The Role of Pds1 in Cell Size Control in Budding Yeast Cells
Physical and Biological Sciences
Kellogg Lab
Cell size is controlled by cell size checkpoints, which ensure that key cell cycle transitions only occur when sufficient growth has been achieved. Previous studies have suggested that control of cell growth and size occurs primarily in G1 phase; however, our recent studies have shown that growth and size are controlled primarily during mitosis. We have also shown that a phosphatase called PP2ARts1 controls the amount of growth that occurs during mitosis, although the targets of PP2ARts1 are poorly understood. A key player in mitotic control is Pds1, which controls metaphase duration by inhibiting cleavage of proteins that hold chromosomes together. In response to DNA damage, phosphorylation of Pds1 results in a longer metaphase. We hypothesize that phosphorylation of Pds1 in response to nutrient changes controls the duration of growth during mitosis, and that PP2ARts1 controls Pds1 phosphorylation. To test this hypothesis, we will use Phos-tag™ gels to analyze phosphorylation of Pds1 cells growing in rich or poor nutrients, which show different durations of growth in mitosis. We will also generate a mutant version of Pds1 that cannot be phosphorylated and determine whether it causes defects in cell size control. Our hypothesis predicts that the pds1 phosphorylation site mutant will have a shortened metaphase and a reduced cell size.
