title: DNA regions bound at low occupancy by transcription factors do not drive patterned reporter gene expression in Drosophila.
abstract: In animals, each sequence-specific transcription factor typically binds to thousands of genomic regions in vivo. Our previous studies of 20 transcription factors show that most genomic regions bound at high levels in Drosophila blastoderm embryos are known or probable functional targets, but genomic regions occupied only at low levels have characteristics suggesting that most are not involved in the cis-regulation of transcription. Here we use transgenic reporter gene assays to directly test the transcriptional activity of 104 genomic regions bound at different levels by the 20 transcription factors. Fifteen genomic regions were selected based solely on the DNA occupancy level of the transcription factor Kruppel. Five of the six most highly bound regions drive blastoderm patterns of reporter transcription. In contrast, only one of the nine lowly bound regions drives transcription at this stage and four of them are not detectably active at any stage of embryogenesis. A larger set of 89 genomic regions chosen using criteria designed to identify functional cis-regulatory regions supports the same trend: genomic regions occupied at high levels by transcription factors in vivo drive patterned gene expression, whereas those occupied only at lower levels mostly do not. These results support studies that indicate that the high cellular concentrations of sequence-specific transcription factors drive extensive, low-occupancy, nonfunctional interactions within the accessible portions of the genome.
authors.affiliation: Department of Genome Dynamics, Division of Life Sciences, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
authors.forename: William W
authors.initials: WW
authors.lastname: Fisher
authors.forename: Jingyi Jessica
authors.initials: JJ
authors.lastname: Li
authors.forename: Ann S
authors.initials: AS
authors.lastname: Hammonds
authors.forename: James B
authors.initials: JB
authors.lastname: Brown
authors.forename: Barret D
authors.initials: BD
authors.lastname: Pfeiffer
authors.forename: Richard
authors.initials: R
authors.lastname: Weiszmann
authors.forename: Stewart
authors.initials: S
authors.lastname: MacArthur
authors.forename: Sean
authors.initials: S
authors.lastname: Thomas
authors.forename: John A
authors.initials: JA
authors.lastname: Stamatoyannopoulos
authors.forename: Michael B
authors.initials: MB
authors.lastname: Eisen
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Bickel
authors.forename: Mark D
authors.initials: MD
authors.lastname: Biggin
authors.forename: Susan E
authors.initials: SE
authors.lastname: Celniker
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D004247:DNA / Q000378:metabolism*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics*; D004625:Embryo, Nonmammalian / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter / Q000235:genetics*; D049750:Genome, Insect / Q000235:genetics; D051741:Kruppel-Like Transcription Factors / Q000378:metabolism; D008297:Male; D011485:Protein Binding / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D029721:Drosophila Proteins; D051741:Kruppel-Like Transcription Factors; D014157:Transcription Factors; D004247:DNA