Transcription stimulation of the adenovirus type-12 E1a gene in vitro by a novel factor bound to a region adjacent to a TATA box.

The E1a gene of adenovirus (Ad) type-12 possesses two transcription start points (tsp) separated by 139 nucleotides (nt). We previously found that transcription from a tsp distal to the coding region is preferentially stimulated in a cell-free reaction by nuclear factor I (NF-I) bound to a region near the left end of the virus genome. We report here on the identification of a cis-acting DNA region and a trans-acting factor for transcription initiated at the proximal tsp of the Ad12 E1a gene. A deletion in the region between nt -50 and -36 relative to the proximal tsp at +1 caused a significant decrease in the proximal transcription in a cell-free reaction using nuclear extracts of HeLa cells. A cellular factor binding to this region was shown to be responsible for transcription stimulation. This E1A-stimulating factor (ESF-1) appeared to recognize the sequence 5'-TGTCA-3' located immediately upstream from a TATA box. Unlike NF-I, the ESF-1 activity did not seem to be influenced by the E1A protein. Our results indicated that ESF-1 stimulates the proximal transcription of the Ad12 E1a gene by binding to the region adjacent to a TATA box.