[Degradation of messenger RNA, ribosomal RNA and 2-5A-dependent inhibition of protein biosynthesis]. / Degradatsiia matrichnoi RNK, ribosomnoi RNK i 2-5A-zavisimoe ingibirovanie biosinteza belka.

In rabbit reticulocyte lysates the addition of exogenous 2-5A leads after 10-20 minutes to the inhibition of protein synthesis. This inhibition can be blocked by rat antiserum to 2-5A. In intact ribosomes the ribosomal RNA is cleaved after 2-5A addition, but this cleavage is not in correlation with the protein synthesis shutoff. Ribosomal 5S RNA and 5,8S RNA are not cleaved even after several hours of incubation with 2-5A. The degradation of polysome associated mRNA correlates with the protein synthesis inhibition as revealed by Northern blot hybridization of globin mRNA with 32P-labelled p beta G plasmid. The addition of 2-5A antiserum to the rabbit reticulocyte lysate also inhibits the degradation of polysome bound globin mRNA.

[Secondary structure of the 5'-terminal region of the 18S ribosomal RNA5.3S fragment from the rat liver]. / Vtorichnaia struktura 5'-kontsevogo 5,3S fragmenta 18S ribosomnoi RNK pecheni krys.

Two small RNA fragments, 5,3S and 4,7S, were observed in gel electrophoretic analysis of RNA of the 40S ribosomal subunit of rat liver. 5,3S RNA (134-136 nucleotides long) proved to be 5'-terminal fragment of 18S ribosomal RNA, whereas 4,7 RNA is the degradation product of 5,3S RNA with 27-28 5'-terminal nucleotides lost. The secondary structure of 5,3S RNA was probed with two structure-specific nucleases, S1 nuclease and the double-strand specific cobra venom endoribonuclease. The nuclease digestion data agree well with the computer generated secondary structure model for 5,3S RNA. This model predicts that the 5'-terminal part of rat liver ribosomal 18S RNA forms an independent structural domain. The affinity chromatography experiments with the immobilized 5,3S fragment show that 5,3S RNA does not bind rat liver ribosomal proteins.

[Binding of Escherichia coli 50S ribosomal subunit proteins with two large 5S RNA fragments]. / Sviazyvanie belkov 50S subchastitsy ribosomy Escherichia coli s dvumia krupnymi fragmentami 5S RNK.

Two fragments containing sequences from 1-41 nucleotide (small fragment) and from 42-120 nucleotide (large fragment) were isolated from E. coli 5S RNA T1 RNase partial digest. Affinity chromatography of 50S ribosomal proteins on the immobilized 5S RNA fragments revealed the ability of the large fragment to give a complex only with protein L25. The small fragment did not bind ribosomal proteins. The intact and reassociated 5S RNA forms a complex consisting of proteins L5, L18, L25.

[Conformational isomers of rat liver 5S ribosomal RNA]. / Konformatsionnye izomery 5S RNK ribosom pecheni krysy.

The rat liver 5S RNA when denaturated by urea or EDTA, or even without any special treatment, undergoes conformational changes leading to the formation of three electrophoretically distinct isomeres of the molecules with relative mobilities 0.39, 0.44 and 0.47. The band with the slowest mobility corresponds apparently to the native 5S RNA since it is specific for both freshy isolated and renaturated 5S RNA. Moreover, it was found that denaturation of the immobilized 5 S RNA decreases significantly its ability to form a complex with the rat liver 60S ribosomal subunit proteins L6, L7, L8, L18 and L35.