Previous Article | Next Article ![]()
Mol. Cell. Biol., Jun 1996, 2977-2986, Vol 16, No. 6
C Antoniewski, B Mugat, F Delbac and JA Lepesant
The steroid hormone 20-hydroxyecdysone plays a key role in the induction
and modulation of morphogenetic events throughout Drosophila development.
Previous studies have shown that a heterodimeric nuclear receptor composed
of the EcR and USP proteins mediates the action of the hormone at the
transcriptional through binding to palindromic ecdysteroid mediates the
action of the hormone at the transcriptional level through binding to
palindromic ecdysteroid response elements (EcREs) such as those present in
the promoter of the hsp27 gene or the fat body-specific enhancer of the
Fbp1 gene. We show that in addition to palindromic EcREs, the EcR/USP
heterodimer can bind in vitro with various affinities to direct repetitions
of the motif AGGTCA separated by 1 to 5 nucleotides (DR1 to DR5), which are
known to be target sites for vertebrate nuclear receptors. At variance with
the receptors, EcR/USP was also found to bind to a DR0 direct repeat with
no intervening nucleotide. In cell transformation assays, direct repeats
DR0 to DR5 alone can render the minimum viral tk or Drosophila Fbp1
promoter responsive to 20-hydroxyecdysone, as does the palindromic hsp27
EcRE. In a transgenic assay, however, neither the palindromic hsp27 element
nor direct repeat DR3 alone can make the Fbp1 minimal promoter responsive
to premetamorphic ecdysteroid peaks. In contrast, DR0 and DR3 elements,
when substituted for the natural palindromic EcRE in the context of the
Fbp1 enhancer, can drive a strong fat body- specific ecdysteroid response
in transgenic animals. These results demonstrate that directly repeated
EcR/USP binding sites are as effective as palindromic EcREs in vivo. They
also provide evidence that additional flanking regulatory sequences are
crucially required to potentiate the hormonal response mediated by both
types of elements and specify its spatial and temporal pattern.
Copyright © 1996, American Society for Microbiology
Direct repeats bind the EcR/USP receptor and mediate ecdysteroid responses in Drosophila melanogaster
Institut Jacques Monod, CNRS et Universite Paris, France.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»