Molecular characterization of a cyprinid fish (Ancherythroculter nigrocauda) TBK1 and its kinase activity in IFN regulation

Abstract

TANK-binding kinase 1 (TBK1) plays a vital role in activating interferon (IFN) production and positively regulating antiviral response in mammals. Research on more species of fish is necessary to clarify whether the function of fish TBK1 is conserved compared to that in mammals. Here, a cyprinid fish (Ancherythroculter nigrocauda) TBK1 (AnTBK1) was functionally identified and characterized. The full-length open reading frame (ORF) of AnTBK1 consists of 2184 nucleotides encoding 727 amino acids and contains a conserved Serine/Threonine protein kinase catalytic domain (S_TKc) in the N-terminal, similar to TBK1 in other species. The transcripts of AnTBK1 were found in all the tissues evaluated and the cellular distribution indicated that AnTBK1 was localized in the cytoplasm. In terms of functional identification, AnTBK1 induced a variety of IFN promoter activities as well as the expression of downstream IFN-stimulated genes (ISGs). In addition, AnTBK1 interacted with and significantly phosphorylated IFN regulatory factor 3 (IRF3), exhibiting the canonical kinase activity of TBK1. Finally, AnTBK1 presented strong antiviral activity against spring viremia of carp virus (SVCV) infection. Taken together, our research on the features and functions of AnTBK1 demonstrated that AnTBK1 plays a central role in IFN induction against SVCV infection.