Plo1(+) regulates gene transcription at the M-G(1) interval during the fission yeast mitotic cell cycle.

The regulation of gene expression plays an important part in cell cycle controls. We describe the molecular machinery that co-ordinates gene transcription at the M-G(1) interval during the fission yeast mitotic cell cycle. A sequence is identified in the cdc15(+) promoter that we call a PCB (pombe cell cycle box), which confers M-G(1)-specific transcription. Sequences similar to the PCB are present in the promoters of seven other genes, spo12(+), cdc19(+), fin1(+), sid2(+), ppb1(+), mid1(+)/dmf1(+) and plo1(+), which we find to be transcribed at M-G(1). A transcription factor complex is identified that binds to the PCB sequence, which we name PBF, for PCB-binding factor. Finally, we show that PBF binding activity and consequent gene transcription are regulated by the Plo1p protein kinase, thus invoking a potential auto-feedback loop mechanism that regulates mitotic gene transcription and passage through septation and cytokinesis.