Genotype-dependent activation or repression of HBV enhancer II by transcription factor COUP-TF1

AIM: To study the expression of HBV enhancer H by transcription factor COUP-TF1. METHODS: In order to study the regulation of HBV variants in the vicinity of the NRRE we cloned luciferase constructs containing the HBV enhancer II from variants and from HBV genotypes A and D and cotransfected them together with expression vectors for COUP-TF1 into HepG2 cells. RESULTS: Our findings show that enhancer 11 of HBV genotype A is also repressed by COUP-TF1. In contrast, two different enhancer 11 constructs of HBV genotype D were activated by COUP-TF1. The activation was independent of the NRRE because a natural variant wit a deletion of nt 1763-1770 was still activated by COUP-TFI. CONCLUSION: Regulation of transcription of the HBV genome seems to differ among HBV genomes derived from different genotypes. These differences in transcriptional control among HBV genotypes may be the molecular basis for differences in the clinical course among HBV genotypes. (C) 2006 The WJG Press. All rights reserved.