MULTIPLE DOWNSTREAM PROMOTER MODULES REGULATE THE TRANSCRIPTION OF THE DROSOPHILA-MELANOGASTER-I, DOC-ELEMENTS AND F-ELEMENTS

The basal promoters of three Drosophila long interspersed nuclear elem ents (LINEs), the I factor and the F and Doc elements, have the same a rchitecture. In each, transcription is directed by an initiator which is faithfully and efficiently recognized only when flanked 3' by a DNA segment similar to 20 bp in length called the B region. The B regions of the three promoters are interchangeable and have a complex structu re, comprising three functionally distinct elements: de1, de2 and de3. While de2 is relatively conserved, fitting the consensus RGACGTGY, de l and de3 vary among the three promoters. At different levels, each do wnstream element is able to ensure accurate recognition of the initiat or. The de2 domain stimulates transcription of the F, I and Doc promot ers to the same extent. In contrast, the I de1 domain stimulates trans cription much more efficiently than the corresponding domains of the F and Doc elements. The finding that de2 is selectively required in ord er to detect full activity of enhancer sequences found in the F elemen t suggests that del and de2 interact with different proteins. The B re gions can be replaced by and synergize with a TATA element, can functi onally substitute for downstream promoter sequences in the Drosophila hsp70 gene, and significantly activate the mouse terminal deoxynucleot idyl transferase initiator. Our data suggest that the B regions stimul ate transcription by providing sites of interaction for the TFIID comp lex. Sequences homologous to the del to de3 array are found downstream from the transcription start site(s) both in TATA-less and TATA-conta ining promoters. (C) 1997 Academic Press Limited.