Nuclear export signal of PRRSV NSP1α is necessary for type I IFN inhibition

The nonstructural protein 1 alpha (NSP1 alpha) of porcine reproductive and respiratory syndrome virus (PRRSV) is a nucleo-cytoplasmic protein that suppresses the production of type I interferon (IFN). In this study, we investigated the relationship between the subcellular distribution of NSP1 alpha and its inhibition of type I IFN. NSP1 alpha was found to contain the classical nuclear export signal (NES) and NSP1 alpha nuclear export was CRM-1-mediated. NSP1 alpha was shuttling between the nucleus and cytoplasm. We also showed that the nuclear export of NSP1 alpha was necessary for its ability for type I IFN inhibition. NSP1 alpha was also found to interact with CBP, which implies a possible mechanism of CBP degradation by NSP1 alpha. Taken together, our results describe a novel mechanism of PRRSV NSP1 alpha for type I IFN inhibition and suppression of the host innate antiviral response. (C) 2016 Published by Elsevier Inc.