In vitro accurate initiation of transcription on the adenovirus type 2 IVa2 gene which does not contain a TATA box.

In vitro initiation of transcription has been studied on the IVa2 gene of the adenovirus type 2 ( Ad2 ) which is expressed at intermediate time after infection. This gene does not contain a TATA box around 30 bp upstream from the cap site. By analyses of the in vitro runoff products by size and by single strand nuclease protection mapping, it was concluded that the in vitro initiation occurred accurately at two in vivo cap sites with low but detectable efficiency. By using cloned IVa2 DNA, which is free from the major late promoter, it was suggested that the low efficiency of the in vitro initiation on the IVa2 gene may not be due to close location of the two genes but may rather reflect the efficiency of the promoter itself. The cell-free extracts from both uninfected and infected HeLa cells supported the accurate initiation of transcription in vitro with almost the same efficiency. In addition, the cell free extract directed an artificial initiation of transcription in vitro by recognizing a TATA box located 140 bp upstream from the cap sites.