Structural and energetic characterization of the major DNA adduct formed from the food mutagen ochratoxin A in the NarI hotspot sequence: influence of adduct ionization on the conformational preferences and implications for the NER propensity
Date
2014
Authors
Sharma, Purshotam
Manderville, Richard A.
Wetmore, Stacey D.
Journal Title
Journal ISSN
Volume Title
Publisher
Oxford University Press
Abstract
The nephrotoxic food mutagen ochratoxin A (OTA)
produces DNA adducts in rat kidneys, the major lesion
being the C8-linked-2 -deoxyguanosine adduct
(OTB-dG). Although research on other adducts
stresses the importance of understanding the structure
of the associated adducted DNA, site-specific
incorporation of OTB-dG into DNA has yet to be attempted.
The present work uses a robust computational
approach to determine the conformational
preferences of OTB-dG in three ionization states at
three guanine positions in the NarI recognition sequence
opposite cytosine. Representative adducted
DNA helices were derived from over 2160 ns of simulation
and ranked via free energies. For the first
time, a close energetic separation between three distinct
conformations is highlighted, which indicates
OTA-adducted DNA likely adopts a mixture of conformations
regardless of the sequence context. Nevertheless,
the preferred conformation depends on
the flanking bases and ionization state due to deviations
in discrete local interactions at the lesion
site. The structural characteristics of the lesion thus
discerned have profound implications regarding its
repair propensity andmutagenic outcomes, and support
recent experiments suggesting the induction of
double-strand breaks and deletion mutations upon
OTA exposure. This combined structural and energetic
characterization of the OTB-dG lesion in DNA
will encourage future biochemical experiments on
this potentially genotoxic lesion.
Description
Sherpa Romeo green journal, open access
Keywords
DNA adduct , NarI , Ionization , OTB-dG
Citation
Purshotam, S., Manderville, R. A., & Wetmore, S. D. (2014). Structural and energetic characterization of the major DNA adduct formed from the food mutagen ochratoxin A in the NarI hotspot sequence: influence of adduct ionization on the conformational preferences and implications for the NER propensity. Nucleic Acids Research, 42(18), 11831-11845. doi: 10.1093/nar/gku821