Mazin A L, Boĭko L M, Ogarkova O A, Vaniushin B F
Mol Biol (Mosk). 1988 Nov-Dec;22(6):1688-96.
From nucleotide sequences of mitochondrial and chloroplast genes the probable frequency of the CpG----TpG + CpA substitutions was determined. These substitutions may indicate the level of prior DNA methylation. It was found that the level of this methylation is significantly lower in mitochondrial DNA (mtDNA) and chloroplast DNA (chDNA) than in nuclear DNA (nDNA) of the same species. The species (taxon) specificity of mtDNA and chDNA methylation was revealed. A correlation was found between the level of CpG methylation in nDNA, and mtDNA and chDNA in different organisms. It is shown that cytosine residues in CpG were not subjected to significant methylation in the fungi and invertebrate mtDNA and also in the algae chDNA. In contrast, the vertebrate mtDNA bears the impress of CpG-supression, which is confirmed by direct data on methylation of these DNA. Here the first data on the possible enzymatic methylation of the plant mtDNA and chDNA were obtained. It was shown that the degree of CpG-suppression in the 5S rRNA nuclear genes of lower and higher plants is significantly higher in the chloroplast genes of 4,5S and 5S rRNA. From data on pea chDNA hydrolysis with MspI and HpaII it was established that in CCGG sequences this DNA is not methylated. The role of DNA methylation in increasing the mutation rate and in accelerating the evolutionary rates of vertebrate mtDNA is discussed.
通过线粒体和叶绿体基因的核苷酸序列，确定了CpG----TpG + CpA替换的可能频率。这些替换可能表明先前DNA甲基化的水平。研究发现，同一物种的线粒体DNA（mtDNA）和叶绿体DNA（chDNA）中的这种甲基化水平明显低于核DNA（nDNA）。揭示了mtDNA和chDNA甲基化的物种（分类群）特异性。发现不同生物体中nDNA、mtDNA和chDNA中CpG甲基化水平之间存在相关性。结果表明，真菌和无脊椎动物的mtDNA以及藻类的chDNA中，CpG中的胞嘧啶残基未发生显著甲基化。相反，脊椎动物的mtDNA带有CpG抑制的印记，这一点已被这些DNA甲基化的直接数据所证实。这里获得了关于植物mtDNA和chDNA可能发生酶促甲基化的首批数据。结果表明，低等和高等植物5S rRNA核基因中CpG抑制程度在4,5S和5S rRNA叶绿体基因中明显更高。从豌豆chDNA用MspI和HpaII水解的数据可以确定，在CCGG序列中该DNA未被甲基化。讨论了DNA甲基化在增加脊椎动物mtDNA突变率和加速其进化速率方面的作用。
