Functional characterization of an IRF7 homologue in large yellow croaker (Larimichthys crocea)

Interferon regulatory factor 7 (IRF7) functions as a central orchestrator of type I interferon (IFN) responses in mammals, yet the functional mechanisms of its homologue in teleost remains incompletely understood. Here, we characterized an IRF7 homologue (LcIRF7) in large yellow croaker (Larimichthys crocea). The expression of LcIRF7 was strongly induced by poly (I:C), lipopolysaccharide (LPS), and recombinant type I IFN (rLcIFNi). These inductions were dependent on the JAK-STAT signaling pathway, suggesting that LcIRF7 is an interferon-stimulated gene (ISG). Overexpression of LcIRF7 significantly enhanced the activity of two type I IFNs (LcIFNi and LcIFNd) promoters and promoted antiviral responses in cells infected with spring viremia of carp virus (SVCV). Protein pull-down assays confirmed that LcIRF7 interacts with LcTBK1 and undergoes LcTBK1-mediated phosphorylation. In addition to forming homodimers, LcIRF7 can also heterodimerize with LcIRF11, an IRF family member absent in tetrapods, suggesting a potential lineage-specific mechanism of IRF7-mediated antiviral responses. Collectively, these findings provide insights into the antiviral signaling mechanisms mediated by teleost IRF7.