Structural organization of pregenomic RNA and the carboxy-terminal domain of the capsid protein of hepatitis B virus

PLoS Pathog. 2012 Sep;8(9):e1002919. doi: 10.1371/journal.ppat.1002919. Epub 2012 Sep 20.

Abstract

The Hepatitis B Virus (HBV) double-stranded DNA genome is reverse transcribed from its RNA pregenome (pgRNA) within the virus core (or capsid). Phosphorylation of the arginine-rich carboxy-terminal domain (CTD) of the HBV capsid protein (Cp183) is essential for pgRNA encapsidation and reverse transcription. However, the structure of the CTD remains poorly defined. Here we report sub-nanometer resolution cryo-EM structures of in vitro assembled empty and pgRNA-filled Cp183 capsids in unphosphorylated and phosphorylation-mimic states. In empty capsids, we found unexpected evidence of surface accessible CTD density partially occluding pores in the capsid surface. We also observed that CTD organization changed substantively as a function of phosphorylation. In RNA-filled capsids, unphosphorylated CTDs favored thick ropes of RNA, while the phosphorylation-mimic favored a mesh of thin, high-density strands suggestive of single stranded RNA. These results demonstrate that the CTD can regulate nucleic acid structure, supporting the hypothesis that the HBV capsid has a functional role as a nucleic acid chaperone.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Capsid / metabolism
  • Capsid / ultrastructure*
  • Capsid Proteins / chemistry*
  • Capsid Proteins / metabolism*
  • DNA, Viral / genetics
  • DNA, Viral / metabolism
  • Genome, Viral
  • Hepatitis B virus / chemistry*
  • Hepatitis B virus / genetics*
  • Hepatitis B virus / ultrastructure
  • Molecular Chaperones
  • Phosphorylation
  • Protein Structure, Tertiary
  • RNA, Viral / genetics
  • RNA, Viral / metabolism*
  • Virus Assembly*

Substances

  • Capsid Proteins
  • DNA, Viral
  • Molecular Chaperones
  • RNA, Viral