Nuclear Import of Hepatitis B Virus Capsids and Release of the Viral Genome

While studying the import of the hepatitis B virus genome into the nucleus of permeabilized tissue culture cells, we found that viral capsids were imported in intact form through the nuclear pore into the nuclear basket. Import depended on phosphorylation of the capsid protein and was mediated by th...

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Published inProceedings of the National Academy of Sciences - PNAS Vol. 100; no. 17; pp. 9849 - 9854
Main Authors Rabe, Birgit, Vlachou, Angelika, Panté, Nelly, Helenius, Ari, Kann, Michael
Format Journal Article
LanguageEnglish
Published United States National Academy of Sciences 19.08.2003
National Acad Sciences
Subjects
Active Transport, Cell Nucleus
alpha Karyopherins - metabolism
beta Karyopherins - metabolism
Biological Sciences
Capsid
Capsid proteins
Capsid Proteins - chemistry
Capsid Proteins - physiology
Cell Line
Cell lines
Cell nucleus
Cell Nucleus - virology
DNA
DNA, Viral - genetics
DNA, Viral - metabolism
Genome, Viral
Genomes
Genomics
Hepatitis
Hepatitis B
Hepatitis B virus
Hepatitis B virus - genetics
Hepatitis B virus - pathogenicity
Hepatitis B virus - physiology
Humans
Imports
Phosphorylation
Proteins
ran GTP-Binding Protein - metabolism
Viruses
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Summary:While studying the import of the hepatitis B virus genome into the nucleus of permeabilized tissue culture cells, we found that viral capsids were imported in intact form through the nuclear pore into the nuclear basket. Import depended on phosphorylation of the capsid protein and was mediated by the cellular transport receptors importin α and β. Virus-derived capsids that contained the mature viral genome were able to release the viral DNA and capsid protein into the nucleoplasm. The uncoating reaction was independent of Ran, a GTP-binding enzyme responsible for dissociating other imported cargoes from the inner face of the nuclear pore. Immature capsids that did not contain the mature viral genome reached the basket but did not release capsid proteins nor immature genomes into the nucleoplasm. The different fate of mature and immature capsids after passing the nuclear pore indicates that the outcome of a nuclear import event may be regulated within the nuclear basket.
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To whom correspondence should be addressed. E-mail: michael.kann@viro.med.unigiessen.de.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations: NPC, nuclear pore complex; Impβ, importin β; Impα, importin α; HBV, hepatitis B virus; PG, pregenomic RNA; NLS, nuclear localization signal; P-C, capsids devoid of viral polymerase; ImmatC, immature capsids; ImmatC-Inh, capsids derived from HepG2.2.15 cells treated with the reverse-transcription inhibitor foscarnet; MatC, mature capsids; EcC, capsid protein in E. coli; EcPC, E. coli-derived recombinant capsids with some of the capsid proteins phosphorylated with trapped PKC; WGA, wheat germ agglutinin.
Edited by Francis V. Chisari, The Scripps Research Institute, La Jolla, CA, and approved June 30, 2003
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.1730940100