title: Non-consensus GLI binding sites in Hedgehog target gene regulation.
abstract: BACKGROUND
  The GLI transcription factors, mediators of the hedgehog signal bind with high affinity to the consensus sequence GACCACCCA. The affinity of variant single substitutions in GLI binding sites has been measured systematically, but the affinities of the variant binding sites appears low compared to the frequency of occurrence of variant sites in known GLI target gene promoters.
  
  
  RESULTS
  We quantified transcriptional activation by GLI using PTCH1 promoter based luciferase reporters containing all single substitutions of the GLI consensus binding site. As expected variants with very low affinity did not activate the reporter. Many lower affinity binding sequences are, however, functional in the presence of moderate GLI concentration. Using two natural non-consensus GLI site promoters we showed that substitution of the variant sequences by consensus leads to comparable activity.
  
  
  CONCLUSIONS
  Variant GLI binding sites with relatively low affinity can within natural promoters lead to strong transcriptional activation. This may facilitate the identification of additional direct GLI target genes.
authors.affiliation: Department of Molecular Biology, University of Salzburg, Hellbrunnerstrasse 34, 5020 Salzburg, Austria.
authors.forename: Martina
authors.initials: M
authors.lastname: Winklmayr
authors.forename: Carmen
authors.initials: C
authors.lastname: Schmid
authors.forename: Sandra
authors.initials: S
authors.lastname: Laner-Plamberger
authors.forename: Alexandra
authors.initials: A
authors.lastname: Kaser
authors.forename: Fritz
authors.initials: F
authors.lastname: Aberger
authors.forename: Thomas
authors.initials: T
authors.lastname: Eichberger
authors.forename: Anna-Maria
authors.initials: AM
authors.lastname: Frischauf
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D016384:Consensus Sequence; D053823:Hedgehog Proteins / Q000378:metabolism*; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D000072079:Patched Receptors; D000072081:Patched-1 Receptor; D011401:Promoter Regions, Genetic; D011956:Receptors, Cell Surface / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D000071676:Zinc Finger Protein GLI1
chemical_list: C400551:GLI1 protein, human; D053823:Hedgehog Proteins; C000606236:PTCH1 protein, human; D000072079:Patched Receptors; D000072081:Patched-1 Receptor; D011956:Receptors, Cell Surface; D014157:Transcription Factors; D000071676:Zinc Finger Protein GLI1; D008156:Luciferases