ROLE OF RNA IN ENZYMATIC-ACTIVITY OF THE REVERSE-TRANSCRIPTASE OF HEPATITIS-B VIRUSES

The hepadnavirus reverse transcriptase is a multifunction enzyme. In a ddition to its role in DNA synthesis, the polymerase is required for R NA packaging and also functions as the primer for minus-strand DNA syn thesis. Previously, we demonstrated that the protein-priming activity of the polymerase requires a viral RNA segment, termed epsilon, which serves as a template for the synthesis of a short DNA oligomer that is covalently attached to the reverse transcriptase (G.-H. Wang and C. S eeger, J. Virol. 67:6507-6512, 1993). We now report that epsilon is su fficient for activation of the reverse transcriptase to prime DNA synt hesis through the formation of a stable RNA-protein (RNP) complex. We also demonstrate that the binding reaction depends on sequence-specifi c determinants on epsilon. Moreover, our results indicate that two gen etically separated domains of the reverse transcriptase are required f or formation of the RNP complex. Finally, we show that the polymerase has a DNA polymerase activity in the absence of epsilon which does not depend on the protein-priming mechanism.