Role of RS-1 derivatives in homology-directed repair at the human genome ATG5 locus.

Genome editing is a useful tool in basic and clinical research. Among the several approaches used in genome editing, the CRISPR-Cas9 system using clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein 9 (Cas9) along with a guide RNA has been developed recently. The CRISPR/Cas9 system induces site-specific double-stranded DNA breaks, which result in DNA repair via non-homologous end joining (NHEJ) or homology-directed repair (HDR). However, HDR efficiency is lower than that of NHEJ and accordingly poses a challenge in genome modification studies. Several chemical compounds including RS-1 have been shown to enhance the HDR knock-in process by two- to six-fold in HEK 293 cells and rabbit embryos. Based on this finding, we developed an antibiotic resistance system to screen RS-1 chemical derivatives, which may promote efficient HDR. In this study, we report several chemical compounds with high knock-in efficiency at the ATG5 gene locus, using HeLa cell-based assays.