λ噬菌体阻抑物基因表达调控的随机稳态结构

Stochastic stability structure of the regulatory expression of the repressor inλphage

[目的]本文旨在研究λ噬菌体自阻抑蛋白CI降解对基因表达稳态的影响。[方法]根据λ噬菌体阻抑物基因cI表达调控的化学反应,针对线性降解和非线性降解情形,分别建立化学主方程。通过无量纲化速率方程的分支分析,确定2种稳态结构的降解速率范围,画出参数平面上的分支图。应用蒙特卡洛模拟探究cI基因表达稳态结构及其转换。[结果]随着蛋白降解速率常数的减小,蛋白的降解方式由线性降解变为非线性降解,细菌由裂解态经过不稳定的双稳态转换到溶原态。[结论]阻抑物蛋白CI的降解率及降解方式的变化可能是噬菌体溶原/裂解途径决定的一种新机制。

[Objectives]This article aimed to study the effect of the degradation rate of self-repressor protein CI inλphage on the gene expression homeostasis.[Methods]Based on the chemical reactions in the self-regulated expression ofλphage repressor gene cI,the chemical master equations were established for the cases of linear degradation and nonlinear degradation,respectively.Bifurcation analysis of rate equation determined the range of degradation rate for the two homeostases.The bifurcation diagram was depicted in the parameter plane.Monte Carlo simulation was carried out to explore the steady-state structure and conversion between cell states in the stochastic model.[Results]With the decrease of protein degradation rate,the protein degrades from linear to nonlinear and the cell transits from lysogeny,via a switching stage,to lysis.[Conclusions]The degradation rate and way of degradation of repressor protein CI was a new and important mechanism for the lysogeny/lysis decision.