Hepadnavirus assembly and reverse transcription require a multi-component chaperone complex which is incorporated into nucleocapsids.
Assembly of hepadnaviruses depends on the formation of a ribonucleoprotein (RNP) complex comprising the viral polymerase polypeptide and an RNA segment, epsilon, present on pregenomic RNA. This interaction, in turn, activates the reverse transcription reaction, which is primed by a tyrosine residue on the polymerase. We have shown recently that the formation of this RNP complex in an avian hepadnavirus, the duck hepatitis B virus, depends on cellular factors that include the heat shock protein 90 (Hsp90). We now report that RNP formation also requires ATP hydrolysis and the function of p23, a recently identified chaperone partner for Hsp90. Furthermore, we also provide evidence that the chaperone complex is incorporated into the viral nucleocapsids in a polymerase-dependent reaction. Based on these findings, we propose a model for hepadnavirus assembly and priming of viral DNA synthesis where a dynamic, energy-driven process, mediated by a multi-component chaperone complex consisting of Hsp90, p23 and, potentially, additional factors, maintains the reverse transcriptase in a specific conformation that is competent for RNA packaging and protein priming of viral DNA synthesis.
Hu
J
J
Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, PA 19111, USA.
Toft
D O
DO
Seeger
C
C
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D018833:Chaperonins / Q000378:metabolism*; D002645:Chickens; D004279:DNA, Viral / Q000096:biosynthesis; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism; D015611:Hepatitis B Virus, Duck / Q000235:genetics / Q000502:physiology*; D006801:Humans; D018832:Molecular Chaperones; D019251:Nucleocapsid / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D000071876:Prostaglandin-E Synthases; D012367:RNA, Viral / Q000378:metabolism; D012194:RNA-Directed DNA Polymerase / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D014407:Tumor Cells, Cultured; D019065:Virus Assembly
D004279:DNA, Viral; D018841:HSP90 Heat-Shock Proteins; D018832:Molecular Chaperones; D010750:Phosphoproteins; D012367:RNA, Viral; D011994:Recombinant Proteins; D000255:Adenosine Triphosphate; D012194:RNA-Directed DNA Polymerase; D018833:Chaperonins; C490849:PTGES3 protein, human; D000071876:Prostaglandin-E Synthases