The DNA damage-sensing NER repair factor XPC-RAD23B does not recognize bulky DNA lesions with a missing nucleotide opposite the lesion.
DNA Repair (Amst)
; 96: 102985, 2020 12.
Article
in En
| MEDLINE
| ID: mdl-33035795
ABSTRACT
The Nucleotide Excision Repair (NER) mechanism removes a wide spectrum of structurally different lesions that critically depend on the binding of the DNA damage sensing NER factor XPC-RAD23B (XPC) to the lesions. The bulky mutagenic benzo[a]pyrene diol epoxide metabolite-derived cis- and trans-B[a]P-dG lesions (G*) adopt base-displaced intercalative (cis) or minor groove (trans) conformations in fully paired DNA duplexes with the canonical C opposite G* (G*C duplexes). While XPC has a high affinity for binding to these DNA lesions in fully complementary double-stranded DNA, we show here that deleting only the C in the complementary strand opposite the lesion G* embedded in 50-mer duplexes, fully abrogates XPC binding. Accurate values of XPC dissociation constants (KD) were determined by employing an excess of unmodified DNA as a competitor; this approach eliminated the binding and accumulation of multiple XPC molecules to the same DNA duplexes, a phenomenon that prevented the accurate estimation of XPC binding affinities in previous studies. Surprisingly, a detailed comparison of XPC dissociation constants KD of unmodified and lesion-containing G*Del complexes, showed that the KD values were -2.5-3.6 times greater in the case of G*Del than in the unmodified GDel and fully base-paired GC duplexes. The origins of this unexpected XPC lesion avoidance effect is attributed to the intercalation of the bulky, planar B[a]P aromatic ring system between adjacent DNA bases that thermodynamically stabilize the G*Del duplexes. The strong lesion-base stacking interactions associated with the absence of the partner base, prevent the DNA structural distortions needed for the binding of the BHD2 and BHD3 ß-hairpins of XPC to the deletion duplexes, thus accounting for the loss of XPC binding and the known NER-resistance of G*Del duplexes.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide
/
DNA Adducts
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Saccharomyces cerevisiae Proteins
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DNA-Binding Proteins
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DNA Repair
Limits:
Humans
Language:
En
Journal:
DNA Repair (Amst)
Journal subject:
BIOLOGIA MOLECULAR
/
BIOQUIMICA
Year:
2020
Document type:
Article
Affiliation country:
Estados Unidos