Regulation and function of interferon regulatory factors of Atlantic salmon

MyD88 Interacts with Interferon Regulatory Factor (IRF) 3 and IRF7 in Atlantic Salmon (Salmo salar)

“…The results presented in Fig. 2A show that when overexpressed alone, SsIRF3 induced the highest IFNa1 promoter activity as compared with IRF7A/B, which confirms previously published data (30). Co-transfection of CHSE cells with SsIRF3 and SsMyD88 resulted in a synergistic up-regulation of all of the tested reporters, whereas no significant cooperation was detected between SsMyD88 and SsIRF7A/B.…”

“…Unlike MyD88, whose amino acid sequence is relatively well conserved, the sequences of the IRFs have diverged to a much greater extent throughout the vertebrate evolution (36). Among the IRFs, IRF3 and IRF7 share the greatest amino acid sequence identity; however, their homology is limited mainly to the N-terminal DNA-binding domain, whereas the IRF association domain is much less conserved (30). This domain is important for the homo-or heterodimerization of the IRFs, and it is also involved in their interactions with other transcriptional and signaling mediators, including MyD88 (9).…”

“…A major difference between IRF3 and IRF7 is that, unlike IRF3, which is ubiquitously expressed and noninducible by IFN stimulation or viral infections, IRF7 has more restricted expression and is critical for the robust IFN production by dendritic cells (40). However, this is not the case for Atlantic salmon, where recent results have revealed that transcription of both salmon IRF3 and IFR7 in TO cells is induced by IFNa1 (30). In addition to IFNs, both IRF3 and IRF7 are known to activate the expression of other genes that contain ISRE elements (41,42), and it has been shown that IRF7 is more "liberal" in respect with its ISRE binding specificity (43), a property that can explain its ability to trigger the expression of larger number of genes as compared with IRF3.…”

“…The firefly luciferase reporter gene constructs used in this study include a minimal IFNa1 promoter from Atlantic salmon (containing two IRF-E binding sites and one NF-B binding site) and an Mx1 promoter of rainbow trout (containing only one ISRE), both of which have previously been used to study activity of IRFs (30,31). A commercial luciferase reporter from SABiosciences that contains tandem ISRE repeats was also included in this study.…”

Expression regulation of zebrafish interferon regulatory factor 9 by promoter analysis

“…Although fish IRF3, resembling mammalian counterparts, exerts a conserved function , it displays a different expression property. Unlike mammalian IRF3 showing a constitutive expression and unresponsiveness to IFN treatment (Au et al, 1995), fish IRF3 is upregulated by either virus infection or IFN treatment (Bergan et al, 2010;Holland et al, 2008;Sun et al, 2010;Yu et al, 2010). This difference raises an interest to study the expression regulation of fish IRF9 homologues.…”