Biomedical subjects

L L Kiselev

Publications and source records attributed to L L Kiselev.

At least 73 records · Page 4Linked to original sources

PubMedDate not supplied

[Activation of RHOA gene transcription in epithelial tumors may be caused by gene amplification and/or demethylation of its promotor region].

RHOA protein, a member of small GTPases family, is implicated in cell morphogenesis, adhesion, and in cell cycle regulation. RHOA gene (3p21.31) exhibits cell transformation activity, and therefore gene is considered as a potential oncogene. The aim of this study was to investigate RHOA transcription and copy number changes in three epithelial tumors (breast, renal cell and epithelial ovarian carcinomas, 45 tumor/normal pairs altogether). EII, HhaI, AciI n Bsh1236I). Hypomethylation of the RHOA promoter region in tumor DNA was observed two times more frequently than increased methylation. Moreover, all (15) cancer cases with hypomethylation of the RHOA gene showed a 2-10 fold increased expression of RHOA. It was concluded that gene copy multiplication and demethylation of the RHOA promoter region can contribute to transcription activation of this gene in epithelial tumors.

Breast Neoplasms↗

PubMedDate not supplied

[Transcription TIMP3, DAPk1 and AKR1B10 genes in squamous cell lung cancer].

Lung cancer is one of the most frequent neoplasia in the Russia, the United States and Europe. This cancer is associated with functional activity changes of many genes. In the present study TIMP3, DAPK1 and AKR1B10 genes transcription analysis of squamous cell lung cancer specimens was carried out using reverse transcription-PCR. Substantial increasing of AKR1B10 transcription level is revealed in 80% tumor samples. TIMP3 and DAPK1 transcription level is considerably decreased in 76 and 72% tumor specimens, accordingly. These results may point out that all three genes are important for squamous cell lung cancer tumorogenesis while AKR1B10 is potential oncogene whereas TIMP3 and DAPK1 are potential tumor suppressor genes. We suggest that revealed substantial transcription level-changes of investigated genes may be used for oncodiagnostics.

Adult↗

PubMedDate not supplied

[Aggregation of tryptophanyl-tRNA synthetase depending on temperature. Study by a low-angle scatter x-ray method].

By means of small angle X-ray scattering, an aggregation of beef pancreas Trp-tRNA synthetase (EC 6.1.1.2) was observed at physiological temperatures. A Trp-tRNA synthetase preparation which is homogeneous after PAGE in beta-ME-SDS was found to be heterogeneous in particle sizes even at low (4-8 degrees C) temperature. At heating up to 30-45 degrees C, the oligomer sizes increased as well as its proportion depending on the incubation time and temperature; very large aggregates were observed 10 times exceeding the sizes of initial particles. Cooling to 20 degrees C caused no disaggregation due to disulphide bond formation between associated subunits of Trp-tRNA synthetase. A hypothesis is proposed that the aggregation of bovine Trp-tRNA synthetase evaluated in vitro and not observed earlier with any aminoacyl-tRNA synthetases of unicellular organisms might serve as one of the mechanisms of its compartmentation in pancreas.

Animals↗

PubMedDate not supplied

[Tryptophanyl tRNA synthetase: isolation and characteristics of the tryptophanyl-enzyme].

The catalytic groups, involved in aminoacyl-tRNA formation remain unknown. The isolation and identification of an active covalent complex between the enzyme and substrate is an essential step in understanding the reaction mechanism. We identified and isolated the covalent complex of tryptophanyl-tRNA synthetase (EC 6.1.1.2) and tryptophane which was able to aminoacylate the tRNATrp in the absence of ATP. In beef pancreas tryptophanyl-tRNA synthetase preparations, isolated by the previously described method, a tightly bound tryptophan was revealed which could not be removed by charcoal treatment, by gel-filtration and by replacement with the excess of typtamine, a competitive inhibitor of tryptophane. This tightly bound tryptophane is able to exchange rapidly and specifically with radioactive tryptophane allowing to obtain [14C]tryptophane-tryptophanyl-tRNA synthetase complex. After the reaction of this complex with NH2OH at neutral pH tryptophanyl hydroxamate is formed proving the activated state of the tryptophane in the initial complex with the enzyme. No nucleotide impurites were noticed in the enzyme preparation; the complex is stable at denaturation. A conclusion is made that the tryptophanyl-tRNA synthetase isolated by our method is a tryptophanyl-enzyme. The tryptophanyl residue could be specifically transferred to tRNATrp in the absence of other substrates of the reaction, the efficiency of the transfer does not exceed 25%. The content of the covalently bound tryptophane never exceeds 1 mole per mole of the dimeric enzyme. The total content of tryptophane in the forms of tryptophanyl-enzyme and tryptophanyl adenylate enzyme complex equals 2 moles per mole of the enzyme. The tryptophanyl-enzyme is destroyed during incubation with AMP or with pyrophosphate. The role of the tryptophanyl-enzyme as a possible intermediate in the course of aminoacylation of tRNATrp is discussed.

