2–Aminofluorene modified DNA duplex exists in two interchangeable conformations

Eckel, Linda M.; Krugh, Thomas R.

doi:10.1038/nsb0294-89

Cited by 65 publications

(89 citation statements)

References 34 publications

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“…1 2 homoduplex. All these observations are in Eckel and Krugh, 1994;MilhC et al, 1994). External N-2-acetylaminofluorene exhibits signals between 7.5 ppm and 8.5 ppm (MilhC et al, 1994).…”

Section: Banementioning

confidence: 76%

NMR Data Show that the Carcinogen N‐2‐Acetylaminofluorene Stabilises an Intermediate of −2 Frameshift Mutagenesis in a Region of High Mutation Frequency

Milhe

Fuchs

Lefèvre

1996

European Journal of Biochemistry

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The heteroduplex, d(ACCGGCGCCACA) . d(TGTGG-CCGGT), containing two bulged bases, a cytosine and the guanine G7, either unmodified or modified with the carcinogen N-2-acetylaminofluorene, have been studied by NMR as models of slipped-mutagenic intermediates (SMI). The melting temperature of the modified heteroduplex is strongly increased compared with that of the unmodified heteroduplex. NMR studies have shown that all the bases of the unmodified heteroduplex are stacked within the helix, without any disruption of the sequential connectivities. The two strands are in a B-like conformation. Nevertheless, exchangeable-proton studies have revealed that base pairing is very weak, or even lacking, over two base pairs apart from the bulge. Concerning the modified heteroduplex, no B-like connectivity is observed in the G5-C9 segment. Moreover, the cytosine C8 is rejected outside the helix, whereas the N-2-acetylaminofluorene moiety is inserted within the helix. The G5 . C18, C6 . G17 and C9 . GI6 bases are remarkably stable when the temperature is increased, in agreement with the high melting temperature. Some small unassigned peaks reveal the presence of the minor conformation in equilibrium. The strong stabilisation of the N-2-acetylaminofluorene-modified heteroduplex compared with the unmodified duplex is in agreement with the high N-2-acetylaminofluorene-induced mutation frequency compared with the spontaneous frequency and with the hypothesis of mutagenesis occurring during replication.

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“…1 2 homoduplex. All these observations are in Eckel and Krugh, 1994;MilhC et al, 1994). External N-2-acetylaminofluorene exhibits signals between 7.5 ppm and 8.5 ppm (MilhC et al, 1994).…”

Section: Banementioning

confidence: 76%

NMR Data Show that the Carcinogen N‐2‐Acetylaminofluorene Stabilises an Intermediate of −2 Frameshift Mutagenesis in a Region of High Mutation Frequency

Milhe

Fuchs

Lefèvre

1996

European Journal of Biochemistry

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“…Eckel and Krugh (15) considered both anti and syn conformations at the [AF]dG adduct site in the AF-intercalated conformer and concluded that the anti conformation with displacement of the modified guanine into the minor groove best fits their data. A key conclusion of this study was that the glycosidic torsion angles were anti for both the AF-external and AFintercalated conformers that were in slow exchange for [AF]-dG positioned opposite dC at the DNA oligomer duplex level (14,15).…”

mentioning

confidence: 97%

Solution Structure of the Aminofluorene [AF]-Intercalated Conformer of the syn-[AF]-C⁸-dG Adduct Opposite dC in a DNA Duplex

et al. 1998

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We report below on a conformational equilibrium between AF-intercalated and AF-external states in slow exchange for the [AF]dG lesion positioned opposite dC in the d(C-[AF]G-C).d(G-C-G) sequence context. The slow exchange between states is attributed to interconversion between syn glycosidic torsion angle in the AF-intercalated and anti torsion angle in AF-external conformers of the [AF]dG opposite dC containing duplex. The present paper describes an NMR-molecular mechanics study that defines the solution structure of the AF-intercalated conformer for the case of [AF]dG adduct positioned opposite dC in the d(C-[AF]G-C).d(G-C-G) sequence context. The structure is of the base displacement-intercalation type where the aminofluorene ring is intercalated into the helix between intact Watson-Crick dG.dC base pairs, which results in a displacement of the modified guanine ring into the major groove where it stacks with the major groove edge of its 5'-flanking cytosine in the adduct duplex. The conformational equilibrium between AF-intercalated conformer (approximately 70%) with a syn alignment and AF-external conformer (approximately 30%) with an anti alignment for the [AF]dG adduct positioned opposite dC in the d(C-[AF]G-C).d(G-C-G) sequence context can be contrasted with our earlier demonstration that the population is 100% for the AP-intercalated conformer with a synalignment at the N-(deoxyguanosin-8-yl)-2-aminopyrene ([AP]dG) adduct site positioned opposite dC in the same sequence context [Mao, B., Vyas, R. R., Hingerty, B. E., Broyde, S., Basu, A. K., and Patel, D. J. (1996) Biochemistry, 35, 12659-12670]. This shift in population may reflect the much larger size of the pyrenyl ring of the [AP]dG adduct compared to the fluorenyl ring of the [AF]dG adduct which in turn might provide for a greater overlap of the aromatic amine with the flanking base pairs in the intercalated conformer of the former adduct in DNA.

