Effects of naturally occurring mutations in hepatitis B virus core promoter on transcriptional activity

Abstract Hepatitis B virus (HBV) with mutations in the core promoter is thought to be selected naturally during chronic infection. In this study, effects of naturally occurring mutations in the HBV core promoter on transcriptional activity are anlayzed. To evaluate whether mutations in the core promoter affect transcriptional activity, chloramphenicol acetyltransferase (CAT) assay was performed. When CAT plasmids were transfected into human hepatoma cells, the double mutation (A to T at nucleotide (nt) 1762 and G to A at nt 1764) resulted in increased core promoter activity and an additional mutation (T to C at nt 1753) further enhanced the transcriptional activity. In the gel mobility shift assay, the double mutation and a T-to-C mutation altered the protein binding to the corresponding element. The results suggest that a T-to-C mutation at nt 1753, in addition to the double mutation, significantly influences the HBV core promoter activity.