Recombination Hot Spot of Hepatitis B Virus Genome Binds to Members of the HMG Domain Protein Family and the Y Box Binding Protein Family; Implication of These Proteins in Genomic Instability

OBJECTIVE: Previously we hypothesized that the occurrence of hepatocellular carcinoma (HCC) is enhanced by genomic instability induced by the integrated hepatitis B virus (HBV) DNA. Using an in vitro recombination assay, we showed that a subgenomic fragment of HBV DNA designated 15AB (nt1855-1914) is indispensable for in vitro recombination, and also showed the existence of 15AB binding protein. On the assumption that the 15AB binding protein may be a candidate cellular recombinogenic protein which accelerates genomic instability and hepatocarcinogenesis, we tried to isolate it by southwestern screening. RESULTS AND CONCLUSION: We obtained several positive clones including mouse upstream binding factor (UBF) and DNA binding protein A (dbpA). UBF belongs to an HMG domain protein family and dbpA belongs to a Y box binding protein family. 15AB binding seemed to be mediated by the conserved DNA binding domains in these families, because other members in the families such as HMG1 and YB-1 also bound to 15AB. We report them here because several documents have already suggested the possible association of these families and DNA recombination.