Overexpression of CDP represses the −102 to +12 bp gp91^phox promoter. HEL and primary keratinocyte cultures were cotransfected with the −102 to +12 bp gp91^phox promoter/luciferase vector and either a CDP expression vector (CDP sense), the expression vector containing the CDP cDNA in the antisense orientation (CDP antisense), or the expression vector lacking a cDNA insert (vector). Transfections were performed as described in Materials and Methods. Data represent the mean ± standard error of at least 3 transfections, with at least 2 distinct plasmid preparations. The level of luciferase expression generated in cotransfections containing the expression vector lacking an insert is defined as 100%.