Genome editing using zinc-finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs)

Abstract

Targetable nucleases, including zinc-finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated (Cas), induce DNA double- strand breaks (DSBs) into user-defined sites. DSBs are immediately repaired through the evolutionarily conserved pathways of error-prone non-homologous end joining (NHEJ) or homology-directed repair (HDR). With the utilization of these repair processes, researchers have been able to disrupt specific genes, add exogenous DNA elements into intended genomic sites, introduce single-nucleotide substitutions, and perform many other applications. Consequently, this “genome editing” technology has revolutionized the life science field. In addition, this technology has the potential to improve agricultural products and be applicable to therapeutic use. Here, we will introduce a brief history of targetable nuclease-mediated genome editing and the applications of the tools that the technology provides. In this chapter, we will primarily focus on ZFNs and TALENs, which are artificial proteins composed of a specific DNA-binding domain and a restriction enzyme FokI DNAcleavage domain. We will also review the properties and construction methods of these nucleases.