Nucleic Acids Research Advance Access originally published online on May 8, 2007
Nucleic Acids Research 2007 35(11):3646-3653; doi:10.1093/nar/gkm203
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Nucleic Acids Research, 2007, Vol. 35, No. 11 3646-3653
© 2007 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Structural Biology |
G-quadruplex formation in human telomeric (TTAGGG)4 sequence with complementary strand in close vicinity under molecularly crowded condition
1Laboratory of Biochemistry and Biophysics, College of Life Sciences, 2College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, P. R. China and 3State Key Laboratory of Biomembrane and Membrane Biotechnology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100080, P. R. China
*To whom correspondence should be addressed. Tel: +86 27 6875 4351; Fax: +86 27 6875 6661; Email: tanclswu{at}public.wh.hb.cn, z.tan{at}ioz.ac.cn The authors wish it to be known that, in their opinion, the first three authors should be regarded as joint First Authors
Received November 4, 2006. Revised March 21, 2007. Accepted March 23, 2007.
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.
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