卷 43, 编号 1 (2017)

We have investigated the role of Tyr-203, His-270, and Lys-249 amino acid residues from the 8-oxoguanine glycosylase (hOGG1) active site in the process of recognition of 7,8-dihydro-8-oxoguanine (oxoG) damaged nucleotide and in the catalytic stages of enzymatic reaction. The pre-steady state kinetic analysis of conformational transitions of mutant forms of the enzyme and model DNA substrates during the enzymatic process revealed that the studied amino acid residues are involved in the specific binding of DNA substrates. The Tyr-203 is responsible for recognition of the damaged nucleotide; interaction between His-270 and DNA is necessary for the formation of the catalytically active complex with the oxoG-containing DNA. The Lys-249 acts not only as one of the catalytically important amino acids of the active site of the enzyme, but also plays a significant role in the formation of specific enzyme–substrate complex. The present study significantly complements the molecular-kinetic model of the enzymatic reaction and helps to clarify the origin of the high specificity of hOGG1 to oxidized bases in DNA.

Many proteins specific for rare targets in DNA, such as transcription factors, restriction endonucleases, and DNA repair enzymes, search for their targets by one-dimensional diffusion along DNA. One of these proteins is uracil-DNA glycosylase (Ung), which excises the uracil bases formed by rare events of cytosine deamination. We have studied the ability of Ung to move along DNA with its path hindered by bulky DNA covalent adducts (fluorescein) or ligands blocking the major or minor DNA groove. The fluorescein adduct strongly inhibits translocation only along double-stranded DNA, whereas noncovalently bound ligands partly inhibit DNA cleavage but barely affect translocation. The ability of uracil-DNA glycosylase to search for its targets in the presence of molecules competing for DNA binding may be important for DNA repair in the intracellular environment.

N-Sulfonyl phosphoramidate derivatives of oligodeoxyribonucleotides containing N-tosyl phosphoramidate groups are first reported. The synthesis is based on Staudinger reaction between tosyl azide and 3′,5′-dinucleoside β-cyanoethyl phosphite comprising the immobilized oligonucleotide, which is obtained by the phosphoramidite coupling during the solid-phase oligonucleotide synthesis. The N-tosyl phosphoramidate group was stable under conditions of the oligonucleotide synthesis, in particular, upon acidic detritylation followed by the removal of protective groups and cleavage from the polymer support by the treatment with concentrated aqueous ammonia at 55°C. The stability of DNA and RNA duplexes of the model oligonucleotides containing N-tosyl phosphoramidate groups was only slightly lower than that of native DNA:DNA and DNA:RNA duplexes, respectively.

Short double-stranded RNAs, depending on their structure, sequence, and the method of delivery to cells, can activate the system of innate and adaptive immunity. The immunostimulatory activity of nucleic acids can be used in antitumor and antiviral therapy. We have previously identified a biologically active immunostimulatory 19-bp dsRNA (isRNA) with 3′-nucleotide overhangs, which inhibits the proliferation of tumor cells, stimulates interferon synthesis, and suppresses the growth and metastasis of tumors. Here, we have studied the impact of chemical modifications in the isRNA structure and the type of the transfection agent on the antiproliferative and immunostimulatory properties of isRNA. It has been shown that the attachment of an aminohexyl group or a cholesterol residue to the 5′-terminus of the first strand of the isRNA duplex does not impair its antiproliferative and immunostimulatory properties in vitro and in vivo when it is used in complex with a transfection agent, whereas the modification at the 5′-end of the second strand has an adverse effect on the biological activity of isRNA. It has been found that, when used without the transfection agent, isRNA conjugated with a cholesterol residue does not display antiproliferative and immunostimulatory properties. The use of isRNA in complex with low-toxicity liposomes 2Х3-DOPE enhances its activity: the intravenous injection of the isRNA/2Х3-DOPE complex induces a 55-fold increase in the level of interferon α (INF-α) in the murine blood 6 h after the injection, which is significantly higher than the INF-α level after the injection of the isRNA/Lipofectamine 2000 complex. The cytoplasmic localization of isRNA is crucially important for the manifestation of its antiproliferative activity since the selective inhibition of the dsRNA cytoplasmic sensor PKR (dsRNA-dependent protein kinase R) by 2-aminopurine completely blocks the antiproliferative effect of isRNA.

The development of nanodevices for the efficient transport of therapeutic molecules is one of the most urgent problems of modern molecular medicine. Noncovalent agents for the delivery of nucleic acids (NA) including those based on gold nanoparticles (GNPs) represent an attractive alternative to covalent systems, since it is easier in this case to provide the controlled release of NA. We have demonstrated the possibility to create potentially biocompatible associates of GNPs containing alternating layers of oligonucleotides and other polymers as a promising platform for the delivery of oligonucleotides into living cells. The multilayer (five layers) coated GNPs can be assembled by the sequential treatment of gold nanoparticles with nonthiolated oligonucleotide (ON), thiolated carboxyl-polyethylene glycol (SH-PEG3000-COOH), and linear polyethyleneimine (PEI). We have developed an algorithm for the analysis of multilayer coated GNPs by gel electrophoresis, photon correlation spectroscopy, and transmission electron microscopy. The assembly of associates bearing two oligonucleotide layers and having a net positive surface charge has been described. Multilayer coated GNPs were shown not to degrade in the presence of a high concentration of the major blood protein, serum albumin.

A convenient approach has been proposed to the synthesis of nicotinamide adenine dinucleotide (NAD⁺) mimetics, which comprise morpholino analogues of nucleosides. The approach is based on the use of ADP conjugates containing an amino group, which is tethered to the terminal phosphate through the aliphatic linker by the phosphodiester bond. We have synthesized four series of the NAD⁺ mimetics, which differ in the type of the modified nucleoside (2-aminomethylmorpholine (Mor) or 2-aminomethyl-4-carboxymethylmorpholine (MorGly) derivatives), in the linker length, and in the manner of the nucleoside attachment to the ADP derivative. We have studied the efficiency of NAD⁺ mimetics in the inhibition of the auto-poly(ADP-ribosyl)ation by the PARP 1 enzyme. The linker length, the mode of the attachment of the morpholino nucleoside analogue, and the nature of the heterocyclic base of the modified nucleoside were shown to inf luence the inhibition efficiency.

Antihistamine activity of recombinant peptides, Kunitz-type serine protease inhibitors of the sea anemone Heteractis crispa, was studied. It was shown that the peptides rHCGS1.19 and rHCGS1.36 at a concentration 10 μM inhibit an increase in the calcium ion concentration in macrophages elicited by histamine at 62.2 and 84.0%, respectively. The anti-inflammatory effect can be seen as the result of mediated reactions between peptides and proteases involved in these processes, as with the histamine H₁-type receptor blocking.