABSTRACT Regulated transcription of most protein-encoding genes in Saccharomyces cerevisiae requires an upstream activating sequence (UAS); in the absence of UAS elements, little or no transcription occurs. In certain mutant strains, however, promoters that have been deleted for their UAS can direct significant levels of transcription, indicating that the remaining promoter elements (the basal promoter) are capable of directing higher levels of transcription, but they are normally represented in wild-type strains. To analyze this repression, we have selected for mutations that cause increased transcription of the SUC2 gene in the absence of its UAS. In addition to some previously studied genes, this selection has identified five genes that we have designated BUR1, BUR2, BUR3, BUR5 and BUR6 (for Bypass UAS Requirement). The bur mutations cause pleiotropic phenotypes, indicating that they affect transcription of many genes. Furthermore, some bur mutations suppress the requirement for the SNF5 trans-activator at both SUC2 and Ty. Additional analysis has demonstrated that BUR1 is identical to SGV1, which encodes a CDC28-related protein kinase. This result indicates that protein phosphorylation is important for repression of the SUC2 basal promoter as well as other aspects of transcription in vivo. Finally, BUR5 is identical to HHT1, encoding histone H3, further implicating chromatin structure as important for expression of SUC2.

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    • "The SPT genes encode many proteins important in transcription, including subunits of the SAGA histone-modifying complex (Grant et al. 1998), TBP itself, and histones (Clark-Adams et al. 1988; Winston and Sudarsanam 1998; Yamaguchi et al. 2001). SPT10 is not an essential gene, but the null allele is associated with very slow growth and defects in gene regulation (Denis and Malvar 1990; Natsoulis et al. 1991; Prelich and Winston 1993; Yamashita 1993; Dollard et al. 1994; Natsoulis et al. 1994). Spt10 contains a histone acetyltransferase (HAT) domain similar to that of Gcn5 (Neuwald and Landsman 1997), but it has not been possible to demonstrate HAT activity, despite many attempts by our laboratory and others. "
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    ABSTRACT: We discuss the regulation of the histone genes of the budding yeast Saccharomyces cerevisiae. These include genes encoding the major core histones (H3, H4, H2A, and H2B), histone H1 (HHO1), H2AZ (HTZ1), and centromeric H3 (CSE4). Histone production is regulated during the cell cycle because the cell must replicate both its DNA during S phase and its chromatin. Consequently, the histone genes are activated in late G1 to provide sufficient core histones to assemble the replicated genome into chromatin. The major core histone genes are subject to both positive and negative regulation. The primary control system is positive, mediated by the histone gene-specific transcription activator, Spt10, through the histone upstream activating sequences (UAS) elements, with help from the major G1/S-phase activators, SBF (Swi4 cell cycle box binding factor) and perhaps MBF (MluI cell cycle box binding factor). Spt10 binds specifically to the histone UAS elements and contains a putative histone acetyltransferase domain. The negative system involves negative regulatory elements in the histone promoters, the RSC chromatin-remodeling complex, various histone chaperones [the histone regulatory (HIR) complex, Asf1, and Rtt106], and putative sequence-specific factors. The SWI/SNF chromatin-remodeling complex links the positive and negative systems. We propose that the negative system is a damping system that modulates the amount of transcription activated by Spt10 and SBF. We hypothesize that the negative system mediates negative feedback on the histone genes by histone proteins through the level of saturation of histone chaperones with histone. Thus, the negative system could communicate the degree of nucleosome assembly during DNA replication and the need to shut down the activating system under replication-stress conditions. We also discuss post-transcriptional regulation and dosage compensation of the histone genes.
    Genetics 05/2012; 191(1):7-20. DOI:10.1534/genetics.112.140145 · 4.87 Impact Factor
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    • "First, it was shown that suppressors of snf2/swi2 mutations included mutations in HTA1-HTB1, encoding histones H2A-H2B, and in SPT6, encoding a histone chaperone (Neigeborn et al. 1986, 1987; Clark-Adams and Winston 1987; Hirschhorn et al. 1992). This genetic relationship between Swi/Snf and chromatin was fortified by other results that showed that suppressors of swi1, swi2, and swi3 mutations were in histone H3-and H4-encoding genes (Prelich and Winston 1993; Kruger et al. 1995). Thus, genetics suggested that the transcriptional activation defects caused by loss of Swi/Snf could be bypassed by reducing or altering nucleosome function. "
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    ABSTRACT: Understanding the mechanisms by which chromatin structure controls eukaryotic transcription has been an intense area of investigation for the past 25 years. Many of the key discoveries that created the foundation for this field came from studies of Saccharomyces cerevisiae, including the discovery of the role of chromatin in transcriptional silencing, as well as the discovery of chromatin-remodeling factors and histone modification activities. Since that time, studies in yeast have continued to contribute in leading ways. This review article summarizes the large body of yeast studies in this field.
    Genetics 02/2012; 190(2):351-87. DOI:10.1534/genetics.111.132266 · 4.87 Impact Factor
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    • "Notably , we were aided in our identification of three of the complementation groups—EWE3/MED7, EWE4/SRB7, and EWE5/NUT2—by use of a novel conditional growth phenotype, enhanced sensitivity to 300 mm urea. It is surprising that our screen failed to pull out genes encoding chromatin-associated proteins, especially since a previous screen, using a similar strategy (selection of bypass suppressors of a UAS deletion, in the earlier case of SUC2), isolated recessive mutations in several chromatin-associated proteins, including H2A, H2B, H3, Spt6, Spt10, and Spt16, in addition to three others: Bur1 and Bur2, which compose a cyclin/cyclindependent kinase heterodimer, and Bur6, a subunit of the heterodimeric NC2 negative general transcription factor (Prelich and Winston 1993). The EWE screen isolated none of these. "
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    ABSTRACT: We report the results of a genetic screen designed to identify transcriptional coregulators of yeast heat-shock factor (HSF). This sequence-specific activator is required to stimulate both basal and induced transcription; however, the identity of factors that collaborate with HSF in governing noninduced heat-shock gene expression is unknown. In an effort to identify these factors, we isolated spontaneous extragenic suppressors of hsp82-deltaHSE1, an allele of HSP82 that bears a 32-bp deletion of its high-affinity HSF-binding site, yet retains its two low-affinity HSF sites. Nearly 200 suppressors of the null phenotype of hsp82-deltaHSE1 were isolated and characterized, and they sorted into six expression without heat-shock element (EWE) complementation groups. Strikingly, all six groups contain alleles of genes that encode subunits of Mediator. Three of the six subunits, Med7, Med10/Nut2, and Med21/Srb7, map to Mediator's middle domain; two subunits, Med14/Rgr1 and Med16/Sin4, to its tail domain; and one subunit, Med19/Rox3, to its head domain. Mutations in genes encoding these factors enhance not only the basal transcription of hsp82-deltaHSE1, but also that of wild-type heat-shock genes. In contrast to their effect on basal transcription, the more severe ewe mutations strongly reduce activated transcription, drastically diminishing the dynamic range of heat-shock gene expression. Notably, targeted deletion of other Mediator subunits, including the negative regulators Cdk8/Srb10, Med5/Nut1, and Med15/Gal11 fail to derepress hsp82-deltaHSE1. Taken together, our data suggest that the Ewe subunits constitute a distinct functional module within Mediator that modulates both basal and induced heat-shock gene transcription.
    Genetics 05/2006; 172(4):2169-84. DOI:10.1534/genetics.105.052738 · 4.87 Impact Factor
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