MicroRNA-16 feedback loop with p53 and Wip1 can regulate cell fate determination between apoptosis and senescence in DNA damage response

Cell fate regulation is an open problem whose comprehension impacts several areas of the biosciences. DNA damage induces cell cycle checkpoints that activate the p53 pathway to regulate cell fate mechanisms such as apoptosis or senescence. Experiments with different cell types show that the p53 pathway regulates cell fate through a switch behavior in its dynamics. For low DNA damage the pathway presents an oscillatory pattern associated with intense DNA damage repair while for high damage there are no oscillations and either p53 concentration increases inducing apoptosis or the cell enters a senescence state. Apoptosis and senescence phenotypes seem to have compensatory functions in tissues and the microRNA 16–1 (miR-16) is involved in the regulation of the fate between both phenotypes in cancer cells. To investigate the regulation of cell fate we developed a logical model of the G1/S checkpoint in DNA damage response that takes into account different levels of damage and contemplates the influence of miR-16 through its positive feedback loop formed with p53 and Wip1. The model reproduces the observed cellular phenotypes in experiments: oscillatory (for low DNA damage) regulated by negative feedback loops involving mainly p53 and Mdm2 and apoptotic or senescent (for high DNA damage) regulated by the positive p53/Wip1/miR-16 feedback loop. We find good agreement between the level of DNA damage and the probability of the phenotype produced according to experiments. We also find that this positive feedback makes senescent and apoptotic phenotypes to be determined stochastically (bistable), however controlling the expression level of miR-16 allows the control of fate determination as observed experimentally.

细胞命运调控是一个尚未解决的开放性问题，对其的理解可影响生物科学的多个研究领域。DNA损伤会激活细胞周期检验点，进而启动p53通路以调控细胞命运相关机制，例如凋亡或细胞衰老。针对不同细胞类型开展的实验表明，p53通路可通过其动力学层面的开关行为调控细胞命运。当DNA损伤程度较低时，该通路会呈现出与活跃DNA损伤修复相关的振荡模式；而当损伤程度较高时，则无振荡现象，此时要么p53浓度升高诱导细胞凋亡，要么细胞进入衰老状态。凋亡与衰老表型在组织中似乎存在代偿功能，而microRNA 16–1（miR-16）参与调控癌细胞中这两种表型之间的细胞命运抉择。为探究细胞命运的调控机制，我们构建了DNA损伤应答通路中G1/S检验点的逻辑模型，该模型考虑了不同程度的DNA损伤，并纳入了miR-16通过与p53及Wip1形成的正反馈环路所产生的调控影响。该模型复现了实验中观测到的细胞表型：低DNA损伤条件下的振荡表型由主要涉及p53与Mdm2的负反馈环路调控，而高DNA损伤条件下的凋亡或衰老表型则由p53/Wip1/miR-16正反馈环路调控。我们发现，DNA损伤程度与实验中观测到的表型发生概率之间具有良好的一致性。我们同时发现，该正反馈环路使得衰老与凋亡表型呈现随机决定的双稳态特性；而正如实验中观测到的那样，调控miR-16的表达水平可实现对细胞命运抉择过程的控制。