[DNA Sequence-Specific Ligands. 19. Synthesis, Spectral Properties, Virological and Biochemical Studies of DB3(n) Fluorescent Dimeric Trisbenzimidazoles].

In this work, we synthesized and characterized the properties of a series of new fluorescent DB3(n) narrow-groove ligands. DB3(n) compounds based on dimeric trisbenzimidazoles have the ability to bind to the AT regions of DNA. The synthesis of DB3(n), whose trisbenzimidazole fragments are linked by oligomethylene linkers of different lengths (n = 1, 5, 9), is based on the condensation of the MB3 monomeric trisbenzimidazole with α,ω-alkyldicarboxylic acids. DB3 (n) proved to be effective inhibitors of the catalytic activity of HIV-1 integrase at submicromolar concentrations (0.20-0.30 µM). DB3(n) was found to inhibit the catalytic activity of DNA topoisomerase I at low micromolar concentrations.

[SFPQ and NONO Proteins and Long Non-Coding NEAT1 RNA: Cellular Functions and Role in the HIV-1 Life Cycle].

About 20 years ago, large RNA-protein complexes called paraspeckles were discovered in cell nuclei. The main components of these complexes are SFPQ and NONO proteins and the long noncoding RNA NEAT1. Later, these proteins were found free in the nucleus and even in the cytoplasm. The functions of NEAT1 and paraspeckle proteins are quite diverse including retention of RNAs subjected to multiple editing of adenosine to inosine in the nucleus, response to DNA damage, transcription regulation, control of mRNA stability, regulation of splicing, and participation in the cell response to viral infection. Thus, there are numerous, albeit contradictory, data on the involvement of NEAT1, SFPQ, and NONO in the HIV-1 replicative cycle at its various stages. Here, we tried to briefly review the main cellular functions of NEAT1 RNA and SFPQ and NONO proteins. The goal of this review was also to summarize and, if possible, systematize the existing data on their role in the HIV-1 life cycle.

Genetic Engineering Systems to Study Human Viral Pathogens from the Coronaviridae Family.

The COVID-19 pandemic caused by the previously unknown SARS-CoV-2 Betacoronavirus made it extremely important to develop simple and safe cellular systems which allow manipulation of the viral genome and high-throughput screening of its potential inhibitors. In this review, we made an attempt at summarizing the currently existing data on genetic engineering systems used to study not only SARS-CoV-2, but also other viruses from the Coronaviridae family. In addition, the review covers the basic knowledge about the structure and the life cycle of coronaviruses.

[Genetic Engineering Systems to Study Human Viral Pathogens from the Coronaviridae Family].

The COVID-19 pandemic caused by the previously unknown SARS-CoV-2 Betacoronavirus made it extremely important to develop simple and safe cellular systems which allow manipulation of the viral genome and high-throughput screening of its potential inhibitors. In this review, we made an attempt at summarizing the currently existing data on genetic engineering systems used to study not only SARS-CoV-2, but also other viruses from the Coronaviridae family. In addition, the review covers the basic knowledge about the structure and the life cycle of coronaviruses.

[Main Approaches to Controlled Protein Degradation in the Cell].

One of the most informative methods to study the roles of individual proteins in cell functions is based on changing their intracellular concentrations. Genetic knockouts or knockdowns are most commonly used for the purpose. However, acting directly at the level of an expressed protein is more informative or convenient to perform in some cases. This action should ideally be controlled in time and reversible. The review analyzes the current data on systems developed to achieve controlled degradation of proteins via their ubiquitination with subsequent proteasome-mediated degradation or other mechanisms.

[Role of Cellular DNA Repair Systems in HIV-1 Replication].

A serious problem in the treatment of HIV infection is the emergence of drug-resistant forms of the virus. One promising approach to solving this problem is the development of inhibitors of the interaction between viral proteins with cellular co-factors. However, the development of this approach is hampered due to the lack of knowledge about the involvement of cellular proteins in the pathogenesis of HIV infection. In particular, it is known that the integration of viral DNA into the host genome generates numerous lesions in the cellular DNA, the repair of which is absolutely necessary for successful replication of the virus. However, it is still unknown which cellular proteins are involved in repairing this damage. In this review, we summarize what is known to date about the role of cellular repair systems in the replication of HIV-1 in general, and in the repair of damage that occurs during the integration of viral DNA into a cell's genome, in particular.

Consensus Integrase of a New HIV-1 Genetic Variant CRF63_02A1.

