Effect of mutating the two cysteines required for HBe antigenicity on hepatitis B virus DNA replication and virion secretion.
Hepatitis B virus (HBV) variants with impaired expression of e antigen (HBeAg) frequently arise at the chronic stage of infection, as exemplified by precore and core promoter mutants. Since an intramolecular disulfide bond maintains the secondary structure of HBeAg, we explored effect of missense mutations of either cysteine codon. Consistent with earlier reports, substitution of each cysteine rendered HBeAg nearly undetectable. With underlying nucleotide changes at the loop of pregenome encapsidation signal, the C-7 mutants were severely impaired in pregenomic RNA packaging and hence DNA replication. Although none of the missense mutations at C61 reduced DNA replication, replacement with arginine, but not alanine, aspartic acid, phenylalanine, or serine, blocked virion secretion. Consistent with the detection of C61R genome from a patient serum, secretion block of the C61R mutant could be overcome by co-expression of wild-type core protein. In conclusion, point mutations of the C61 codon may generate viable HBeAg-negative variants.
Bang
Genie
G
The Liver Research Center, Rhode Island Hospital and Brown Medical School, 55 Claverick Street, 4th Floor, Providence, RI 02903, USA.
Kim
Kyun-Hwan
KH
Guarnieri
Michael
M
Zoulim
Fabien
F
Kawai
Shigenobu
S
Li
Jisu
J
Wands
Jack
J
Tong
Shuping
S
D003062:Codon; D003545:Cysteine / Q000235:genetics / Q000276:immunology / Q000502:physiology*; D004261:DNA Replication; D004279:DNA, Viral / Q000096:biosynthesis; D006514:Hepatitis B Surface Antigens / Q000276:immunology*; D006515:Hepatitis B virus / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D011401:Promoter Regions, Genetic; D012367:RNA, Viral; D014758:Viral Core Proteins / Q000235:genetics / Q000378:metabolism*; D014771:Virion / Q000378:metabolism / Q000502:physiology*; D014779:Virus Replication
D003062:Codon; D004279:DNA, Viral; D006514:Hepatitis B Surface Antigens; D012367:RNA, Viral; D014758:Viral Core Proteins; D003545:Cysteine