[Intragenomic polymorphism of the primary structure of 5S rRNA gene variants of the loach (Misgurnus fossilis L.). Determination of the transcriptional activity]. / Vnutrigenomnyi polimorfizm pervichnoi struktury variantov genov 5S rRNK v'iuna (Misgurnus fossilis L.). Opredelenie transkriptsionnoi aktivnosti.

The primary structure of 12 cloned repeats of loach oocyte 5S rRNA genes was determined. The heterogeneity of nucleotide sequences was revealed in the coding regions and spacer of the genes. The results of the study on in vivo transcriptional activity of the cloned 5S rRNA gene variants are consistent with the localisation of site specific base substitutions in the coding part affecting the transcription. We have compared the nucleotide sequences of loach 5S rRNA gene variants and of Xenopus laevis, X. borealis and Bombyx mori 5S genes which can be actively transcribed in X. laevis oocyte nuclei. As a result we could propose a consensus nucleotide sequence in the internal control region (from 45-th up to 100-th nucleotide) of the eukaryotic 5S rRNA gene. This sequence comprises a RNA-polymerase III promotor and stretches interacting with transcriptional factors. We have considered the base substitutions in the nucleotide sequences of 5S gene variants exerted on the experimental model of loach 5S rRNA secondary structure. All base substitutions in actively transcribed genes do not influence the general double-stranded structures of the transcripts. However in 5S RNA transcripts from genes with low transcriptional activity base substitutions affecting the box c RNA-polymerase III promoter destroy hairpin II interacting with ribosomal proteins. We have concluded that two factors can restrict the divergency of 5S rRNA genes: (1) conservation of the nucleotide sequence in the gene internal control region, and (2) conservation of the general double stranded structures in 5S rRNA transcripts.

[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.