PurA is an abundant and an evolutionary conserved protein that is known to bind to single stranded DNA or RNA and regulate both transcription and translation. PurA has been shown to be implicated in many neurological and neurodevelopmental deficits due to its multifunctional roles. In this study, we have studied the cells’ stress response in the presence and absence of PurA by introducing oxidative stress to the cells derived from wildtype (PurA+/+) mouse embryo fibroblasts (MEFs) and (PurA -/-) knockout mice. Our observations indicated that the presence of PurA is making cells more sensitive to toxicity compared to those cells lacking PurA, emphasizing on the importance of PurA in cell survival and cell cycle regulation. Our MTT results and western blot analysis were in agreement with each other confirming PurA ‘s importance in normal cell response against stress, in particular oxidative stress induced by Paraquat. PurA+/+ wildtype MEFs showed more sensitivity and a decrease in relative cell viability after 24 Hrs. exposure to 1.5 mM paraquat while less sensitivity was observed in PurA -/- knockout MEFs under same conditions. Western blot analysis showed a significantly increased expression of the apoptotic marker cleaved caspase3 in PurA+/+ wildtype MEFs under oxidative stress induction compared to PurA -/- knockout MEFs. Also, autophagy activation was measured by checking the expression of LC3-I and LC3-II in both MEFs under control and stressed conditions and the results were confirming that autophagy induction under oxidative stress is greater in the presence of PurA. PurA appears to be very critical for cell survival, and any alteration in its expression may lead to undesired consequences. / Biology