title: Initiator elements function to determine the activity state of BX-C enhancers.
abstract: A >300 kb cis-regulatory region is required for the proper expression of the three bithorax complex (BX-C) homeotic genes. Based on genetic and transgenic analysis, a model has been proposed in which the numerous BX-C cis-regulatory elements are spatially restricted through the activation or repression of parasegment-specific chromatin domains. Particular early embryonic enhancers, called initiators, have been proposed to control this complex process. Here, in order to better understand the process of domain activation, we have undertaken a systematic in situ dissection of the iab-6 cis-regulatory domain using a new method, called InSIRT. Using this method, we create and genetically characterize mutations affecting iab-6 function, including mutations specifically modifying the iab-6 initiator. Through our mutagenesis of the iab-6 initiator, we provide strong evidence that initiators function not to directly control homeotic gene expression but rather as domain control centers to determine the activity state of the enhancers and silencers within a cis-regulatory domain.
authors.affiliation: National Centre of Competence in Research (NCCR) Frontiers in Genetics and Department of Zoology and Animal Biology, University of Geneva, Geneva, Switzerland.
authors.forename: Carole
authors.initials: C
authors.lastname: Iampietro
authors.forename: Maheshwar
authors.initials: M
authors.lastname: Gummalla
authors.forename: Annick
authors.initials: A
authors.lastname: Mutero
authors.forename: François
authors.initials: F
authors.lastname: Karch
authors.forename: Robert K
authors.initials: RK
authors.lastname: Maeda
mesh_terms: D000818:Animals; D004330:Drosophila / Q000196:embryology* / Q000235:genetics* / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D018507:Gene Expression Regulation, Developmental; D016296:Mutagenesis; D050436:Regulatory Elements, Transcriptional
chemical_list: D029721:Drosophila Proteins