Full-length hepatitis B virus core protein packages viral and heterologous RNA with similarly high levels of cooperativity

J. Zachary Porterfield, Mary Savari Dhason, Daniel D. Loeb, Michael Nassal, Stephen J. Stray, Adam Zlotnick

Research output: Contribution to journalArticlepeer-review

123 Scopus citations


A critical feature of a viral life cycle is the ability to selectively package the viral genome. In vivo, phosphorylated hepatitis B virus (HBV) core protein specifically encapsidates a complex of pregenomic RNA (pgRNA) and viral polymerase; it has been suggested that packaging is specific for the complex. Here, we test the hypothesis that core protein has intrinsic specificity for pgRNA, independent of the polymerase. For these studies, we also evaluated the effect of core protein phosphorylation on assembly and RNA binding, using phosphorylated core protein and a phosphorylation mimic in which S155, S162, and S170 were mutated to glutamic acid. We have developed an in vitro system where capsids are disassembled and assembly-active core protein dimer is purified. With this protein, we have reassembled empty capsids and RNA-filled capsids. We found that core protein dimer bound and encapsidated both the HBV pregenomic RNA and heterologous RNA with high levels of cooperativity, irrespective of phosphorylation. In direct competition assays, no specificity for pregenomic RNA was observed. This suggests that another factor, such as the viral polymerase, is required for specific packaging. These results also beg the question of what prevents HBV core protein from assembling on nonviral RNA, preserving the protein for virus production.

Original languageEnglish
Pages (from-to)7174-7184
Number of pages11
JournalJournal of Virology
Issue number14
StatePublished - Jul 2010

ASJC Scopus subject areas

  • Microbiology
  • Immunology
  • Insect Science
  • Virology


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