Nuclear entry of hepatitis B virus capsids involves disintegration to protein dimers followed by nuclear reassociation to capsids.
Assembly and disassembly of viral capsids are essential steps in the viral life cycle. Studies on their kinetics are mostly performed in vitro, allowing application of biochemical, biophysical and visualizing techniques. In vivo kinetics are poorly understood and the transferability of the in vitro models to the cellular environment remains speculative. We analyzed capsid disassembly of the hepatitis B virus in digitonin-permeabilized cells which support nuclear capsid entry and subsequent genome release. Using gradient centrifugation, size exclusion chromatography and immune fluorescence microscopy of digitonin-permeabilized cells, we showed that capsids open and close reversibly. In the absence of RNA, capsid re-assembly slows down; the capsids remain disintegrated and enter the nucleus as protein dimers or irregular polymers. Upon the presence of cellular RNA, capsids re-assemble in the nucleus. We conclude that reversible genome release from hepatitis B virus capsids is a unique strategy different from that of other viruses, which employs irreversible capsid destruction for genome release. The results allowed us to propose a model of HBV genome release in which the unique environment of the nuclear pore favors HBV capsid disassembly reaction, while both cytoplasm and nucleus favor capsid assembly.
Rabe
Birgit
B
Institute of Virology, Justus Liebig University, Giessen, Germany.
Delaleau
Mildred
M
Bischof
Andreas
A
Foss
Michael
M
Sominskaya
Irina
I
Pumpens
Paul
P
Cazenave
Christian
C
Castroviejo
Michel
M
Kann
Michael
M
D021581:Active Transport, Cell Nucleus; D002213:Capsid / Q000378:metabolism*; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000821:virology*; D002499:Centrifugation, Density Gradient; D002850:Chromatography, Gel; D004279:DNA, Viral / Q000378:metabolism; D004587:Electrophoresis, Agar Gel; D004926:Escherichia coli / Q000378:metabolism / Q000821:virology; D006515:Hepatitis B virus / Q000378:metabolism / Q000472:pathogenicity*; D006801:Humans; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D010759:Phosphorus Isotopes; D055503:Protein Multimerization; D012367:RNA, Viral / Q000378:metabolism; D014771:Virion / Q000378:metabolism / Q000472:pathogenicity*; D018406:Virus Physiological Phenomena
D004279:DNA, Viral; D010759:Phosphorus Isotopes; D012367:RNA, Viral