title: Direct repair of 3,N(4)-ethenocytosine by the human ALKBH2 dioxygenase is blocked by the AAG/MPG glycosylase.
abstract: Exocyclic ethenobases are highly mutagenic DNA lesions strongly implicated in inflammation and vinyl chloride-induced carcinogenesis. While the alkyladenine DNA glycosylase, AAG (or MPG), binds the etheno lesions 1,N(6)-ethenoadenine (ɛA) and 3,N(4)-ethenocytosine (ɛC) with high affinity, only ɛA can be excised to initiate base excision repair. Here, we discover that the human AlkB homolog 2 (ALKBH2) dioxygenase enzyme catalyzes direct reversal of ɛC lesions in both double- and single-stranded DNA with comparable efficiency to canonical ALKBH2 substrates. Notably, we find that in vitro, the non-enzymatic binding of AAG to ɛC specifically blocks ALKBH2-catalyzed repair of ɛC but not that of methylated ALKBH2 substrates. These results identify human ALKBH2 as a repair enzyme for mutagenic ɛC lesions and highlight potential consequences for substrate-binding overlap between the base excision and direct reversal DNA repair pathways.
authors.affiliation: Department of Biological Engineering, and Biology, Center for Environmental Health Sciences, David H. Koch Center for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, United States.
authors.forename: Dragony
authors.initials: D
authors.lastname: Fu
authors.forename: Leona D
authors.initials: LD
authors.lastname: Samson
mesh_terms: D000071499:AlkB Homolog 2, Alpha-Ketoglutarate-Dependent Dioxygenase; D003596:Cytosine / Q000031:analogs & derivatives* / Q000378:metabolism; D004249:DNA Damage; D045647:DNA Glycosylases / Q000378:metabolism*; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000302:isolation & purification / Q000378:metabolism*; D004262:DNA Restriction Enzymes / Q000378:metabolism; D049308:Dioxygenases / Q000302:isolation & purification / Q000378:metabolism*; D006801:Humans; D013379:Substrate Specificity
chemical_list: C018289:3,N(4)-ethenocytosine; D003596:Cytosine; D049308:Dioxygenases; C486440:ALKBH2 protein, human; D000071499:AlkB Homolog 2, Alpha-Ketoglutarate-Dependent Dioxygenase; D004262:DNA Restriction Enzymes; C021565:3-methyladenine-DNA glycosylase; D045647:DNA Glycosylases; D045643:DNA Repair Enzymes
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