Fig. 1

HIV-1 escapes from Cas9/sgRNA. Cas9 is directed to HIV-1 DNA by sgRNA, then cleaves the target DNA at a position 3 nucleotides from the PAM. When the NHEJ machinery repairs the double-stranded DNA break, short nucleotide insertions, deletions and substitutions are generated at the cleavage site. Many of these mutations abrogate viral gene function and thus kill the virus. However, some mutations do not harm the virus and can promote viral escape. PAM, protospacer adjacent motif. sgRNA, single guide RNA. NHEJ non-homologous end joining. * substituted or inserted nucleotides. Δ, deleted nucleotides