Metabolism and non-random occurrence of nonnascent short chains in the DNA of Ehrlich ascites cells.
The DNA of Ehrlich ascites cells was labeled with radioactive thymidine using different labeling schedules: Incubation periods between 15 s and 4 h; pulse/pulse-chase experiments with pulses in the range of a few minutes; longtime incubation followed by a longtime chase (both in the range of 1 cell generation). From the purified DNA of the labeled cells a fraction (0.3-0.4%) of short chains was separated and partially fractionated by means of a hydroxyapatite thermochromatography procedure. The evaluation of the labelling patterns of the short chains indicated that less than 5% of them can be regarded as replication intermediates ('Okazaki pieces'). The rest, termed nonnascent pieces, exhibited a slow turnover. The life span of the nonnascent pieces was estimated to be about 1 cell generation. On helical DNA, nonnascent pieces were distributed in a non-random manner. Their preferential localisation was nearby sites which caused binding of the DNA, after purification, to nitrocellulose and which occurred about every 60-80 microns on the nuclear DNA of the cells.
D000818:Animals; D002286:Carcinoma, Ehrlich Tumor / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D051379:Mice; D009690:Nucleic Acid Conformation; D013936:Thymidine / Q000378:metabolism
D004247:DNA; D013936:Thymidine