High level transactivation by the ecdysone receptor complex at the core recognition motif

• Published in: Nucleic acids research Vol. 26; no. 10; pp. 2407 - 2414
• Main Authors: Vogtli, M, Elke, C, Imhof, M.O, Lezzi, M
• Format: Journal Article
• Language: English
• Published: England Oxford University Press 15-05-1998
• Subjects: Animals; Base Sequence; Binding Sites; Cell Line; Dimerization; DNA - genetics; DNA - metabolism; DNA-Binding Proteins - metabolism; Drosophila melanogaster; Drosophila melanogaster - genetics; Drosophila Proteins; ecdysteroids; Ecdysterone - analogs & derivatives; Ecdysterone - pharmacology; heat shock proteins; hormone receptors; Ligands; palindromic sequences; Receptors, Steroid - agonists; Receptors, Steroid - metabolism; Recombinant Fusion Proteins; regulatory sequences; repetitive sequences; transcription (genetics); transcription factors; Transcription Factors - metabolism; transcriptional activation; Transcriptional Activation - genetics; Transfection; ultraspiracle protein
• ISSN: 0305-1048; 1362-4962
• DOI: 10.1093/nar/26.10.2407

Ecdysteroid signaling in insects is mediated by the ecdysone receptor complex that is composed of a heterodimer of the ecdysone receptor and Ultraspiracle. The DNA binding specificity plays a critical role of defining the repertoire of target genes that respond to the hormone. We report here the determination of the preferred core recognition motif by a binding site selection procedure. The consensus sequence consists of a perfect palindrome of the heptameric half-site sequence GAGGTCA that is separated by a single A/T base pair. No binding polarity of the ecdysone receptor/Ultraspiracle heterodimer to the core recognition motif was observed. This core motif mediated the highest level of ligand-induced transactivation when compared to a series of synthetic ecdysone response elements and to the natural element of the Drosophila hsp27 gene. This is the first report of a palindromic sequence identified as the highest affinity DNA binding site for a heterodimeric nuclear hormone receptor complex. We further present evidence that the ligand of the ecdysone receptor preferentially drives Ultraspiracle from a homodimer into a heterodimer. This mechanism might contribute additionally to a tight control of target gene expression.