| Popis: |
The hepatitis B virus has a compact genome, yet codes for at least seven primary translation products. Not surprisingly, the cis-acting elements that regulate gene expression overlap each other and the open reading frames extensively, rendering dissection of each element difficult. Nevertheless, various groups have identified and characterized four promoters and two enhancers, whose combined actions lead to preferential gene expression in hepatocytes, thereby partially explaining the hepatotropism of the virus. In addition, the X gene product trans-activates transcription from a wide variety of promoters, both cellular and viral, by as yet unclear mechanisms, while a core gene product may negatively regulate gene expression. The HBV genome thus provides a well-defined system for studying complex cis- and trans-regulation of eucaryotic gene expression. |
