3.2. s7ORF1 and s8ORF2 do not inhibit IPS-1 mediated activation of
the IFNa1 promoter
Virus RNA trigger IFN-transcription in cells by binding to the
cytoplasmic helicases RIG-I and MDA5, which then interact with
mitochondrial adaptor protein IPS-1 to activate NF-kB and IRF3
and/or IRF7. We therefore studied whether s7ORF1 or s8ORF2
influenced IPS-1 mediated IFNa1 promoter activation (Fig. 2). As
shown in previous work [21], overexpression of IPS-1 strongly upregulated
IFN promoter activity in TO cells (Fig. 2). Surprisingly,
however, co-transfection of pIPS-1 together with ps7ORF1 or
ps8ORF2, resulted in increased rather than decreased promoter
activity. This suggests that none of the two viral proteins antagonizes
signal transduction generated by IPS-1.