Protein kinase C stimulates human B cell activating factor gene expression through reactive oxygen species-dependent c-Fos in THP-1 pro-monocytic cells.

BAFF is associated with various immunological diseases. Previously, we have reported that mouse B cell activating factor (mBAFF) expression was dependent on nuclear localization of co-activator, p300 and the activation of transcription factors including NF-κB and CREB. Here, we investigated whether transcription factor, c-Fos, regulates human (h) BAFF expression through promoter activation by PMA-induced reactive oxygen species (ROS) production. We cloned hBAFF promoter into luciferase-expressing pGL3-basic vector. The activity of 1.0 kb hBAFF promoter was higher than that in 0.75, 0.5 or 0.25 kb hBAFF promoter. The existence of three AP-1 binding motifs was computer-analyzed in hBAFF promoter. The stimulation with PMA and ionomycin (IOM) increased 1.0 kb hBAFF promoter activity, time-dependently. PMA/IOM-stimulation rapidly enhanced c-Fos expression in THP-1 human pro-monocytic cells. Binding of c-Fos to hBAFF promoter was detected by chromatin immunoprecipitation (ChIP) assay. hBAFF expression and its promoter activity were decreased by the transfection with small interference (si) RNA of c-Fos. ROS production in THP-1 cells was increased by PMA/IOM-stimulation. In addition, hBAFF activity stimulated by PMA/IOM was reduced by N-acetyl-cysteine (NAC), a well-known ROS scavenger. Serum starvation (0.5% FBS) producing ROS and the exogenous H(2)O(2) treatment also enhanced hBAFF promoter activity. c-Fos expression and AP-1 binding to oligonucleotide were reduced by the treatment with NAC. H(2)O(2) was not able to induce hBAFF expression in the presence of staurosporine, PKC inhibitor. Data suggest that hBAFF expression could be regulated by promoter activation through c-Fos association, which might be dependent on PMA-induced ROS production.