Southern blot analysis of Epo-R–infected TEPC clones. Ten micrograms of Bgl II-digested genomic DNAs from different clones was analyzed on 1% agarose gel, blotted, and hybridized with a ³²P NEO DNA probe. P, parental TEPC cells; E1 to E7, Epo-R–infected clones; N1, NEO-infected clone; T1, NEO-infected FDCP-1 clone; T2, Epo-R virus-producing cells.