8-oxoguanine incorporation into DNA repeats in vitro and mismatch recognition by MutSalpha.
DNA 8-oxoguanine (8-oxoG) causes transversions and is also implicated in frameshifts. We previously identified the dNTP pool as a likely source of mutagenic DNA 8-oxoG and demonstrated that DNA mismatch repair prevented oxidation-related frameshifts in mononucleotide repeats. Here, we show that both Klenow fragment and DNA polymerase alpha can utilize 8-oxodGTP and incorporate the oxidized purine into model frameshift targets. Both polymerases incorporated 8-oxodGMP opposite C and A in repetitive DNA sequences and efficiently extended a terminal 8-oxoG. The human MutSalpha mismatch repair factor recognized DNA 8-oxoG efficiently in some contexts that resembled frameshift intermediates in the same C or A repeats. DNA 8-oxoG in other slipped/mispaired structures in the same repeats adopted configurations that prevented recognition by MutSalpha and by the OGG1 DNA glycosylase thereby rendering it invisible to DNA repair. These findings are consistent with a contribution of oxidative DNA damage to frameshifts. They also suggest how mismatch repair might reduce the burden of DNA 8-oxoG and prevent frameshift formation.
Macpherson
Peter
P
Cancer Research UK London Research Institute, Clare Hall Laboratories South Mimms, Herts, EN6 3LD, UK.
Barone
Flavia
F
Maga
Giovanni
G
Mazzei
Filomena
F
Karran
Peter
P
Bignami
Margherita
M
D000241:Adenosine / Q000737:chemistry; D020137:Base Pair Mismatch; D003596:Cytosine / Q000737:chemistry; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D045647:DNA Glycosylases / Q000378:metabolism; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism*; D003848:Deoxyguanine Nucleotides / Q000378:metabolism; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D006157:Guanosine Monophosphate / Q000031:analogs & derivatives / Q000378:metabolism; D051718:MutS Homolog 2 Protein; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D012091:Repetitive Sequences, Nucleic Acid
D004268:DNA-Binding Proteins; D003848:Deoxyguanine Nucleotides; C094443:G-T mismatch-binding protein; D011518:Proto-Oncogene Proteins; C078206:8-oxodeoxyguanosine triphosphate; C024829:8-hydroxyguanine; D006147:Guanine; D006157:Guanosine Monophosphate; C039543:8-oxoguanosine 2'-phosphate; D003596:Cytosine; D004247:DNA; D045647:DNA Glycosylases; C479058:oxoguanine glycosylase 1, human; D051718:MutS Homolog 2 Protein; D000241:Adenosine