Whi5 phosphorylation embedded in the G1/S network dynamically controls critical cell size and cell fate

In budding yeast the G1/S transition requires the attainment of a critical cell size. Here the authors unravel its basic control mechanism by integrating simulations of a mathematical model of multisite phosphorylation of Whi5 by Cln3–Cdk1, with molecular analyses of a Whi5 phospho-mimetic mutant.