Abstract
Hepatitis B virus (HBV) expresses co-terminal large (L), middle (M), and small (S) envelope proteins. S protein drives virion and subviral particle secretion, whereas L protein inhibits subviral particle secretion but coordinates virion morphogenesis. We previously found that preventing S protein expression from a subgenomic construct eliminated M protein. The present study further examined impact of S protein on L and M proteins. Mutations were introduced to subgenomic construct of genotype A or 1.1 mer replication construct of genotype A or D, and viral proteins were analyzed from transfected Huh7 cells. Mutating S gene ATG to prevent expression of full-length S protein eliminated M protein, reduced intracellular level of L protein despite its blocked secretion, and generated a truncated S protein through translation initiation from a downstream ATG. Truncated S protein was secretion deficient and could inhibit secretion of L, M, S proteins from wild-type constructs. Providing full-length S protein in trans rescued L protein secretion and increased its intracellular level from mutants of lost S gene ATG. Lost core protein expression reduced all the three envelope proteins. In conclusion, full-length S protein could sustain intracellular and extracellular L and M proteins, while truncated S protein could block subviral particle secretion.
Highlights
Hepatitis B virus (HBV) is an enveloped DNA virus with a small circular genome of3.2 kb [1,2]
Much increased gp19/p16 expression led to the reappearance of M protein for N67b+1 and N67b+2 (Figure 3A, second panel, lanes 9, 10). These findings suggest that truncated S protein could sustain intracellular level of L protein, but not as efficiently as the full-length S protein even when expressed at higher level
The Smutant was generated by mutating its S gene ATG into GCG, as the double-nucleotide substitution should prevent translation initiation even from a non-ATG codon
Summary
Hepatitis B virus (HBV) is an enveloped DNA virus with a small circular genome of. 3.2 kb [1,2]. The S protein is expressed at much higher level than L and M proteins and is the most abundant envelope protein on the. The S protein is expressed at much higher level than L and M proteins and is the most abundant envelope protein on the 42-nm virions. S and M proteins are secreted without internal core particles as the 22-nm subviral particles (SVPs), which exceed vias the 22-nm subviral particles (SVPs), which exceed virions by up to 100,000-fold [3,4,5]. L/S protein ratio while efficient ratio while efficient virion secretion requires a proper (not too high or too low). Sprotein on intracellular and extracellular levels of L protein, in the both in the context of 0.7 mer and full-length genome Schematic representation of of thetheDNA usedinin present study and summary their
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