The Forkhead Transcription Factor Fkh2 Regulates the Cell Division Cycle of Schizosaccharomyces pombe

ABSTRACT

In eukaryotes the regulation of gene expression plays a key role in controlling cell cycle progression. Here, we demonstrate that a forkhead transcription factor, Fkh2, regulates the periodic expression of cdc15⁺ and spo12⁺ in the M and G₁ phases of the cell division cycle in the fission yeast Schizosaccharomyces pombe. We also show that Fkh2 is important for several cell cycle processes, including cell morphology and cell separation, nuclear structure and migration, and mitotic spindle function. We find that the expression of fkh2⁺ is itself regulated in a cell cycle-dependent manner in G₁ coincident with the expression of cdc18⁺, a Cdc10-regulated gene. However, fkh2⁺ expression is independent of Cdc10 function. Fkh2 was found to be phosphorylated during the cell division cycle, with a timing that suggests that this posttranslational modification is important for cdc15⁺ and spo12⁺ expression. Related forkhead proteins regulate G₂ and M phase-specific gene expression in the evolutionarily distant Saccharomyces cerevisiae, suggesting that these proteins play conserved roles in regulating cell cycle processes in eukaryotes.