RelA is a key transcription factor regulating IFN-β expression in response to LPS. (A-C) Depletion of RelA levels greatly reduces IFN-β gene expression in HEK-293-TLR4/CD14-Md2 cells. (A) IFN-β mRNA expression in cells transfected with siRNAs targeting NFκB RelA (siRelA) presented as percent of expression in the control cells transfected with nontargeting siRNA (siC). Data shown are the mean + SEM from 3 independent experiments. ***P < .001 (Student t test). (B) Western blots showing the siRelA induced degradation of RelAwt and unaffected expression of RelAmut and are representatives of 3 experiments. (C) LPS-induced IFN-β mRNA expression in cells complemented with RelAwt or RelAmut shown as fold induction over the level in nonstimulated control cells transfected with nontargeting siRNA (siC). Data shown are the mean + SD of a representative of 2 independent experiments each performed in triplicate. (D-F) Inhibition of RelA significantly reduces IFN-β mRNA expression in MDDCs. (D) IFN-β mRNA expression in cells transfected with siRNAs targeting NF-κB RelA (siRelA) presented as percent of expression in the control cells transfected with nontargeting siRNA (siC). Data shown are the mean + SEM from 5 independent donors. **P < .01 (Student t test). (E) IFNβ mRNA expression in MDDCs infected with increasing concentrations of adenovirus carrying IκBαSR: normalized against cells infected with adenovirus carrying an empty expression vector pBent and shown as the mean + SD of a representative of 3 independent experiments. (F) Efficiency of ΝF-κB activity suppression by IκBαSR in MDDCs estimated using luciferase reporter assay with NF-κB-luc virus: shown as the mean + SD of a representative of 3 independent experiments each performed in triplicate.