TALENs stands for Transcription Activator-Like Effector Nucleases. These are proteins like restriction endonucleases. They bind to both strand of DNA and cut both strand. So, the double stranded break of the DNA is repaired by Non-homologous End Joining repair (NHEJ) or by Homology Directed Repair mechanism.
Structurally, TALE have DNA binding domain and functional domain. DNA binding domain is the repeat of 33-35 amino acid residues with highly variable Repeat Variables Di-residues at 12th and 13th position which binds to single nucleotide sequence of DNA. The last repeat of DNA binding domain has only about 20 amino acid residues. So, this is also called as half repeat. Functional domain of TALE can contain either nucleases, activator, repressor, methylases or intgraeses. The gap between two DNA binding domain is called as spacer where the functional domain cut the double strands of DNA.
TALENs were discovered in Xanthomonas species of bacteria. They increase pathogenicity of bacteria by facilitating the infection in plant. In 2007, two group of researchers found that they can bind to double strand of DNA and act as transcription factor in eukaryotes.
We can design TALE’s both the DNA binding domain and the functional domain according to the site where we want to cut the DNA. So, its specificity makes TALENs very effective gene editing technique.
