[An inhibitor of translation in cellular mRNA containing the 100S structure from Krebs II ascites carcinoma cells infected with encephalomyocarditis virus]. / Ingibitor transliatsii v sostave soderzhashchego kletochnuiu mRNK 100S-struktury v zarazhennykh virusom éntsefalomiokardita kletkakh astsitnoi kartsinomy Krebs II.

As shown previously, the bulk of cellular mRNA in Krebs II ascite carcinoma cells infected with encephalomyocarditis virus during active virus-specific synthesis is bound to ribosomes within the 100S structure which is inactive in protein synthesis. In order to elucidate the reasons for the translation repression of cellular mRNA within the 100S structure, a fraction of loosely bound proteins which are liberated by treatment of the 100S structure with 0.5 M KCl an which contain sum translation factors, was obtained. This fraction was shown to contain an inhibitor which non-specifically represses the translation of endogenous viral and cellular mRNA within the composition of polyribosomes and of exogenous poly(A)-containing cellular mRNAs from ascite carcinoma cells.

[4,5-S-RNAI in virus-specific polyribosomes from ascitic Krebs 2 carcinoma cells infected with encephalomyocarditis virus]. / 4,5S-RNKI v sostave virusspetsificheskikh poliribosom iz kletok astsitnoi kartsinomy Krebs 2, zarazhennykh virusom éntsefalomiokardita.

Polyribosomes of Krebs 2 ascite carcinoma cells non-infected and infected with encephalomyocarditis (EMC) virus contain a heterogeneous population of low molecular weight small RNAs. Analysis of the RNAs by polyacrylamide gel electrophoresis did not reveal any qualitative differences in the small RNA sets within the composition of polyribosomes from virus-infected and non-infected cells. However, the content of one of the small RNAs was markedly elevated in polyribosomes from virus-infected cells. As can be followed from partial determination of its primary structure, this small mRNA is identical to 4,5S-RNAI previously detected in the nuclei of Novikov hepatoma cells of the rat. The data obtained suggest that 4,5S-RNAI can be involved in the regulation of protein synthesis in virus-infected cells.

[Ability of translation factors from infected encephalomyocarditis viruses of ascites carcinoma cells to maintain the protein-synthetizing activity of cellular polyribosomes]. / Sposobnost' faktorov transliatsii iz zarazhennykh virusom éntsefalomiokardita kletok astsitnoi kartsinomy podderzhivat' beloksinteziruiushchuiu aktivnost' kletochnykh poliribosom.

A highly effective protein-synthesizing system fully dependent on translation factors was isolated from the ascite Krebs-2 carcinoma. The effect of EMC-infection on the ability of these factors to maintain the translation of polyribosomes containing cell mRNA was studied. It was shown that the activity of translation factors of infected cells does not differ from that of non-infected cells in terms of their ability to maintain the protein-synthesizing activity of cell polyribosomes in vitro.

[Structure containing cellular mRNA in picornavirus infections]. / Struktura, soderzhashchaia kletochnuiu mRNK pri pikornavirusnoi infektsii.

The fate of cellular mRNA upon infection of Krebs-2 ascites carcinoma cells with encephalomyocarditis (EMC) virus was investigated. The cell mRNA was discovered in a structure with a sedimentation coefficient of about 100S and a buoyant density of 1.50--1.519 g/cm3 during active virus-specific synthesis (3.0--4.0 hr post infection). The template activity of the 100S structure in a cell-free protein-synthesizing system and of mRNA isolated from it was studied and the nature of synthesized products was analyzed. It was shown that the 100S structure seems to be translationally inactive. On the contrary, the RNA isolated from its is functionally active.

[Virus-specific proteins associated with components of protein-synthesizing systems in Krebs II ascites carcinoma cells infected with encephalomyocarditis virus]. / Virusspetsificheskie belki, sviazannye s komponentami beloksinteziruiushchei sistemy v kletkakh astsitnoi kartsinomy Krebc II, zarazhennyx virysom zntsefalomiokardita.

Extracts from encephalomyocarditis (EMS) virus infected Krebs II ascites carcinoma cells pulse-labeled during the active virus-specific synthesis and then chased were fractionated in a sucrose concentration gradient. It has shown that some radioactivity was detectable in the polysome region as well as in the regions of ribosome monomers and ribosomal subunits. An analysis of the radioactive material in a CsCl density gradient and by polyacrylamide gel electrophoresis has shown that components of the protein-synthesizing system in infected cells are bound to some proteins, the electrophoretic mobility of which corresponds to that of polypeptides found in the infected cells, namely, polypeptides G 16 (18 kdalton) and 22 (22 kdalton). The ribosomes from normal cells were also found to be associated with three labeled polypeptides, their molecular weight (89-90, 43-48 and 39-40 kdalton) being different from those of the polypeptides bound to the ribosomes from the infected cells. Thus, the presence of polypeptides G and 22 is specific for ribosomes isolated from the infected cells. The possible significance of this binding is discussed.