title: Suppression of X-ray-induced chromatid breaks in human tumor cells by introduction of normal chromosome 4.
abstract: Human tumor cells in culture frequently show an infinite lifespan and are characterized by an abnormally high frequency of chromatid breaks after x-irradiation during G(2) phase of the cell cycle. This abnormally high frequency of persistent chromatid breaks results from deficient repair of the radiation-induced DNA damage. In three of four tumor cell lines, addition of a single human chromosome 4 from normal cells by microcell fusion resulted in efficient repair as evidenced by suppression of radiation-induced chromatid breaks to the level in normal cells. With respect to senescence-related gene (s), two of these four tumor cell lines belonged to complementation group A and one each to groups C and D. Chromosome 4 restored DNA repair efficiency in only one of the two tumor cell lines of complementation group A. These results suggest that chromosome 4 carries a DNA repair gene or gene(s) that complement the repair deficiency in three of these four tumor lines. Furthermore, the gene(s) involved in cellular senescence on chromosome 4 appear to differ from the gene(s) for repair of radiation-induced DNA damage during G(2).
authors.affiliation: Department of Pathology, Howard University College of Medicine, Washington, DC 20059, USA.
authors.forename: R
authors.initials: R
authors.lastname: Parshad
authors.forename: Y
authors.initials: Y
authors.lastname: Ning
authors.forename: K K
authors.initials: KK
authors.lastname: Sanford
mesh_terms: D002455:Cell Division / Q000528:radiation effects; D002459:Cell Fusion; D016922:Cellular Senescence / Q000235:genetics / Q000528:radiation effects; D002842:Chromatids / Q000235:genetics* / Q000528:radiation effects*; D019457:Chromosome Breakage / Q000235:genetics*; D002894:Chromosomes, Human, Pair 4 / Q000235:genetics* / Q000502:physiology; D003260:Contact Inhibition / Q000235:genetics; D004249:DNA Damage / Q000235:genetics / Q000528:radiation effects*; D004260:DNA Repair / Q000235:genetics / Q000502:physiology; D005354:Fibrosarcoma / Q000235:genetics / Q000473:pathology; D016195:G2 Phase; D005816:Genetic Complementation Test; D006801:Humans; D009369:Neoplasms / Q000235:genetics* / Q000473:pathology; D012516:Osteosarcoma / Q000235:genetics / Q000473:pathology; D010641:Phenotype; D011003:Ploidies; D014407:Tumor Cells, Cultured; D001749:Urinary Bladder Neoplasms / Q000235:genetics / Q000473:pathology