Crystallographic studies on damaged DNAs IV. N( 4)-methoxycytosine shows a second face for Watson-Crick base-pairing, leading to purine transition mutagenesis.

ABSTRACT: To investigate the mutation mechanism of purine transitions in DNA damaged with methoxyamine, a DNA dodecamer with the sequence d(CGCAAATTmo(4)CGCG), where mo(4)C is 2'-deoxy-N(4)-methoxycytidine, has been synthesized and the crystal structure determined by X-ray analysis. The duplex structure is similar to that of the original undamaged B-form dodecamer, indicating that the methoxylation does not affect the overall DNA conformation. Electron density maps clearly show that the two mo(4)C residues form Watson-Crick-type base pairs with the adenine residues of the opposite strand and that the methoxy groups of mo(4)C adopt the anti conformation to N(3) around the C(4)-N(4) bond. For the pair formation through hydrogen bonds the mo(4)C residues are in the imino tautomeric state. Together with

SUBMITTER: Hossain MT 

PROVIDER: S-EPMC60249 | biostudies-literature | 2001 Oct

REPOSITORIES: biostudies-literature