Expression mechanism of the hepatitis B virus (HBV) C gene and biosynthesis of HBe antigen.
The C gene of the hepatitis B virus, which contains two in-phase initiation codons delimiting the pre-C sequence and the C region, directs the synthesis of the major protein of the capsid (HBcAg) and of a precore protein which upon processing results in the secretion of the HBeAg. We used an adenovirus-based vector to study in the human 293 cell line the C gene products, the intermediates of the precore protein processing and the kind of protease involved in this processing. The synthesis of the 21-kDa HBcAg polypeptide was dependent on the deletion of the pre-C sequence suggesting that a pre-C mRNA is not used for the synthesis of the major capsid protein. With the construct containing the complete C gene, two proteins of 25 and 22 kDa were detected intracellularly, corresponding to the unprocessed and partially processed precore protein, respectively. In addition, a 15-kDa protein (HBeAg) was secreted in the culture medium. Using pepstatin, an inhibitor specific for aspartyl proteinases, reduction of HBeAg secretion and accumulation of the 22-kDa processing intermediate were observed, suggesting the involvement of an aspartyl proteinase in the conversion of the 22-kDa protein into HBeAg.
Jean-Jean
O
O
Laboratory de Biologie Moléculaire de la Réplication, (ER 272-CNRS), I.R.S.C., Villejuif, France.
Levrero
M
M
Will
H
H
Perricaudet
M
M
Rossignol
J M
JM
D015153:Blotting, Western; D002478:Cells, Cultured; D004279:DNA, Viral / Q000235:genetics; D005814:Genes, Viral; D005822:Genetic Vectors; D006512:Hepatitis B Core Antigens / Q000096:biosynthesis; D006513:Hepatitis B e Antigens / Q000096:biosynthesis*; D006515:Hepatitis B virus / Q000235:genetics*; D008970:Molecular Weight; D010447:Peptide Hydrolases / Q000378:metabolism; D014176:Protein Biosynthesis; D011499:Protein Processing, Post-Translational
D004279:DNA, Viral; D006512:Hepatitis B Core Antigens; D006513:Hepatitis B e Antigens; D010447:Peptide Hydrolases