[The use of nucleolytic enzymes (ribonucleases, polynucleotide phosphorylases and endonuclease from Serratia marcescens) for producing initial blocks of synthetic endoribonucleases].

The simplest variant of synthetic substrate-ribozyme complex has been proposed. The schemes of potential ribozyme "subunits" synthesis have been worked out: R1--GCUUGAAACAAA; R2--AAAAACUGAUGAAAGC. The macroscale synthesis of dinucleoside monophosphate ApU, GpC, CpU catalyzed by immobilized ribonucleases of different specificity and preparation of oligoadenylates by hydrolysis of poly-A in the presence of endonuclease Serratia marcescens, as well the synthesis of conservative sequences of potential ribozyme such as ApUpG, CpUpG, GpApU, ApApApG and others have been described.

[Substrate specificity of T4 RNA-ligase. The effect of the nucleotide composition of substrates and the size of phosphate donor on the effectiveness of intermolecular ligation].

Nucleoside 2' (3'),5'-diphosphates, dinucleotides pApA, pApC, pApU, pGpC, pCpC, pUpU (phosphate donors), and trinucleoside diphosphates, such as NpCpC, NpCpU, NpUpC, NpUpU and GpApN (N = U, C, A or G; phosphate acceptors) were used to study the substrate specificity of T4 RNA ligase. Relative efficiency of the mono- and dinucleotide donors depends on the 5'-terminal nucleoside moiety of the dinucleotide: upon ligation with the minimal phosphate acceptor GpUpC, dinucleotides pApA, pApC, and pApU are more effective than nucleotide diphosphate pAp; pGpC is more effective than pGp; efficiencies of pCpC and pCp are almost identical, and efficiency of pUpU is slightly lower than that of pUp. In relative efficiency, dinucleotide donors, varying only in 5'-terminal unit, do not correspond to mononucleotides: pApC greater than pCpC greater than pGpC and pCp greater than pUp approximately pAp much greater than pGp.

[Enzymatic incorporation into oligonucleotides of modified nucleosides].

Behaviour of modified nucleosides, tRNA components, and their analogues has been studied in the internucleotide bond formation catalysed by ribonucleases of various substrate specificity, polynucleotide phosphorylases, and T4 RNA ligase and the results are summarised in this paper. Pseudouridine, dihydrouridine, ribothymidine, 5-methylcytidine, inosine, and 6-methyladenosine can participate in the reaction of internucleotide bond formation the presence of most ribonucleases used, viz. Pb2, Pcl2, Pb1, Pch1, C2, T1, pancreatic RNase.

[Synthesis of fragments of the D-branch of yeast valine tRNA1 and their analogs].

Nonanucleotide GpUpCpUpApGpDpCpGp corresponding to the fragment 10-18 of the yeast tRNA1Val with pseudouridine-13 replaced by uridine has been synthesized. Dihydrouridine derivatives were studied as substrated of ribonucleases with various specificity and of RNA ligase.