Variation through the Cell Cycle in the Dose-response of DNA Neutral Filter Elution in X-irradiated Synchronous CHO-cells

作者：Ryuichi Okayasu, Detlef Bloecher, George E. Iliakis · 发表于：International Journal of Radiation Biology · 年份：1988 · DOI：10.1080/09553008814551101 · 被引用次数：69 · 研究领域：DNA Repair Mechanisms、Carcinogens and Genotoxicity Assessment、DNA and Nucleic Acid Chemistry

Dose-response curves for DNA neutral (pH 9.6) filter elution were obtained with synchronized CHO cells exposed to X-rays at various phases of the cell cycle. The dose response was similar in synchronized and plateau-phase G1 cells, as well as in cells that were arrested at the G1/S border using aphidicolin; it flattened as cells progressed into S phase and reached a minimum in the middle of this phase. An increase in DNA elution dose response, to values only slightly lower than those obtained with G1 cells, was observed as cells entered G2 phase. Significant alterations in the sedimentation properties of the DNA during S phase were also observed in Ehrlich ascites tumor cells using the neutral sucrose gradient centrifugation technique. A significant proportion of the DNA from S cells irradiated with 10 Gy sedimented at speeds (350S-700S) well above the maximum sedimentation speed expected for free sedimenting DNA molecules (Smax = 350S), indicating the formation of a DNA complex. DNA from G1, G1/S, or G2 + M cells sedimented as expected for free sedimenting molecules. These results indicate significant alterations in the physicochemical properties of the DNA--probably caused by DNA replication-associated alterations in DNA structure and chromatin conformation--as cells enter S phase, and are invoked to explain the observed variation in DNA elution dose response throughout the cycle. It is proposed that the formation of a complex DNA structure, resistant to the proteolytic enz...