title: G2 phase repair of X-ray-induced chromosomal DNA damage in trichothiodystrophy cells.
abstract: The repair of X-ray-induced DNA damage during G2 cell-cycle phase has been examined in lines of skin fibroblasts from three patients with trichothiodystrophy (TTD), one with apparently normal and two with defective nucleotide excision repair (NER). These responses are compared with those of five lines from clinically normal controls, lines from xeroderma pigmentosum (XP), Cockayne syndrome (CS), Down syndrome (DS), and ataxia telangiectasia (AT) patients. Chromosomal DNA repair was measured as the chromatid aberration frequency (CAF) or total number of chromatid breaks and long gaps per 100 metaphase cells, determined 0.5-1.5 h after X-irradiation (53 rad). Chromatid breaks and gaps (as defined herein) represent unrepaired DNA strand breaks. Only one of the TTD lines, TTD 1BR, showed an abnormally high CAF. This line was shown subsequently to be of a different complementation group, representing a new nucleotide excision repair gene. An abnormally high CAF was also observed, as reported previously, in XP-C, AT and DS but not in CS skin fibroblasts. In addition, cell lines were examined for DNA incision activity by an indirect method in which chromatid aberrations were enumerated with or without ara-C, an inhibitor of repair synthesis, added after X-irradiation. All TTD lines had abnormally low incision activity.
authors.affiliation: Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, MD 20892.
authors.forename: K K
authors.initials: KK
authors.lastname: Sanford
authors.forename: R
authors.initials: R
authors.lastname: Parshad
authors.forename: F M
authors.initials: FM
authors.lastname: Price
authors.forename: R E
authors.initials: RE
authors.lastname: Tarone
authors.forename: A R
authors.initials: AR
authors.lastname: Lehmann
mesh_terms: D000015:Abnormalities, Multiple / Q000378:metabolism*; D001260:Ataxia Telangiectasia / Q000378:metabolism; D002460:Cell Line; D002869:Chromosome Aberrations; D002877:Chromosomes, Human / Q000528:radiation effects*; D003057:Cockayne Syndrome / Q000378:metabolism; D003561:Cytarabine / Q000494:pharmacology; D004249:DNA Damage; D004260:DNA Repair / Q000502:physiology*; D004314:Down Syndrome / Q000378:metabolism; D016195:G2 Phase / Q000502:physiology*; D006197:Hair / Q000002:abnormalities*; D006801:Humans; D012867:Skin / Q000166:cytology / Q000378:metabolism; D012871:Skin Diseases / Q000378:metabolism*; D014965:X-Rays; D014983:Xeroderma Pigmentosum / Q000378:metabolism
chemical_list: D003561:Cytarabine