Regulation of wee1+ expression during meiosis in fission yeast

Abstract

In eukaryotes, the cyclin-dependent kinase Cdk1p (Cdc2p) plays a central role in entry into and progression through nuclear division during mitosis and meiosis. Cdk1p is activated during meiotic nuclear divisions by dephosphorylation of its tyrosine-15 residue. The phosphorylation status of this residue is largely determined by the Wee1p kinase and the Cdc25p phosphatase. In fission yeast, the forkhead-type transcription factor Mei4p is essential for entry into the first meiotic nuclear division. We recently identified cdc25+ as an essential target of Mei4p in the control of entry into meiosis I. Here, we show that wee1+ is another important target of Mei4p in the control of entry into meiosis I. Mei4p bound to the upstream region of wee1+ in vivo and in vitro and inhibited expression of wee1+, whereas Mei4p positively regulated expression of the adjacent pseudogene. Overexpression of Mei4p inhibited expression of wee1+ and induced that of the pseudogene. Conversely, deletion of Mei4p did not decrease expression of wee1+ but inhibited that of the pseudogene. In addition, deletion of Mei4p-binding regions delayed repression of wee1+ expression as well as induction of expression of the pseudogene. These results suggest that repression of wee1+ expression is primarily owing to Mei4p-mediated transcriptional interference.