Architectural Determinants of Genome-Editing Outcomes: A Comparative Analysis of DNA Recognition and Cleavage Mechanisms in ZFNs, TALENs, and CRISPR-Cas9

Genome editing has been well recognized as a genome engineering tool that allows scientists to permanently modify the DNA contented at a particular genomic location. Earlier, it was carried out by delivering a DNA template with a long homologous arm to the targeted genomic site. This process was time-consuming and required synthesis and the delivery of a long DNA template. Zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 are three extensively used genome editing technologies that were developed in response to these limitations. This paper provides a comparative analysis of the origin, structure, function, and working advantages over each other, limitations, and their application in different organisms for disease treatment and genetic modifications of these three technologies. ZFNs are earliest genome editing technology. ZFN is a protein having Zn finger domains that recognize the DNA and the Fok domain that cuts the DNA sequences. TALENs are similar to ZFNs but use transcription activator-like effectors instead of zinc fingers to recognize DNA. CRISPR-Cas9 is more recent technology that uses RNA guides to target specific DNA sequences. One advantage of ZFNs and TALENs is their high specificity but they are time-consuming and expensive processes to design and synthesize each nuclease for a specific target sequence. Whereas CRISPR-Cas9 is faster and more cost-effective, as it requires only simple RNA guide design to target specific DNA sequence. In conclusion, ZFNs, TALENs, and CRISPR-Cas9 are all useful genome editing technologies. Each of these technologies have advantages and limitations that will be discussed in the article.