Relative contributions of MCM1 and STE12 to transcriptional activation of a- and α-specific genes from Saccharomyces cerevisiae

Abstract

We have examined the relative contributions of MCM1 and STE12 to the transcription of the a-specific STE2 gene by using a 367 bp fragment from the STE2 5'-noncoding region to drive expression of a reporter lacZ gene. Mutation of the MCM1 binding site destroyed MCM1.alpha 2-mediated repression in alpha cells and dramatically reduced expression in a cells. The residual expression was highly stimulated by exposure of cells to pheromone. Likewise, the loss of STE12 function reduced lacZ expression driven by the wild-type STE2 fragment. In the absence of both MCM1 and STE12 functions, no residual expression was observed. Thus, the STE2 fragment appears to contain two distinct upstream activation sequences (UASs), one that is responsible for the majority of expression in cells not stimulated by pheromone, and one that is responsible for increased expression upon pheromone stimulation. In further support of this idea, a chemically synthesized version of the STE2 MCM1 binding site had UAS activity, but the activity was neither stimulated by pheromone nor reduced in ste12 mutants. Although transcription of alpha-specific genes also requires both MCM1 and STE12, these genes differ from a-specific genes in that they have a single, MCM1-dependent UAS system. The activity of the minimal 26 bp UAS from the alpha-specific STE3 gene was both stimulated by pheromone and reduced in ste12 mutants. These data suggest that at alpha-specific genes STE12 and MCM1 exert their effects through a single UAS.

A novel Mcm1-dependent element in the SWI4, CLN3, CDC6, and CDC47 promoters activates M/G1-specific transcription.

“…However, some of the S. cerevisiae genes required for mating contain Mcm 1-binding sites that are quite similar to ECB elements, and two of these (STE2 and MFA2) are also cell cycle regulated (Oehlen et al 1996). These promoters also contain consensus binding sites for Stel2, which cooperates with Mcml to increase basal transcription and to confer pheromone inducibility (Hwang-Shum et al 1991;Errede and Ammerer 1989). However, the STE2 Mcml-binding site is capable of activating transcription on its own (Hwang-Shum et al (lanes 3,4), CLN3 (lanes 6,7), CDC6 (lanes 8,9), and CDC47 (lanes 10,I1) promoters added in 10 and 100 M excess.…”

The mapping of nucleosomes and regulatory protein binding sites at the Saccharomyces cerevisiae MFA2 gene: a high resolution approach

“…In α cells gene products of MATα are the α1 and α2 proteins, essential factors for the regulation of mating type-specific genes in α cells. Mating type-specific gene regulation also requires the product of MCM1, the transcription factor PRTF/GRM (pheromone receptor transcription factor/general regulator of mating), which can bind to the P box (Mcm1 binding site) and act synergistically with the α1 protein as a co-activator of α-specific genes or with the α2 protein as a co-repressor of a-specific genes in α cells (2)(3)(4)(5). In S.cerevisiae, five a-specific genes, MFA1, MFA2, STE2, STE6 and BAR1, have an α2 operator, a 31 bp sequence ∼200 bp upstream of the transcription start point (6) consisting of a P box (Mcm1 binding site) flanked by two α2 binding sites.…”

Transcriptional Regulation of MDR1 , Encoding a Drug Efflux Determinant, in Fluconazole-Resistant Candida albicans Strains through an Mcm1p Binding Site

“…Repression of a-specific genes in ␣ haploid cells and a/␣ diploid cells requires cooperative binding of ␣2p and Mcm1p to adjacent binding sites and subsequent recruitment of the Ssn6-Tup1 repression complex (27). In contrast, no ␣2p is present in a cells and therefore no Ssn6-Tup1 complex is recruited; in this situation, Mcm1p cooperates with the transcription factor Ste12p to activate transcription (30). In S. cerevisiae, the only binding sites for coregulators that flank the Mcm1p binding site and are in opposite orientation are ␣2 boxes with the core sequence 5Ј-TGTA-3Ј.…”