POLYMERASE GENE-PRODUCTS OF HEPATITIS-B VIRUSES ARE REQUIRED FOR GENOMIC RNA PACKAGING AS WELL AS FOR REVERSE TRANSCRIPTION

ALL reactions involving reverse transcription of RNA are segre-gated from the cytosol within a subviral particle or capsid composed of the major capsid protein, the polymerase and the RNA tem-plate1. A key step in the formation of these particles is the selective encapsidation of the RNA template. Although an important gen-eral feature of the reverse transcription pathway, encapsidation has been carefully studied only for retrovirqses2-5. We have now examined the encapsidation reaction in a family of enveloped DNA viruses that replicate by reverse transcription-the hepatitis B viruses (hepadnaviruses). Our results indicate that the hepadnaviral polymerase (P) gene product is required for RNA packag-ing, and that the encapsidation function of the enzyme can be separated from its DNA polymerase activity. To our knowledge, this is the first description of a role for polymerase gene products in this step of the reverse transcription pathway. © 1990 Nature Publishing Group.