title: Modulated contact frequencies at gene-rich loci support a statistical helix model for mammalian chromatin organization.
abstract: BACKGROUND
  Despite its critical role for mammalian gene regulation, the basic structural landscape of chromatin in living cells remains largely unknown within chromosomal territories below the megabase scale.
  
  
  RESULTS
  Here, using the 3C-qPCR method, we investigate contact frequencies at high resolution within interphase chromatin at several mouse loci. We find that, at several gene-rich loci, contact frequencies undergo a periodical modulation (every 90 to 100 kb) that affects chromatin dynamics over large genomic distances (a few hundred kilobases). Interestingly, this modulation appears to be conserved in human cells, and bioinformatic analyses of locus-specific, long-range cis-interactions suggest that it may underlie the dynamics of a significant number of gene-rich domains in mammals, thus contributing to genome evolution. Finally, using an original model derived from polymer physics, we show that this modulation can be understood as a fundamental helix shape that chromatin tends to adopt in gene-rich domains when no significant locus-specific interaction takes place.
  
  
  CONCLUSIONS
  Altogether, our work unveils a fundamental aspect of chromatin dynamics in mammals and contributes to a better understanding of genome organization within chromosomal territories.
authors.affiliation: Institut de Génétique Moléculaire de Montpellier (IGMM), UMR5535 CNRS, Universités Montpellier 1 et Montpellier 2, 1919, Route de Mende, 34293 Montpellier Cedex 5, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Court
authors.forename: Julie
authors.initials: J
authors.lastname: Miro
authors.forename: Caroline
authors.initials: C
authors.lastname: Braem
authors.forename: Marie-Noëlle
authors.initials: MN
authors.lastname: Lelay-Taha
authors.forename: Audrey
authors.initials: A
authors.lastname: Brisebarre
authors.forename: Florian
authors.initials: F
authors.lastname: Atger
authors.forename: Thierry
authors.initials: T
authors.lastname: Gostan
authors.forename: Michaël
authors.initials: M
authors.lastname: Weber
authors.forename: Guy
authors.initials: G
authors.lastname: Cathala
authors.forename: Thierry
authors.initials: T
authors.lastname: Forné
mesh_terms: D000818:Animals; D002843:Chromatin / Q000737:chemistry / Q000235:genetics*; D002874:Chromosome Mapping / Q000379:methods*; D002875:Chromosomes; D019295:Computational Biology / Q000379:methods*; D019143:Evolution, Molecular; D056426:Genetic Loci; D016678:Genome; D023281:Genomics / Q000379:methods*; D006801:Humans; D008322:Mammals; D051379:Mice; D015233:Models, Statistical; D009690:Nucleic Acid Conformation; D060888:Real-Time Polymerase Chain Reaction
chemical_list: D002843:Chromatin