[DNA-methylating system of chicken liver nuclei under normal conditions and in viral transformation]. / DNK-metiliruiushchaia sistema iader pecheni tsypliat v norme i pri virusnoi transformatsii.

The DNA methylating system of cellular nuclei from intact or virus transformed chicken liver was studied. The presence of multiple forms of methylases different in hydrophobic properties and isoelectric focusing points has been proved. The isoelectrofocusing made it possible to differentiate between the enzymes methylating preferably nonmethylated in vitro or methylated in vivo DNA. The DNA-methylases pool contains both types of methylases (de novo and supporting ones) in intact cells and at neoplastic transformation, however, the specificity of methylation and level of several enzymes in transformed cells is changed in the direction of broad specificity and lower activity. The general level of methylase activity at viral transformation is by 18-20% lower, while the content of 5-methylcytosine in hepatoma cells DNA is twofold lower as compared with the content in the DNA of intact cells.

[Multiple forms of DNA methylases in hepatic cell nuclei of animals in the normal state and in pathology]. / Mnozhestvennye formy DNK-metilaziz iader pechenizhivotnykh v norme i pri patologii.

Using hydrophobic chromatography multiple nature of DNA-methylating enzymes have been revealed. It was established that the most active enzymatic fraction of rats' liver and that of chicken are completely identical.

[Effect of various conditions on the stability of DNA-methylases from Mycobacterium smegmatis butyricum cells]. / Vliianie razlichnykh uslovii na stabil'nost' DNK-metilaz iz kletok Mycobacterium smegmatis butyricum.

DNA-methylases from M. sm. butyricum, produced by means of isoelectrofocusing, were characterized by slow spontaneous variations in the activity with amplitude of 75-80% under conditions of storage in glycerol at -10 degrees. Effect of various conditions on stabilization of activity of adenine methylases MMbu4,2 and MMbu7,2 was studied. Alterations in the enzymatic activity were not found in presence of substances applied usually to stabilize the enzymes, blood serum albumin and cations of two valent metals as the values of the alterations occurred in the ranges of the enzyme activity variations.

[Isolation and fractionation of DNA methylases from Mycobacterium butyricum]. / Vydelenie i fraktsionirovanie DNK-metilaz Mycobacterium butyricum.

Properties of total preparation of methylases from M. butyricum strain were studied using various methods of column chromatography. Distinct heterogeneity of the methylase preparation was demonstrated by gel filtration, anion exchange chromatography on diethyl aminoethyl cellulose and affinity chromatography on Sepharose blue. Several methylases, dissimilar both in physico-chemical properties and in their specificity to nitrogenous bases, were found in M. butyricum cells. In the strain studied methylases of adenine and cytosine were found, which were responsible for biosynthesis of 6-methyl adenine and 5-methyl cytosine in the acceptor DNA at the ratio 9 : 1.

[Relations between the condition of growth and activity of DNA-methylases of Mycobacteria butyricum]. / Aktivnost' DNK-metilaz Mycobacteria butyricum v zavisimosti ot uslovii vyrashchivaniia.

Conditions for cultivation of Mycobacteria butiricum were studied. Optimal conditions were selected to maintain maximal rate of DNA-metylase activity keeping of unspecific nuclease activity in cells at a low level. Analyses of plots of the time- dependent DNA methylation by the enzymes, isolated from bacterial preparations cultivated under various conditions (solid and liquid synthetic and organic media with earation and without of it), demonstrated that aeration and organic medium were the deciding conditions responsible for high level of the methylase activity. The shape of plot of DNA methylation by the enzymes from M. butiricum was similar irrespective of the conditions of cultivation--maximal rate of methylation occurred within 2-3 hrs of incubation and was maintained within 22 hrs. The stable content of methylated DNA-acceptor, within long-term periods of incubation, correlated with the low level of nucleases since viscosity of DNA from Cd phage was unaltered after incubation with the enzyme preparation from M. butiricum. The M. butiricum strain appears to be valuable for identification of restrictases.