Advance trends in targeting homology-directed repair for accurate gene editing: An inclusive review of small molecules and modified CRISPR-Cas9 systems

Introduction: Clustered regularly interspaced short palindromic repeat and its associated protein (CRISPRin host genome by inducing site-specific double-strand breaks (DSBs) that can serve as a substrate for homologydirected repair (HDR) in both in vitro and in vivo models. HDR pathway could enhance incorporation of exogenous DNA templates into the CRISPR-Cas9-mediated DSB site. Owing to low rate of HDR pathway, the efficiency of accurate genome editing is diminished. Enhancing the efficiency of HDR can provide fast, easy, and accurate technologies based on CRISPR-Cas9 technologies. Methods: The current study presents an overview of attempts conducted on the precise genome editing strategies based on small molecules and modified CRISPR-Cas9 systems. Results: In order to increase HDR rate in targeted cells, several logical strategies have been introduced such as generating CRISPR effector chimeric proteins, anti-CRISPR proteins, modified Cas9 with donor template, and using validated synthetic or natural small molecules for either inhibiting non-homologous end joining (NHEJ), stimulating HDR, or synchronizing cell cycle. Recently, high-throughput screening methods have been applied for identification of small molecules which along with the CRISPR system can regulate precise genome editing through HDR. Conclusion: The stimulation of HDR components or inhibiting NHEJ can increase the accuracy of CRISPR-Cas-mediated engineering systems. Generating chimeric programmable endonucleases provide this opportunity to direct DNA template close proximity of CRISPR-Cas-mediated DSB. Small molecules and their derivatives can also proficiently block or activate certain DNA repair pathways and bring up novel perspectives for increasing HDR efficiency, especially in human cells. promising chemicals that improve HDR efficiency and CRISPR-Cas9 systems.

Automated summary

This study presents an overview of precise genome editing strategies based on small molecules and modified CRISPR-Cas9 systems. Different strategies, such as generating CRISPR effector chimeric proteins, anti-CRISPR proteins, modified Cas9 with donor template, and using small molecules to inhibit non-homologous end joining (NHEJ) or stimulate HDR, have been introduced to increase the HDR rate in targeted cells. High-throughput screening methods have also been applied to identify small molecules that can regulate precise genome editing through HDR when combined with the CRISPR system. Promising chemicals and modifications to the CRISPR-Cas9 system can enhance HDR efficiency for accurate genome editing.