FIG. 6.

HiNF-P and NPAT-dependent activation of histone H4 gene transcription requires an intact HiNF-P binding element. Saos-2 cells were transfected with wild-type H4 promoter luciferase reporter constructs or the corresponding constructs containing mutated HiNF-P binding sites together with HiNF-P and/or NPAT expression vectors (diagrams are shown at the top of each panel). (a) Histone H4/n promoter; (b) promoter with multimerized HiNF-P elements fused to a minimal TATA box. Relative promoter activity (measured as luciferase activity) is shown as a function of the presence (+) or absence (−) of cytomegalovirus-driven HiNF-P (200 ng/well) or NPAT (300 ng/well) expression vectors. Expression of either HiNF-P or NPAT alone results in activation of histone H4 transcription from the wild-type (left) but not the HiNF-P mutant (right) promoters. However, coexpression of HiNF-P and NPAT elevates wild-type promoter activity above that of either factor alone.