Establishment of cell lines that ectopically express Egr-1. (A) Northern blot analysis of Egr-1 expression in M1, M1neo, and M1Egr-1 clones. Ten micrograms of total RNA was analyzed by Northern blots as described in Materials and Methods. (B) Southern blot analysis of genomic DNA from parental M1, M1neo, and M1Egr-1 clones. Genomic DNA (10 μg) was digested with EcoRI, resolved on a 1% agarose gel, transferred to Gene Screen Plus membranes (NEN, Boston, MA), and hybridized to a murine Egr-1 cDNA probe.