A cDNA encoding the human PML-RARA fusion with nucleotide substitution resulting in the amino acid substitutions of arginine for valine at positions 420 and 432 (V420 and V423R) was inserted into the 5'UTR along with a floxed neo cassette. Cre-mediated recombination removed the neo cassette. The amino acid substitutions generate a protease cleavage-resistant PML-RARA product. (J:166479)