Different binding site requirements for binding and activation for the bipartite enhancer factor EF-1A

The human transcription factor EF-1A binds to the purine-rich E1A core enhancer sequence in the adenovirus E1A and E4 and polyomavirus enhancer regions. The consensus binding site for EF-1A resembles that of members of the ets domain protein family. EF-1A activation of transcription requires a dimeric binding site. Analysis of binding sites containing point mutations revealed that EF-1A binding is determined by the core nucleotides of the binding site, while transcriptional activation is determined both by the core and some peripheral nucleotides that do not affect binding. We have purified EF-1A and analyzed its two constituent subunits, EF-1A α and EF-1A β. EF-1A α (MW ∼60 kD) makes the primary DNA contacts. EF-1A β (MW ∼50 kD) forms heteromultimeric complex with EF-1A α both in solution and on a dimeric binding site. Binding of both EF-1A subunits is necessary, but not sufficient, for transcriptional activation. We present immunochemical and functional evidence that EF-1A α is related to the murine ets-related protein GABP α and that EF-1A β is related to the murine protein GABP β.