Target residence of Cas9: challenges and opportunities in genome editing

Abstract

CRISPR/Cas9 genome editing is a latest success in biotechnology that repurposes a natural biological system for a practical tool in genetic engineering. Site-specific DNA double strand breaks (DSB) induced by the CRISPR nuclease Cas9 allows endogenous cellular repair apparatus to generate desired repair products. Residence of Cas9 on cleaved DNA conceals the DNA ends from recognition by response and repair apparatus, delaying DNA damage response (DDR) and repair. Thus, tight-binding and long residence of Cas9 on DNA target are proposed as a new determinant of DSB repair pathway choice and may collaborate with other endogenous pathway choice regulators to control DSB repair. Accordingly, harnessing the binding and resident behavior of Cas9 not only broadens the application of CRISPR/dCas9 platform, which at least in part depends upon the tight binding and long residence of dCas9, but also minimizes the undesired outcomes of CRISPR/Cas9 genome editing.