A TATA element is required for tRNA promoter activity and confers TATA-binding protein responsiveness in Drosophila Schneider-2 cells

In contrast to yeast and mammalian systems, which depend principally on int ernal promoter elements for tRNA gene transcription, insect systems require additional upstream sequences. To understand the function of the upstream sequences, we have asked whether the Bombyx mori tRNA(C)(Ala) and tRNA(SG)( Ala) genes, which are absolutely dependent on these sequences in vitro, als o require them for transcription in vivo, We introduced wild-type and mutan t versions of the Bombyx tRNA(Ala) genes into Drosophila Schneider-2 cells and found that the tRNA(C)(Ala) gene is efficiently transcribed and that it s transcription depends strongly on the distal segment of its upstream prom oter. In contrast, the tRNA(SG)(Ala) gene is inefficiently transcribed, and this inefficiency results from lack of a specific sequence within the dist al tRNA(C)(Ala) upstream promoter. This sequence, 5'-TTTATAT-3', is suffici ent to increase the activity of the tRNA(SG)(Ala) promoter to that of the t RNA(C)(Ala) promoter. Moreover, promoters containing the 5'-TTTATAT-3' elem ent are stimulated by increased levels of cellular TATA-binding protein. To gether these results indicate that, in insect cells, a TATA-like element is specifically required to form functional TATA-binding protein-containing c omplexes that promote efficient transcription of tRNA genes.