The TIAR-mediated Nrf2 response to oxidative stress is mediated through the Nrf2 noncoding 3'untranslated region in Spodoptera litura

Nrf2 is a key regulator in the maintenance of cellular redox balance by regulating the expression of genes related to antioxidative responses and detoxification. Nrf2 protein levels are increased in response to oxidative stress. However, the regulation of the Nrf2 3′UTR on Nrf2 translation is unclear. Here, we report that the translational activity of the 3′UTR is required for Spodoptera litura Nrf2 protein expression. Experiments showed that the 3′UTR translation activity of S. litura Nrf2 was much higher than that of the 5′UTR. RNA interference (RNAi) of the expression of T cell internal antigen-related protein (TIAR), an RNA-binding protein that interacts with the 3′UTR of S. litura Nrf2, resulted in Nrf2 mRNA movement out of translationally active polysomes and a decrease in cellular Nrf2 protein levels. TIAR interacted with poly(A)-binding protein (PABP) and translation initiation factors eIF2-2 and eIF2-3 to enhance Nrf2 translation, indicating that the 3′UTR regulates Nrf2 translation. Diethyl maleate (DEM) treatment increased reactive oxygen species (ROS) in cells and enhanced Nrf2 levels, which had been reduced by cycloheximide (CHX), an inhibitor of de novo protein synthesis; Tiar RNAi increased ROS levels in DEM-treated cells, suggesting TIAR-mediated 3′UTR involvement in Nrf2 translation in response to DEM treatment. Thus, we reveal a posttranscriptional regulation mechanism of Nrf2, in which TIAR binds with the Nrf2 mRNA 3′UTR to enhance Nrf2 translation, facilitating the increase in Nrf2 protein levels in response to oxidative stress.