NF-κB- and c-Jun-dependent regulation of human cytomegalovirus immediate-early gene enhancer/promoter in response to lipopolysaccharide and bacterial CpG-oligodeoxynucleotides in macrophage cell line RAW 264.7

Abstract

The cytomegalovirus immediate-early (CMV IE) gene enhancer/promoter regulates the expression of immediate-early gene products and initiation of CMV replication. TNF-α and lipopolysaccharide (LPS) strongly activate the promoter, possibly involving NF-κB. CpG-oligodeoxy-nucleotides (CpG-ODNs), which contain unmethylated CpG dinucleotides in the context of particular base sequences, have gained attention because of their stimulating effects, via NF-κB, which have a strong innate immune response. To study the effects of LPS and CpG-ODNs, as well as the mechanisms of their actions regarding CMV IE enhancer/promoter activation, we used a macrophage cell line, RAW 264.7. Stimulation of the cells with LPS or CpG-ODNs resulted in the activation of the CMV IE enhancer/ promoter. We examined the involvement of NF-κB and c-Jun transcription factors by promoter deletion/site-specific mutation analysis and ectopic expression, and found them to have additive effects. Involvement of myeloid differentiation protein, an upstream regulator of NF-κB and c-Jun, was also investigated. Experimental results indicate that both LPS-induced and CpG-ODN-induced activations of CMV IE enhancer/promoter are mediated by Toll-like receptor signaling molecules. Several lines of evidence suggest the potential contribution of bacterial infection in CMV reactivation along with the potential application of CpG-ODNs in gene therapy as a stimulator for the optimal expression of target genes under the control of the CMV IE enhancer/promoter.