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Some fractions of low molecular weight (LMW) nuclear RNAs were shown to be present in the cytoplasm of rat liver cells. In addition to known 4S tRNA, 5S and 5,8S rRNAs U3 and 8S1 LMW nuclear RNAs, 8SII and 8SIII LMW RNAs have been detected in RNA preparations of free total and membrane-bound polysomes. The U3 and 8SI polysoma I RNAs seem to be associated with high molecular weight polysomal RNA. Using thermal phenol fractionation, that some LMW RNAs were shown to be slightly bound to the cellular structures whereas some others are bound more tightly. Considerable amounts of LMW RNAs are tightly bound to the chromosome-nucleolar apparatus. They can be extracted only at 85 degrees C. The data presented are discussed with regard to LMW nuclear and polysomal RNAs functions.

The fractional composition of serum lipoproteids in patients with malignant tumours and in noncancerous disorders as well as in healthy donors has been investigated to detect the cancer specificity of the appearance of the additional abnormal RNA-lipoprotein fraction. No distinct correlation is found between the presence of the additional serum lipoprotein fraction and human malignancy.

Pepsinogen mRNA is shown to be the major fraction of rat poly (A)+RNA. It codes polypeptide with molecular weight of about 45 kD. Changes in the pepsinogen mRNA content at the early stage of carcinogenesis are nonspecific and are due to the toxic effect of MNNG. Steady shifts in the quantity of pepsinogen mRNA are found between the 1st and 3d months. Pepsinogen mRNA content decreases down to the half of the normal one between the 3d and 6th months. A quantity of RNA capable to be a template for pepsinogen synthesis is reduced by more than 90% in the MNNG induced tumour. The pepsinogen production defect in gastric mucosa neoplasia is mainly due to pepsinogen mRNA synthesis damage.

An attempt was made to elucidate the possible participation of low molecular weight nuclear RNAs in the transcription process. The parameters of the RNA synthesis cell-free system in isolated rat liver nuclei were studied for this purpose. Tissue homogenization in isotonic sucrose during isolation of the nuclei resulted in a loss of 4S nuclear RNA. The dependence of RNA synthesis on the salt concentration in the incubation medium is indicative of possible initiation of the RNA synthesis in this system. At salt concentration of 0.08 M 50-75% of incorporation is due to the activity of RNA polymerase II. Under these conditions the electrophoretically homogenous individual fractions of low molecular weight nuclear RNAs do not affect specifically the activity of RNA polymerase II. No evidence for the participation of low molecular weight nuclear RNAs in the mechanisms of heterogeneous nuclear RNA synthesis were obtained.

The results of investigations on total nucleic acids content and RNA turnover in the cells of tumor NK/Ly and of the spleen in tumor-bearing mice after single exposure to fast electrons are described. In every case the irradiation results in reliable changes of parameters under study. The pattern of changes in nucleic acids content and turnover in the spleen after the exposure to fast electrons is in a good agreement with the available data concerning the influence of x- and y-radiation. The irradiation action on nucleic acids content and turnover in ascites tumor NK/Ly cells is qualitatively and quantitatively similar to that in splenic cells.

Apart from heterogeneous high-molecular DNAs, two fractions corresponding to 17 and 20 MD of DNA and homogeneous with respect to mobility are to be found in preparations of nucleic acids of rat blood serum. The former fraction (17 Md) is greater than the latter in healthy animals. This ratio is reversed in the blood serum of rats with Zajdela's hepatoma. The relative predominance of 20 Md DNA is still more pronounced in ascitic liquid which washes tumor cells.

We have shown that 8S and U2 fractions of low molecular weight nuclear RNA lmwn RNA) have tow stable conformational states with different electrophoretic mobilities. We have shown also that fractions UIa and UIb are conformational isomers. Fractions 8S and U2 are present only in one conformational state during electrophoresis, while UI RNA is always represented by both conformations. The conformation of lmwn RNAs is dependent upon conditions of isolation of nuclei and of extraction of RNA. It may change during storage of water solution of RNA at -20 degrees. Conformational changes discovered are not the result of degradation. Only one of two stable conformations of any lmwn RNA may be physiologically active, as it is the case of 5S rRNA and tRNAS. One ought to keep this in mind while studying the functions of low molecular weight nuclear RNAs.

The cell-free translation method has shown that pepsinogen mRNA is a predominant fraction in the total poly(A)+ RNA from human gastric mucosa. The pepsinogen protein with the molecular weight of 45 kDa has been identified. The level of pepsinogen mRNA decreased in tumours as compared with normal mucosa but in most cases pepsinogen mRNA synthesis depression was not total.

An attempt was made to elucidate possible participation of low molecular weight nuclear RNA's (LMWN RNA's) in the transcription process. For this purpose, we studied the effect of individual fractions of LMWN RNA's, isolated by polyacrylamide gel electrophoresis, on the endogenous RNA synthesis in isolated nuclei. We have found no influence of LMWN RNA's on the incorporation of labeled precursors in the acid-insoluble material under the conditions when RNA polymerase I is predominantly active. The results obtained thus indicate that LMWN RNA's do not participate in the regulation of 45S pre-rRNA synthesis and they do not belong to limiting factors in pre-rRNA synthesis.

Low molecular weight nuclear RNAs (LMWN RNAs) from rat liver, Zajdela hepatoma and rat hepatoma induced by DENA have been studied. The changes in the relative content of nucleoplasmic U1 and U2 RNAs, nucleolus U3 RNA and chromatine 5S RNA have been discovered in both hepatomas. Whereas 8S1 and U3 RNA were found in polysomes from rat liver but not in those from Zajdela hepatoma.

The standard analytical and preparative electrophoresis in polyacrylamide gel did not reveal qualitative differences in the fraction composition of c-RNA of the ascitic tumour cells (Zaidel hepatoma, Ehrlich carcinoma, NK/ly lymphoma) and normal liver cells. In vitro the tumour and normal cells efficiently incorporated the labeled uridine into the all main classes of c-RNA (4S, 18S, 28S, fractions above 28S), the process being more intensive in the tumour cells. The presence of tumours in the animal organism had a significant effect on RNA biosynthesis in the liver, the effect being dependent on the tumor nature. Lucantone (miracyl D) had practically no effect in vitro on the quantitative content of the summation c-RNA and its fractions in all cells studied. However, it markedly inhibited the metabolism of the main fractions of c-RNA in the cells of Zaidel hepatoma and Ehrlich carcinoma. The effect of lucatone in the cells of NK/ly lymphoma was contrary.