title: A Hox Transcription Factor Collective Binds a Highly Conserved Distal-less cis-Regulatory Module to Generate Robust Transcriptional Outcomes.
abstract: cis-regulatory modules (CRMs) generate precise expression patterns by integrating numerous transcription factors (TFs). Surprisingly, CRMs that control essential gene patterns can differ greatly in conservation, suggesting distinct constraints on TF binding sites. Here, we show that a highly conserved Distal-less regulatory element (DCRE) that controls gene expression in leg precursor cells recruits multiple Hox, Extradenticle (Exd) and Homothorax (Hth) complexes to mediate dual outputs: thoracic activation and abdominal repression. Using reporter assays, we found that abdominal repression is particularly robust, as neither individual binding site mutations nor a DNA binding deficient Hth protein abolished cooperative DNA binding and in vivo repression. Moreover, a re-engineered DCRE containing a distinct configuration of Hox, Exd, and Hth sites also mediated abdominal Hox repression. However, the re-engineered DCRE failed to perform additional segment-specific functions such as thoracic activation. These findings are consistent with two emerging concepts in gene regulation: First, the abdominal Hox/Exd/Hth factors utilize protein-protein and protein-DNA interactions to form repression complexes on flexible combinations of sites, consistent with the TF collective model of CRM organization. Second, the conserved DCRE mediates multiple cell-type specific outputs, consistent with recent findings that pleiotropic CRMs are associated with conserved TF binding and added evolutionary constraints.
authors.affiliation: Division of Developmental Biology, Cincinnati Children's Hospital, Cincinnati, Ohio, United States of America.|Graduate Program in Molecular and Developmental Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, Ohio, United States of America.
authors.forename: Juli D
authors.initials: JD
authors.lastname: Uhl
authors.affiliation: Division of Developmental Biology, Cincinnati Children's Hospital, Cincinnati, Ohio, United States of America.|Graduate Program in Molecular and Developmental Biology, Cincinnati Children's Hospital Research Foundation, Cincinnati, Ohio, United States of America.
authors.forename: Arya
authors.initials: A
authors.lastname: Zandvakili
authors.affiliation: Division of Developmental Biology, Cincinnati Children's Hospital, Cincinnati, Ohio, United States of America.
authors.forename: Brian
authors.initials: B
authors.lastname: Gebelein
mesh_terms: D000818:Animals; D051943:Antennapedia Homeodomain Protein / Q000235:genetics; D001665:Binding Sites / Q000235:genetics; D017124:Conserved Sequence / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000196:embryology* / Q000235:genetics; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D050436:Regulatory Elements, Transcriptional / Q000235:genetics*; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D051943:Antennapedia Homeodomain Protein; C497974:Antp protein, Drosophila; D004268:DNA-Binding Proteins; C114754:DmX protein, Drosophila; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D014157:Transcription Factors; C117261:distal-less protein, insect; C083405:exd protein, Drosophila; C108704:hth protein, Drosophila; C074839:slp2 protein, Drosophila