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  • Title: The effect of the 2-amino group of 7,8-dihydro-8-oxo-2'-deoxyguanosine on translesion synthesis and duplex stability.
    Author: Oka N, Greenberg MM.
    Journal: Nucleic Acids Res; 2005; 33(5):1637-43. PubMed ID: 15778433.
    Abstract:
    Replication of DNA containing 7,8-dihydro-8-oxo-2'-deoxyguanosine (OxodG) gives rise to G --> T transversions. The syn-isomer of the lesion directs misincorporation of 2'-deoxyadenosine (dA) opposite it. We investigated the role of the 2-amino substituent on duplex thermal stability and in replication using 7,8-dihydro-8-oxo-2'-deoxyinosine (OxodI). Oligonucleotides containing OxodI at defined sites were chemically synthesized via solid phase synthesis. Translesion incorporation opposite OxodI was compared with 7,8-dihydro-8-oxo-2'-deoxyguanosine (OxodG), 2'-deoxyinosine (dI) and 2'-deoxyguanosine (dG) in otherwise identical templates. The Klenow exo- fragment of Escherichia coli DNA polymerase I incorporated 2'-deoxyadenosine (dA) six times more frequently than 2'-deoxycytidine (dC) opposite OxodI. Preferential translesion incorporation of dA was unique to OxodI. UV-melting experiments revealed that DNA containing OxodI opposite dA is more stable than when the modified nucleotide is opposed by dC. These data suggest that while duplex DNA accommodates the 2-amino group in syn-OxodG, this substituent is thermally destabilizing and does not provide a kinetic inducement for replication by Klenow exo-.
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