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“…While the nonacetylated lesions exist both in syn and anti conformation (14,15), the corresponding acetylated lesions seem to adopt the syn-conformation with high preference (10,16,17). Crystal structures of Ellenberger, Beese, and Patel, showing the nonacetylated AF-dG-lesion inside different polymerases, prove that the lesion is indeed bound in anti conformation, allowing Watson-Crick base pairing with an incoming dCTP (18)(19)(20).…”

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confidence: 99%

Mechanism of replication blocking and bypass of Y-family polymerase η by bulky acetylaminofluorene DNA adducts

Schorr

Schneider²,

Lammens³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Heterocyclic aromatic amines produce bulky C8 guanine lesions in vivo, which interfere and disrupt DNA and RNA synthesis. These lesions are consequently strong replication blocks. In addition bulky adducts give rise to point and frameshift mutations. The translesion synthesis (TLS) DNA polymerase η is able to bypass slowly C8 bulky adduct lesions such as the widely studied 2-aminofluorene-dG and its acetylated analogue mainly in an error-free manner. Replicative polymerases are in contrast fully blocked by the acetylated lesion. Here, we show that TLS efficiency of Pol η depends critically on the size of the bulky adduct forming the lesion. Based on the crystal structure, we show why the bypass reaction is so difficult and we provide a model for the bypass reaction. In our model, TLS is accomplished without rotation of the lesion into the anti conformation as previously thought.DNA damage | DNA polymerase | translesion DNA synthesis | aromatic amines A romatic amines are known to be strong carcinogens. After metabolic activation, aromatic amines react as electrophilic arylnitrenium ions with nucleophilic functionalities of the DNA duplex. Preferred reaction sides are the amino groups of adenine and guanine and particularly the C8-position of guanine (1, 2). The latter reaction gives rise to the so called C8-bulky adduct lesions, which interfere with the replication process leading to mutations (2). Two types of aromatic amine lesions are known. The nonacetylated lesions depicted in Fig. 1A reduce the replication efficiency but are in general faithfully bypassed by highfidelity polymerases (3). In contrast, the acetylated derivatives ( Fig. 1B) block replicative polymerases (3, 4), but can be bypassed with special low-fidelity polymerases (5-9). Moreover, if these acetylated lesions are present in certain repetitive sequences, they are known to induce frameshift mutations (4,(10)(11)(12). Recently, in vivo experiments revealed that the low-fidelity Y-family polymerase η is able to replicate DNA containing acetylated aromatic amine lesions such as the acetylated analogue of 2-aminofluorene-dG (AF-dG), 2-acetylaminofluorene-dG (AAF-dG) (13). Replication through the lesion is even for Pol η very difficult and hence slow, but if it occurs it is typically error free.The distinct mutagenic properties of the acetylated and nonacetylated aromatic amine lesions are caused by their different conformational preferences. While the nonacetylated lesions exist both in syn and anti conformation (14, 15), the corresponding acetylated lesions seem to adopt the syn-conformation with high preference (10,16,17). Crystal structures of Ellenberger, Beese, and Patel, showing the nonacetylated AF-dG-lesion inside different polymerases, prove that the lesion is indeed bound in anti conformation, allowing Watson-Crick base pairing with an incoming dCTP (18)(19)(20). While bypass of the nonacetylated lesions by high-fidelity polymerases is rather well understood, the mechanism that allows low-fidelity polymerases such as Pol η to replicate...

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2–Aminofluorene modified DNA duplex exists in two interchangeable conformations

Cited by 65 publications

References 34 publications

NMR Data Show that the Carcinogen N‐2‐Acetylaminofluorene Stabilises an Intermediate of −2 Frameshift Mutagenesis in a Region of High Mutation Frequency

NMR Data Show that the Carcinogen N‐2‐Acetylaminofluorene Stabilises an Intermediate of −2 Frameshift Mutagenesis in a Region of High Mutation Frequency

Solution Structure of the Aminofluorene [AF]-Intercalated Conformer of the syn-[AF]-C⁸-dG Adduct Opposite dC in a DNA Duplex

Mechanism of replication blocking and bypass of Y-family polymerase η by bulky acetylaminofluorene DNA adducts

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2–Aminofluorene modified DNA duplex exists in two interchangeable conformations

Cited by 65 publications

References 34 publications

NMR Data Show that the Carcinogen N‐2‐Acetylaminofluorene Stabilises an Intermediate of −2 Frameshift Mutagenesis in a Region of High Mutation Frequency

NMR Data Show that the Carcinogen N‐2‐Acetylaminofluorene Stabilises an Intermediate of −2 Frameshift Mutagenesis in a Region of High Mutation Frequency

Solution Structure of the Aminofluorene [AF]-Intercalated Conformer of the syn-[AF]-C8-dG Adduct Opposite dC in a DNA Duplex

Mechanism of replication blocking and bypass of Y-family polymerase η by bulky acetylaminofluorene DNA adducts

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Solution Structure of the Aminofluorene [AF]-Intercalated Conformer of the syn-[AF]-C⁸-dG Adduct Opposite dC in a DNA Duplex