Exposure of Tetrahymena pyriformis (W) cells to gamma-radiation (200 krad) caused strand-breaks in nuclear and mitochondrial DNAs as assayed by sedimentation analysis in alkaline sucrose density gradients using lysates of nuclei and mitochondria (prelabeled with [3 H]thymidine). Postirradiation incubation of the cells in the growth medium at 25°C resulted in restitution of single-strand breaks in these DNAs. Both the subcellular organelles exhibited ability to rejoin single-strand scissions in their DNAs (caused by 200 krad gamma-radiation in vitro) when incubated in isotonic buffer at 25°C. The in vitro repair by the subcellular organelles was inhibited by EDTA (1× 10-3 M). 2,4-Dinitrophenol (5× 10-5 M) and procaine hydrochloride (3× 10-3 M) effectively inhibited mitochondrial DNA repair but nuclear DNA repair was not inhibited even at higher concentrations of the chemicals.
Repair of Radiation-Induced Strand Scissions in Nuclear and Mitochondrial DNAs in Tetrahymena pyriformis
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Karpagam Pasupathy, M. S. Netrawali, D. S. Pradhan, A. Sreenivasan; Repair of Radiation-Induced Strand Scissions in Nuclear and Mitochondrial DNAs in Tetrahymena pyriformis. Radiat Res 1 April 1976; 66 (1): 147–157. doi: https://doi.org/10.2307/3574363
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