Suppression of X-ray-induced chromatid breaks in human tumor cells by introduction of normal chromosome 4.
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).
Parshad
R
R
Department of Pathology, Howard University College of Medicine, Washington, DC 20059, USA.
Ning
Y
Y
Sanford
K K
KK
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