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Title: Streamlining effects of extra telomeric repeat on telomeric DNA folding revealed by fluorescence-force spectroscopy
Abstract A human telomere ends in a single-stranded 3′ tail, composed of repeats of T2AG3. G-quadruplexes (GQs) formed from four consecutive repeats have been shown to possess high-structural and mechanical diversity. In principle, a GQ can form from any four repeats that are not necessarily consecutive. To understand the dynamics of GQs with positional multiplicity, we studied five and six repeats human telomeric sequence using a combination of single molecule FRET and optical tweezers. Our results suggest preferential formation of GQs at the 3′ end both in K+ and Na+ solutions, with minor populations of 5′-GQ or long-loop GQs. A vectorial folding assay which mimics the directional nature of telomere extension showed that the 3′ preference holds even when folding is allowed to begin from the 5′ side. In 100 mM K+, the unassociated T2AG3 segment has a streamlining effect in that one or two mechanically distinct species was observed at a single position instead of six or more observed without an unassociated repeat. We did not observe such streamlining effect in 100 mM Na+. Location of GQ and reduction in conformational diversity in the presence of extra repeats have implications in telomerase inhibition, T-loop formation and telomere end protection.  more » « less
Award ID(s):
1430124
PAR ID:
10171409
Author(s) / Creator(s):
;
Date Published:
Journal Name:
Nucleic Acids Research
Volume:
47
Issue:
21
ISSN:
0305-1048
Page Range / eLocation ID:
11044 to 11056
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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