Two RNA binding proteins Msa1 and Msa2 inhibitory to sexual differentiation in fission yeast.
Hee Tae Jeong, Yasuo Oowatari, Katsunori Tanaka, Hideyuki Matsuda, Makoto Kawamukai
Life & Environmental Science, Shimane University, 1060 Nishikwatsu, Matsue, 690-8504, Japan
Sexual differentiation in the fission yeast Schizosaccharomyces pombe is triggered by nutrient starvation and by the presence of mating pheromones. We identified two genes, msa1, and msa2/nrd1 as encoding RNA-binding proteins that inhibit sexual differentiation. Genetic analysis suggested that the function of msa1 is independent of the cAMP pathway and stress responsive pathway. Deletion of the ras1 gene in diploid cells inhibited sporulation and in haploid cells decreased expression of mating pheromone-induced genes such as mei2, mam2, ste11, and rep1 ; simultaneous deletion of msa1 reversed both phenotypes. Overexpression of msa1 decreased activated Ras1 Val17 -induced expression of mam2. Phenotypic hypersporulation was similar between cells with deletion of only rad24 and both msa1 and rad24, but simultaneous deletion of msa1 and msa2 additively increased hypersporulation. Msa2 interacted with Cpc2, a fission yeast homologue of the RACK1. Epistatic analysis of msa2 and cpc2 suggested that Msa2 is an upstream regulator for Cpc2. Localization analysis of Cpc2 and Msa2 indicated both proteins predominantly localized in the cytoplasm. We suggest that the primary function of Msa1 and Msa2 are to negatively regulate sexual differentiation by controlling the expression of Ste11-regulated genes and by controlling Cpc2, respectively. *Jeong et al., Genetics 167:77- (2004), **Jeong et al. Biosci. Biotech. Biochem. 68:1489- (2004).