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Sequence‐Based Structural Stability Modulate Biological Processing of AFB 1 ‐Fapy‐dG Adduct by NEIL1 DNA glycosylase
Author(s) -
Tomar Rachana,
Minko Irina,
Kellum Andrew,
Voehler Markus,
McCullough Amanda,
Lloyd R.,
Stone Michael
Publication year - 2021
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2021.35.s1.05386
Subject(s) - dna glycosylase , guanine , base excision repair , chemistry , dna , dna damage , base pair , ap site , dna repair , dna adduct , biochemistry , microbiology and biotechnology , biology , nucleotide , gene
Dietary exposure to aflatoxin B 1 (AFB 1 ) is a significant risk factor for developing hepatocellular carcinomas (HCCs). Following ingestion and bioactivation by microsomal P450s, AFB 1 reacts with the N7‐position of guanine, leading to formation of highly genotoxic AFB 1 ‐Fapy‐dG adducts. AFB 1 5′‐interface intercalation stabilizes DNA duplex significantly through strong base‐stacking interactions with neighbor base‐pairs. Also being sterically bulky DNA lesion, it was unexpectedly found to be excised by DNA glycosylase NEIL1, base‐excision repair enzyme, from DNA in both synthetic oligodeoxynucleotides and liver DNA of exposed mice. We hypothesized that the DNA sequence context in which the AFB 1 ‐Fapy‐dG adduct is formed might modulate duplex stability and consequently alter the efficiencies of NEIL1‐initiated repair, ultimately contributing towards AFB 1 associated mutational spectrum. To test this, site‐specific AFB 1 ‐Fapy‐dG adducts were synthesized in three sequence contexts where 5′ neighbor base was varied. We observed differential DNA thermal stability specific to 5′‐neighbor base‐pair using UV absorbance and NMR‐based melting studies. Furthermore, sequence‐dependent stability differences also guided NEIL1‐mediated base removal tendency where single turnover kinetic analyses showed an inverse correlation between the modified duplex stability and the NEIL1‐catalyzed excision rates.