Roles of Cro 2 and CI 2 binding to O R operators in controlling lysogeny stability during prophage induction
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The lysogeny-lysis switch in bacteriophage lambda serves as a model for understanding cell fate decisions. The molecular network controlling this switch has been explored through extensive experimental and computational studies. Yet, the specific role of protein-DNA interactions, like the binding of CI 2 and Cro 2 proteins to operator sites, in regulating lysogeny stability during prophage induction remains less understood. This study employs a minimalistic model and the Accurate Chemical Master Equation (ACME) method to construct detailed probability landscapes of the network's behavior under varying conditions, such as different dissociation and CI 2 degradation rates which simulate UV irradiation effects. Our findings indicate that Cro 2 binding at O R 3 and CI 2 at O R 1 significantly influence lysogeny stability, with the former destabilizing and the latter stabilizing it. Conversely, interactions at O R 1 by Cro 2 and O R 3 by CI show minimal impact on this stability. Through the ACME approach, we could examine the network's global behavior under conditions unapproachable by conventional stochastic simulations. This study highlights the critical roles of specific protein-DNA interactions in maintaining lysogeny and provides insight into the broader dynamics of the lysogeny-lysis switch under various physiological stresses.
