title: Repair of propanodeoxyguanosine by nucleotide excision repair in vivo and in vitro.
abstract: Repair of the exocyclic DNA adduct propanodeoxyguanosine (PdG) was assessed in both in vivo and in vitro assays. PdG was site-specifically incorporated at position 6256 of M13MB102 DNA, and the adducted viral genome was electroporated into repair-proficient and repair-deficient Escherichia coli strains. Comparable frequencies of PdG --> T and PdG --> A mutations at position 6256 were detected following replication of the adducted genomes in wild-type E. coli strains. A 4-fold increase in the frequencies of transversions and transitions was observed in E. coli strains deficient in Uvr(A)BC-dependent nucleotide excision repair. A similar increase in the replication of the adduct containing strand was observed in the repair-deficient strains. No change in the frequency of targeted mutations was observed in strains deficient in one or both of the genes coding for 3-methyladenine glycosylase. Incubation of purified E. coli Uvr(A)BC proteins with a duplex 156-mer containing a single PdG adduct resulted in removal of a 12-base oligonucleotide containing the adduct. Incubation of the same adducted duplex with Chinese hamster ovary cell-free extracts also resulted in removal of the adduct. PdG was a better substrate for repair by the mammalian nucleotide excision repair complex than the bacterial repair complex and was approximately equal to a thymine-thymine dimer as a substrate for the former. The results of these in vivo and in vitro experiments indicate that PdG, a homolog of several endogenously produced DNA adducts, is repaired by the nucleotide excision repair pathway.
authors.affiliation: Department of Biochemistry, Center in Molecular Toxicology and the Vanderbilt Cancer Center, Vanderbilt University School of Medicine, Nashville, Tennessee 37232, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Johnson
authors.forename: S P
authors.initials: SP
authors.lastname: Fink
authors.forename: L J
authors.initials: LJ
authors.lastname: Marnett
mesh_terms: D000818:Animals; D017104:Bacteriophage M13 / Q000235:genetics; D016466:CHO Cells; D002474:Cell-Free System; D006224:Cricetinae; D018736:DNA Adducts / Q000378:metabolism*; D004260:DNA Repair; D004261:DNA Replication; D004279:DNA, Viral / Q000378:metabolism; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000378:metabolism; D004706:Endodeoxyribonucleases / Q000378:metabolism; D029968:Escherichia coli Proteins
chemical_list: D018736:DNA Adducts; D004279:DNA, Viral; D029968:Escherichia coli Proteins; C060195:cyclic 1,N(2)-propanodeoxyguanosine; D004706:Endodeoxyribonucleases; C036385:endodeoxyribonuclease uvrABC; D003849:Deoxyguanosine