Hepatitis B Virus (HBV) infection induces a disease state which manifests itself in a variety of ways, characterized by the extent of liver damage, inflammation and viral persistence. HBV infection is also associated with a 100 fold increased risk of hepatocellular carcinoma and currently infects over 250 million people worldwide. HBV has a partially double stranded 3.2 kilobase DNA genome which contains four open reading frames. One of these encodes a 154 amino acid protein called the HBx protein. HBx has been shown to be a transcriptional transactivator of both viral and cellular promoters. Lacking a DNA binding domain and nuclear localization signal, HBx is believed to exert transcriptional activity through protein protein interaction.Synonyms: HBV surface antigen, Hepatitis B Virus