title: G-quadruplex and G-rich sequence stimulate Pif1p-catalyzed downstream duplex DNA unwinding through reducing waiting time at ss/dsDNA junction.
abstract: Alternative DNA structures that deviate from B-form double-stranded DNA such as G-quadruplex (G4) DNA can be formed by G-rich sequences that are widely distributed throughout the human genome. We have previously shown that Pif1p not only unfolds G4, but also unwinds the downstream duplex DNA in a G4-stimulated manner. In the present study, we further characterized the G4-stimulated duplex DNA unwinding phenomenon by means of single-molecule fluorescence resonance energy transfer. It was found that Pif1p did not unwind the partial duplex DNA immediately after unfolding the upstream G4 structure, but rather, it would dwell at the ss/dsDNA junction with a 'waiting time'. Further studies revealed that the waiting time was in fact related to a protein dimerization process that was sensitive to ssDNA sequence and would become rapid if the sequence is G-rich. Furthermore, we identified that the G-rich sequence, as the G4 structure, equally stimulates duplex DNA unwinding. The present work sheds new light on the molecular mechanism by which G4-unwinding helicase Pif1p resolves physiological G4/duplex DNA structures in cells.
authors.affiliation: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.affiliation: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Wen-Qiang
authors.initials: WQ
authors.lastname: Wu
authors.affiliation: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Na-Nv
authors.initials: NN
authors.lastname: Liu
authors.affiliation: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China.
authors.forename: Xiao-Lei
authors.initials: XL
authors.lastname: Duan
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics and CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Ming
authors.initials: M
authors.lastname: Li
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics and CAS Key Laboratory of Soft Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Shuo-Xing
authors.initials: SX
authors.lastname: Dou
authors.affiliation: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China houximiao@nwsuaf.edu.cn.
authors.forename: Xi-Miao
authors.initials: XM
authors.lastname: Hou
authors.affiliation: College of Life Sciences, Northwest A&F University, Yangling, Shaanxi 712100, China Laboratoire de Biologie et Pharmacologie Appliquée, Ecole Normale Supérieure de Cachan, Centre National de la Recherche Scientifique, 61 Avenue du Président Wilson, 94235 Cachan, France xxi01@ens-cachan.fr.
authors.forename: Xu-Guang
authors.initials: XG
authors.lastname: Xi
mesh_terms: D001483:Base Sequence; D055162:Biocatalysis; D004247:DNA / Q000378:metabolism*; D004265:DNA Helicases / Q000378:metabolism*; D004261:DNA Replication; D004277:DNA, Single-Stranded / Q000378:metabolism*; D054856:G-Quadruplexes; D009691:Nucleic Acid Denaturation; D055503:Protein Multimerization; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D013379:Substrate Specificity; D013997:Time Factors
chemical_list: D004277:DNA, Single-Stranded; D029701:Saccharomyces cerevisiae Proteins; D004247:DNA; C085463:PIF1 protein, S cerevisiae; D004265:DNA Helicases