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J Virol. 2010 Jul;84(14):7174-84. doi: 10.1128/JVI.00586-10. Epub 2010 Apr 28.

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

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  • 1Department of Molecular and Cellular Biochemistry, Indiana University, 212 S. Hawthorne Dr., Simon Hall 220D, Bloomington, IN 47405-7003, USA.

Abstract

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.

PMID:
20427522
[PubMed - indexed for MEDLINE]
PMCID:
PMC2898219
Free PMC Article
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