File:Designer nucleases for inactivating viral oncogenes.webp

English: Designer nucleases for inactivating viral oncogenes. Schematics of four different designer nucleases are shown. a ZFNs contain individual ZFPs that each bind 3 bp and are combined to form a ZFP array. b TALE arrays consist of repeat domains, each binding a unique nucleotide through an RVD (red X). ZFNs and TALENs are generated by fusing a ZFP/TALE to a FokI nuclease. Pairs of effectors bind opposite strands flanking the cleavage site and, through FokI dimerization, results in a DSB (red line). c CRISPR/Cas consists of a Cas9 nuclease guided to the target by an sgRNA and through ~ 20 nt complementary to the target DNA, the Cas9 generates a DSB. d A meganuclease (homing endonuclease) consists of a heterodimer protein evolved to bind two half-sites, which can be fused to a TALE array (megaTAL) to improve specificity. The DSB in the viral oncogene results in anti-tumor effects either through activation of the NHEJ pathway that introduces deleterious mutations into the viral oncogene, activation of the DNA damage response, or elimination of episomes or proviral excision