The function of a TATA element in RNA polymerase (EC 2.7.7.6) III transcription 
of a naturally TATA-containing U6 snRNA gene and a naturally TATA-less tRNA gene 
was probed by transcription and Ty3 transposition analyses. Deletion of the TATA 
box from a U6 minigene did not abolish transcription and Ty3 integration but 
changed the positions of initiation and insertion. Insertion of the U6 TATA box 
at three positions upstream of the TATA-less SUP2 tRNA(Tyr) gene resulted in 
novel transcription initiation and Ty3 integration patterns that depended upon 
position of the insertion. Nevertheless, the predominant tRNA gene initiation 
sites were not affected by insertion of the TATA sequence and remained at a 
fixed distance from the internal box A promoter element. Insertions of the TATA 
box upstream of a SUP2 box A mutant affected the level of transcription and 
restricted the use of upstream start sites, but they neither enhanced the use of 
TATA-dependent initiation sites nor restored expression to the level of the 
wild-type gene. We conclude that (i) the U6 TATA box is essential in vivo for 
correct initiation but not for transcription, (ii) a TATA box does not 
compensate for a weak box A sequence and so cannot perform equivalently, and 
(iii) the TATA-binding protein, and probably components of transcription factor 
IIIB, are present on the target at the time of Ty3 integration.