THE PRES2/S REGION OF INTEGRATED HEPATITIS-B VIRUS-DNA ENCODES A TRANSCRIPTIONAL TRANSACTIVATOR

HEPATITIS B virus (HBV) is regarded as the main aetiologic factor in the development of human hepatocellular carcinoma (HCC), one of the most frequent fatal malignancies worldwide1,2. Detection of integrated HBV sequences in the cellular DNA of almost all HCCs studied2-17, and the recent finding that the integrated HBV open reading frame (orf) X encodes a trans-activating activity18, supports the notion that integrated HBV DNA could contribute to liver carcinogenesis by activation of cellular genes in trans 18,20. But not all HCCs seem to harbour a functional orf X 2-17. We report here that 3′-truncated preS2/Ssequences in integrated HBV DNA of liver cell carcinomas encode a so far unidentified transcriptional trans-activation activity. This activity is also produced by an artificially 3′-truncated preS2/S gene of the wild-type HBV genome. Besides the simian virus 40 promoter of the reporter plasmid pSV2CAT, the promoter of the human c-myc oncogene can also be activated. These results, taken together with the fact that preS/S is the only HBV gene found to be integrated in almost every HBV-related HCC analysed so far2-17, indicate that trans-activation by integrated preS2/S sequences is a possible mechanism for HBV-associated oncogenesis. © 1990 Nature Publishing Group.