title: G-quadruplex formation in human telomeric (TTAGGG)4 sequence with complementary strand in close vicinity under molecularly crowded condition.
abstract: Chromosomes in vertebrates are protected at both ends by telomere DNA composed of tandem (TTAGGG)n repeats. DNA replication produces a blunt-ended leading strand telomere and a lagging strand telomere carrying a single-stranded G-rich overhang at its end. The G-rich strand can form G-quadruplex structure in the presence of K+ or Na+. At present, it is not clear whether quadruplex can form in the double-stranded telomere region where the two complementary strands are constrained in close vicinity and quadruplex formation, if possible, has to compete with the formation of the conventional Watson-Crick duplex. In this work, we studied quadruplex formation in oligonucleotides and double-stranded DNA containing both the G- and C-rich sequences to better mimic the in vivo situation. Under such competitive condition only duplex was observed in dilute solution containing physiological concentration of K+. However, quadruplex could preferentially form and dominate over duplex structure under molecular crowding condition created by PEG as a result of significant quadruplex stabilization and duplex destabilization. This observation suggests quadruplex may potentially form or be induced at the blunt end of a telomere, which may present a possible alternative form of structures at telomere ends.
authors.affiliation: Laboratory of Biochemistry and Biophysics, College of Life Sciences, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China.
authors.forename: Zhong-yuan
authors.initials: ZY
authors.lastname: Kan
authors.forename: Yi
authors.initials: Y
authors.lastname: Lin
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.forename: Xin-ying
authors.initials: XY
authors.lastname: Zhuang
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhao
authors.forename: Dai-wen
authors.initials: DW
authors.lastname: Pang
authors.forename: Yu-hua
authors.initials: YH
authors.lastname: Hao
authors.forename: Zheng
authors.initials: Z
authors.lastname: Tan
mesh_terms: D001483:Base Sequence; D003553:Cystine / Q000737:chemistry; D004247:DNA / Q000737:chemistry* / Q000648:ultrastructure; D054856:G-Quadruplexes; D006147:Guanine / Q000737:chemistry; D006801:Humans; D018625:Microscopy, Atomic Force; D011092:Polyethylene Glycols / Q000737:chemistry; D020080:Tandem Repeat Sequences; D016615:Telomere / Q000737:chemistry*
chemical_list: D011092:Polyethylene Glycols; D003553:Cystine; D006147:Guanine; D004247:DNA