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Translational regulation of hepatitis B viral gene expression
Author(s) -
LO S. J.,
SHEU S. Y.,
LIN CG.
Publication year - 1993
Publication title -
journal of gastroenterology and hepatology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.214
H-Index - 130
eISSN - 1440-1746
pISSN - 0815-9319
DOI - 10.1111/j.1440-1746.1993.tb01681.x
Subject(s) - messenger rna , microbiology and biotechnology , reticulocyte , protein biosynthesis , rna , hepatitis b virus , antigen , biology , gene expression , in vivo , transfection , in vitro , gene , virology , virus , biochemistry , immunology , genetics
At least five species of unspliced mRNA of the hepatitis B virus (HBV), which are 3.5, 3.4, 2.4, 2.1 and 0.8 kb, have been identified. To study this amount of HBV proteins they were translationally regulated and both in vitro and in vivo experiments performed. The four in vitro synthesized RNA corresponding to the 2.1, 2.4, 3.4, and 3.5 kb mRNA, respectively, were translated in a rabbit reticulocyte lysate. In conjunction with in vivo transfection experiments, it was demonstrated that: (i) a preferential translational initiation is involved in the differential amount of surface antigens; (ii) the 2.1 kb mRNA is the template for the synthesis of the middle and major surface antigens in a ratio of about 1 : 4; (iii) the 2.4 kb mRNA, although containing sequences for coding the large, middle and major surface antigen, is primarily used for the synthesis of large surface antigens; (iv) both the core and pol proteins can be independently synthesized from the 3.4 kb mRNA (pregenome RNA) and the synthesis of pol protein is favourably carried out via a leaky scanning mechanism; (v) the 3.5 kb mRNA (pre‐C mRNA) is the template for the production of precore protein (the precursor of hepatitis B e antigen) but not for the synthesis of both core and pol proteins. Taken together, the results indicate that: (i) the translational initiation context of each HBV‐encoded protein plays a key role in determining the level of protein synthesis; (ii) the occurrence of bifunctional mRNA of pregenome RNA and 2.1 kb mRNA provides another alternative means for minimization of the viral genome size; (iii) the leaky scanning mechanism is involved in the expression of the second protein in bifunctional mRNA.