The high genetic variability of the human immunodeficiency virus (HIV-1) leads to a constant emergence of new genetic variants, including the recombinant virus CRF63_02A1, which is widespread in the Siberian Federal District of Russia. We studied HIV-1 CRF63_02A1 integrase (IN_CRF) catalyzing the incorporation of viral DNA into the genome of an infected cell. The consensus sequence was designed, recombinant integrase was obtained, and its DNA-binding and catalytic activities were characterized. The stability of the IN_CRF complex with the DNA substrate did not differ from the complex stability for subtype A and B integrases; however, the rate of complex formation was significantly higher. The rates and efficiencies of 3'-processing and strand transfer reactions catalyzed by IN_CRF were found to be higher, too. Apparently, all these distinctive features of IN_CRF may result from specific amino acid substitutions in its N-terminal domain, which plays an important role in enzyme multimerization and binding to the DNA substrate. It was also found that the drug resistance mutations Q148K/G140S and G118R/E138K significantly reduce the catalytic activity of IN_CRF and its sensitivity to the strand transfer inhibitor raltegravir. Reduction in sensitivity to raltegravir was found to be much stronger in the case of double-mutation Q148K/G140S.

[Nitrobenzofuroxane derivatives as dual action hiv-1 inhibitors]. / Proizvodnye nitrobenzofuroksanov v kachestve ingibitorov VICh-1 dvoinogo deistviia.

Human immunodeficiency virus first type (HIV-1) is a main cause of one of the most dangerous diseases, AIDS. The search for new inhibitors of the virus still remains an urgent task. One approach to suppress the HIV infection is to use a double-acting inhibitors, i.e. inhibitors directed to two stages of the viral life cycle. The catalytic domain of HIV-1 integrase has a similar spatial organization with ribonuclease (RNase H) domain of HIV-1 reverse transcriptase, and approach aimed to create HIV-1 integrase and RNase H double-acting is very promising. In this work we synthesized a series of 6-nitrobenzofuroxane derivatives and studied their ability to inhibit two viral enzymes - integrase and RNase H HIV-1.

[Role of DNA-dependent protein kinase in the HIV-1 replication cycle].

Human immunodeficiency virus type 1 (HIV-1) is among the best-studied viruses, but some aspects of HIV-1 biology remain obscure. The role of cell proteins in virus replication raises especially many questions. One of the proteins is DNA-dependent protein kinase (DNA-PK), which performs crucially important functions in the human body. DNA-PK is known to influence at least two stages in the HIV-1 life cycle, the integration of viral genome in cell DNA and transcription of the integrated provirus. Many details regarding this influence remain unresolved. The review summarizes the known data on the DNA-PK role in the HIV-1 life cycle and its influence on the replication of other members of the family Retroviridae. In the beginning of this review there is a short explanation of the DNA-PK cellular functions that are especially important for understanding its role in the HIV-1 replication.

Host Proteins Ku and HMGA1 As Participants of HIV-1 Transcription.

Human immunodeficiency virus type 1 is known to use the transcriptional machinery of the host cell for viral gene transcription, and the only viral protein that partakes in this process is Tat, the viral trans-activator of transcription. During acute infection, the binding of Tat to the hairpin at the beginning of the transcribed viral RNA recruits the PTEFb complex, which in turn hyperphosphorylates RNA-polymerase II and stimulates transcription elongation. Along with acute infection, HIV-1 can also lead to latent infection that is characterized by a low level of viral transcription. During the maintenance and reversal of latency, there are no detectable amounts of Tat protein in the cell and the mechanism of transcription activation in the absence of Tat protein remains unclear. The latency maintenance is also a problematic question. It seems evident that cellular proteins with a yet unknown nature or role regulate both transcriptional repression in the latent phase and its activation during transition into the lytic phase. The present review discusses the role of cellular proteins Ku and HMGA1 in the initiation of transcription elongation of the HIV-1 provirus. The review presents data regarding Ku-mediated HIV-1 transcription and its dependence on the promoter structure and the shape of viral DNA. We also describe the differential influence of the HMGA1 protein on the induced and basal transcription of HIV-1. Finally, we offer possible mechanisms for Ku and HMGA1 proteins in the proviral transcription regulation.

Influence of Drug Resistance Mutations on the Activity of HIV-1 Subtypes A and B Integrases: a Comparative Study.

