Structural Insights into the Nonmutagenicity of 2-Haloacetophenone
A wide variety of endogenous and exogenous alkylating agents covalently modify DNA to produce N7-alkyl-2′-deoxyguanosine (N7-alkylG) adducts as major DNA lesions. The mutagenic potentials of many N7-alkylG adducts with an intercalatable moiety remain poorly understood. We have discovered that the an...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2025-03-01
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| Series: | Molecules |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1420-3049/30/6/1264 |
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| Summary: | A wide variety of endogenous and exogenous alkylating agents covalently modify DNA to produce N7-alkyl-2′-deoxyguanosine (N7-alkylG) adducts as major DNA lesions. The mutagenic potentials of many N7-alkylG adducts with an intercalatable moiety remain poorly understood. We have discovered that the antiriot agent 2-chloroacetophenone readily reacts with dG to produce N7-acetophenone-dG adducts, implicating the genotoxic properties of 2-chloroacetophenone. 2-Chloroacetophenone, however, has been found to be nonmutagenic in both bacterial and mammalian cells. To gain insights into the nonmutagenic nature of N7-acetophenone-dG, we prepared N7-acetophenone-dG-containing oligonucleotide via 2′-fluorine-mediated transition-state destabilization and conducted kinetic and structural studies of human DNA polymerase eta (polη) incorporating nucleotide opposite 2′-F-N7-acetophenone-dG. The kinetic experiments reveal that the presence of the lesion at the templating position greatly hinders nucleotide incorporation. A crystal structure of polη bound to a nonhydrolyzable dCTP analog opposite 2′-F-N7-acetophenone-dG shows that the templating N7-acetophenone-dG is in a <i>syn</i> conformation, precluding binding of an incoming nucleotide in the catalytic site. These unusual conformations explain the observed inefficient incorporation of nucleotide opposite the lesion. Our studies suggest that certain bulky N7-alkylG lesions adopt a <i>syn</i> conformer and present an intercalatable moiety into the nascent base-pairing site, deterring nucleotide incorporation and thus lowering mutagenicity. |
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| ISSN: | 1420-3049 |