Vanyushin B F, Kirnos M D
Mol Biol (Mosk). 1976 Jul-Aug;10(4):715-24.
The nucleotide composition, relative concentration of pyrimidine clusters, and the degree of methylation of the mitochondrial and nuclear DNA's of various vertebrates and the protozoan Crithidia oncopelti have been studied. With respect to the relative concentration of GC pairs, the mtDNA of animals (bull, rat) does not differ from the corresponding nDNA. The relative concentration of GC pairs in the mtDNA of certain fish and birds is 1.5-2.5 mole% higher than in the respective nDNA. The kinetoplast DNA of the protozoan C. oncopelti (where the relative concentration of the GC pairs is 42.9 mole %) differs very sharply in composition from the nDNA (where the relative concentration of GC pairs is 51.3 mole %). The mtDNA's and kDNA's studied are distinguished from the respective nDNA'S by a lower degree of clustering of pyrimidine nucleotides. The proportion of mono- and dipyrimidine fragments in the mtDNA and kDNA is 30 mole %, while in the nDNA it does not exceed 23 mole %. The relative concentration of long pyrimidine clusters (hexapyrimidine clusters of larger) in the mtDNA is smaller than in the nDNA by a factor of 2-5. The low degree of clustering of the pyrimidine nucleotides is apparently characteristic of all the known mtDNA's and may support the fact that they have a single type of organization and are of a single origin. All the vertebrate mtDNA's studied contain 5-methylcytosine as a minor base (1.5-3.15 mole %), and their level of methylation is 1.5-2 times greater than that in the respective nDNA's. It has been shown that animals display species specificity with respect to the 5-methylcytosine content in the mtDNA. Its distribution among the pyrimidine clusters in the bovine heart mtDNA differs substantially from that in the nDNA. This suggests that the methylation specificities of nuclear and mitochondrial DNA are different. A DNA methylase, which effects the in vitro methylation of cytosine residues both in the homologous mtDNA and in different heterologous DNA's, has been found in rat liver and bovine heart mitochondria. The specificity of the in vitro methylation of the cytosine residues in the same heterologous Escherichia coli B DNA by the nuclear and mitochondrial enzymes is different: The mitochondrial enzyme methylates predominantly in monopyrimidine fragments, and the nuclear enzyme methylates mostly in di- and tripyrimidine fragments. They, therefore, recognize different nucleotide sequences.
已对各种脊椎动物以及原生动物克氏锥虫的线粒体和核DNA的核苷酸组成、嘧啶簇的相对浓度以及甲基化程度进行了研究。就GC对的相对浓度而言，动物（公牛、大鼠）的线粒体DNA与相应的核DNA并无差异。某些鱼类和鸟类的线粒体DNA中GC对的相对浓度比各自的核DNA高1.5 - 2.5摩尔%。原生动物克氏锥虫的动质体DNA（其中GC对的相对浓度为42.9摩尔%）在组成上与核DNA（其中GC对的相对浓度为51.3摩尔%）差异非常显著。所研究的线粒体DNA和动质体DNA与各自的核DNA的区别在于嘧啶核苷酸的聚类程度较低。线粒体DNA和动质体DNA中单嘧啶和双嘧啶片段的比例为30摩尔%，而在核DNA中不超过23摩尔%。线粒体DNA中长嘧啶簇（更大的六嘧啶簇）的相对浓度比核DNA小2 - 5倍。嘧啶核苷酸的低聚类程度显然是所有已知线粒体DNA的特征，这可能支持它们具有单一组织类型且起源单一这一事实。所有研究的脊椎动物线粒体DNA都含有5 - 甲基胞嘧啶作为次要碱基（1.5 - 3.15摩尔%），其甲基化水平比各自的核DNA高1.5 - 2倍。已表明动物在线粒体DNA中5 - 甲基胞嘧啶含量方面表现出物种特异性。其在牛心脏线粒体DNA的嘧啶簇中的分布与核DNA中的分布有很大不同。这表明核DNA和线粒体DNA的甲基化特异性不同。在大鼠肝脏和牛心脏线粒体中发现了一种DNA甲基化酶，它能使同源线粒体DNA以及不同的异源DNA中的胞嘧啶残基发生体外甲基化。核酶和线粒体酶对同一异源大肠杆菌B DNA中胞嘧啶残基的体外甲基化特异性不同：线粒体酶主要在单嘧啶片段中甲基化，而核酶主要在双嘧啶和三嘧啶片段中甲基化。因此，它们识别不同的核苷酸序列。
