A regulatory interplay: hnRNP A1 and AUF1 compete for the same IRES domain to regulate viral translation in EV71

Abstract

Enterovirus 71 (EV71), a single‐stranded RNA virus, represents a persistent global health threat against which there is no FDA‐approved vaccine or treatment. Enteroviruses use a type I IRES to facilitate protein synthesis and genome replication by recruiting multiple host RNA‐binding proteins (ITAFs) that fine‐tune translation. HnRNP A1 and AUF1 are antagonistic ITAFs that interact with the EV71‐IRES to upregulate or downregulate viral translation, respectively. However, the molecular mechanisms driving the IRES‐ITAFs interactions to regulate EV71 translation remain poorly understood. Compelled by these challenges, we pursue to identify the nature of the specific recognition between IRES‐ITAFs interactions and its effect on modulating viral replication. Here, using isothermal titration calorimetry (ITC) and Nuclear Magnetic Resonance (1H‐13C HSQC), we found a competition between hnRNP A1 and AUF1 for the same binding site on stem loop II (SL‐II) within the EV71 IRES which has been proven to be a vital RNA element for the virus. Specifically, we observed that, at high concentrations, hnRNP A1 can disrupt the AUF1‐SLII complex while AUF1 cannot outcompete hnRNP A1 for SL‐II binding when the reverse experiment is performed. Furthermore, we also identify conditions to obtain both antagonistic ITAFs bound to the SL‐II at their respective binding sites. Our observations fill important knowledge gaps as the data upholds a regulatory mechanistic model in which hnRNP A1 and AUF1 compete for association to the same IRES domain (SL‐II). Hence, the interaction of hnRNP A1 with SL‐II blocks AUF1 binding thus, activating viral translation which is vital for the virus. In conclusion, our observations enhance our understanding of how an ITAF interplay plays a key role in modulating viral translation and replication, and how EV71 IRES structure adapts to hijack cellular proteins.Support or Funding InformationNIHR01GM126833This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.