Analysis of nuclear protein bindings to the GATA and HNF3 sites of E1 promoter in hepatoma and nonhepatoma cells. A, RT-PCR analysis of the expression of E1 and E1-b transcripts in HepG2, Huh7, 293A, and HeLa cells. The E1- (320 bp) and E1-b–(208 bp) specific PCR products together with referenced β-actin fragments were visualized by ethidium bromide staining. B, analysis of binding complexes for the E1-GATA site by nonradioactive chemiluminescent EMSA using a biotin-labeled −123/−93 GATA probe. C, analysis of binding complexes for the E1-HNF3 site by either radioactive (I) or nonradioactive (II) EMSA, using 32P- and biotin-labeled −103/−83 HNF3 probes, respectively. A 100× molar excess amount of unlabeled probes were used as competitors. The arrow indicates the specific binding complexes for each probe. A nonspecific (ns) band was present in all of the nonradioactive chemiluminescent EMSA assays. Its nonspecificity was demonstrated in HepG2 nuclear extracts run without the addition of any DNA probe in the binding reaction.