[CG-methylation and mutagenesis of human mitochondrial DNA]

It is demonstrated that human mitochondrial DNA (mtDNA) exhibits the chain asymmetry of TG and CA dinucleotide frequencies presumably due to replicative and postreplicative methylation of CG sites of mtDNA and specific mitochondrial genome replication. The analysis of population data on human mtDNA variability has revealed two mutation flows: one intense G-->A and C-->T and less intense A-->G, T-->C and C-->G flows; the letter results in formation of G,C-enriched mtDNA palindromic structures and CG dinucleotides. The interaction of these two mutation flows through the system of DNA methylation/deamination enables to consider the above mentioned processes as a mechanism of DNA evolution maintaining certain level of mtDNA diversity in human populations.