nsP4 Is a Major Determinant of Alphavirus Replicase Activity and Template Selectivity
Laura Sandra Lello, Koen Bartholomeeusen, Sainan Wang, Sandra Coppens, Rennos Fragkoudis, Luke Alphey, Kevin K. Ariën, Andres Merits, Age Utt
Abstract
A key element of every virus with an RNA genome is the RNA replicase. Understanding the principles of RNA replicase formation and functioning is therefore crucial for understanding and responding to the emergence of new viruses. Reconstruction of the replicases of nine alphaviruses from nsP4 and P123 polyproteins revealed that the nsP4 of the majority of alphaviruses, including the mosquito-specific Eilat virus, could form a functional replicase with P123 originating from a different virus, and the corresponding chimeric viruses were replication-competent. nsP4 also had an evident role in determining the template RNA preference and the efficiency of RNA synthesis. The revealed broad picture of the compatibility of the replicase components of alphaviruses is important for understanding the formation and functioning of the alphavirus RNA replicase and highlights the possibilities for recombination between different alphavirus species.