A Growth and cycle model for Saccharomyces cerevisiae

A low granularity model is proposed, aiming to describe the major features of cell growth and cell cycle in budding yeast Saccharomyces cerevisiae. Central for the construction of the Growth and Cycle Model (GCM) has been the presence of a large literature covering the description of cellular growth in steady-state and perturbed growth conditions in terms of ribosome and protein contents. As far as the cycle model, it complies the Sizer mechanism, a molecular machinery allowing a cell to "weigh" its mass before committing to a specific event, such as the G1/S transition. The GCM is substantially composed of three modules: i) a dynamical cell growth module described by a set of ODEs, which represents the dynamics of synthesis and degradation of ribosomes and proteins; ii) a molecular triggering mechanism, linking cell growth to cell cycle, described by a set of ODEs detailing the dynamics of the growth-controlled activator Cln3 and of its cognate inhibitor Far1; iii) a set of three consecutive timers (T1b, T2 and TB) that temporally account for the yeast cell cycle after the Cln3/Far1 molecular machinery is triggered, underlying the length of the G1 phase (including T1b and T2) and of the budded phase (timer TB).