Transcription within condensed chromatin: Steric hindrance facilitates elongation.
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.
Bécavin
Christophe
C
Institut des Hautes Etudes Scientifiques, Bures-sur-Yvette, France.
Barbi
Maria
M
Victor
Jean-Marc
JM
Lesne
Annick
A
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
D002843:Chromatin; D009707:Nucleosomes; D012321:DNA-Directed RNA Polymerases