The pat1 protein kinase controls transcription of the mating-type genes in fission yeast.
The developmental programme of fission yeast brings about a transition from mitotic cell division to the dormant state of ascospores. In response to nitrogen starvation, two cells of opposite mating type conjugate to form a diploid zygote, which then undergoes meiosis and sporulation. This differentiation process is characterized by a transcriptional induction of the mating-type genes. Conjugation can also be induced in pat1-ts mutants by a shift to a semi-permissive temperature. The pat1 gene encodes a protein kinase, which also functions further downstream in the developmental pathway controlling entry into meiosis. We have analysed transcriptional induction of mating-type genes in various strains--with and without a pat1-ts allele. In wild-type cells of P-mating type derepression occurs in two rounds. First, the mat1-Pc gene is induced in response to nitrogen starvation. Mutants in the map1 gene are defective in this process. In the following step the mat1-Pm gene is expressed in response to a pheromone signal generated by cells of M mating type. Both these controls are derepressed in the pat1-ts mutant at semipermissive temperature. Previous work has established that expression of the mating-type genes in the zygote leads to complete loss of pat1 protein kinase activity causing entry into meiosis. Thus, pat1 can promote its own inactivation. We suggest a model according to which a stepwise inactivation of pat1 leads to sequential derepression of the processes of conjugation and meiosis.
Nielsen
O
O
Institute of Genetics, University of Copenhagen, Denmark.
Egel
R
R
D003227:Conjugation, Genetic / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal / Q000235:genetics; D005800:Genes, Fungal / Q000502:physiology*; D049770:Genes, Mating Type, Fungal; D008540:Meiosis / Q000235:genetics; D008954:Models, Biological; D011494:Protein Kinases / Q000235:genetics / Q000502:physiology*; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D004718:Saccharomycetales / Q000201:enzymology*; D012568:Schizosaccharomyces / Q000201:enzymology* / Q000254:growth & development; D013696:Temperature; D014157:Transcription Factors / Q000502:physiology*; D014158:Transcription, Genetic
D005656:Fungal Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D011494:Protein Kinases