Barbado, CasimiroCordoba-Cañero, DoloresAriza, Rafael RRoldan-Arjona, Teresa2023-01-252023-01-252018-01-16Barbado C, Córdoba-Cañero D, Ariza RR, Roldán-Arjona T. Nonenzymatic release of N7-methylguanine channels repair of abasic sites into an AP endonuclease-independent pathway in Arabidopsis. Proc Natl Acad Sci U S A. 2018 Jan 30;115(5):E916-E924http://hdl.handle.net/10668/12021Abasic (apurinic/apyrimidinic, AP) sites in DNA arise from spontaneous base loss or by enzymatic removal during base excision repair. It is commonly accepted that both classes of AP site have analogous biochemical properties and are equivalent substrates for AP endonucleases and AP lyases, although the relative roles of these two types of enzymes are not well understood. We provide here genetic and biochemical evidence that, in Arabidopsis, AP sites generated by spontaneous loss of N7-methylguanine (N7-meG) are exclusively repaired through an AP endonuclease-independent pathway initiated by FPG, a bifunctional DNA glycosylase with AP lyase activity. Abasic site incision catalyzed by FPG generates a single-nucleotide gap with a 3'-phosphate terminus that is processed by the DNA 3'-phosphatase ZDP before repair is completed. We further show that the major AP endonuclease in Arabidopsis (ARP) incises AP sites generated by enzymatic N7-meG excision but, unexpectedly, not those resulting from spontaneous N7-meG loss. These findings, which reveal previously undetected differences between products of enzymatic and nonenzymatic base release, may shed light on the evolution and biological roles of AP endonucleases and AP lyases.enAttribution-NonCommercial-NoDerivatives 4.0 Internationalhttp://creativecommons.org/licenses/by-nc-nd/4.0/AP endonucleasesAP lyasesN7-methylguanineAbasic sitesBase excision repairArabidopsisArabidopsis proteinsBinding sitesCatalysisCell-free systemDNA damageDNA methylationDNA repairDNA-(apurinic or apyrimidinic site) lyaseEndonucleasesGene expression regulation, plantGuanineMutationProtein domainsresearch article29339505open accessCatálisisDaño del ADNDominios proteicosEndonucleasasGuaninaMetilación de ADNMutaciónProteínas de arabidopsisRegulación de la expresión génica de las plantas10.1073/pnas.17194971151091-6490PMC5798382https://doi.org/10.1073/pnas.1719497115https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5798382/pdf