The p53 tumor suppressor proteins plays a critical role in cellular

The p53 tumor suppressor proteins plays a critical role in cellular stress and cancer prevention. the cellular performance of p53 with the microRNA feedback pathways we developed a mathematical model of the core p53-MDM2 module coupled with three microRNA-mediated positive feedback loops involving miR-192 miR-34a and miR-29a. Simulations and bifurcation analysis in relationship to extrinsic noise reproduce the oscillatory behavior of p53 under DNA damage in single cells and notably show that specific microRNA abrogation can disrupt the wild-type cellular phenotype when the ubiquitous cell-to-cell variability is taken into account. To assess these results we conducted microRNA-perturbation experiments in MCF7 breast cancer cells. Time-lapse microscopy of cell-population behavior in response to DNA double-strand breaks together with image classification of single-cell phenotypes across a population confirmed that the cellular p53 oscillations are compromised after miR-192 perturbations matching well with the model predictions. Our study via modeling in combination with quantitative experiments provides new evidence on the role of microRNA-mediated positive feedback loops in conferring robustness to the system performance of stress-induced response of p53. Author Summary DNA damage triggered activities of the tumor suppressor protein p53 could be significantly dynamical. The functional role of p53 oscillations in cellular decision making during cancer development has been appreciated. A set of recent studies have revealed extensive crosstalk between the p53 network and microRNAs but the specifics of the participation of microRNAs in the regulation of the p53 signaling pathway remains largely elusive. Here we investigated microRNAs that form feedback regulation with p53. We enumerated the molecular interactions among these microRNAs and the p53 Metformin HCl core and developed a mathematical model to reproduce the DNA damage induced p53 Metformin HCl oscillations in single cells. We performed computer simulations and system analysis in combination with experimental assessment to probe the behavior of p53 under microRNA-inhibited conditions. We show that the robust cellular performance of the stress response of p53 in a breast cancer cell line is controlled by miR-192 which forms positive feedback loops with p53. Introduction Cells depend on complex intracellular signaling to process and react to external stimuli. One prominent type of dynamic response is the periodic accumulation of key transcription factors in the nucleus where they elicit temporally controlled gene activation [1-4]. The tumor suppressor protein p53 a pivotal player involved in cancer initiation and prevention [5] undergoes oscillations in response to extracellular stress signals. Experiments show that transient DNA lesion of double-strand breaks induced by acute application of γ-irradiation trigger oscillatory response of the p53 protein and its negative regulator MDM2 [6-8]. At a single-cell level the oscillation of p53 is undamped and the mean period of the pulses are constant and independent on the damage level [7]. While the cellular function of the oscillatory dynamics of these transcription factors is unclear investigations have started to probe the significance of the p53 oscillations in inducing downstream effect such as apoptosis. For instance recent results demonstrate that the dynamical pattern and not the absolute degree of p53 proteins settings the life-or-death destiny decision in response to DNA harm at mobile level highlighting the part of p53 oscillations in mobile decision producing in tumor [9 10 Adverse feedback gets the potential to create limit-cycle oscillations and can be regarded as a necessary framework for biochemical oscillators [11 12 Certainly there is a consensus in the books how the p53-MDM2 adverse autoregulatory loop Hoxa2 is vital for the stress-induced p53 oscillations [3 13 Several mathematical versions that typically believe an explicit period hold off in the primary p53-MDM2 autoregulatory loop can reproduce the undamped p53 Metformin HCl oscillations [14-16]. Even more generally coupled positive and negative feedback loops can provide rise to oscillatory phenotypes [11 17 The structures of positive responses loops together with a negative responses loop can endow efficiency Metformin HCl properties like the tunability of rate of recurrence entrainability to cycles and robustness under.