The aromatic nitroketone 3-nitrobenzanthrone (3-NBA) was found to be present in many environmental samples, including diesel exhaust and bound to the surface of airborne particulate matters.  3-NBA is one of the most potent mutagens and carcinogens, which led to its description as the 'devil in the diesel' by popular press.  In vivo short-term studies have shown that nitroreduction followed by DNA adduction, which gives rise to C8 and N2 adducts with dG, is likely to play a major role in its mutagenicity and carcinogenicity.We have constructed a plasmid vector containing a single dG-C8-ABA and studied translesion synthesis (TLS) across it.  In human embryonic kidney 293T cells, dG-C8-ABA is mutagenic, inducing primarily G?T (11%), but G?A (2%) and G?C (<0.5%) also occurred. siRNA knock-down of the TLS polymerases revealed that both the extent and fidelity of bypass are dependent on these polymerases. Mutation frequency (MF) was 40% reduced when pol ? was knocked down, whereas 60% reduction in MF was observed with REV1 knock-down.  In contrast, MF was increased more than 60% in pol ? knock-down cells.  Additionally, 73% reduction in MF was noted when both pol ? and pol ? were knocked down.  But in pol?/pol?-, pol?/pol?-, or pol?/REV1-deficient cells, there was little additional effect of the second polymerase knock-down.  On the basis of these results, we conclude that pol ? and pol ? together play critical roles in mutagenic TLS of dG-C8-ABA and that REV1 is also important.  Since pol ? has been reported to be an extender, it seems likely that it extends correct dG-C8-ABA base pair with C more efficiently than the wrong base pair.     [This research was supported by the National Institute of Environmental Health Sciences grant ES009127]

Mutagenicity of C8-guanine adduct formed by 3-nitrobenzanthrone in human cells

248th National Meeting (2014)

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