The initiation accuracy of the SV40 early transcription is determined by the functional domains of two TATA elements.

To locate the boundaries of the TATA element in the SV40 early promoter, point mutations have been constructed such as to cover the whole T + A-rich region of the replication origin. The effects of these mutations on the rate of transcription in vivo show that this region actually contains two TATA elements I and II, each independently directing the accurate initiation of transcription from a specified set of start sites, EES1 and EES2, respectively. The sequence of TATA element I fits best with the compiled 'consensus' sequence found in eukaryotic gene promoters and is the most efficient in directing transcription initiation. Mutations which improve this fit can still increase the rate of transcription, confirming the theory of a correlation between the nucleotide sequence of a TATA element and its functional efficiency. Moreover, some mutations which simultaneously modify the angle of DNA curvature in the T + A-rich promoter region and the rate of transcription reveal a correlation between DNA bending and transcription initiation.