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Absorption of Low-Energy UV Radiation by Human Telomere G-Quadruplexes Generates Long-Lived Guanine Radical Cations (1 views)

Banyasz A, Martinez-fernandez L, Balty C, Perron M, Douki T, Improta R, Markovitsi D

J Am Chem Soc (ISSN: 1520-5126electronic, 0002-7863linking), 2017 Aug 2; 139(30): 10561-10568.

Telomeres, which are involved in cell division, carcinogenesis, and aging and constitute important therapeutic targets, are prone to oxidative damage. This propensity has been correlated with the presence of guanine-rich sequences, capable of forming four-stranded DNA structures (G-quadruplexes). Here, we present the first study on oxidative damage of human telomere G-quadruplexes without mediation of external molecules. Our investigation has been performed for G-quadruplexes formed by folding of GGG(TTAGGG)3 single strands in buffered solutions containing Na(+) cations (TEL21/Na(+)). Associating nanosecond time-resolved spectroscopy and quantum mechanical calculations (TD-DFT), it focuses on the primary species, ejected electrons and guanine radicals, generated upon absorption of UV radiation directly by TEL21/Na(+). We show that, at 266 nm, corresponding to an energy significantly lower than the guanine ionization potential, the one-photon ionization quantum yield is 4.5 x 10(-3). This value is comparable to that of cyclobutane thymine dimers (the major UV-induced lesions) in genomic DNA; the quantum yield of these dimers in TEL21/Na(+) is found to be (1.1 +/- 0.1) x 10(-3). The fate of guanine radicals, generated in equivalent concentration with that of ejected electrons, is followed over 5 orders of magnitude of time. Such a quantitative approach reveals that an important part of radical cation population survives up to a few milliseconds, whereas radical cations produced by chemical oxidants in various DNA systems are known to deprotonate, at most, within a few microseconds. Under the same experimental conditions, neither one-photon ionization nor long-lived radical cations are detected for the telomere repeat TTAGGG in single-stranded configuration, showing that secondary structure plays a key role in these processes. Finally, two types of deprotonated radicals are identified: on the one hand, (G-H2)(*) radicals, stable at early times, and on the other hand, (G-H1)(*) radicals, appearing within a few milliseconds and decaying with a time constant of approximately 50 ms.

Affiliations ▼
*** IBB - CNR Affiliation

LIDYL, CEA, CNRS, Universite Paris-Saclay , F-91191 Gif-sur-Yvette, France., Istituto Biostrutture e Bioimmagini, Consiglio Nazionale delle Ricerche , Via Mezzocannone 16, I-80134 Napoli, Italy., CEA, INAC-SyMMES Laboratoire des Lesions des Acides Nucleiques, F-38000 Grenoble, France.,

Details ▼
Impact factor: 9.023, 5-year impact factor: 8.981

Paper type: Journal Article

Keywords: Not available.

Url: Not available.

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* Multi-pathway excited state relaxation of adenine oligomers in aqueous solution: A joint theoretical and experimental study (49 views)
Banyasz A, Gustavsson T, Onidas D, Changenet-Barret P, Markovitsi D, Improta R
Chemistry (ISSN: 0947-6539, 1521-3765, 1521-3765electronic), 2013 Mar; 19(11): 3762-3774.

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* Electronic excited states responsible for dimer formation upon UV absorption directly by thymine strands: Joint experimental and theoretical study (58 views)
Banyasz A, Douki T, Improta R, Gustavsson T, Onidas D, Vaya I, Perron M, Markovitsi D
J Am Chem Soc (ISSN: 0002-7863, 0002-2786, 1520-5126), 2012 Sep 12; 134(36): 14834-14845.

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* Influence of base stacking on excited-state behavior of polyadenine in water, based on time-dependent density functional calculations (37 views)
Santoro F, Barone V, Improta R
Proc Natl Acad Sci U S A (ISSN: 0027-8424, 1091-6490, 0027-8424print), 2007; 104(24): 9931-9936.

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3 Records (3 excluding Abstracts and Conferences).
Total impact factor: 25.971 (25.971 excluding Abstracts and Conferences).
Total 5-year impact factor: 26.214 (26.214 excluding Abstracts and Conferences).

Your bibliography query: (([btitle, keywords, abstract] ABSORPTION AND [btitle, keywords, abstract] ENERGY AND [btitle, keywords, abstract] RADIATION)) AND NOT [id] = 53640

Last modified by Gennaro Angrisano on Thursday 04 January 2018, 15:15:43
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