title: Dynamics of bridge helix bending in RNA polymerase II.
abstract: One of critical issues for RNA polymerase is how the enzyme translocates along the DNA substrate during transcription elongation cycle. Comparisons of the structure of RNA polymerase II (Pol II) with that of bacterial enzyme have suggested that the transition of the bridge helix (BH) from straight to flipped-out conformations facilitates the translocation of upstream DNA-RNA hybrid. However, the flipped-out conformation of BH in Pol II has not been observed up to now and the detailed mechanism of how the BH facilitating upstream hybrid translocation still remains obscure. Here we use all-atom molecular dynamics simulations to study the transition dynamics of BH in Pol II. Two different flipped-out conformations (termed as F1 and F2) are derived from our simulation trajectories, both of which could contribute to upstream hybrid translocation. In particular, the structure of BH in F2 conformation shows nearly identical to that observed in free bacterial enzyme, showing the existence of the flipped-out conformation in Pol II. Analysis of hydrogen bonds and salt bridge formed intra BH in different conformations indicates that the flipped-out conformations are more unstable than the straight conformation. Moreover, a detailed understanding of how the transition of BH conformations facilitating upstream hybrid translocation is given. Proteins 2017; 85:614-629. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Key Laboratory of Soft Matter Physics and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
authors.forename: Zhan-Feng
authors.initials: ZF
authors.lastname: Wang
authors.affiliation: Key Laboratory of Soft Matter Physics and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
authors.forename: Yi-Ben
authors.initials: YB
authors.lastname: Fu
authors.affiliation: Key Laboratory of Soft Matter Physics and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
authors.forename: Peng-Ye
authors.initials: PY
authors.lastname: Wang
authors.affiliation: Key Laboratory of Soft Matter Physics and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China.
authors.forename: Ping
authors.identifier: 0000-0001-6722-2298
authors.initials: P
authors.lastname: Xie
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D004247:DNA / Q000737:chemistry* / Q000378:metabolism; D006860:Hydrogen Bonding; D056004:Molecular Dynamics Simulation; D011485:Protein Binding; D000072756:Protein Conformation, alpha-Helical; D054730:Protein Interaction Domains and Motifs; D012313:RNA / Q000737:chemistry* / Q000378:metabolism; D012319:RNA Polymerase II / Q000737:chemistry* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000737:chemistry* / Q000201:enzymology / Q000235:genetics; D016963:Thermus thermophilus / Q000737:chemistry* / Q000201:enzymology / Q000235:genetics; D014158:Transcription, Genetic
chemical_list: D012313:RNA; D004247:DNA; D012319:RNA Polymerase II
keywords: RNA polymerase; bridge-helix conformation; transcription elongation; translocation