title: Recognition of distinct target sites by a unique Labial/Extradenticle/Homothorax complex.
abstract: Hox genes encode evolutionarily conserved transcriptional regulators, which define regional identities along the anteroposterior axis of multicellular animals. In Drosophila, Hox proteins bind to target DNA sequences in association with the Extradenticle (Exd) and Homothorax (Hth) co-factors. The current model of Hox-binding selectivity proposes that the nucleotide sequence identity defines the Hox protein engaged in the trimeric complex, implying that distinct Hox/Exd/Hth complexes select different binding sites and that a given Hox/Exd/Hth complex recognizes a consensus DNA sequence. Here, we report that the regulation of a newly identified Lab target gene does not rely on the previously established consensus Lab/Exd/Hth-binding site, but on a strongly divergent sequence. Thus Lab, and most probably other Hox proteins, selects different DNA sequences in regulating downstream target genes. These observations have implications with regard to the current model of Hox-binding selectivity.
authors.affiliation: Biozentrum der Universität Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
authors.forename: Andreas
authors.initials: A
authors.lastname: Ebner
authors.forename: Clemens
authors.initials: C
authors.lastname: Cabernard
authors.forename: Markus
authors.initials: M
authors.lastname: Affolter
authors.forename: Samir
authors.initials: S
authors.lastname: Merabet
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D019295:Computational Biology; D016384:Consensus Sequence; D004330:Drosophila / Q000196:embryology* / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004742:Enhancer Elements, Genetic; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D014157:Transcription Factors; C083405:exd protein, Drosophila; C108704:hth protein, Drosophila; C059843:lab protein, Drosophila