The pre-S region determines the intracellular localization and appearance of hepatitis B virus.
The functional role of the hepatitis B virus (HBV) pre-S region for assembly and appearance of the virus is not completely understood. In this study, 3 natural-occurring mutants were investigated. Three mutants of the pre-S region-a point mutation in the CCAAT box (MUT1), a 6-bp deletion (MUT2) 3' of the CCAAT box, and a 153-bp deletion (MUT3) in the preS2 domain-were cloned alone or in combinations in replication-competent HBV plasmids and transfected in hepatoma cells. The impact on HBV assembly and appearance was studied by Northern Blot, primer extension analysis, immunofluorescence studies, enzyme-linked immunosorbent assay, and electron microscopy. An inversed ratio of pre-S/S mRNA transcripts compared with wild-type (wt) HBV was found when either MUT1 or -2 were included into the plasmid. Intracellular localization with both mutants showed retention of large S-protein in the endoplasmic reticulum and nuclear accumulation of core protein. The extracellular amount of S-protein was reduced with MUT1 and -2 or combinations in which 1 of the mutants was included. However, the extracellular appearance of viral products was comparable with wtHBV. In contrast, MUT3 showed major changes. Virion-like particles had a fried-egg, and filaments a screw-like appearance. The S-promoter mutations MUT1 and MUT2 correlated with viral retention. MUT3 leads to malformed viral particles. Therefore, different regions in the pre-S domain are essential to determine the intracellular localization and extracellular appearance of HBV, and might contribute to the prognosis of chronic HBV infection.
Department of Gastroenterology and Hepatology, Medizinische Hochschule Hannover, Hannover, Germany.
C T
CT
Bock
H L
HL
Tillmann
M P
MP
Manns
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C
Trautwein
D006515:Hepatitis B virus / Q000235:genetics* / Q000502:physiology; D006801:Humans; D009154:Mutation; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D014407:Tumor Cells, Cultured; D014771:Virion / Q000502:physiology; D019065:Virus Assembly
D012333:RNA, Messenger