[Effect of of distamycin A on histone H1 methylation, extraction and formation of UV-inducible crosslinks with DNA in the interphase rat liver nucleus].

Incubation in vitro of rat liver nuclei in the presence of S-adenosyl[methyl-(3)H]methionine ([(3)H] SAM) leads to incorporation of the radioactive label not only into core-histones H3 and H4, but also into linker histone H1. Addition of distamycine A to the incubation medium stimulates label incorporation into histone H1 ~ in 6 times and into histone H3 ~ in 2 times. The presence of distamycine facilitates histone H1 extraction by polyglutamic acid (poly(Glu)) and decreases of UV-induced DNA-histone cross-links formation. These effects give evidence of weakening of H1-chromatin interaction by distamycin to be results of histone H1 position change relative to nucleosome and(or) disturbance of histones H1-H3 interactions so as these histones are exposed to additional methylation.

[Dependence of RNA synthesis in the cell of Physarum polycephalum on concentration and activity of RNA-polymerase II]. / Sintez RNK v kletochnom tsikle Physarum polycephalum v zavisimosti kontsentratsii i udel'noi aktivnosti RNK-polimerazy II.

The RNA synthesis detected by incorporation of [H3]uridine chase label proceeds in macroplasmodium and in isolated nuclei throughout the cell cycle of a synchronous myxomycetes culture of Physarum polycephalum, producing two well-shaped peaks at the postmitotic and premitotic steps. Such RNA synthesis is due to the activity of alpha-amanitin-sensitive RNA-polymerase II. Concentrations of RNA-polymerase II at various steps of the cell cycle were determined by alpha-amanitin titration; the specific activity of the enzyme was assayed. The increase in the rate of mRNA synthesis was accompanied by a rise in the concentration and specific activity of the enzyme: for the postmitotic peak, for instance, the corresponding values were about 2-2.5 and 2-4 times as high as minimum values revealed during the cycle. The results obtained are discussed in terms of transcription control in eukaryotic systems.