Fig. 1

Cpf1–Flip–Cre-inducible sequential mutagenesis by a single crRNA FlipArray. a Schematic of vectors used in the study. The Cpf1-Flip construct contains an EFS promoter driving expression of Cpf1 and puromycin resistance, and a U6 expression cassette containing two inverted BsmbI restriction sites, flanked by a lox66 sequence and an inverted lox71 sequence. After BsmbI digestion, a crRNA FlipArray is cloned in. The FlipArray inverts upon Cre recombination, thereby switching the crRNA that is expressed. b Schematic of experimental design. Cells were first infected with lentivirus containing EFS-Cpf1-puro; U6-FlipArray. After 7 days, cells were then infected with lentivirus containing EFS-Cre to induce inversion of the FlipArray. Prior to Cre recombination, only crNf1 is expressed; following Cre recombination, crPten becomes expressed. c Sequences of the FlipArray construct before and after Cre recombination. Red boxes denote mutants from wild-type loxP. Prior to Cre, single mutant lox66 and lox71 sites are present. After Cre recombination, a wild-type loxP site and a double mutant lox72 site are generated