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.
Bock
C T
CT
Department of Gastroenterology and Hepatology, Medizinische Hochschule Hannover, Hannover, Germany.
Tillmann
H L
HL
Manns
M P
MP
Trautwein
C
C
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