Molecular cloning and characterization of Interferon regulatory factor 1 (IRF1) in Sevenband grouper, Hyporthodus septemfasciatus

Abstract

Interferon regulatory factors (IRF) are transcription factors that are crucial in various physiological processes, including viral infection, cell growth regulation, autophagy, and tumor suppression. Among these, IRF1 is activated by interferon-gamma (IFN-γ) and interferon- alpha/beta (IFN-α/β), inducing antiviral gene expression via its DNA-binding domain (DBD), thereby inhibiting viral replication, and promoting infected cell apoptosis. In this study, we identified the IRF1 gene in sevenband grouper, Hyporthordus septemfasciatus, sg_IRF1, analyzed its expression levels across different tissues, and assessed its antiviral activity. The results showed that the open reading frame of the sg_IRF1 cDNA was 906 bp long and encoded 301 amino acids. The sg_IRF1 protein possesses a DNA-binding domain typical of the IRF family, containing six conserved tryptophan residues. Previous studies demonstrate that IRF1 lacking the DBD exhibits weakened intrinsic antiviral activity. Therefore, in this study, we designated the IRF1 variant without the DBD as sg_dIRF1. In vivo experiments revealed that under normal physiological conditions, sg_IRF1 transcription was highest in the spleen. Moreover, in infected with NNV, IRF1 expression significantly increased spleen from days 2 to 4 post-infection. Furthermore, in SSN-1 cells, sg_IRF1 expression reduced viral RNA2 replication by approximately 4.61-fold, while the expressing sg_dIRF1 exhibited only approximately a 2.00-fold decrease compared to the control group. These findings suggest that sg_IRF1 may play an antiviral role in NNV infection, with the DBD of IRF1 contributing to this process. However, further studies are needed to elucidate its association with other immune-related genes involved in the innate immune response of sevenband grouper.