FACTORS INVOLVED IN SPECIFIC TRANSCRIPTION BY MAMMALIAN RNA POLYMERASE-II - ROLE OF FACTOR-IID AND FACTOR-MLTF IN TRANSCRIPTION FROM THE ADENOVIRUS MAJOR LATE AND IVA2 PROMOTERS

Abstract

The role of the adenovirus major late upstream transcription from the adenovirus major late and the IV a2 promoters was studied. The transcription initiation site of the IVa2 promoter is located 210 nucleotides upstream from the CAP site of the major promoter. Transcription from these two promoters occurs on different DNA strands. Thus, this divergent transcription suggests that the same factor could simultaneously regulate the expression of two different genes. This was investigated utilizing a reconstituted transcription system in vitro. The addition of MLTF to reaction mixtures containing the purified general transcription factors and the major late promoter resulted in a 10-12 fold stimulation of transcription. This stimulation was because of an increase of the stability of the preinitiation complex. MLTF allowed DNA template molecules to undergo multiple rounds of transcription. MLTF also stimulated transcription from the adenovirus-encoded IVa2 promoter. Surprisingly, recontitution experiments indicated that transcription from the IVa2 promoter which does not have a TATA sequence required all the previously described general transcription factors, including TFIID, the TATA binding protein. The requirement for TFIID was demonstrated by reconstitution experiments as well as by olygonucleotide competition experiments. The implications of this observation are discussed.