Repair of O6‐ethylguanine DNA lesions in isolated cell nuclei
- 1 November 1983
- journal article
- research article
- Published by Wiley in European Journal of Biochemistry
- Vol. 136 (3), 453-460
- https://doi.org/10.1111/j.1432-1033.1983.tb07763.x
Abstract
Cell nuclei prepared from rat liver were alkylated in vitro with ethylnitrosourea; the nuclear DNA was found to lose O6-ethylguanine and 7-ethylguanine during a subsequent incubation at 37.degree. C. The rate of O6-ethylguanine loss is comparable to that observed in vivo, indicating that no cytoplasmic component is needed for the repair; no free O6-ethylguanine was found in the incubation medium of the ethylated nuclei. The rate of 7-ethylguanine loss is higher than the spontaneous depurination in vitro and an amount of free 7-ethylguanine equivalent to that lost by the nuclear DNA was found in the incubation medium; this DNA lesion is apparently excised by a DNA glycosylase. The proteins of the chromatin prepared from the isolated nuclei induced the disappearance of O6-ethylguanine from an added ethylated DNA. No free O6-ethylguanine was released, indicating that the repair is not catalyzed by a DNA glycosylase; no oligonucleotides enriched in O6-ethylguanine were released either, indicating that the disappearance of O6-ethylguanine from DNA is not the result of the cooperative action of a specific endonuclease and an exonuclease. Activities capable of removing O6-ethylguanine from DNA were found in other cell compartments; most of it is in the nucleus where the main location is chromatin. A pretreatment of the rats with daily low doses of diethylnitrosamine during 3 or 4 wk increased 2-3 times the repair activity of the chromatin proteins.This publication has 12 references indexed in Scilit:
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