Figure 3.

Mapping of the HBx sequences necessary for coactivation and ‘transactivation’. (a) The amino acid sequence of HBx and a library of the clustered alanine substitution mutants (Cm1–Cm21) are shown. Each HBx‐Cm mutant harbors six or seven amino acid substitutions in a row.^{( 27 )} Transient expression of the HBx‐Cm mutants was similar to that of the wild HBx.^{( 27 )} (b) Transcription assay in vivo using luciferase reporters. Top is the coactivation assay. HepG2 cells were transiently introduced by pGalVP16 expressing the transactivator, pFR‐luc harboring the DNA‐binding sites for Gal4 and the luciferase gene, and the HBx expression plasmid. Control is the vacant plasmid, HBx‐D1 (aa 51–154) harbors the coactivation domain, and HBx‐D5 (aa 1–50) includes the negative regulatory domain. Bottom is the ‘transactivation’ assay using AP1‐Luc reporter and the HBx expression plasmid. A series of mutants, X‐Cm1 to X‐Cm21, are shown in (a). The results were according to the report by Tang et al.^{( 27 )}