[The effect of modification of tRNA nucleotide-37 on the tRNA interaction with the P- and A-site of the 70S ribosome Escherichia coli].

A modified nucleotide on the 3'-side of the anticodon loop of tRNA is one of the most important structure element regulating codon-anticodone interaction on the ribosome owing to the stacking interaction with the stack of codon-anticodon bases. The presence and identity (pyrimidine, purine or modified purine) of this nucleotide has an essential influence on the energy of the stacking interaction on A- and P-sites of the ribosome. There is a significant influence of the 37-modification by itself on the P-site, whereas there is no such one on the A-site of the ribosome. Comparison of binding enthalpies of tRNA interactions on the P- or A-site of the ribosome with the binding enthalpies of the complex of two tRNAs with the complementary anticodones suggests that the ribosome by itself significantly endows in the thermodynamics of codon-anticodon complex formation. It happens by additional ribosomal interactions with the molecule of tRNA or indirectly by the stabilization of codon-anticodon conformation. In addition to the stacking, tRNA binding in the A and P sites is futher stabilized by the interactions involving some magnesium ions. The number of them involved in those interactions strongly depends on the nucleotide identity in the 37-position of tRNA anticodon loop.

[Selective effect of inductors of apoptosis on the endoribonuclease activity of 26S proteasomes and alpha-RNP particles in K562 cells: possible involvement of 26S proteasomes and alpha-RNP in the regulation of RNA stability]. / Differentsial'naia reguliatsiia éndoribonukleaznoi aktivnosti 26S-proteasom i alpha-RNP-chastits pri deistvii induktorov apoptoza na kletki linii K562: vozmozhnoe uchastie alpha-RNP-chastits i proteasom v kontrole nad stabil'nost'iu RNK pri programmirovannoi kletochnoi gibeli.

It has been shown that endoribonuclease activity of alpha-RNP particles and 26S proteasomes are changed under the action of inductors of programmed cell death. Treatment of K562 cells with inductors of apoptosis--doxorubicin (adriamycin) and diethylmaleate--lead to a significant stimulation of RNAse activity of alpha-RNP and to reduction of proteasome RNase activity. The enzymatic activity under study has been shown to be specifically and selectively dependent on phosphorylation of subunits of alpha-RNP particles and 26S proteasomes. The characteristics of RNAse activity of different subpopulations of proteasomes differ. The specificity of a subpopulation of proteasomes exported from the cell has been demonstrated. Proteasome and alpha-RNP involvement in the coordinated control of stability of various specific messenger RNA molecules is suggested, and one of the mechanisms of this control might be the export of specific subpopulation of proteasomes from the cell.