Adenosine Triphosphate↗

PubMedDate not supplied

[Aminoacyl-tRNA synthetases (codases) and their noncanonical functions].

The aim of this review is to summarize the data obtained in the author's laboratory during the last decade. The main objects of these investigations were mammalian aminoacyl-tRNA synthetases, mainly bovine tryptophanyl-tRNA synthetase (EC 6.1.1.2). The data are discussed and compared with those described in literature. In the course of these studies it turned out that some properties of mammalian aminoacyl-tRNA synthetases for instance, nuclear location of some of the synthetases, presence of extra-domain in bovine tryptophanyl-tRNA synthetase capable of catalyzing hydrolysis of ATP and GTP in the absence of Zn2+ ions and normal aminoacylation capacity, ability to bind to one of the glycolytic enzymes, glyceraldehyde-3-phosphate dehydrogenase, formation of aminoacylated and pyrophosphorylated forms of tryptophanyl-tRNA synthetase etc., seem to be unrelated to the main function of the synthetases, catalysis of aminoacyl-tRNA formation, and, therefore, might be classified as noncanonical ones. Comparison of prokaryotic and eukaryotic aminoacyl-tRNA synthetases indicates the multipotential nature of the latter.

Adenosine Triphosphate↗

PubMedDate not supplied

[Nucleotide sequence of the fragment of transcriptionally active locus in rat genome and analysis of a putative protein product].

Part of the transcriptionally active rat genomic locus, K51, has been sequenced (2,321 b.p.). The coding DNA chains was identified and two long open reading frames (ORF) were found by computer analysis one of which seems to be much less probable. By transcriptional mapping, at least two exons (A - about 110 b.p., B - 549 b.p.) were revealed. Computer search showed that the deciphered nucleotide and amino acid sequence was absent in the data-banks up to the end of 1988. Numerous GC rich direct repeats were noticed in the fragment. At protein level, resemblance with hypervariable N- and C-terminal domains of cytokeratins was visualized. Some regions of the putative protein product possess relatedness with some other gene products, particularly with ATP binding domains of mos oncoprotein.

Amino Acid Sequence↗

PubMedDate not supplied

[Inhibition of replication of human hepatitis B virus].

Several nucleoside 5'-triphosphate analogs were investigated as inhibitors of human hepatitis B virus replication. Different analogs inhibited DNA synthesis differently, 3'-azido-2',3'-dideoxythymidine 5'triphosphate being the most active compound. This inhibitor blocked DNA synthesis by 50% at inhibitor: substrate molar ratio 1:8, and by 80% - at 1:1. The hypothesis is formulated that 3'-azido-2',3'-dideoxythymidine 5'-triphosphate inhibits RNA directed viral DNA replication due to incorporation of this compound into 3'-termini of newly synthesized DNA chains. The phenomenon observed opens new possibilities for chemotherapy of acute and chronic human hepatitis B.

Antiviral Agents↗

PubMedDate not supplied

[The tRNA anticodon is recognized by aminoacyl-tRNA-synthetase].

Data concerning the regions of tRNA molecules recognized by cognate aminoacyl-tRNA synthetases and obtained recently by the new methods (the synthesis of mutant tRNA genes and their transcription in vitro, chimeric suppressor tRNA, RNA engineering) are briefly discussed. The results of several laboratories are in full agreement with the hypothesis proposed earlier on the role of a tRNA anticodon as a specific region by which the enzyme identifies various tRNAs. More than half of tRNAs belong to the group recognized by the aminoacyl-tRNA synthetases by this mechanism. The behavior of natural and artificially constructed tRNAs which contain modified anticodons, but conserve amino acid specificity in the reaction of aminoacylation, indicates that in some tRNAs the role of the anticodon in the tRNA identity is minor if any. This group of tRNA is recognized by the aminoacyl-tRNA synthetases predominantly via the double helical region of the molecule. The authors discuss the significance of the absence of topographic conservatism in the mechanism by which tRNAs are recognized by the aminoacyl-tRNA synthetases.

Amino Acyl-tRNA Synthetases↗

PubMedDate not supplied

[Oncoproteins--the products of oncogenes. Tyrosine protein kinases].

The review summarizes the data mostly published in 1982 and 1983 concerning isolation, identification, cellular localization, deciphering of primary structure, and properties of the proteins coded by the retroviral oncogenes. A tentative classification of oncoproteins is suggested. The main part of the review is devoted to oncoproteins with tyrosine specific protein kinase activity. A hypothesis is proposed concerning the possible mode of action of these proteins on transforming cells. It is stressed in conclusion that the remarkable progress of our knowledge in this field has been mostly achieved due to recombinant DNA technique successfully and widely applied for studying oncogene structure and function.

