1H NMR chemical exchange techniques reveal local and global effects of oxidized cytosine derivatives
2022-02-11
Romeo Cosimo Arrigo Dubini, Eva Korytiaková, Thea Schinkel, Pia Heinrichs, Thomas Carell, Petra Rovó
ACS Phys. Chem Au, 2, 237−246, 2022
5-carboxycytosine (5caC) is a rare epigenetic modification found in nucleic acids of all domains of life. Despite its sparse genomic abundance, 5caC is presumed to play essential regulatory roles in transcription, maintenance and base-excision processes in DNA. In this work, we utilize nuclear magnetic resonance (NMR) spectroscopy to address the effects of 5caC incorporation into canonical DNA strands at multiple pH and temperature conditions. Our results demonstrate that 5caC has a pH-dependent global destabilizing and a base-pair mobility enhancing local impact on dsDNA, albeit without any detectable influence on the ground-state B-DNA structure. Measurement of hybridization thermodynamics and kinetics of 5caC-bearing DNA duplexes highlighted how acidic environment (pH 5.8 and 4.7) destabilizes the double-stranded structure by ≈10-20 kJ mol-1 at 37 °C when compared to the same sample at neutral pH. Protonation of 5caC results in a lower activation energy for the dissociation process and a higher barrier for annealing. Studies on conformational exchange on the µs time scale regime revealed a sharply localized base-pair motion involving exclusively the modified site and its immediate surroundings. By direct comparison with canonical and 5-formylcytosine (5fC)-edited strands, we were able to address the impact of the two most oxidized naturally occurring cytosine derivatives in the genome. These insights on 5caC's subtle sensitivity to acidic pH contribute to the long standing questions of its capacity as a substrate in base excision repair processes and its purpose as an independent, stable epigenetic mark.
Speaker: Prof. Dr. Thomas Carell
Ludwig-Maximilians-Universität München
Institut für Chemische Epigenetik (ICEM)
Department of Chemistry
Office:
Würmtalstrasse 201
81377 Munich
Germany
Mailing address:
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Phone: +49 (0)89 2180-77750
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Secretary: Birgit Carell
Institute for Chemical Epigenetics Munich (ICEM)
Office:
Würmtalstrasse 201, Haus L - EG / Room: 007
81377 Munich
Germany
Mailing address:
Butenandtstr. 5 - 13
81377 Munich
Germany
Phone: +49 (0)89 2180-77751
Fax: +49 (0)89 2180-77881
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Prof. Dr. Lena Daumann
LMU Munich
Department of Chemistry
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Dr. Sabine Schneider
LMU Munich
Institute for Chemical Epigenetics
Butenandtstr. 5 - 13
House L
81377 Munich, Germany
Phone: +49 89 2180 77716
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Dr. Martin Sumser (Coordinator)
LMU Munich
Institute for Chemical Epigenetics
Butenandtstr. 5 - 13
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81377 Munich, Germany
Phone: +49 89 2180 77765
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