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i-Motif formation and spontaneous deletions in human cells

Martella, Marianna; Pichiorri, Flavia; Chikhale, Rupesh V; Abdelhamid, Mahmoud AS; Waller, Zoë AE; Smith, Steven S; (2022) i-Motif formation and spontaneous deletions in human cells. Nucleic Acids Research , Article gkac158. 10.1093/nar/gkac158. (In press). Green open access

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Abstract

Concatemers of d(TCCC) that were first detected through their association with deletions at the RACK7 locus, are widespread throughout the human genome. Circular dichroism spectra show that d(GGGA)n sequences form G-quadruplexes when n > 3, while i-motif structures form at d(TCCC)n sequences at neutral pH when n ≥ 7 in vitro. In the PC3 cell line, deletions are observed only when the d(TCCC)n variant is long enough to form significant levels of unresolved i-motif structure at neutral pH. The presence of an unresolved i-motif at a representative d(TCCC)n element at RACK7 was suggested by experiments showing that that the region containing the d(TCCC)9 element was susceptible to bisulfite attack in native DNA and that d(TCCC)9 oligo formed an i-motif structure at neutral pH. This in turn suggested that that the i-motif present at this site in native DNA must be susceptible to bisulfite mediated deamination even though it is a closed structure. Bisulfite deamination of the i-motif structure in the model oligodeoxynucleotide was confirmed using mass spectrometry analysis. We conclude that while G-quadruplex formation may contribute to spontaneous mutation at these sites, deletions actually require the potential for i-motif to form and remain unresolved at neutral pH.

Type: Article
Title: i-Motif formation and spontaneous deletions in human cells
Location: England
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/nar/gkac158
Publisher version: https://doi.org/10.1093/nar/gkac158
Language: English
Additional information: © The Author(s) 2022. Published by Oxford University Press on behalf of Nucleic Acids Research. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
UCL classification: UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > UCL School of Pharmacy > Pharma and Bio Chemistry
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Life Sciences > UCL School of Pharmacy
URI: https://discovery.ucl.ac.uk/id/eprint/10144972
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