CCAAT/Enhancer-binding Proteins α and β Negatively Influence the Capacity of Tumor Necrosis Factor α to Up-regulate the Human Cytomegalovirus IE1/2 Enhancer/Promoter by Nuclear Factor κB during Monocyte Differentiation

• Published in: The Journal of biological chemistry 2001-11, Vol.276 (44), p.40712-40720
• Main Authors: Prösch, Susanna, Heine, Anne-Kathrin, Volk, Hans-Dieter, Krüger, Detlev H.
• Format: Article
• Language: English
• Subjects: C/EBP^a protein; C/EBP^a/^b protein; C/EBP^b protein; C/EBPa protein; C/EBPb protein; Human cytomegalovirus; NF-^KB protein
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M009815200

Recently we demonstrated that the ability of tumor necrosis factor α (TNFα) to stimulate the human cytomegalovirus (HCMV) IE1/2 enhancer/promoter activity in myeloid progenitor-like cells decreases when these cells differentiate into promonocytic cells. In addition, TNFα stimulation in the progenitor-like cell line HL-60 was shown to be mediated by nuclear factor κB (NF-κB) activation and its binding to the 18-base pair sequence motifs of the IE1/2 enhancer. We demonstrate here that the cell differentiation-dependent reduction of TNFα stimulation is not due to insufficient NF-κB activation but correlates with increased synthesis of the monocyte differentiation-associated factors CCAAT/enhancer-binding protein (C/EBP) α and β. Overexpression of C/EBPα/β in HL-60 cells, which normally produce only very small amounts of C/EBP, stimulated the basal activity of the promoter in the absence of NF-κB but suppressed the stimulatory effect of TNFα. A novel C/EBP-binding site was identified in the IE1/2 enhancer directly downstream of a NF-κB site. In order to understand the mechanisms of interaction, we used an IE1/2 promoter mutant that failed to bind C/EBP at this position and several constructs that contained exclusively NF-κB- and/or C/EBP-binding sites upstream of the minimal IE1/2 promoter. We could demonstrate that C/EBPα/β interacts with NF-κB p65 and displays inhibitory activity even in the absence of direct DNA binding by forming p65-C/EBP-containing protein complexes bound to the NF-κB site. Moreover, C/EBP binding to the DNA adjacent to NF-κB supports the down-regulatory effect of C/EBPs possibly due to stabilization of a multimeric NF-κB-C/EBP complex. Our results show that cell differentiation factors may interfere with TNFα-induced human cytomegalovirus gene (re)activation.