Flanking base effects on the structural conformation of the (+)-trans-anti-benzo[α]pyrene diolepoxide adduct to N-dg in sequence-defined oligonucleotides

Myungkoo Suh, R. Jankowiak*, F. Ariese, B. Mao, Nicholas E. Geacintov, Gerald J. Small

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


Conformations of the trans adduct of (+)-anti-benzo[a]8- pyrene -7,8-dihydrodiol-9,10-epoxide (BPDE) to N2-guanine, the major stable DNA adduct of the environmental carcinogen benzo[a]pyrene, were studied as a function of flanking bases in single-stranded and in double-stranded oligonucleotides. Three llmer oligonucleotides d(CTATG1G2G3TATC) were synthesized containing the (+)-transanti-BPDE adduct at one specific guanine of the GGG sequence (a known mutational hot spot). Polyacrylamide gel electrophoresis of the three single-stranded oligonucleotides showed that the adduct bound to G2 or G3 (5'-flanking base guanine) caused significantly stronger retardation than the same adduct bound to Gt (5'-flanking base thymine). The strength of the carcinogen-base interaction was reflected in the spectroscopic properties of the pyrenyl moiety. Low temperature fluorescence measurements under line-narrowing (FLN) or non-line-narrowing (NLN) conditions showed that in single-stranded form the adduct at G2 or G3 (5'-flanking base guanine) adopts a conformation with strong interaction with the bases. This was also observed for the same adduct at the sequence AGA. In contrast, the (+)-trans-anti-BPDE adduct with a 5' -flanking thymine exists in a primarily helix-external conformation. Similar differences were observed in the double-stranded oligonucleotides: the adducts at G2 and G3 were found to exist in similar conformational equilibria, again with significant carcinogen-base interactions, while the adduct at G1 showed a predominantly external conformation. The nature of the 3'-flanking base appeared to have little influence on the conformational equilibrium of the (+)-trans-anti-BTDE-guanine adduct The results could provide insight into the mutational specificity and flanking base effects observed for (+)-anti-BPDE.

Original languageEnglish
Pages (from-to)2891-2898
Number of pages8
Issue number12
Publication statusPublished - Dec 1994


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