Structural basis for enzymatic excision of N1-methyladenine and N3-methylcytosine from DNA.
N(1)-methyladenine (m(1)A) and N(3)-methylcytosine (m(3)C) are major toxic and mutagenic lesions induced by alkylation in single-stranded DNA. In bacteria and mammals, m(1)A and m(3)C were recently shown to be repaired by AlkB-mediated oxidative demethylation, a direct DNA damage reversal mechanism. No AlkB gene homologues have been identified in Archaea. We report that m(1)A and m(3)C are repaired by the AfAlkA base excision repair glycosylase of Archaeoglobus fulgidus, suggesting a different repair mechanism for these lesions in the third domain of life. In addition, AfAlkA was found to effect a robust excision of 1,N(6)-ethenoadenine. We present a high-resolution crystal structure of AfAlkA, which, together with the characterization of several site-directed mutants, forms a molecular rationalization for the newly discovered base excision activity.
Leiros
Ingar
I
The Norwegian Structural Biology Centre, University of Tromsø, Tromsø, Norway.
Nabong
Marivi P
MP
Grøsvik
Kristin
K
Ringvoll
Jeanette
J
Haugland
Gyri T
GT
Uldal
Lene
L
Reite
Karen
K
Olsbu
Inger K
IK
Knaevelsrud
Ingeborg
I
Moe
Elin
E
Andersen
Ole A
OA
Birkeland
Nils-Kåre
NK
Ruoff
Peter
P
Klungland
Arne
A
Bjelland
Svein
S
D000595:Amino Acid Sequence; D019611:Archaeoglobus fulgidus / Q000235:genetics*; D001483:Base Sequence; D018360:Crystallography, X-Ray; D004249:DNA Damage; D045647:DNA Glycosylases / Q000737:chemistry* / Q000235:genetics*; D017931:DNA Primers; D004260:DNA Repair / Q000235:genetics*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D015394:Molecular Structure; D016297:Mutagenesis, Site-Directed; D017422:Sequence Analysis, DNA
D017931:DNA Primers; D045647:DNA Glycosylases; C076131:DNA-3-methyladenine glycosidase II