Expression of human inducible nitric oxide synthase is regulated by both promoter and 3'-regions.

One of the mechanisms underlying the induction of human inducible nitric oxide synthase (hiNOS) by cytokines is transcriptional regulation. However, previous reports suggest that in human cells, the cytokine activation of the hiNOS expression is accompanied by a drastic increase in cellular mRNA and protein content, but by little increment in transcriptional activity. We designed luciferase reporter constructs containing the hiNOS 5'-flanking region and 3'-untranslated region (UTR). The construct containing both 5'-flanking region and 3'-UTR plus its downstream canceled the constitutive activity of the reporter gene, and was more responsive to the cytokines. This is an initial attempt to highlight the important role played by the 3'-region of the hiNOS gene. Our studies provide the evidence that the cooperative interaction between the 5'-promoter and the 3'-region conveys marked induction of the gene in the presence of cytokines.