Integration of hepatitis B virus DNA: evidence for integration in the single-stranded gap.

The DNA of hepatitis B virus (HBV) can integrate into the genomes of infected human liver cells and may be related to the development of primary liver carcinoma (PLC). This report describes the analysis of three integrated HBV DNA sequences cloned from DNA of the human PLC cell line PLC/PRF/5. In all these sequences, integration of the viral DNA is at a site that is single-stranded (gap) in the unintegrated HBV DNA. Contrary to some speculations, there are no large terminal redundancies flanking the inserts as found in retroviral proviruses. The viral sequences show no obvious rearrangements in these clones, but integration can be associated with deletions in the viral DNA and also apparently in the host DNA.