A novel chromosome region maintenance 1-independent nuclear export signal of the large form of hepatitis delta antigen that is required for the viral assembly.
Hepatitis delta virus (HDV) is a satellite virus of hepatitis B virus, as it requires hepatitis B virus for virion production and transmission. We have previously demonstrated that sequences within the C-terminal 19-amino acid domain flanking the isoprenylation motif of the large hepatitis delta antigen (HDAg-L) are important for virion assembly. In this study, site-directed mutagenesis and immunofluorescence staining demonstrated that in the absence of hepatitis B virus surface antigen (HBsAg), the wild-type HDAg-L was localized in the nuclei of transfected COS7 cells. Nevertheless, in the presence of HBsAg, the HDAg-L became both nuclei- and cytoplasm-distributed in about half of the cells. An HDAg-L mutant with a substitution of Pro-205 to alanine could neither form HDV-like particles nor shift the subcellular localization in the presence of HBsAg. In addition, nuclear trafficking of HDAg-L in heterokaryons indicated that HDAg-L is a nucleocytoplasmic shuttling protein. A proline-rich HDAg peptide spanning amino acid residues 198 to 210, designated NES(HDAg-L), can function as a nuclear export signal (NES) in Xenopus oocytes. Pro-205 is critical for the NES function. Furthermore, assembly of HDV is insensitive to leptomycin B, indicating that the NES(HDAg-L) directs nuclear export of HDAg-L to the cytoplasm via a chromosome region maintenance 1-independent pathway.
Lee
C H
CH
Institute of Biochemistry, College of Medicine, National Taiwan University, No. 1, Jen-Ai Rd., First Section, Taipei, Taiwan.
Chang
S C
SC
Wu
C H
CH
Chang
M F
MF
D021581:Active Transport, Cell Nucleus; D000818:Animals; D002460:Cell Line; D002875:Chromosomes / Q000502:physiology*; D003593:Cytoplasm / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D018963:Hepatitis Antigens / Q000378:metabolism*; D006514:Hepatitis B Surface Antigens / Q000032:analysis; D003698:Hepatitis Delta Virus / Q000187:drug effects / Q000502:physiology*; D035923:Hepatitis delta Antigens; D006801:Humans; D051379:Mice; D019065:Virus Assembly / Q000187:drug effects
D005231:Fatty Acids, Unsaturated; D018963:Hepatitis Antigens; D006514:Hepatitis B Surface Antigens; D035923:Hepatitis delta Antigens; C442244:hepatitis delta virus large antigen; C038753:leptomycin B