Zinc Finger Nucleases: A technique for genome editing

Dr. Abhijeeta Nandha

Assistant Professor, 

Department of Biotechnology, 

Division of Life-Science, 

Kalinga University

Abhijeeta.nandha@kalingauniversity.ac.in

Zinc finger nucleases (ZFNs) are a type of engineered DNA-cutting enzymes that canbe used to edit the genetic material of organisms. They are designed to target specificDNA sequences and introduce precise modifications, such as insertions, deletions, or

replacements, at those locations. ZFNs consist of two main components: a DNA-binding domain and a nucleasedomain. The DNA-binding domain is engineered using zinc finger proteins, whicharenaturally occurring DNA-binding motifs. These proteins can be customizedtorecognize specific DNA sequences of interest. The nuclease domain, usually derivedfrom the FokI restriction enzyme, is responsible for cutting the DNAat the targetedsite. The design of ZFNs involves combining multiple zinc finger domains, eachrecognizing a specific nucleotide triplet, to create a protein capable of bindingtoadesired DNA sequence. By fusing the nuclease domain to this engineered DNA- binding protein, the resulting ZFN can be programmed to cut the DNAat the desiredlocation. The FokI endonuclease is a type of restriction enzyme that naturally cleaves DNA. InZFNs, the DNA-cleavage domain of FokI is used to induce a double-strand breakat
the target site recognized by the zinc finger DNA-binding domain. The double-strandbreak stimulates the cell’s natural DNA repair mechanisms, which can lead to genemodifications, such as gene knockout or gene insertion. Once the DNA is cleaved by the ZFN, the cell’s natural DNA repair machineryis
activated. This repair process can lead to the introduction of genetic changes throughthe error-prone non-homologous end joining (NHEJ) pathway or through homology- directed repair (HDR) using a donor DNA template. These repair mechanisms canbeharnessed to introduce specific modifications in the DNA sequence, such as geneknockouts, insertions, or corrections. ZFNs were one of the first genome editing tools developed, and their use has
contributed to significant advancements in genetic research. However, since theadvent of newer and more efficient genome editing technologies such as CRISPR- Cas9, the use of ZFNs has declined in recent years. CRISPR-Cas9 offers several
advantages over ZFNs, including ease of design, higher efficiency, and lower cost. Nonetheless, ZFNs played an important role in the development of genome editingtechnologies and continue to be used in specific cases where CRISPR-Cas9 maynot
be suitable or effective.