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Mutational analysis of hepatitis B virus enhancer 2.

Hepatitis B virus (HBV) infection is associated with the development of hepatocellular carcinoma in humans. HBV infection is primarily restricted to hepatocytes, and replication and gene expression of HBV require liver-specific transcription factors. Regulation of HBV gene expression has been shown to be controlled by two enhancers, and liver-specific gene expression of HBV can be attributed largely to the activity of enhancer 2. In this study, we have used mutational analysis to identify a 20-base-pair sequence motif essential for the liver-specific enhancer 2 activity. Analysis of the sequence reveals that this motif is similar to the regulatory region of several other liver-specific cellular genes, suggesting that common transcription factors may be involved in the activation of cellular as well as HBV gene expression in hepatocytes.