Identification of a DNA segment that is necessary and sufficient for alpha-specific gene control in Saccharomyces cerevisiae: implications for regulation of alpha-specific and a-specific genes.

Abstract

STE3 mRNA is present only in Saccharomyces cerevisiae a cells, not in a or ala cells, and the transcript level increases about fivefold when cells are treated with a-factor mating pheromone. Deletions in the 5' noncoding region of STE3 defined a 43-base-pair (bp) upstream activation sequence (UAS) that can impart both modes of regulation to a CYCI-lacZ fusion when substituted for the native CYCI UAS. UAS activity required the al product of MATa, which is known to be required for transcription of a-specific genes. A chromosomal deletion that removed only 14 bp of the STE3 UAS reduced STE3 transcript levels 50-to 100-fold, indicating that the UAS is essential for expression. The STE3 UAS shares a 26-bp homology with the 5' noncoding sequences of the only other known a-specific genes, MFal and MFa2. We view the homology as having two componentsa nearly palindromic 16-bp "P box" and an adjacent 10-bp "Q box." A synthetic STE3 P box was inactive as a UAS; a perfect palindrome P box was active in all three cell types. We propose that the P box is the binding site for a transcription activator, but that al acting via the Q box is required for this activator to bind to the imperfect P boxes of a-specific genes. Versions of the P box are also found upstream of a-specific genes, within the binding sites of the repressor a2 encoded by MATa. Thus, the products of MATa may render gene expression a or a-specific by controlling access of the same transcription activator to its binding site, the P box.Cell specialization is vital to the sexual life cycle of the yeast Saccharomyces cerevisiae. In S. cerevisiae, three types of cells occur. The two haploid cell types, a and a, are specialized for mating, whereas the a/a diploid cell type formed by mating of a and a cells is specialized for meiosis and sporulation. Each of the two haploid cell types expresses a specific set of genes that allows it to mate with cells of the opposite type. Among the cell-type-specific gene products are the small peptide pheromones, a factor and a factor, and the receptors for these pheromones. For example, only a cells secrete a factor and produce the cell surface receptor for a factor. These mating pheromones and receptors are the major components of a system that enables efficient mating of haploid cells of opposite type (for reviews, see references 20,21,41,47).How is this cell specialization controlled? The ultimate determinant of the cell type (mating type) of yeast cells is the MAT locus. Haploid a cells contain the MATa allele, which encodes two regulators, al and a2 (45). al is an activator of a-specific genes, which include the a-factor structural genes, MFaJ (26,39) and MFa2 (39), and the gene that encodes the a-factor receptor, STE3 (3,16,27,34). Conversely, the a2 product represses a-specific genes, which include the afactor structural genes, MFal and MFa2 (7), the a-factor receptor gene, STE2 (19,23,27,34), and two genes whose products are involved in pheromone metabolism, STE6 (9, 50) and BAR] (42). For both a-and a-specific genes, regu...

Comprehensive Identification of Cell Cycle–regulated Genes of the YeastSaccharomyces cerevisiaeby Microarray Hybridization

“…Some of these genes (MF␣1, MF␣2, and STE3) are specific for MAT␣ cells (Jarvis et al, 1988) and so are significantly expressed only in the cdc15 experiment, which was done with a MAT␣ strain. Other genes in the cluster (KAR4, AGA1, SST2, and FUS1) are induced by ␣ factor and so are very strongly expressed at the beginning of the ␣ factor experiment.…”

Interaction of the Endocytic Scaffold Protein Pan1 with the Type I Myosins Contributes to the Late Stages of Endocytosis

“…From ϳ750,000 transformants, 25 positive clones were obtained, and the activation domain library plasmid was rescued and confirmed by retransforming into AH109 with pBW530 before being sequenced. For quantitative analysis, SFY526 cells transformed with a Gal-DNA-binding domain plasmid (pBW530) and transcriptional-activation domain plasmid were grown in selective liquid culture to mid-log phase and assayed for the expression of Galp-LacZ as described previously (Jarvis et al, 1988). Each value represents the average and SD for three independent quantifications.…”

MCM1 binds to a transcriptional control element in Ty1.

“…Another difference is that the PAL sequence activates transcription in all cell types whereas the tandem copies of Tyl fragment H activate transcription in the haploid but not diploid cell type (6,18). The additional sequence features of the Tyl fragment provide a reasonable explanation for the cell type specificity imposed on the MCM1-mediated transcriptional effects.…”

“…1, fragment H) (6,13 Although MCM1 is the proposed transcriptional activator associated with the distal Tyl regulatory region, there are differences in the transcriptional activation properties of the Tyl site and the PAL sequence. A single copy of the PAL sequence functions as a UAS (18). In contrast, significant activation of reporter gene expression has been demonstrated only with multiple tandem copies of a 57-bp Tyl fragment that encompasses the MCM1-binding sequence (Fig.…”

“…Other DNA-binding proteins are also important for the transcriptional regulation of celltype-specific genes. For example, the MCM1 transcription factor cooperates with the al protein for expression of ax-specific genes and with the a2 protein for repression of a-specific genes (1,2,18,20,26). At some cell-type-specific promoters, MCM1 cooperates with the STE12 transcription factor (9,25,28).…”