Dual luciferase reporter gene assay
The full-length mouse Bsep gene was amplified by PCR from HepG2 cDNA. The mouse Bsep gene promoter (−3218 to -198 bp) was amplified by PCR using mouse genomic DNA and inserted into a pGL3-basic luciferase reporter vector (−3218 Luc). A series of 5’ truncated constructs of the Bsep gene promoter (−3218 Luc, −2178 Luc, −1363 Luc) were prepared by PCR using −3218 Luc as a template. All constructs were confirmed by DNA sequencing analysis. For dual luciferase reporter gene assays, HepG2 were transfected with corresponding plasmids, as well as renilla luciferase. Firefly and renilla luciferase activities were then measured by a dual-luciferase reporter gene system (Promega, Madison, WI, USA).