ObjectiveA silencer within the renin first intron (intron A) was identified using Calu-6 cells, a pulmonary carcinoma cell line which produced renin. In the present study, a dissection of the first intron was performed to determine precisely thecis-regulatory elements involved in the silencer transcriptional effects.Materials and methodsIntron A was completely sequenced to characterize potential binding sites for known transcription factors. Partial portions of intron A were subcloned upstream the 892 bp of the renin promoter and transfected in different models of renin-producing cells: primary culture of human chorionic cells, human Calu-6 cells and mouse As4.1 cells.ResultsThere is significant DNA homology (67%) between the 3′ and 5′ ends of the human and rat renin first intron. Several transcription factor binding sites identified in human first intron, but not in rat intron, do not contribute to the reported silencer activity. Transfections of renin/luciferase constructs containing partial portions of first intron inserted upstream of the 892 bp in both renin-producing cells do not allow the precise characterization of cis-elements involved in the silencer effect.ConclusionsThe silencer located renin intron A is cell specific. The integrity of the human first intron seems necessary for its repressor activity on renin proximal promoter in renin-producing cells.