Figure 2

Mapping putative E-boxes (CANNTG) onto a global HTLV-1 phylogeny. HTLV-1 strains have been gathered into 6 groups of common ancestry (clades) named a to e, with HTLV-1a being often referred to as the Cosmopolitan clade [21]. This phylogenetic tree depicts the relationships of 127 strains (appearing as terminal, non-interior branches) among which >100 belong to the Cosmopolitan clade (the only pandemic HTLV-1 clade, solid line polygon). HTLV-1a is here largely overrepresented, which fits the reality of the pandemic; the other group distribution areas being much more restricted (e.g. Central Africa). Putative E-boxes have been mapped onto this phylogeny through the appending of a color code (blue = CANNTG consensus sequence; black = other sequences). This makes evident the presence of putative E-boxes in nearly all Cosmopolitan strains, which sharply contrasts with the situation prevailing in the other clades. This tree has been obtained through the analysis of a dataset derived from Coulthart et al.[22].