Assessment of the long-term transcriptional activity of a 550-bp-long human β-actin promoter region.

β-actin (ACTB) is one of the genes expressed most abundantly and ubiquitously in human non-muscular tissues. Here, we investigated the long-term activity of a 550-bp-long human ACTB promoter region in human cells in comparison with other commonly used constitutive promoters. We first constructed plasmid vectors expressing enhanced green fluorescent protein (GFP) driven by one of the 5 promoters, human ACTB, human elongation factor-1α (EF1α), cytomegalovirus early enhancer/chicken β-actin (CAG), cytomegalovirus (CMV), and herpes simplex virus thymidine kinase, and transfected them into multiple human somatic cell lines. Stable transfectants were maintained for 45 days, and GFP signals from the cells were quantified by fluorescence flow cytometry. GFP signals driven by the human ACTB and the CMV promoters were also compared over time for up to 60 days following transfection. We observed robust, prolonged transcriptional activity with the human ACTB promoter that is comparable to the human EF1α and the CAG promoters and significantly more stable than the CMV promoter.