title: HMG I/Y regulates long-range enhancer-dependent transcription on DNA and chromatin by changes in DNA topology.
abstract: The nature of nuclear structures that are required to confer transcriptional regulation by distal enhancers is unknown. We show that long-range enhancer-dependent beta-globin transcription is achieved in vitro upon addition of the DNA architectural protein HMG I/Y to affinity-enriched holo RNA polymerase II complexes. In this system, HMG I/Y represses promoter activity in the absence of an associated enhancer and strongly activates transcription in the presence of a distal enhancer. Importantly, nucleosome formation is neither necessary for long-range enhancer regulation in vitro nor sufficient without the addition of HMG I/Y. Thus, the modulation of DNA structure by HMG I/Y is a critical regulator of long-range enhancer function on both DNA and chromatin-assembled genes. Electron microscopic analysis reveals that HMG I/Y binds cooperatively to preferred DNA sites to generate distinct looped structures in the presence or absence of the beta-globin enhancer. The formation of DNA topologies that enable distal enhancers to strongly regulate gene expression is an intrinsic property of HMG I/Y and naked DNA.
authors.affiliation: Regulatory Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
authors.forename: R
authors.initials: R
authors.lastname: Bagga
authors.forename: S
authors.initials: S
authors.lastname: Michalowski
authors.forename: R
authors.initials: R
authors.lastname: Sabnis
authors.forename: J D
authors.initials: JD
authors.lastname: Griffith
authors.forename: B M
authors.initials: BM
authors.lastname: Emerson
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D002843:Chromatin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D003850:Deoxyribonuclease I / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000235:genetics*; D005786:Gene Expression Regulation; D005914:Globins / Q000235:genetics; D025741:HMGA1a Protein; D006367:HeLa Cells; D006609:High Mobility Group Proteins / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D020035:Holoenzymes / Q000378:metabolism; D006801:Humans; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D012319:RNA Polymerase II / Q000378:metabolism; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D014158:Transcription, Genetic / Q000235:genetics*
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D020035:Holoenzymes; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D025741:HMGA1a Protein; D005914:Globins; D004247:DNA; D012319:RNA Polymerase II; D003850:Deoxyribonuclease I