title: Loss of MUTYH function in human cells leads to accumulation of oxidative damage and genetic instability.
abstract: The DNA glycosylase MUTYH (mutY homolog (Escherichia coli)) counteracts the mutagenic effects of 8-oxo-7,8-dihydroguanine (8-oxodG) by removing adenine (A) misincorporated opposite the oxidized purine. Biallelic germline mutations in MUTYH cause the autosomal recessive MUTYH-associated adenomatous polyposis (MAP). Here we designed new tools to investigate the biochemical defects and biological consequences associated with different MUTYH mutations in human cells. To identify phenotype(s) associated with MUTYH mutations, lymphoblastoid cell lines (LCLs) were derived from seven MAP patients harboring missense as well as truncating mutations in MUTYH. These included homozygous p.Arg245His, p.Gly264TrpfsX7 or compound heterozygous variants (p.Gly396Asp/Arg245Cys, p.Gly396Asp/Tyr179Cys, p.Gly396Asp/Glu410GlyfsX43, p.Gly264TrpfsX7/Ala385ProfsX23 and p.Gly264TrpfsX7/Glu480del). DNA glycosylase assays of MAP LCL extracts confirmed that all these variants were defective in removing A from an 8-oxoG:A DNA substrate, but retained wild-type OGG1 activity. As a consequence of this defect, MAP LCLs accumulated DNA 8-oxodG in their genome and exhibited a fourfold increase in spontaneous mutagenesis at the PIG-A gene compared with LCLs from healthy donors. They were also hypermutable by KBrO3--a source of DNA 8-oxodG--indicating that the relatively modest spontaneous mutator phenotype associated with MUTYH loss can be significantly enhanced by conditions of oxidative stress. These observations identify accumulation of DNA 8-oxodG and a mutator phenotype as likely contributors to the pathogenesis of MUTYH variants.
authors.affiliation: Department of Environment and Primary Prevention, Istituto Superiore di Sanità, Roma, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Ruggieri
authors.forename: E
authors.initials: E
authors.lastname: Pin
authors.forename: M T
authors.initials: MT
authors.lastname: Russo
authors.forename: F
authors.initials: F
authors.lastname: Barone
authors.forename: P
authors.initials: P
authors.lastname: Degan
authors.forename: M
authors.initials: M
authors.lastname: Sanchez
authors.forename: M
authors.initials: M
authors.lastname: Quaia
authors.forename: A
authors.initials: A
authors.lastname: Minoprio
authors.forename: E
authors.initials: E
authors.lastname: Turco
authors.forename: F
authors.initials: F
authors.lastname: Mazzei
authors.forename: A
authors.initials: A
authors.lastname: Viel
authors.forename: M
authors.initials: M
authors.lastname: Bignami
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D011125:Adenomatous Polyposis Coli / Q000235:genetics / Q000378:metabolism; D000328:Adult; D002460:Cell Line; D004249:DNA Damage; D045647:DNA Glycosylases / Q000235:genetics* / Q000378:metabolism*; D004260:DNA Repair; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D004789:Enzyme Activation; D005260:Female; D015870:Gene Expression; D042822:Genomic Instability; D006579:Heterozygote; D006801:Humans; D008297:Male; D008565:Membrane Proteins / Q000235:genetics; D008875:Middle Aged; D009154:Mutation; D059645:Mutation Rate; D018384:Oxidative Stress; D010641:Phenotype
chemical_list: D008565:Membrane Proteins; C080086:phosphatidylinositol glycan-class A protein; D000080242:8-Hydroxy-2'-Deoxyguanosine; D045647:DNA Glycosylases; C061738:mutY adenine glycosylase; D003849:Deoxyguanosine