Structural highlights
Publication Abstract from PubMedDiastereomeric 8,5'-cyclopurine 2'-deoxynucleosides, containing a covalent bond between the deoxyribose and the purine base, are induced in DNA by ionizing radiation. They are suspected to play a role in the etiology of neurodegeneration in xeroderma pigmentosum patients. If not repaired, the S-8,5'-cyclo-2'-deoxyguanosine lesion (S-cdG) induces Pol V-dependent mutations at a frequency of 34% in Escherichia coli. Most are S-cdG --> A transitions, suggesting mis-incorporation of dTTP opposite the lesion during replication bypass, although low levels of S-cdG --> T transversions, arising from mis-incorporation of dATP, are also observed. We report the structures of 5'-d(GTGCXTGTTTGT)-3'.5'-d(ACAAACAYGCAC)-3', where X denotes S-cdG and Y denotes either dA or dT, corresponding to the situation following mis-insertion of either dTTP or dATP opposite the S-cdG lesion. The S-cdG.dT mismatch pair adopts a wobble base pairing. This provides a plausible rationale for the S-cdG --> A transitions. The S-cdG.dA mismatch pair differs in conformation from the dG.dA mismatch pair. For the S-cdG.dA mismatch pair, both S-cdG and dA intercalate, but no hydrogen bonding is observed between S-cdG and dA. This is consistent with the lower levels of S-cdG --> T transitions in E. coli. Structures of (5'S)-8,5'-Cyclo-2'-deoxyguanosine Mismatched with dA or dT.,Huang H, Das RS, Basu AK, Stone MP Chem Res Toxicol. 2012 Feb 20;25(2):478-90. Epub 2012 Feb 6. PMID:22309170[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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