To scale diagrams of the histone H3/k promoter: luc+, firefly luciferase coding sequence; arrow, transcription start site; black boxes, TATA box; white boxes, CCAAT boxes. At the bottom of each diagram, the wild-type sequence of the region surrounding the proximal CCAAT box (upper panel) and the distal CCAAT box (lower panel) and the mutated sequence of the mutation constructs are shown (mutated bases are inversely shaded). The reporter gene activity of the constructs in the HEK-293 cell line is shown below each diagram as a statistical mean for four independent experiments [relative to the wild-type promoter K5 (wt), which is set to the value of 1.0; error bars, S.E.M.].