Isolated human Fos promoter in plasmid DNA is overactive

Changes in intracellular concentrations of Na+ and K+ are shown to alter Fos gene expression. Here, we obtained a genetic construct encoding TurboGFP-dest1 gene under control of the human Fos promoter (-549; +155) and studied its expression in HEK293T. Amplification of the Fos promoter sequence from genomic DNA was only efficient in the presence of Li+ ions. Ouabain and medium with replacement of Na+ with Li+ ions resulted in the accumulation of Na+ and Li+ in cells, respectively. These stimuli increased the mRNA level of endogenous Fos and the average fluorescence intensity of TurboGFP-dest1 in transfected cells. The mRNA level of TurboGFP-dest1 was extremely higher than the mRNA level of endogenous Fos and was little affected by the stimuli.