title: Transcription within condensed chromatin: Steric hindrance facilitates elongation.
abstract: During eukaryotic transcription, RNA-polymerase activity generates torsional stress in DNA, having a negative impact on the elongation process. Using our previous studies of chromatin fiber structure and conformational transitions, we suggest that this torsional stress can be alleviated, thanks to a tradeoff between the fiber twist and nucleosome conformational transitions into an activated state named "reversome". Our model enlightens the origin of polymerase pauses, and leads to the counterintuitive conclusion that chromatin-organized compaction might facilitate polymerase progression. Indeed, in a compact and well-structured chromatin loop, steric hindrance between nucleosomes enforces sequential transitions, thus ensuring that the polymerase always meets a permissive nucleosomal state.
authors.affiliation: Institut des Hautes Etudes Scientifiques, Bures-sur-Yvette, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Bécavin
authors.forename: Maria
authors.initials: M
authors.lastname: Barbi
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Victor
authors.forename: Annick
authors.initials: A
authors.lastname: Lesne
mesh_terms: D055592:Biophysical Phenomena; D002843:Chromatin / Q000235:genetics*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D007700:Kinetics; D008954:Models, Biological; D009690:Nucleic Acid Conformation; D009707:Nucleosomes / Q000737:chemistry / Q000378:metabolism; D013816:Thermodynamics; D013997:Time Factors; D014158:Transcription, Genetic
chemical_list: D002843:Chromatin; D009707:Nucleosomes; D012321:DNA-Directed RNA Polymerases