Hepatitis-B Virus-associated Deoxyribonucleic Acid Polymerase: A Partial Characterization by the Use of Chemical Agents* **

The very limited coding capacity of the HBV-DNA led us to study the nature of the HBV (Dane particle) — associated DNA polymerase. The HBV-associated DNA polymerase met in many respects the characteristics of the repair enzyme of the host: the DNA polymerase beta. It operates under high salt conditions, and exhibits similar salt effects with NaCl, KCL, and PO 4 3− . It is insensitive to sulf-hydryl group blockers, such as p-hydroxymercuribenzoate and N-ethylmaleimide, is resistant to phosphonoacetic acid, and not inhibited by 5 mol/l urea. It requires a divalent cation (Mg2+) for activity, the Mg2+ concentration revealing optimal activity is somewhat higher than that described for most DNA polymerases beta. The HBV-associated DNA polymerase differs also from most DNA polymerases beta in its sensitivity to ddTTP and its optimal pH. The fact that DNA polymerases beta of different origin vary considerably in their response to chemical agents and that the DNA polymerase beta from human liver has not been studied allows no definite conclusion as to the nature of the Dane particle-associated DNA polymerase.