A view of an elemental naturalist at the DNA world (Base composition,sequences, methylation) |
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Authors: | B F Vanyushin |
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Institution: | (1) Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119992 Moscow, Russia |
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Abstract: | The pioneering data on base composition and pyrimidine sequences in DNA of pro-and eukaryotes are considered, and their significance
for the origin of genosystematics is discussed. The modern views on specificity and functional role of enzymatic DNA methylation
in eukaryotes are described. DNA methylation controls all genetic functions and is a mechanism of cellular differentiation
and gene silencing. A model of regulation of DNA replication by methylation is suggested. Adenine DNA methylation in higher
eukaryotes (higher plants) was first observed, and it was established that one and the same gene can be methylated at both
cytosine and adenine moieties. Thus, there are at least two different and seemingly interdependent DNA methylation systems
present in eukaryotic cells. The first eukaryotic adenine DNA-methyltransferase is isolated from wheat seedlings and described:
the enzyme methylates DNA with formation of N6-methyladenine in the sequence TGATCA → TGm6ATCA. It is found that higher plants have endonucleases that are dependent on S-adenosyl-L-methionine (SAM) and sensitive
to DNA methylation status. Therefore, as in bacteria, plants seem to have a restriction-modification (R-M) system. A system
of conjugated up-and down-regulation of SAM-dependent endonucleases by SAM modulations is found in plants. Revelation of an
essential role of DNA methylation in regulation of genetic processes is a fundament of materialization of epigenetics and
epigenomics.
Published in Russian in Biokhimiya, 2007, Vol. 72, No. 12, pp. 1583–1593. |
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Keywords: | genosystematics DNA base composition DNA-methylation N6-methyladenine 5-methylcytosine cancer replication aging evolution plant endonucleases epigenetics |
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