High level transactivation by the ecdysone receptor complex at the core recognition motif.
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.
Vögtli
M
M
Institute for Cell Biology, ETH-Hönggerberg, CH-8093 Zürich, Switzerland. voegtli@cell.biol.ethz.ch
Elke
C
C
Imhof
M O
MO
Lezzi
M
M
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D004247:DNA / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D019281:Dimerization; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000235:genetics*; D004441:Ecdysterone / Q000031:analogs & derivatives / Q000494:pharmacology; D008024:Ligands; D011987:Receptors, Steroid / Q000819:agonists / Q000378:metabolism*; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors / Q000378:metabolism; D015533:Transcriptional Activation / Q000235:genetics*; D014162:Transfection
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D008024:Ligands; D011987:Receptors, Steroid; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C066030:USP protein, Drosophila; C055469:ecdysone receptor; C055348:muristerone A; D004441:Ecdysterone; D004247:DNA