A fused human MYC and ESR1 (ERT2) sequence, preceded by a CAG promoter and floxed neo cassette with a triple polyadenylation sequence and followed by an IRES-EGFP, was inserted into the ROSA locus. Expression of the fusion product can only be achieved through cre mediated removal of the neo cassette along with its polyadenlylation sequences. (J:289102)