title: Cooperative E-box regulation of human GLI1 by TWIST and USF.
abstract: Sonic hedgehog signaling plays a critical role in vertebrate patterning, and signaling defects are associated with severe birth defects and cancer in man. GLI1 encodes a critical transcription activator in this pathway. GLI1 is expressed in human basal cell carcinomas and sarcomas. Despite the significance of the GLI1 gene in human disease, few immediate upstream regulators of GLI1 expression are known. We previously demonstrated that a 5' region, including 5' flanking sequence, an untranslated exon, and 425 bp of the first intron, regulates the human GLI1 gene. Here we show that inactivating mutations in E-box, GC box, AP-2, GATA, GSG, PuF, and Zeste sites identified three critical regulatory elements, including a GC box that binds Sp1 and two intronic E-boxes that bind USF proteins or Twist. Expression of Twist but not a frame shift mutation of Twist activates the wild-type human GLI1 regulatory sequences but not with inactivating mutations of the E-boxes. Twist activates GLI1 reporter expression through E-box +482 but requires binding of USF proteins to E-box +157. Twist mutations cause human birth defects and Twist is overexpressed in many rhabdomyosarcomas, suggesting that one of Twist's primary roles is the regulation of GLI1.
authors.affiliation: Children's Memorial Institute for Education and Research, Northwestern University Medical School, 2300 Children's Plaza, Chicago, IL 60614, USA.
authors.forename: Elisabeth H
authors.initials: EH
authors.lastname: Villavicencio
authors.forename: Joon Won
authors.initials: JW
authors.lastname: Yoon
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Frank
authors.forename: Ernst-Martin
authors.initials: EM
authors.lastname: Füchtbauer
authors.forename: David O
authors.initials: DO
authors.lastname: Walterhouse
authors.forename: Philip M
authors.initials: PM
authors.lastname: Iannaccone
mesh_terms: D003001:Cloning, Molecular; D004268:DNA-Binding Proteins; D005786:Gene Expression Regulation; D006367:HeLa Cells; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins; D015513:Oncogene Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D015534:Trans-Activators; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D051879:Twist-Related Protein 1; D051720:Upstream Stimulatory Factors; D000071676:Zinc Finger Protein GLI1; D016335:Zinc Fingers
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D015513:Oncogene Proteins; D011994:Recombinant Proteins; C103173:TWIST1 protein, human; D015534:Trans-Activators; D014157:Transcription Factors; D051879:Twist-Related Protein 1; C497181:USF1 protein, human; D051720:Upstream Stimulatory Factors; D000071676:Zinc Finger Protein GLI1