The Tup1-Ssn6 general repressor is involved in repression of IME1 encoding a transcriptional activator of meiosis in Saccharomyces cerevisiae

Abstract

Ime1 plays a pivotal role in the initiation of meiosis in a/alpha diploid cells of Saccharomyces cerevisiae. In the absence of glucose and nitrogen, IME1 expression is greater in a/alpha cells than in either a or alpha cells and therefore only a/alpha, but not a/a or alpha/alpha, cells are committed to sporulation. It is known that IME1 expression is positively regulated by Mck1, Rim1, Ime4 and the Swi-Snf complex but other factors may also be involved. In addition, Rme1 is assumed to repress IME1 expression. To provide more details of the repression of expression of IME1, we have isolated mutants in which the IME1p-PHO5 fusion gene integrated at the ura3 locus is expressed in alpha cells under nutritionally rich conditions. We found that mutations occurred in TUP1, SSN6, SIN4 and RGR1, among which TUP1 and SSN6 were identified for the first time as negative regulators of IME1 expression. Deletion of the Rme1-binding site from the IME1 promoter did not result in activation of the expression of IME1 under nutritionally rich conditions, suggesting that Rme1 does not function as a DNA-binding protein with the Tup1-Ssn6 repression complex. We also demonstrated that the 294-bp fragment from nucleotide position -914 to -621 and the 301-bp fragment from nucleotide position -1215 to -915 of the IME1 promoter region contain elements acting as URS and UAS in TUP1+ and tup1 mutant cells, respectively. These findings indicate that IME1 is negatively regulated by the Tup1-Ssn6 repressor complex through two distinct upstream regions in conjunction with unidentified DNA-binding proteins.

RIM101-Dependent and -Independent Pathways Govern pH Responses in Candida albicans

“…It is intriguing that Rim101p and Tup1p together regulate transcription from the Saccharomyces IME1 and DIT1/DIT2 promoters (2,7,17). In fact, regulation of these target genes in Saccharomyces is parallel to the regulation of filamentation in C. albicans: they are positively regulated by Rim101p and negatively regulated by Tup1p.…”

O2R, a Novel Regulatory Element Mediating Rox1p-Independent O 2 and Unsaturated Fatty Acid Repression of OLE1 in Saccharomyces cerevisiae

“…The OLE1 promoter was divided into three subregions, i.e., the region harboring the FAR element and the regions upstream and downstream of this region, and these regions were inserted into the region upstream of the PHO84p-PHO5 reporter gene in the activation and repression assay vector pRAV (31). The transcription of the PHO84p-PHO5 reporter gene is repressed when cells are cultivated under conditions whereby a sufficient amount of P i is used, such as YPDA medium (31). The levels of expression of these reporter genes were measured as rAPase activities under aerobic and anaerobic conditions (Fig.…”

“…Construction of plasmid p1166, which contains a 935-bp fragment upstream of OLE1 fused with the structural region of PHO5 encoding repressible acid phosphatase (rAPase; EC 3.1.3.2), was described previously (16). The activation and repression assay vector pRAV, containing the UAS PHO84 E-PHO84p-PHO5 reporter gene, was constructed previously (31). The UAS PHO84 E-PHO84p-PHO5 reporter gene consists of a 272-bp fragment upstream of PHO84 containing Pho4p binding site E fused with the PHO5 ORF.…”

Shields up: the Tup1–Cyc8 repressor complex blocks coactivator recruitment: Figure 1.

“…The S. cerevisiae Mediator complex associates with the C-terminal domain of the largest subunit of RNA polymerase II and contributes to both transcriptional activation and repression (Bjö rklund and Gustafsson 2005;Kornberg 2005). A number of genetic screens that identified Tup1-Cyc8 as repressing gene transcription also identified Mediator subunits, suggesting that Tup1-Cyc8 and Mediator both contribute to repression (Wahi and Johnson 1995;Friesen et al 1998;Mizuno et al 1998;Kunoh et al 2000). Additionally, mutations in unc-37/Groucho, the C. elegans Tup1 homolog, show genetic interactions with Mediator mutations (Zhang and Emmons 2002).…”