title: The effect of heat and radiation on the initiation and elongation processes of DNA synthesis.
abstract: The pH step alkaline elution and alkaline sucrose gradient techniques were utilized to evaluate alterations in DNA replication (initiation and elongation) induced by heat and low dose X-irradiation is synchronized Chinese hamster ovary cells. The initiation and elongation process of DNA synthesis were radioresistant at the G1/S boundary (4 hours after mitosis) while in mid S phase (9 hours after mitosis) DNA initiation and elongation were sensitive to X-irradiation. The initiation and elongation processes of DNA synthesis which were radiation resistant at the G1/S boundary could be inhibited by a hyperthermia treatment (43 degrees C for 1 hour beginning at 4 hours after mitosis). The impairment of initiation in the heated cells was maintained through late S phase while that of elongation was reversible as judged by full recovery at 15 hours after mitosis. These data suggest that the known synergistic lethality of heat and radiation may be mediated by an impairment of initiation of DNA synthesis.
mesh_terms: D000818:Animals; D002453:Cell Cycle; D002455:Cell Division / Q000528:radiation effects; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004261:DNA Replication / Q000528:radiation effects; D006358:Hot Temperature