Dependence of lethality induced by a direct DNA perturbation of synchronized human diploid fibroblasts on different periods of the DNA synthetic period (S Phase)

✍ Scribed by Takeki Tsutsui; Manabu Ohmori; Nobuko Suzuki; Heiji Maizumi

• Publisher: John Wiley and Sons
• Year: 1984
• Tongue: English
• Weight: 603 KB
• Volume: 120
• Category: Article
• ISSN: 0021-9541
• DOI: 10.1002/jcp.1041200216

✦ Synopsis

The cytotoxic effect of a direct perturbation of DNA during various portions of the DNA synthetic period (S phase) of cultured human diploid fibroblasts was examined. The cells were synchronized by a period of growth in low serum with a subsequent blockage of the cells at the GI/S boundary by hydroxyurea. This method resulted in over 90% synchrony, although approximately 20% of the cells were noncycling. Synchronized cells were treated for each of four 2-hour periods during t h e S phase with 5-bromodeoxyuridine (0.1-10 pM), followed by irradiation with near-UV (5-10 min). The 5-bromodeoxyuridine-plus-irradiation treatment was cytotoxic, while treatment with 5brornodeoxyuridine alone or irradiation alone was not cytotoxic. T h e cytotoxicity was dependent upon the periods of S phase during which treatment was administered. The highest lethality was observed for treatment in early to middle S phase, particularly in the first 2 hours of S phase, whereas scarce lethality was observed in late S phase. The extent of substitution of 5-bromodeoxyuridine for thymidine in newly synthesized DNA was similar in every period of the S phase. Furthermore, no specific period during S phase was significantly more sensitive to treatment with respect to DNA damage, as determined by an induction of unscheduled DNA synthesis. These results suggest that a certain region or regions in t h e DNA of human diploid fibroblasts, as designated by their specific temporal relationship in the S phase, may be more sensitive to the DNA perturbation by 5-bromodeoxyuridine treatment plus near-UV irradiation for cell survival.