Transactivating function of integrated hepatitis B virus.

HBV DNAs are often found in integrated forms in human hepatocellular carcinoma (HCC). Discovery of a transactivation function coded by a limited region of the HBV genome has promoted us to survey our collection of HBV integrants with flanking cellular sequences, asking whether they might exhibit a transactivation function. In transient cotransfection assays using the HepG2 cell line, six out of the twelve integrants showed transactivation effects on the expression of cellular genes such as c-fos. These results strongly demonstrate that the transactivating effects of integrated HBV DNA are widely distributed, and some of these effects might be correlated to hepatocarcinogenesis.