[Alkylation of nucleic acid components with ethylenimine and its derivatives. IV. Alkylation of homopolynucleotides and DNA]. / Alkilirovanie komponentov nukleinovykh kislot étileniminom i ego proizvodnymi. IV. Alkilirovanie gomopolinukleotidov i DNK.

Alkylation of homopolynucleotides and DNA by thio TEPA and monoaziridine diethyl phosphate was studied. The modification affected nucleic bases and terminal phosphate groups but not internucleotide phosphate groups. It was shown that the main center of modification in poly(A) was the N1 atom, whereas the products of N6- and N3-alkylations were formed in smaller amounts. In poly(G), the alkylation proceeded predominantly at the N7 and, insignificantly, at the N1 atom of guanine; the pyrimidine N3 atom is alkylated poorly in poly(C) and even worse in poly(U). In the case of DNA, the major alkylated sites are the guanine N7 and the adenine N3; this results in DNA denaturation and the subsequent formation of products modified at N1 and N6 of adenine, N1 of guanine, and N3 of cytosine. An increase in the pH and ionic strength of the solution as well as the DNA denaturation decrease the reaction rate, whereas ultrasonic fragmentation enhances it. Upon alkylation, melting temperatures decrease, CD and UV spectra change, and DNA luminescence appears. To separate the reaction mixtures and identify the DNA alkylation products, chemical hydrolysis, ion-exchange and reverse-phase HPLC, and UV spectroscopy were used.

[The mutagenic effect of the recombinant plasmid pBR322ins carrying a native and a modified human insulin gene]. / Mutagennyi éffekt rekombinantnoi plazmidy pBR322ins, soderzhashchei nativnyi i izmenennyi gen insulina cheloveka.

The mutagenic activity of pBR322 bacterial plasmid DNA and of pBR322ins and pBR322insN recombinant plasmid DNAs has been investigated in Blld-ii-FAF 28 line cultivated fibroblasts of Chinese hamster. The pBR322 bacterial plasmid DNA is shown to induce no resistant mutations to 6-mercaptopurine; the pBR322insN (the frameshift mutation in human insulin gene; this gene is supposed to have no expression in the cells because of frameshift mutation) induces neither such mutations as well. The pBR322ins recombinant plasmid carrying the native human insulin gene induces the gene mutations in this system. The influence of the insulin gene structure on the gene mutations induction is taken into account. The results obtained and the data of other authors illustrate a great interest of recombinant DNA molecules carrying transgenes in the field of mutation research.

[The induction of mutations in 6-mercaptopurine resistance in Chinese hamster cells under the action of the recombinant plasmid pAins containing the human insulin gene]. / Induktsiia mutatsii rezistentnosti k 6-merkaptopurinu v kletkakh kitaiskogo khomiachka pod deistviem rekombinantnoi plazmidy pAins, soderzhashchei gen insulina cheloveka.

The mutagenic activity of the pUC19 bacterial plasmid DNA and the pAins recombinant plasmid DNA carrying human insulin gene has been investigated. Both pUC19 and pAins plasmid DNAs have been shown to induce the gene mutations in hprt locus of Chinese hamster cell line. The high level of the gene mutations (similar to the indices of the gene mutations induced by the chemical mutagens) has been in the focus of attention. The conclusion has been made concerning impossibility to use pAins plasmid DNA in the diabetes mellitus gene therapy. It is necessary to test the mutagenic properties of the DNA molecules produced for gene therapy of human inherited diseases.

[Alkylation of nucleic acid components by ethyleneimine derivatives. I. Alkylation of bases]. / Alkilirovanie komponentov nukleinovykh kislot proizvodnymi étilenimina. I. Alkilirovanie osnovanii.

In the course of investigating the reaction conditions of the nucleic acid components alcylation, the interaction of thioTEPA (N,N',N''-triethylenethiophosphoamide) with hydrochloric and perchloric acids was studied, perchloric acid increasing the alkylation products yield. HPLC and UV spectroscopy were used to isolate and identify products of nucleic bases alkylation by ethylenimine and its derivatives (thioTEPA and monoaziridinediethylphosphate). It is shown that under neutral conditions phosphoaminoethylation takes place, whereas under slightly acidic conditions products of aminoethylation are formed.

[Thymidine transport and its incorporation into the cellular DNA of Ehrlich ascites cancer and Zajdela's ascitic hepatoma in the presence of thiophosphamide and thiophosphamide-modified DNA]. / Transport timidina i vkliuchenie ego v DNK kletok astsitnogo raka Erlikha i astsitnoi gepatomy Zaidela v prisutstvii tiofosfamida i modifitsirovanoi im DNK.

Antitumour agents, thiotepa and alkylated DNA, inhibit the transport of thymidine in the cells within the first minutes of incubation. Penetration of the exogenous DNA in the Ehrlich ascites tumour cells and stimulation of this process with dimethylsulfoxide are shown. The possible mechanism of the antitumour effect of alkylated DNA is discussed.