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1y9h
From Proteopedia
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| Ligands: | , , , , , | ||||||
| Resources: | FirstGlance, OCA, PDBsum, RCSB | ||||||
| Coordinates: | save as pdb, mmCIF, xml | ||||||
Methylation of cytosine at C5 in a CpG sequence context causes a conformational switch of a benzo[a]pyrene diol epoxide-N2-guanine adduct in DNA from a minor groove alignment to intercalation with base displacement
Overview
It is well known that CpG dinucleotide steps in DNA, which are highly methylated at the 5-position of cytosine (meC) in human tissues, exhibit a disproportionate number of mutations within certain codons of the p53 gene. There is ample published evidence indicating that the reactivity of guanine with anti-B[a]PDE (a metabolite of the environmental carcinogen benzo[a]pyrene) at CpG mutation hot spots is enhanced by the methylation of the cytosine residue flanking the target guanine residue on the 5'-side. In this work we demonstrate that such a methylation can also dramatically affect the conformational characteristics of an adduct derived from the reaction of one of the two enantiomers of anti-B[a]PDE with the exocyclic amino group of guanine ([BP]G adduct). A detailed NMR study indicates that the 10R (-)-trans-anti-[BP]G adduct undergoes a transition from a minor groove-binding alignment of the aromatic BP ring system in the unmethylated C-[BP]G sequence context, to an intercalative BP alignment with a concomitant displacement of the modified guanine residue into the minor groove in the methylated meC-[BP]G sequence context. By contrast, a minor groove-binding alignment was observed for the stereoisomeric 10S (+)-trans-anti-[BP]G adduct in both the C-[BP]G and meC-[BP]G sequence contexts. This remarkable conformational switch resulting from the presence of a single methyl group at the 5-position of the cytosine residue flanking the lesion on the 5'-side, is attributed to the hydrophobic effect of the methyl group that can stabilize intercalated adduct conformations in an adduct stereochemistry-dependent manner. Such conformational differences in methylated and unmethylated CpG sequences may be significant because of potential alterations in the cellular processing of the [BP]G adducts by DNA transcription, replication, and repair enzymes.
About this Structure
1Y9H is a Protein complex structure of sequences from [1]. Full crystallographic information is available from OCA.
Reference
Methylation of cytosine at C5 in a CpG sequence context causes a conformational switch of a benzo[a]pyrene diol epoxide-N2-guanine adduct in DNA from a minor groove alignment to intercalation with base displacement., Zhang N, Lin C, Huang X, Kolbanovskiy A, Hingerty BE, Amin S, Broyde S, Geacintov NE, Patel DJ, J Mol Biol. 2005 Mar 4;346(4):951-65. Epub 2004 Dec 31. PMID:15701509[[Category: benzo[a]pyrene]]
Page seeded by OCA on Mon Mar 31 01:00:29 2008
