Galbraith A I, Itzhaki R F, Craig A W, Margison G P
Chem Biol Interact. 1980 Mar;29(3):347-55. doi: 10.1016/0009-2797(80)90153-2.
The removal of the promutagenic DNA alkylation product O6-methylguanine from different fractions of rat liver DNA has been examined using the technique of DNA-DNA reassociation. Male Wistar rats were given a low non-toxic dose of N,N-dimethylnitrosamine (DMN) (2 mg/kg) and killed 3 or 18 h later (a period corresponding to the removal of 50% of the O6-methylguanine from 'total' liver (DNA). DNA was extracted from liver, denatured in alkali and incubated at 60 degrees C for periods corresponding to the reassociation of highly repetitive (polycopy), middle repetitive and 'unique' sequences i.e. different 'kinetic' classes of DNA. Reassociated and single-stranded DNA were separated by hydroxyapatite chromatography and analyse for O6-methylguanine content. Three hours after administration of DMN the levels of O6-methylguanine in the reassociated and single-stranded DNA were the same after each period of reassociation indicating that O6-methylguanine was randomly distributed among the DNA classes. At 18 h the levels of O6-methylguanine were again the same in the reassociated and single-stranded DNA but approx. 50% lower than in the 3 h DNA samples. The rate of loss of O6-methylguanine from the three DNA classes was thus the same and there was therefore no indication of preferential removal of this base from any one kinetic class of DNA under the conditions used.
运用DNA-DNA重缔合技术，对大鼠肝脏DNA不同组分中促诱变DNA烷基化产物O6-甲基鸟嘌呤的去除情况进行了研究。给雄性Wistar大鼠低剂量无毒的N,N-二甲基亚硝胺（DMN）（2毫克/千克），3或18小时后处死（这段时间相当于从“全”肝脏（DNA）中去除50%的O6-甲基鸟嘌呤）。从肝脏中提取DNA，在碱中变性，并在60℃下孵育，孵育时间对应于高度重复（多拷贝）、中度重复和“单一”序列（即不同“动力学”类别的DNA）的重缔合。通过羟基磷灰石色谱法分离重缔合DNA和单链DNA，并分析O6-甲基鸟嘌呤含量。给予DMN 3小时后，在每个重缔合时间段后，重缔合DNA和单链DNA中O6-甲基鸟嘌呤的水平相同，这表明O6-甲基鸟嘌呤在不同DNA类别中随机分布。在18小时时，重缔合DNA和单链DNA中O6-甲基鸟嘌呤的水平再次相同，但比3小时的DNA样品中约低50%。因此，三种DNA类别中O6-甲基鸟嘌呤的损失速率相同，所以在所使用的条件下，没有迹象表明从任何一种动力学类别的DNA中优先去除该碱基。
