A NEGATIVE REGULATORY ELEMENT AND ITS BINDING-PROTEIN IN THE UPSTREAMOF ENHANCER-II OF HEPATITIS-B VIRUS

The hepatitis B virus (HBV) core/pregenomic promoter is regulated by e nhancer I (ENI) and enhancer II (END) which are located upstream of th e initiation sites of core/pregenomic transcripts. In this study, we i dentified a negative regulatory element (NRE) (nt 1576 to 1639) upstre am of ENII by serial deletion analysis; a 33 kDa cellular protein in H epG2 cells binds to this element. The NRE has a significant activity i f it is located upstream of ENII in HepG2 cells. Mutational analysis s howed that the sequence (5'-CCAC-3') from nt 1612 to 1615 is responsib le for the repression activity of NRE. Southwestern blotting and UV-cr osslinking assays with HepG2 nuclear extracts also demonstrated that t he 33 kDa protein in HepG2 cells binds to the sequence. It, thus, appe ars that the 33 kDa protein is responsible for the repression activity of NRE.