Southern blot of genomic DNA from clones of stably transfected kidney
cells digested as follows. Lanes: D, BglII and
AflII; M, BglII, AflII,
and MspI; H, BglII, AflII,
and HpaII. Vc2 and Vc3 are clones stably transfected
with the empty vector. HGc2, HGc5, and HGc7 are clones stably
transfected with 5-MCDG. (These last three clones stain positive for
β-galactosidase activity after ponasterone A treatment). When the
promoter-enhancer is demethylated, digestion with HpaII
gives DNA fragments of 180–300 bp.