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A Photoredox Reaction for the Selective Modification of 5-Carboxycytosine in DNA.

Published version

Published version
Peer-reviewed

Repository DOI


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Authors

Mortishire-Smith, Benjamin J  ORCID logo  https://orcid.org/0000-0002-0733-1676
Balasubramanian, Shankar  ORCID logo  https://orcid.org/0000-0002-0281-5815

Abstract

Covalent epigenetic modifications contribute to the regulation of important cellular processes during development and differentiation, and changes in their genomic distribution and frequency are linked to the emergence of genetic disease states. Chemical and enzymatic methods that selectively target the orthogonal chemical functionality of epigenetic markers are central to the study of their distribution and function, and considerable research effort has been focused on the development of nondestructive sequencing approaches which preserve valuable DNA samples. Photoredox catalysis enables transformations with tunable chemoselectivity under mild, biocompatible reaction conditions. We report the reductive decarboxylation of 5-carboxycytosine via a novel iridium-based treatment, which represents the first application of visible-light photochemistry to epigenetic sequencing via direct base conversion. We propose that the reaction involves an oxidative quenching cycle beginning with single-electron reduction of the nucleobase by the photocatalyst, followed by hydrogen atom transfer from a thiol. The saturation of the C5-C6 backbone permits decarboxylation of the nonaromatic intermediate, and hydrolysis of the N4-amine constitutes a conversion from a cytosine derivative to a T-like base. This conversion demonstrates selectivity for 5-carboxycytosine over other canonical or modified nucleoside monomers, and is thereby applied to the sequencing of 5-carboxycytosine within modified oligonucleotides. The photochemistry explored in this study can also be used in conjunction with enzymatic oxidation by TET to profile 5-methylcytosine at single-base resolution. Compared to other base-conversion treatments, the rapid photochemical reaction takes place within minutes, which could provide advantages for high-throughput detection and diagnostic applications.

Description

Keywords

Cytosine, Oxidation-Reduction, 5-Methylcytosine, DNA

Journal Title

J Am Chem Soc

Conference Name

Journal ISSN

0002-7863
1520-5126

Volume Title

145

Publisher

American Chemical Society (ACS)
Sponsorship
Wellcome Trust (209441/Z/17/Z)
European Commission Horizon 2020 (H2020) Marie Sk?odowska-Curie actions (887491)
Cancer Research UK (19836)
Cancer Research UK (C9681/A29214)
Herchel Smith Fund Marie Curie Individual Fellowship as part of the Horizon 2020 grant program (ID: 887491)