HCV IRES mutations found in sequence signature strains isolated in South America. The 5'NCR sequences of strain HCV1b  is shown. The locations of the nucleotide mutations found in the sequence signature are shown in bold and a solid arrow indicates each particular substitution. Sequences previously identified to belong to a specific IRES domain  are indicated by colours and domain number is indicated bellow the sequence. IRES nucleotide substitutions positions previously reported in the literature  or in the HCV Database  are indicated in bold italics underlined. Each particular previously reported substitution is indicated by a dotted arrow. Δ means deletion. Numbers in the figure denote nucleotide position in HCV sequence according to strain HCV1b .