title: Polycomb group proteins bind an engrailed PRE in both the "ON" and "OFF" transcriptional states of engrailed.
abstract: Polycomb group (PcG) and trithorax Group (trxG) proteins maintain the "OFF" and "ON" transcriptional states of HOX genes and other targets by modulation of chromatin structure. In Drosophila, PcG proteins are bound to DNA fragments called Polycomb group response elements (PREs). The prevalent model holds that PcG proteins bind PREs only in cells where the target gene is "OFF". Another model posits that transcription through PREs disrupts associated PcG complexes, contributing to the establishment of the "ON" transcriptional state. We tested these two models at the PcG target gene engrailed. engrailed exists in a gene complex with invected, which together have 4 well-characterized PREs. Our data show that these PREs are not transcribed in embryos or larvae. We also examined whether PcG proteins are bound to an engrailed PRE in cells where engrailed is transcribed. By FLAG-tagging PcG proteins and expressing them specifically where engrailed is "ON" or "OFF", we determined that components of three major PcG protein complexes are present at an engrailed PRE in both the "ON" and "OFF" transcriptional states in larval tissues. These results show that PcG binding per se does not determine the transcriptional state of engrailed.
authors.affiliation: Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Kristofor K
authors.initials: KK
authors.lastname: Langlais
authors.forename: J Lesley
authors.initials: JL
authors.lastname: Brown
authors.forename: Judith A
authors.initials: JA
authors.lastname: Kassis
mesh_terms: D000818:Animals; D029721:Drosophila Proteins / Q000235:genetics; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D017403:In Situ Hybridization; D063146:Polycomb-Group Proteins / Q000378:metabolism*; D059007:Polytene Chromosomes / Q000235:genetics; D011485:Protein Binding / Q000235:genetics; D022661:RNA, Untranslated / Q000378:metabolism; D020218:Response Elements / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D029721:Drosophila Proteins; C063459:En protein, Drosophila; D018398:Homeodomain Proteins; D063146:Polycomb-Group Proteins; D022661:RNA, Untranslated; D014157:Transcription Factors; C087983:inv protein, Drosophila