Abstract
In the Drosophila I, F and Doc LINEs, basal transcription is ensured by the functional interaction of initiator sequences with intragenic regulatory segments (B regions) which comprise distinct functional modules. Removing the B regions, as changing their composition or location, allowed different activators to stimulate transcription from novel initiators both in Doc and F promoters. The use of distinct initiators plausibly reflects the assembly of transcriptional complexes in which TFIID assumes alternative spatial conformations. The response of I, F and Doc promoters to the same enhancer is significantly influenced by the number, position and type of core elements present.
