A TALE of two nucleases: gene targeting for the masses?

Abstract

Genome editing appears poised to enter an exciting new era. Targeted double-stranded breaks due to custom restriction enzymes are powerful nucleating events for the induction of local changes in the genome. The zinc finger nuclease (ZFN) platform established the potential of this approach for the zebrafish, but access to high quality reagents has been a major bottleneck for the field. However, two groups recently report successful somatic and germline gene modification using a new nuclease architecture, transcription activator-like effector nucleases (TALENs). TALEN construction is simpler, potentially more reliable, and in the few cases examined, shows fewer off-target effects than corresponding ZFNs. TALENs promise to bring gene targeting to the majority of zebrafish laboratories.

FIG. 1.

Engineered transcription activator-like effector Nuclease (TALEN) cartoons. (A) Engineered TALE DNA binding domain recognizes specific bases by using a known cipher involving two key amino acid residues. These amino acids are embedded in a 33–35 amino acid repeat. Nuclear access is provided by the native nuclear localization signal (NLS). (B) Total sequence specificity and formation of a fully functional nuclease is achieved from each of the two TALEN monomers after dimerization on the target sequence in the genome.