Restriction endonuclease mapping of the hepatitis B viral genome isolated from Taiwan

The Eco RI fragment of hepatitis B virus (HBV) DNA isolated from human blood plasma Dane particles were inserted into plasmid pUC8 Eco RI site and transformed into E. coli JM103 host. Two recombinants pTWL1 and pTWL2 were found to carry 3.2 kbp fragment and proved to have HBV genome by Southern hybridization method. The 1.4 kbp Bam HI fragment which carried the hepatitis B viral surface antigen (HBsAg) gene, obtained via Bam HI digestion of Dane particles DNA which was made fully double stranded by endogenous DNA polymerase reaction, was also inserted into plasmid pUC8 Bam HI site. Four recombinant clones, pTWS1, pTWS2, pTWS3, and pTWS4 were found. Only one of the clones pTWS1 carried the HBsAg gene in a correct orientation with respect to the lac promoter sequence. The physical mapping of HBV DNA was performed with several restriction endonucleases. Our results indicated that the HBV DNA insert contains unique XbaI and HpaI cleavage sites and lacks the cleavage sites for the HindIII, SmaI, KpnI, SalI, and SstI endonucleases. The locations of Bam HI, BglII, and HincII endonucleases cleavage sites within the cloned HBV DNA of the pTWL1 plasmid were similar to that HBV DNA of adw and adw2 subtypes.