Amino Acid Sequence↗

PubMedDate not supplied

[Decoding of the primary structure of the son3 region in human genome: identification of a new protein with unusual structure and homology with DNA-binding proteins].

From the human embryonic cDNA library a son3 transcript was cloned and sequenced (1454 base pairs). Determination of its sequence revealed only one open reading frame, whereas five other frames contained a number of termination codons. Translation of the son3 sequence in the unique open reading frame into the amino acid sequence by computer and comparison with the NBRF protein data bank showed that the son3 fragment codes for a new previously unknown polypeptide with the following properties: a) it contains a cluster of short tandemly arranged repeats 7-12 amino acid in length located in the middle part of son3; b) it comprises a region homologous to DNA binding structural proteins (for example, gallin, 55%) and to regulatory proteins coded by the family of proto-oncogene myc; c) it comprises a region homologous to the oncoprotein coded by proto-oncogene mos (human, murine).

Amino Acid Sequence↗

PubMedDate not supplied

[Regions of human genome-containing analogs of oncogenes and retroviral genes. II. A new class of retrovirus-like elements].

Earlier we have found that recombinant phage lambda gp5 contains the sequences homologous to v-mos oncogene and retroviruses. After the nucleotide sequence determination we have found the region with homology to U5 part of retroviral LTR. Adjacent to this region are sequences complementary to 3'-end of tRNAMet. Numerous transcripts reacting with subcloned U5 probe from gp5 are present in polyadenylated RNA fraction from human cells. The humane genome contains several copies of these region, with two of them residing in gp5 locus. On the basis of these data we deduced the presence in the human genome of a new class of retroviral-like elements, existing probably as part of new human endogeneous retrovirus (HuEV).

Bacteriophage lambda↗

PubMedDate not supplied

[Hydrolytic activity of bovine tryptophanyl-tRNA-synthetase cause by removal of Zn2+].

Bovine tryptophanyl-tRNA synthetase (E.C.6.1.1.2) lacking Zn2+ ions removed by chelation with phosphonate analog of P1,P4-bis-(5'-adenosyl)tetraphosphate (Ap4A) was obtained (E-Zn). E-Zn lost the ability to form tryptophanyl adenylate, however it hydrolyses ATP to ADP and further on to AMP and Pi. GTP serves as a substrate with Km approximately 0.6 mM. It is proposed that the hydrolysable nucleotides bind to a nucleotide binding site(s) distinguishable from the substrate (catalytic) ones. After incubation of E-Zn with Zn2+ and Mg2+ the initial catalytic activity (ATP-PPi exchange and amino-acylation reactions) is restored whereas the hydrolytic activity becomes fully suppressed.

Adenosine Diphosphate↗

PubMedDate not supplied

[Autoadenylation of tryptophanyl-tRNA synthetase].

Incubation of bovine tryptophanyl-tRNA synthetase (EC 6.1.1.2) deprived of endogenous tryptophan, with [14C]ATP and without [gamma-32P]ATP, causes an appearance of radioactivity in protein due to formation of adenylated enzyme, [14C]AMP-E. Examination of the properties of the [14C]AMP-E thus obtained led to the conclusion that AMP is linked to the protein molecule via a macroergetic phosphoanhydride bond. ATP is formed when AMP-E is incubated with PPi. However, no tryptophanyl adenylate formation was observed when AMP-E was treated with tryptophan. The functional role of AMP-E remains obscure.

Adenosine Monophosphate↗

PubMedDate not supplied

[Selection of cell lines resistant to tryptophan analogs].

After prolonged cultivation in the presence of increasing amounts of carboxyl-substituted tryptophan analogs (tryptamine and tryptophanol), cell lines resistant to high concentrations of these compounds were obtained. The initial culture was the Madin-Darby line of spontaneously transformed bovine kidney cells. In the resistant lines the amount of tryptophanyl-tRNA synthetase (E. C. 6.1.1.2) is manyfold increased as shown by two criteria: (i) enzymatic activity (ATP-PPi isotopic exchange) per mg of protein, (ii) binding of in vivo 35S-labeled proteins to polyclonal antibodies against tryptophanyl-tRNA synthetase. It was shown that tryptophanyl-tRNA synthetase is phosphorylated in vivo, and the degree of phosphorylation of the enzyme in initial cells seems to be higher then in the resistant ones. The Km value for tryptophan is not significantly changed for the enzyme from resistant cells. The permeability for tryptophan and its analogs is reduced in the resistant cells. It is proposed that the acquisition of the resistance against tryptophan analogs are due to alterations at the genomic level (for example, gene amplification etc.).

Amino Acyl-tRNA Synthetases↗

PubMedDate not supplied