Spatial and temporal control of mitotic commitment (360G-Wellcome-200847_Z_16_Z)

We will use fission yeast to study the decision to divide and how it is re-wired following stresses. Cdk1-Cyclin B activation promotes polo kinase activity to further enhance Cdk1-Cyclin B activity. Events on the spindle pole body (SPB) are key to this feedback loop. Local activation on G2 SPBs is later enhanced to drive commitment to mitosis. Recruitment of protein phosphatase 1 (PP1) to the SPB scaffold protein Cut12 represses activation on late G2 SPBs. Abolition of PP1 recruitment defines an early, PP1 insensitive, portion of G2 (Stage1). We want to determine how the transition from Stage1 to Stage2 is set and what regulates PP1 recruitment within Stage2? Identification of Cut12 partners will be complemented by phosphorylation site studies to determine how the loop is later enhanced to promote mitosis. Mutations in a second SPB component, Sid4, supress Cut12 deficiencies and change the timing of division after heat stress. We will characterise these Sid4 functions and study how and why the configuration of mitotic commitment controls changes after heat stress. Sid2-Mob1 kinase regulates PP1 recruitment to Cut12 during Stage2 and is activated following oxidative but not heat stress, enabling us to compare the impacts of distinct stresses on switch re-configuration.