Integration of human immunodeficiency virus (HIV-1) DNA into the genome of an infected cell is one of the key steps in the viral replication cycle. The viral enzyme integrase (IN), which catalyzes the integration, is an attractive target for the development of new antiviral drugs. However, the HIV-1 therapy often results in the IN gene mutations inducing viral resistance to integration inhibitors. To assess the impact of drug resistance mutations on the activity of IN of HIV-1 subtype A strain FSU-A, which is dominant in Russia, variants of the consensus IN of this subtype containing the primary resistance mutations G118R and Q148K and secondary compensatory substitutions E138K and G140S were prepared and characterized. Comparative study of these enzymes with the corresponding mutants of IN of HIV-1 subtype B strains HXB-2 was performed. The mutation Q148K almost equally reduced the activity of integrases of both subtypes. Its negative effect was partially compensated by the secondary mutations E138K and G140S. Primary substitution G118R had different influence on the activity of proteins of the subtypes A and B, and the compensatory effect of the secondary substitution E138K also depended on the viral subtype. Comparison of the mutants resistance to the known strand transfer inhibitors raltegravir and elvitegravir, and a new inhibitor XZ-259 (a dihydro-1H-isoindol derivative), showed that integrases of both subtypes with the Q148K mutation were insensitive to raltegravir and elvitegravir but were effectively inhibited by XZ-259. The substitution G118R slightly reduced the efficiency of IN inhibition by raltegravir and elvitegravir and caused no resistance to XZ_259.

[The search of novel inhibitors of HIV-1 integrase among 5-(4-halogenophenyl)-5-oxopentyl derivatives of nucleic bases].

By alkylation of uracil, thymine, cytosine, adenine, 6-chloropurine, and 2-amino-6-chloropurine with 5-chloro-1-(4-halogenophenyl)-1-pentanones novel derivatives of nucleic bases were obtained, their physicochemical properties were studied. The influence of synthesized compounds on HIV-1 integrase was investigated.

Structural-Functional Analysis of 2,1,3-Benzoxadiazoles and Their N-oxides As HIV-1 Integrase Inhibitors.

Human immunodeficiency virus type 1 integrase is one of the most attractive targets for the development of anti-HIV-1 inhibitors. The capacity of a series of 2,1,3-benzoxadiazoles (benzofurazans) and their N-oxides (benzofuroxans) selected using the PASS software to inhibit the catalytic activity of HIV-1 integrase was studied in the present work. Only the nitro-derivatives of these compounds were found to display inhibitory activity. The study of the mechanism of inhibition by nitro-benzofurazans/benzofuroxans showed that they impede the substrate DNA binding at the integrase active site. These inhibitors were also active against integrase mutants resistant to raltegravir, which is the first HIV-1 integrase inhibitor approved for clinical use. The comparison of computer-aided estimations of the pharmacodynamic and pharmacokinetic properties of the compounds studied and raltegravir led us to conclude that these compounds show promise and need to be further studied as potential HIV-1 integrase inhibitors.

Clinical Use of Inhibitors of HIV-1 Integration: Problems and Prospects.

The HIV-1 integrase enzyme is responsible for one of the key stages of retroviral replication; it acts as a catalyst for the integration of viral cDNA into the cell's genome. Inhibitors of HIV-1 integration have been under development for over 10 years; yet, only one integration inhibitor, raltegravir, has been approved for clinical use so far. Raltegravir binds two metal ions in the enzyme's active centre and blocks one of the integration stages: the strand transfer. Unfortunately, the clinical use of raltegravir results in the development of viral resistance among some patients. Several more HIV-1 integration inhibitors are undergoing clinical trials at the moment. However, the structure and mechanism of action of those are similar to raltegravir, which results in the emergence of cross resistance with raltegravir. The present review is focused on the history of the development and clinical trials of raltegravir and its analogues, the problems connected with the emergence of viral resistance to integration inhibitors, and the prospect of their future clinical use.

Screening of Potential HIV-1 Inhibitors/Replication Blockers Using Secure Lentiviral in Vitro System.

The development and usage of safe cell systems for testing agents which possess anti-HIV activity is a very important factor in the design of new drugs. We have described in detail a system we designed that is based on lentiviral vectors (Prokofjeva et. al.,Antiviral Therapy,in print) for swift and completely safe screening of potential HIV-1 replication inhibitors. The system enables one to test the efficiency of the inhibitory activity of compounds whose action is directed towards either wild-type HIV-1 reverse transcriptase or integrase, or mutant enzymes corresponding to the drug-resistant virus form. Testing results of a number of already known drugs, which correlate well with published data as well as data on newly synthesized compounds, were obtained. Application of this system substantially broadens the possibilities of preclinical anti-HIV drugs testing.

