The transcriptional activator Pog1 controls cell cycle, and its phosphorylated form is downregulated by the ubiquitin ligase Dma2 in Saccharomyces cerevisiae.

The POG1 gene in Saccharomyces cerevisiae is suggested to encode the transcriptional activator that promotes growth in the presence of a mating pheromone. We previously showed that the overexpression of POG1 conferred tolerance to high concentrations of LiCl and sugar on laboratory and baker's yeast strains, respectively. Here, the overexpression of POG1 was shown to induce cell cycle delay at the G1 phase and morphological abnormality. In addition, by yeast two-hybrid screening, the really interesting new gene (RING)-type ubiquitin ligase Dma2, which is involved in cell cycle regulation, was identified as the protein interacting with Pog1. The gene mutation and deletion analysis revealed that the interaction between Pog1 and Dma2 requires the phosphorylation of Thr253 in Pog1 and the forkhead-associated domain in Dma2. The phosphorylation status of Pog1 changed along with progression of the cell cycle. Interestingly, our results showed that Pog1 might be ubiquitinated by Dma2, but a dephosphorylation-mimic mutation in POG1 increased the cellular Pog1 level possibly due to the failure of ubiquitination. Furthermore, growth of the dma1/2-disrupted strain was greatly inhibited by the overexpression of POG1. These results suggest that Pog1 controls the cell cycle and its phosphorylated form is downregulated by Dma2.