Tobacco-specific nitrosamine-derived O2-alkylthymidines are potent mutagenic lesions in SOS-induced Escherichia coli.
To investigate the biological effects of the O(2)-alkylthymidines induced by the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), we have replicated a plasmid containing O(2)-methylthymidine (O(2)-Me-dT) or O(2)-[4-(3-pyridyl-4-oxobut-1-yl]thymidine (O(2)-POB-dT) in Escherichia coli with specific DNA polymerase knockouts. High genotoxicity of the adducts was manifested in the low yield of transformants from the constructs, which was 2-5% in most strains but increased 2-4-fold with SOS. In the SOS-induced wild type E. coli, O(2)-Me-dT and O(2)-POB-dT induced 21% and 56% mutations, respectively. For O(2)-POB-dT, the major type of mutation was T → G followed by T → A, whereas for O(2)-Me-dT, T → G and T → A occurred in equal frequency. For both lesions, T → C also was detected in low frequency. The T → G mutation was reduced in strains with deficiency in any of the three SOS polymerases. By contrast, T → A was abolished in the pol V(-) strain, while its frequency in other strains remained unaltered. This suggests that pol V was responsible for the T → A mutations. The potent mutagenicity of these lesions may be related to NNK mutagenesis and carcinogenesis.
Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269, USA.
Vijay P
VP
Jasti
Thomas E
TE
Spratt
Ashis K
AK
Basu
D002273:Carcinogens / Q000633:toxicity; D002851:Chromatography, High Pressure Liquid; D015169:Colony Count, Microbial; D018736:DNA Adducts / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage / Q000187:drug effects; D004261:DNA Replication / Q000187:drug effects; D004259:DNA-Directed DNA Polymerase / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D055786:Gene Knockout Techniques; D007527:Isoenzymes / Q000235:genetics* / Q000378:metabolism; D016296:Mutagenesis; D009153:Mutagens / Q000009:adverse effects / Q000633:toxicity; D009602:Nitrosamines / Q000009:adverse effects* / Q000633:toxicity; D010957:Plasmids / Q000235:genetics* / Q000378:metabolism; D011725:Pyridines / Q000737:chemistry / Q000378:metabolism; D013014:SOS Response, Genetics / Q000187:drug effects*; D021241:Spectrometry, Mass, Electrospray Ionization; D013936:Thymidine / Q000031:analogs & derivatives / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana / Q000737:chemistry*
D002273:Carcinogens; D018736:DNA Adducts; D007527:Isoenzymes; D009153:Mutagens; D009602:Nitrosamines; D011725:Pyridines; C016583:4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone; C012439:methylthymidine; D004259:DNA-Directed DNA Polymerase; D013936:Thymidine