title: The Cockayne Syndrome group B gene product is involved in general genome base excision repair of 8-hydroxyguanine in DNA.
abstract: Cockayne Syndrome (CS) is a human genetic disorder with two complementation groups, CS-A and CS-B. The CSB gene product is involved in transcription-coupled repair of DNA damage but may participate in other pathways of DNA metabolism. The present study investigated the role of different conserved helicase motifs of CSB in base excision repair. Stably transformed human cell lines with site-directed CSB mutations in different motifs within its putative helicase domain were established. We find that CSB null and helicase motif V and VI mutants had greater sensitivity than wild type cells to gamma-radiation. Whole cell extracts from CSB null and motif V/VI mutants had lower activity of 8-hydroxyguanine incision in DNA than wild type cells. Also, 8-hydroxyguanine accumulated more in CSB null and motif VI mutant cells than in wild type cells after exposure to gamma-radiation. We conclude that a deficiency in general genome base excision repair of selective modified DNA base(s) might contribute to CS pathogenesis. Furthermore, whereas the disruption of helicase motifs V or VI results in a CSB phenotype, mutations in other helicase motifs do not cause this effect. The biological functions of CSB in different DNA repair pathways may be mediated by distinct functional motifs of the protein.
authors.affiliation: Laboratory of Molecular Gerontology, NIA, National Institutes of Health, Baltimore, Maryland 21224, USA.
authors.forename: J
authors.initials: J
authors.lastname: Tuo
authors.forename: M
authors.initials: M
authors.lastname: Müftüoglu
authors.forename: C
authors.initials: C
authors.lastname: Chen
authors.forename: P
authors.initials: P
authors.lastname: Jaruga
authors.forename: R R
authors.initials: RR
authors.lastname: Selzer
authors.forename: R M
authors.initials: RM
authors.lastname: Brosh
authors.forename: H
authors.initials: H
authors.lastname: Rodriguez
authors.forename: M
authors.initials: M
authors.lastname: Dizdaroglu
authors.forename: V A
authors.initials: VA
authors.lastname: Bohr
mesh_terms: D000595:Amino Acid Sequence; D002461:Cell Line, Transformed; D003057:Cockayne Syndrome / Q000235:genetics*; D004247:DNA / Q000235:genetics*; D004265:DNA Helicases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D004260:DNA Repair / Q000502:physiology*; D045643:DNA Repair Enzymes; D016678:Genome; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry*; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D018384:Oxidative Stress; D000075223:Poly-ADP-Ribose Binding Proteins
chemical_list: D000075223:Poly-ADP-Ribose Binding Proteins; C024829:8-hydroxyguanine; D006147:Guanine; D004247:DNA; D004265:DNA Helicases; C078673:ERCC6 protein, human; D045643:DNA Repair Enzymes