A Stochastic Model of the Yeast Cell Cycle Reveals Roles for Feedback Regulation in Limiting Cellular Variability
Fig 6
Positive feedback in CLN2 activation and the coherence of entry into Start.
A and B. Joint distributions of the times from birth to the activation of the genes for RAD27 (Tbir,RAD27) and CLN2 (Tbir,CLN2) are plotted for WT and cln1Δcln2Δ cells from single-cycle simulations for an extant population of 500 mother (blue) and 500 daughter (red) cells in glucose (μ = 0.007 min−1). In (A1, B1) and (A2, B2) the full data for daughter cells and mother cells are plotted separately. Compare panels A and B to Fig 2e and 2f, respectively, of Skotheim et al [14]. C. As the rate constant for phosphorylation of Whi5 by Cln1,2 (i.e., the strength of the Cln1,2-mediated positive feedback loop) is progressively decreased (in panels C1-C5), the coherence of gene activation upon entry into Start decreases. The coherence of entry into Start cannot be restored by increasing the phosphorylation rate of Whi5 by Cln3 (panel C6; compare to Fig 2i of Skotheim et al). D. The correlation coefficients of Tbir,RAD27 and Tbir,CLN2 for daughter cells and mother cells decrease as the strength of the positive feedback loop decreases. The numbers on the abscissa refer to the data in panels C1-C6.