[Fragmentation of the coding region chromatin of trp-dioxygenase (to) and tyr-aminotransferase (tat) genes in their active and repressed state by micrococcal nuclease].

The blot-hybridization technique-assisted we have studied the pattern of fragmentation by mirococcal nuclease (MNase) of DNA tyr-aminotransferase (tat) and trp-dioxygenase (to) genes in active (in rat cell liver nuclei) and repressed (in brain nuclei) states. It was provided, over a wide range of enzyme concentration two types of fragments are mainly produced: near full-size to- and tat-transcription unit (19,000 and 11,000 bp, respectively) and their large (from 1500 bp) heterogeneous in length. To-and tat-fragments of both kinds are preserved in hydrolyzates at limit of MNase digestion of total chromatin DNA when nuclease breaks occur in nearly all accessible sites of chromatin.

[Contractile proteins in the fractions of soluble and insoluble chromatin of liver and thymus].

The proteins corresponding in molecular weight and solubility in salt solutions to skeletal muscle actin and myosin were revealed in liver and thymus chromatin fragments. When the ionic strength reached 0.3, about 60% of the myosin-like protein identified by electrophoretic mobility of high chains and the K+-EDTA-ATPase activity was cosedimented with nucleohistones.

[Planar model of nucleosome and chromatin structure of high orders].

A model of nucleosome is discussed, which consists of two nucleohistone strand folds, located at the same level, similarly directed and having a rhomboid form. The folds are symmetric to each other. Four histones (H3, H2a, H2b and H4) take part in the formation of each fold.

[Comparative characteristics of the "ultrasonic" fractions of rabbit leukocyte (neutrophil) and brain chromatin].

Ratios and composition of "ultrasonic" fractions of chromatin in cells with different transcription intensity were studied. The hardly extracted residual fraction of chromatin makes up to about 80% DNA in leukocytes (neutrophils) and about 20% in brain tissue. Comparative characterization of fractions showed that residual DNP of brain and liver include, in addition to fragments of inactive condensed chromatin, the sites actively involved in the synthesis of RNA.