Mating pheromone‐induced expression of the MAT1‐Pm gene of Schizosaccharomyces pombe: Identification of signalling components and characterization of upstream controlling elements

Abstract

Transcription of the mat1-Pm gene of Schizosaccharomyces pombe controlling entry into meiosis is stimulated by the mating pheromone, M-factor. We have studied its expression by monitoring beta-galactosidase activity in cells carrying a plasmid-borne mat1-Pm/lacZ fusion construct. Stimulation required the M-factor receptor (Map3) and other proteins (Gpa1, Byr1, Byr2 and Spk1) thought to be involved in propagating the pheromone signal within the cell. Mutational activation of gpa1 encoding an alpha subunit of the receptor-coupled heterotrimeric G protein causes full expression of mat1-Pm even in the absence of pheromone, suggesting that Gpa1 is a key signal transmitter. Furthermore, an activated ras1val17 mutant exhibited a much stronger level of induction than wild-type cells, though full expression needs M-factor treatment. Deletion analysis of the mat1-Pm promoter region identified a stretch of 21 bp that is shown to play a critical role in controlling expression. This region lies just upstream of a TATA-like box and contains a TR-box (TTCTTTGTTY) motif which is the recognition site of a putative transcription factor Ste11. Point mutations in the TR-box motif abolished the expression of mat1-Pm/lacZ. Almost no expression of mat1-Pm was detected in a ste11 deletion mutant, whereas overproduction of Ste11 greatly increased the expression.

Cyclin B Proteolysis and the Cyclin-dependent Kinase Inhibitor rum1p Are Required for Pheromone-induced G1Arrest in Fission Yeast

“…The failure to express pheromone-dependent genes later in the cell cycle could be due to reduced pheromone signaling or because a component of the transcriptional apparatus can only be activated in G 1 . A possible candidate is the transcription factor ste11p , which is required for both nitrogen starvation and pheromone-induced transcription (Aono et al, 1994;Petersen et al, 1995). Pheromone-dependent transcription is also cell cycle regulated in budding yeast (Oehlen and Cross, 1994).…”

Differential effects of RGS proteins on Gαq and Gα11 activity

“…In Sz. pombe both the receptor [15,24] and RGS protein [14] reduce Gpa1 signalling, and we presume that removing these negative regulators increases the rate at which Gα subunits become spontaneously activated to Gα-GTP. Consistent with this suggestion, the activity of both Gα q and Gα 11 was dependent upon binding of GTP and reduced by expression of Rgs1 (Fig.…”

“…Such activation of Gα subunits in the absence of an appropriate receptor has been reported in both Sz. pombe [15,24] and Sc. cerevisiae [25,26], and is consistent with a role for unoccupied receptors in maintaining G proteins in their inactive state.…”

His-to-Asp Phosphorelay Circuitry for Regulation of Sexual Development inSchizosaccharomyces pombe

“…[36][37][38] To determine the relevance of the newly uncovered Phk-mediated regulation, with regard to the classical view at the molecular level, the expression of ste11 + , mam2 + , and mei2 + was directly assessed by Northern hybridization for the phk1 W 2 W 3D cells, grown in either nitrogen-su‹cient or nitrogen-deˆcient medium (Fig. 5(A)).…”