Figure 1. Schematic representation of the Rosa26-floxSTOP/SRF-VP16 DNA targeting construct. The Rosa26-floxSTOP/SRF-VP16 DNA targeting construct (upper) and its integration site in the wild-type genomic Rosa26 locus (lower) are shown. Black arrows indicate EcoRI restriction sites, applied to Southern blot detection of the targeting construct (10 kb band) and the wild-type ROSA26 locus (15 kb band), using the probe indicated. White arrows indicate XbaI restriction sites generated upon the insertion of the floxSTOP/SRF-VP16 construct into the ROSA26–1 vector. The black box depicted upstream of the Puro-PGK cassette represents the splice acceptor. Black triangles indicate the two loxP sites flanking the STOP cassette.