Purification and functional characterization of a cellular transcription factor that binds to an enhancer element within the adenovirus early EIla promoter (affinity chromatography/band-shift/gene regulation/HeLa cells/in vitro transcription)

The adenovirus EIa-inducible early EIIa (EIIaE) promoter is comprised of several sequence elements essential for constitutive and Induced expression. We report here the purification of the host-cell factor that interacts with the major upstream element of this promoter, extending between positions -90 and -70 with respect to the main EIIaE cap site and exhibiting enhancer properties. The puri- fied factor, which corresponds to a 40- to 43-kDa polypeptide, specifically binds to its recognition site and stimulates EIIaE promoter activity when added to an in vitro transcription system, reconstituted from purified factors and RNA polymer- ase. The implication of this factor in the control of the other adenovirus early genes is discussed. Efficient transcription of the adenovirus early transcription units requires the presence of the viral pre-early EIa gene products (1, 2). The mechanism of this transactivation of the early transcription unit is still poorly understood. Extensive deletion and linker scanning mutational analysis (3-5) of the EIa-inducible EIIa early (EIIaE) promoter has indicated that EIa responsiveness involves the same promoter sequences as those required for uninduced expression, suggesting that the same host-cell transcription factors are required in each case. DNA binding studies have identified several of these factors, among which those recognizing sequence elements located between -90 and - 70 (EIIAE-EF (6), EIIaE-B (7,