Krüppel-Like Factor 4 Is a Regulator of Proinflammatory Signaling in Fibroblast-Like Synoviocytes through Increased IL-6 Expression

Figure 5

KLF4 regulates IL-6 promoter activity in RA FLSs. KLF4 transactivates the IL-6 promoter. RA FLSs were cotransfected in triplicate with the indicated IL-6 promoter luciferase plasmids, pcDNA3.1-KLF4 expression plasmid (KLF4), or pcDNA3.1 control vector (Neo) for 48 h and then incubated with TNF-α (20 ng/mL) for 12 h. Transcriptional activity was detected by the Dual Luciferase Assay (a). Data were expressed as means ± SEM (). in comparison to the vector control group (Neo). in comparison to untreated group (Ctrl). KLF4 binds the IL-6 promoter. EMSA was performed with nuclear extracts using a biotinylated probe of the −109 to −90 bp site (b) and −132 to −102 bp site (below) in the IL-6 promoter (c). TNF-α augmented binding of KLF4 to the IL-6 promoter. EMSA was performed with nuclear extracts from cells incubated with TNF-α for 1 or 2 h. The previously described biotinylated probes (−109 to −90 bp and −132 to −102 bp) were used ((d) and (e), resp.).

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