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[en] The E3 ubiquitin ligases ring finger protein (RNF) 8 and RNF168 transduce the DNA double-strand break (DSB) response (DDR) signal by ubiquitinating DSB sites. The depletion of RNF8 or RNF168 suppresses the accumulation of DNA-repair regulating factors such as 53BP1 and RAP80 at DSB sites, suggesting roles for RNF8- and RNF168-mediated ubiquitination in DSB repair. This mini-review provides a brief overview of the RNF8- and RNF168-dependent DDR-signaling and DNA-repair pathways. The choice of DNA-repair pathway when RNF8- and RNF168-mediated ubiquitination-dependent DDR signaling is negatively regulated by deubiquitinating enzymes (DUBs) is reviewed to clarify how the opposing roles of RNF8/RNF168 and DUBs regulate ubiquitination-dependent DDR signaling and the choice of DNA-repair pathway
[en] Background and purposeHPV-positive HNSCC cells are characterized by radiosensitivity, inefficient DNA double-strand break repair and a profound and prolonged arrest in G2. Here we explored the effect of clinically relevant inhibitors of Chk1 and Wee1 to inhibit the radiation-induced G2-arrest in order to achieve further radiosensitization.
[en] Jivanti is a well-known Rasayana in Ayurveda and is being used as an ingredient in various formulations like Jivantadya Gharita, Jivatayadi rasa, Jivantayaditaila, Ashwagandhadi Gharita, Anuthaila, Chandanadithaila which are used in various diseases. Jivanti has been claimed to be useful as galactagogue, antibacterial, lactogenic, hypotensive, restorative, tonic and hypoglycaemic activity. In this study we have isolated aqueous crude extract of Jivanti powder and was evaluated for the presence of different phytochemicals using various qualitative and quantitative assays. Further its antioxidant capacity and radioprotective property were evaluated using various in vitro assays. The total antioxidant capacity was estimated by the DPPH, ABTS+ and NO radical scavenging assays. Its reducing power was analyzed by ferric reduction and Molybdenum reduction assays. At the end, radioprotective property was evaluated using plasmid relaxation, lipid peroxidation and propidium iodide staining. Our study shows that the yield of crude aqueous extract from the raw powder was 1.6%. It exhibited concentration dependent DPPH, ABTS+ and NO radical scavenging activity indicating its significant antioxidant capacity. This extract significantly inhibited DNA strand breaks in plasmid pBR322 DNA and peroxidation of membrane lipids against ionizing radiation. Jivanti crude extract decreased radiation induced cell death in splenocytesas monitored by propidium iodide staining. (author)
[en] A technique of neutral sucrose gradients, developed in the last years, was modified to avoid some often occuring sources of error. The method is based on a mild lysis of the cells with a nonionic detergent in high salt concentration and subsequent centrifugation in a neutral sucrose - etidiumbromide - gradient. The position of the DNA can be seen without fractionating the gradiant because of the fluorescence of the DNA-EtBr complex. In this way it is possible to detect clearly the radiation damage of 100 rad γ-irradiation. (author)
[en] The accuracy of DNA repair may play a role in determining the cytotoxic effect of ionizing radiation. Repair, as measured by DNA strand breakage, often shows little difference between tumor cell lines of widely different radiosensitivity. The mechanism by which DNA fragments are rejoined is poorly understood. This study used plasmid transfection as a probe to assess the balance between correct repair and misrepair. A general trend for sensitive cells to show lower repair fidelity relative to resistant cells was observed. The type of double-strand cleavage of the plasmid (staggered or blunt) made little difference to the measured repair fidelity, in contrast to published studies in which restriction-enzyme breaks had been introduced into DNA within chromatin. Specific comparison of parent lines and their radiosensitive clones showed significant differences in repair fidelity for a relatively small change in radiation response, which was in line with the overall correlation. These same pairs have previously been shown to have no difference in the loss of DNA fragmentation with time after irradiation, and Southern analysis had confirmed the integrated plasmid copy number was similar in the cell lines compared. The number of intact copies of the damaged gene relative to the undamaged gene mirrored the observed repair fidelity. However, in one cell line out of the 10 studied, an exception to the observed trend was found. In comparison of two equally radioresistant bladder cancer cell lines, large differences in repair fidelity were observed. Again, no difference in the integrated copy number was found, and the damaged gene was highly rearranged or deleted in the cell line with low repair fidelity. It is suggested that repair fidelity can be, but is not invariably, a measure of correct repair relative to misrepair, resulting from the processing of double-strand breaks and, hence, the response to ionizing radiation. 24 refs., 2 figs., 2 tabs