The S gene encodes a long ORF with three in-frame ‘start' (ATG) codons that divide the gene into three sections, pre-S1, pre-S2 and S. HBV enters susceptible liver cells when the receptor-binding region of pre-S1 specifically interacts with the functional cellular receptor NTCP (sodium taurocholate cotransporting polypeptide), a multiple transmembrane transporter predominantly expressed in the liver; this results in liver infection and virus replication.213 Persistence of chronic HBV infection for decades is linked to liver cirrhosis and the development of hepatocellular carcinoma (HCC). The gene discussed is SLC10A1; the disease is cirrhosis of liver.