Exocyclic Carbons Adjacent to the N6 of Adenine are Targets for Oxidation by the Escherichia coli Adaptive Response Protein AlkB

The DNA and RNA repair protein AlkB removes alkyl groups from nucleic acids by a unique iron- and α-ketoglutarate-dependent oxidation strategy. When alkylated adenines are used as AlkB targets, earlier work suggests that the initial target of oxidation can be the alkyl carbon adjacent to N1. Such may be the case with ethano-adenine (EA), a DNA adduct formed by an important anticancer drug, BCNU, whereby an initial oxidation would occur at the carbon adjacent to N1. In a previous study, several intermediates were observed suggesting a pathway involving adduct restructuring to a form that would not hinder replication, which would match biological data showing that AlkB almost completely reverses EA toxicity in vivo. The present study uses more sensitive spectroscopic methodology to reveal the complete conversion of EA to adenine; the nature of observed additional putative intermediates indicates that AlkB conducts a second oxidation event in order to release the two-carbon unit completely. The second oxidation event occurs at the exocyclic carbon adjacent to the N[superscript 6] atom of adenine. The observation of oxidation of a carbon at N[superscript 6] in EA prompted us to evaluate N[superscript 6]-methyladenine (m6A), an important epigenetic signal for DNA replication and many other cellular processes, as an AlkB substrate in DNA. Here we show that m6A is indeed a substrate for AlkB and that it is converted to adenine via its 6-hydroxymethyl derivative. The observation that AlkB can demethylate m6A in vitro suggests a role for AlkB in regulation of important cellular functions in vivo.National Institutes of Health (U.S.) (Grant number CA080024)National Institutes of Health (U.S.) (Grant number CA26731)National Institutes of Health (U.S.) (Grant number ES02109

Recognition and processing of a new repertoire of DNA substrates by human 3-methyladenine DNA glycosylase (AAG)

The human 3-methyladenine DNA glycosylase (AAG) recognizes and excises a broad range of purines damaged by alkylation and oxidative damage, including 3-methyladenine, 7-methylguanine, hypoxanthine (Hx), and 1,N[superscript 6]-ethenoadenine (εA). The crystal structures of AAG bound to εA have provided insights into the structural basis for substrate recognition, base excision, and exclusion of normal purines and pyrimidines from its substrate recognition pocket. In this study, we explore the substrate specificity of full-length and truncated Δ80AAG on a library of oligonucleotides containing structurally diverse base modifications. Substrate binding and base excision kinetics of AAG with 13 damaged oligonucleotides were examined. We found that AAG bound to a wide variety of purine and pyrimidine lesions but excised only a few of them. Single-turnover excision kinetics showed that in addition to the well-known εA and Hx substrates, 1-methylguanine (m1G) was also excised efficiently by AAG. Thus, along with εA and ethanoadenine (EA), m1G is another substrate that is shared between AAG and the direct repair protein AlkB. In addition, we found that both the full-length and truncated AAG excised 1,N[superscript 2]-ethenoguanine (1,N[superscript 2]-εG), albeit weakly, from duplex DNA. Uracil was excised from both single- and double-stranded DNA, but only by full-length AAG, indicating that the N-terminus of AAG may influence glycosylase activity for some substrates. Although AAG has been primarily shown to act on double-stranded DNA, AAG excised both εA and Hx from single-stranded DNA, suggesting the possible significance of repair of these frequent lesions in single-stranded DNA transiently generated during replication and transcription.United States. National Institutes of Health (grant ES05355)United States. National Institutes of Health (grant CA75576)United States. National Institutes of Health (grant CA55042)United States. National Institutes of Health (grant ES02109)United States. National Institutes of Health (grant T32-ES007020)United States. National Institutes of Health (grant CA80024)United States. National Institutes of Health (grant CA26731

Structural and Population Polymorphism of RT-Like Sequences in Avian Schistosomes Trichobilharzia szidati (Platyhelminthes: Digenea: Schistosomatidae)

Recently we developed the genus-specific markers of the avian schistosomes of the genus Trichobilharzia, the causative agents of human cercarial dermatitis. The 7 novel genome sequences of T. franki, T. regenti, and T. szidati revealed similarity with genome repeat region of African schistosome Schistosoma mansoni. In the present work we analyzed the 37 new T. szidati sequences to study intragenome variability and host specificity for the parasite from three localities of East Europe. DNAs were isolated from cercariae or single sporocysts obtained from 6 lymnaeid snails Lymnaea stagnalis and L. palustris from Belarus and Russia. All sequences formed three diverged groups, one of which consists of the sequences with multiple deletions; other groups involved two paralogous copies with stop codons and frameshift mutations. Strong association between geographical distribution and snail host specificity cannot be established. All studied sequences have homology with the reverse transcriptase domain (RT) of Penelope-like elements (PLE) of S. mansoni and S. japonicum and new members of RT family were identified. We proposed that three diverged groups RT sequences of T. szidati are results of duplication or transposition of PLE during parasite evolution. Implications of the retroelement dynamics in the life history of avian schistosomes are discussed

