Figure 1.

TAL effector and TALEN structure. (a) Structure of a naturally occurring TAL effector. A consensus repeat sequence is shown with the repeat-variable di-residue (RVD) underlined. The sequence of RVDs determines the target nucleotide sequence. The four most common RVDs, on which our designs and plasmids are based, are shown with their most frequently associated nucleotide. Some evidence suggests that the less common RVD NK (not displayed) has greater specificity for G than NN does and for that reason our plasmid set also includes NK modules. (b) Structure of a TALEN. Two monomeric TALENs are required to bind the target site to enable FokI to dimerize and cleave DNA. NLS, nuclear localization signal(s); AD, transcriptional activation domain; B, BamHI; S, SphI.