Expression of E1A and E1B transactivators in human embryo kidney cell line 293. A Northern blot analysis using equal amounts (30 μg) of total cellular RNA from human embryo kidney 293 cells (HEK293) and NIH/3T3 cells is shown. The blotted RNAs were hybridized with 3.5 × 107 cpm of a [α-32P]dCTP-labelled 2.8-kbp Eco RI/Hind III fragment of clone pAd5Sal IB23 containing complete E1A-gene and partial E1B-gene of Ad5. The autoradiograph was exposed for 3 hours using an intensifying screen. The RNAs were rehybridized with 1.5 × 107 cpm of a [α-32P]dCTP-labelled GAPDH-specific cDNA probe, and filter was re-exposed for 3 hours.