Upregulation of porcine epidemic diarrhea virus (PEDV) RNA translation by the nucleocapsid protein

The role of coronaviral nucleocapsid (N) protein in regulating viral translation remains poorly understood. Here, we showed that the N protein of porcine epidemic diarrhea virus (PEDV) enhances the translation of both virus-like genomic RNA (gRNA) and messenger RNA. Further characterization of the gRNA translation upregulation showed that the N-terminal domain (NTD) + Linker region plays a major role. The stem-loop 1 in the 5' untranslated region (UTR) and the budged stem loop in the 3'UTR are required for viral translation upregulation by PEDV N protein. The signaling kinase Akt exists in three isoforms. We found that Akt1 enhances viral gRNA translation upregulation by the N protein dependent on its kinase activity. We further showed an interaction between Akt1 and PEDV N, that is abolished by the NTD + Linker region. This suggested that the enhancing effect of Akt1 on translation upregulation by the N protein does not require interaction between these two proteins.