Fig. 3. Phosphine control of cloaked CRISPR–Cas9 activity in human cells. (a) Flow cytometric analysis of GFP(+) HeLa cells showing loss of activity of cloaked sgRNA, and restoration of editing with phosphine treatment; (b) chart showing gene editing efficiencies (from flow cytometry data) of untreated, cloaked, and phosphine-uncloaked sgRNA (error bars represent ±s.d., n = 3 and p-values: ***p < 0.001, *p < 0.05.); (c) epifluorescence microscope images showing GFP knockout upon transfection with untreated sgRNA and Cas9 mRNA, lack of editing activity with cloaked sgRNA leaving GFP fluorescence unaffected, and restoration of editing with phosphine treatment of the cells.