Biological ualue and functional activity of the cellular components of blood donors organs

The way of preparation and fractionating of blood from system of the bottom vena cava during operation with drawals of organs with mors of a brain is developed and approved. The new transfusion medium ~ a cellular component of blood of the donors, containing 1,7-5,4 standard doses of erythrocytes and 0,2-0,6 standard medical doses of thrombocytes is received. Biological full value and functional activity of cellular components of blood of donors-organs is shown. This cellular transfusion medium provides effective rising of oxygen-transport function of blood at an acute anaemia, moderate indemnification of a thrombocytopenia at liver transplantation

Социально-экономические факторы устойчивого развития туризма в регионах Российской Федерации в условиях экономических санкций

Major social and economic processes and trends in tourism development in regions of the Russian Federation are examined. Factors of sustainable development of tourism with domestic tourist flow rising are identified. Effective mechanisms of import substitution in the sphere of tourism by developing of social tourism and introduction of tax concession when purchasing tour product are analized.Рассматриваются основные социальные и экономические процессы и тенденции развития туризма в регионах Российской Федерации. Выделяются факторы устойчивого развития туризма в условиях активного роста внутренних туристских потоков. Анализируются эффективные механизмы импортозамещения в туристской сфере, посредством развития социального туризма и введения налоговых льгот при приобретении туристских продуктов

Liver Transplantation in Situs Inversus and Portal Vein Thrombosis (First Case Report in Russia)

Situs inversus is a rare mirror transposition of internal organs relative to the median plane. Liver transplantation in situs inversus is a serious medical challenge imposed by an abnormal arrangement of the recipient's organs.Aim. Clinical description of a successful cadaveric liver transplantation in an adult patient with situs inversus and portal vein thrombosis.Key points. A 32 years-old patient with situs inversus, chronic hepatitis B/D-induced liver cirrhosis and portal vein thrombosis had cadaveric liver transplantation, with the transplant reoriented in abdominal cavity 90° clockwise relative to the median plane. End-to-side cavocaval anastomosis was formed between the donor's retrohepatic and the recipient's main inferior vena cava, with successive portal and arterial anastomoses and complete donor liver reperfusion. A biliary reconstruction was performed with an end-to-end biliobiliary anastomosis. The surgery duration comprised 5 h 20 min, intraoperative blood loss — 2000 mL, cold ischemia time — 4 h. The patient was discharged on the 10th day after surgery in satisfactory condition.Conclusion. Situs inversus is not a contraindication to liver transplantation

In vivo virulence of Beijing genotype Mycobacterium tuberculosis

Mycobacterium tuberculosis Beijing genotype strains comprise 50–80% in Russian Federation, which are divided into the main B0/W148, CladeA, and CAO clusters based on VNTR and SNP analysis. It should be noted that such phylogenetically highly close MTB strains belong to the modern Beijing family, generally demonstrating high transmissibility, association with drug resistance, and prevalence among patients with severe forms of the disease. However, studies on MTB genetic cluster strain-related virulence are scarce and contradictory. Here, we investigated virulence of diverse Mycobacterium tuberculosis strains belonging to the B0/W148, CladeA and CAO clusters and nonclustered strain NK of the Beijing family as well as laboratory strain H37Rv in C57BL/6 mice. It was found that mice infected with NK and B0/W148 vs. CladeA strains revealed the peak and the lowest mortality, respectively, while assessing survival rate in various groups (20 mice per MTB strain examined). Analyzing experimental data in mice demonstrated that all MTB strains were able to cause typical tuberculosis-related pathogenic signs. In particular, time-dependent evaluation of pathological changes (on 1, 3, 7, 14, 21, 28, 60 and 120 day post infection) in the lungs and spleen revealed significant differences among various strains. Tuberculosis progression was observed in the mice infected with B0/W148 and NK strains, whereas CladeA, CAO and H37Rv strains resulted in stabilized course and less marked organs damage. Moreover, we found that bacterial load after infection with Beijing family clustering strains was lower compared to that of the reference H37Rv strain, except NK strain demonstrating the peak bacterial load among the Beijing family comparable to H37Rv strain at 120 dpi. Thus, it was found that the level of virulence between most virulent B0/W148 cluster strain vs. NK strain was similar. Overall, the data obtained indicate that Beijing genotype strains are characterized by a diverse range of phenotypic virulence in vivo