Mei4p coordinates the onset of meiosis I by regulating cdc25~+ in fission yeast

摘要

The kinase Cdc2p is a central regulator of entry into and progression through nuclear division during mitosis and meiosis in eu-karyotes. Cdc2p is activated at the onset of mitosis by dephos-phorylation on tyrosine-15, the phosphorylation status of which is determined mainly by the kinase Wee1p and the phosphatase Cdc25p. In fission yeast, the forkhead-type transcription factor Mei4p is required for expression of many genes during meiosis, with mei4 mutant cells arresting before meiosis I. The mechanism of cell cycle arrest in mei4 cells has remained unknown, however. We now show that cdc25~+ is an important target of Mei4p in control of entry into meiosis I. Forced dephosphorylation of Cdc2p on tyrosine-15 thus induced meiosis i in mei4 mutant cells without a delay, although no spores were formed. We propose that Mei4p acts as a rate-limiting regulator of meiosis I by activating cdc2S~+ transcription in coordination with other meiotic events.