Stimulation of in vitro transcription by the upstream element of the adenovirus-2 major late promoter involves a specific factor.

We have previously reported that sequences located upstream from the TATA box of the Adenovirus-2 major late promoter (Ad2MLP), between -34 and -97, are necessary for efficient transcription in vivo and in vitro (1). We have utilized an in vitro competition assay to demonstrate that the upstream element requirement involves the binding of a specific factor(s), which results in stimulation of in vitro transcription from the Ad2MLP. DNA fragments prepared from Ad2MLP upstream sequence mutants which are transcribed much less efficiently than the wild-type promoter both in vivo and in vitro were shown to be unable to bind this factor. We have also constructed chimeric promoter recombinants containing the 21bp repeat upstream element of the SV40 early promoter inserted upstream from the Ad2MLP TATA box. The SV40 upstream element stimulates in vitro transcription from the heterologous Ad2MLP TATA box element; competition experiments show that the Ad2MLP upstream element-specific factor is different from the SV40-specific factor Sp1.