哺乳類細胞のSister Chromatid Exchangeの生成機構と生物学的意義

概要

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It is well known that SCEs are induced by various DNA-damaging agents such as UV and mitomycin C. Although induction of SCE seems to be best related with either DNA repair or replication, its biological role remains still obscure. Therefore the effects of caffeine on survival as well as on spontaneous and induced SCEs were investigated at various UV fluences and caffeine concentrations in V79 Chinese hamster cells. Survival assay showed that caffeine potentiated UV-killing in its concentration dependent manner. SCEs were detected by the Hoechst 33258-Giemsa method for differential staining of unifiliarly and bifiliarly BrdU-substitued chromatids. SCEs induction increased linearly as a function of UV fluence and though more slightly caffeine concentration. When caffeine was applied after UV-irradiation, induction of SCEs increased synergistically till a plateau was achieved beyond which no enhancement was observed. In a linear-log plot between SCEs and surviving fraction, the number of SCEs increased linearly with decreasing surviving rate till it reached 50%, below which there was no correlation. It is suggested therefore, that pyrimidine dimers might be one of the causes for the induction of SCEs. A possible scheme for the formation of SCEs is presented.
神戸大学の論文