Figure 2.
RNA secondary structure of the ε signal. It covers the 3′ 2/3rds of the precore region and the first 7 nucleotides of the core gene, and contains two base-paired regions (stems), a bulge, and a loop. Translation initiation sites for the uORF and core gene are indicated, as is the site of the 36-nt insertion found in genotype G. Most HBV genotypes have T1858, and the G1896A nonsense mutation would improve a base pair from U:G to U:A. Genotypes A, C1, F2, and F3 have C1858 to preclude the rise of the G1896A mutation.