[Approaches towards directed DNA integration by the use of retroviral integrases and transposases].

The ability of retroviruses and transposases to insert own genome into a host-cell allow us to consider them as a preferable object for constructing gene therapy vectors. However, enzymes that perform the insertion of the genetic material do not display a selectivity towards target nucleotide sequences that results in an almost random DNA introduction into the recipient cell genome. Random insertion leads to mutations which might cause a number of undesirable consequences including neoplastic transformation in the cell. Thereby, in order to achieve a successful functioning of retroviral and trasposonal genetic therapy systems, it is essential to modify them in such a way that directed integration of the vector in a target sequence in the human genome could be achieved. In the review approaches that have been developed for a high specific modification of genome, including the construction of hybrid proteins on the basis of retroviral integrases, transposases, as well as cellular factors interacting with these enzymes, are presented.

[HIV-1 integrase inhibition by dimeric bisbenzimidazoles having different spacers].

HIV-1 integrase is responsible for one of the key steps of the viral replication, integration of the viral cDNA into the host cell genome. Integration inhibition leads to complete block of the virus replication. In this study inhibition of integration by dimeric bisbenzimidazoles DBBI(7) with heptamethylene and DBBI(8) with tri(ethylene glycol) spacers was examined, and it was learned out that IC50 for DBBI(7) was about 0.03 microM, and IC50 for DBBI(8) was about 10 microM. By using cross-linking assays, it was shown that both compounds impeded a proper disposition of DNA-substrate at the active centre of integrase. Dissociation constants for complexes between either DBBI and DNA-substrate of integrase were determined. Calculated Kd values were 270 nM and 140 nM for complexes formed by DBBI(7) and DBBI(8), respectively. Therefore, inhibition of integration does not directly result from the binding of DBBIs with DNA. The dependence of initial rates of enzymatic reaction on the DNA-substrate concentration in presence of different concentrations of inhibitors was found, and inhibition constants were determined. All the data obtained allow us to suppose that the different inhibition activity of DBBI(7) and DBBI(8) results from the different mechanism of their binding: DBBI(7) is a competitive inhibitor of integrase whereas DBBI(8) is assumed to show a more complex mechanism of inhibition.

[Determination of the qualitative and quantitative composition of antocyan pigments as components of dietary supplements and drugs for vision].

Bilberry has been long used in folk medicine and credited for an ability to improve vision, primarily night vision. The major active ingredients of bilberries are antocyans. Experimental and clinical studies confirmed the ability of bilberry antocyans to accelerate the regeneration of the photosensitive pigment rhodopsin, to improve nutrition of the retina, and to restore the tissue mechanisms of its protection. The authors studied the level of bilberry antocyans in 5 samples of dietary supplements and medicines for eyes, which had been bought in Moscow drugstores. The total content of antocyans was determined by pH-differential spectrophotometry. All the test samples were shown to contain antocyan pigments; however, their concentration in different samples varied in a wide range of 0.01 to 4.2%. The maximum content was found in the drug "Focus". The qualitative composition of antocyan pigments was estimated by reverse-phase high performance liquid chromatography. All the test samples other than Vitrum vision forte turned out to contain just bilberry antocyans. The chromatographic profile of a Vitrum vision forte sample was inconsistent with bilberry antocyan pigments and the agent was likely to have another source.

Relative Comparison of Catalytic Characteristics of Human Foamy Virus and HIV-1 Integrases.

Due to their ability to integrate into the host cell's genome, retroviruses represent an optimal basis for the creation of gene therapy vectors. The integration reaction is carried out by a viral enzyme integrase: thus, a detailed research of this enzyme is required. In this work, the catalytic properties of human foamy virus integrase were studied. This virus belongs to the Retroviridae family. The dissociation constant was determined, together with the kinetics of integrase catalytic activity. The data obtained were compared to those for the human immunodeficiency virus integrase and a considerable similarity in the activity of the two enzymes was observed.

[Synthesis and properties of a symmetric dimeric bisbenzimidazole, a DNA-specific ligand].

Dimeric bisbenzimidazole DB(5) fluorescing in the blue spectral area (lambda(em) 476 nm) within the DNA complex was synthesized. DB(5) is bound by a double-strand DNA and can differentially stain human and plant (flax) chromosomes. According to preliminary data, it provides considerably more intensely contrasting chromosome staining than DAPI and Hoechst 33258 dyes. It was also found that DB(5) is an in vitro inhibitor of HIV-1 integrase in the reaction of 3'-processing. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2008, vol. 34, no. 2; see also http://www.maik.ru.