G-quadruplex-based CRISPR photoswitch for spatiotemporal control of genomic modulation.

CRISPR (clustered regularly interspaced short palindromic repeats) technology holds tremendous promise for gene regulation and editing. However, precise control of CRISPR editing is essential to overcome its uncontrollable reaction process and excessive activity that leads to off-target editing. To overcome this problem, we engineered a photoswitch on G-quadruplex gRNA (GqRNA) for precisely controlled gene editing and expression by embedding dicationic azobenzene derivatives (AZD++). Our results demonstrated that rational design of the G-quadruplex onto crRNA conferred higher stability and sequence recognition specificity than unmodified single guide (sgRNA). Light-induced isomerization of AZD++ quickly transformed the on state of GqRNA, which facilitated rapid activation of ribonucleoprotein activity for genome editing of on-target sites in cells with excellent editing efficiency. In turn, AZD++-GqRNA promptly refolded to an off state to inhibit genomic cleavage, and limited the generation of off-target effects and by-products. Therefore, the proposed strategy of a photo-reversible modality presents a new opportunity for CRISPR-Cas9 modulation to improve its safety and applicability.