THE SCHIZOSACCHAROMYCES-POMBE MAP1 GENE ENCODES AN SRF MCM1-RELATED PROTEIN REQUIRED FOR P-CELL SPECIFIC GENE-EXPRESSION/

Cells of Schizosaccharomyces pombe undergo mating and meiosis when sta rved for a nitrogen source. In this process a P and an M cell first ma te to generate a diploid zygote, which subsequently enters meiosis and sporulates. The P mating type is controlled by the mat1-Pc gene at th e mating type locus, together with a gene called map1. We show that th ese two functions are required for expression of the P-specific gene m ap3. We have cloned the map1 gene and show that it encodes a putative MADS-box containing transcription factor related to mammalian Serum Re sponse Factor (SRF) and Saccharomyces cerevisiae MCM1. The Mat1-Pc pro tein contains a motif characteristic for proteins that interact with M ADS-box factors, suggesting that Mat-Pc and Map1 may form a heterodime r that activates the P-specific map3 gene.