[Oligonucleotides of the guanyl ribonuclease digest of yeast valine transfer RNA].
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Actinomyces↗
Biomedical subjects
A A Baev
Publications and source records attributed to A A Baev.
[Organization of genes coding for 5S rRNA in the loach Misgurnus fossilis L].
The organization of 5S rRNA genes in the loach Misgurnus fossilis L. was studied. 5S rDNA was cloned in Escherichia coli using the HindIII-fragments of loach genome DNA fused into the plasmid pBR322 restricted at the same site. The recombinant clones were tested by colony hybridization. The presence of the 5S rDNA structural sequences in cloned fragments was determined by the Southern procedure of hybridization with 5S [32P]rRNA of the loach and transcription in the oocyte test system. It was found that the size of 5S rDNA repetitive units corresponds to 240-250 bp and 450-460 bp. By the CsCl centrifugation and restriction analysis it was shown that the 5S genes in the loach genome are arranged in clusters (5-30 repeats per cluster), the smaller repeat was found to contain one coding sequence while the larger repeat contains two coding sequences of 5S rDNA.
Animals↗
[Comparative study of the tRNA-methylases of normal and tumor tissues. I. Spectrum of renal and carcinoma RA methylases].
A comparative study of rat kidney and carcinoma RA tRNA-methylase activity has been carried out using partially purified enzyme preparations and total E. coli tRNA. Also the nuclease activity of the methylase preparations from kidney and carcinoma was compared. It was established that the methylase activity in carcinoma preparations is higher, whereas the nuclease activity is lower in comparison to the enzyme preparations from liver. No formation of some specific methylated compounds could be established in the case of carcinoma. It was established that the relative contribution of individual methylases to the elevated level of total tRNA-methylase activity in carcinoma is different. Maximal enhancement of activity was established for the methylase forming m5U, whereas the activity of the enzymes, transfering the methyl group to the fifth position of C is practically equal in kidney and carcinoma tissues. Experimental results and theoretical evaluation of the hypotheses suggested to explain the higher methylase activity in tumor tissues allowed to reject some of them.
Animals↗
[Comparative study of the tRNA-methylases of normal and tumor tissues. II. Positional specificity of renal and carcinoma RA methylases].
A comparative study of the position specificity of tRNA-methylases from normal and tumour tissues was performed on yeast tRNA1Val as the substrates using partially purified enzyme preparations from rat kidney and carcinoma RA. As in the case of rat liver and Novikoff hepatoma, two methylated compounds are formed in yeast tRNA1Val under the action of rat kidney and carcinoma enzyme preparations: m5C is formed in the sequence C49--C52 located in the extra loop and A59 in the Tpsi-loop is is converted into m1A. The activity of m5C-methylase [S-Ado-Met-tRNA-(cytosine-5)methyltransferase] (E. C. 2.1.1.29) is approximately equal in both tissues, whereas the activity of m1A-methylase [S-Ado-Met-tRNA-(adenine-1)methyltransferase] (E. C. 2.1.1.36) in carcinoma is twice as high as in the kidney. The two enzymes do not differ in their position specificity.
Animals↗
[Restriction mapping of T4 bacteriophage late gene region which contains the origins of DNA replication].
DNAs of lambda T4 recombinants 596-27 (genes 50-5), 596-30 (genes 50-8), 596-29 (genes 50-12), 591-16 (genes 6-8), 591-1 (genes 9-12), 596-13 (genes 13-16), 596-17 (genes 18-20) and 596-11 (genes 25-29) were mapped with the use of EcoRI, HindIII, SmaI, SalI and BamHI restriction enzymes. T4 dcDNA was digested with HindIII restriction endonuclease and resulting fragments were cloned into HindIII lambda vector 761. The recombinants 761-7, 761-17, 761-19, 761-24, 761-44, 761-50, 761-55 contained the region of genes 25-48 and 761-42, 761-26 and 761-16 contained a single HindIII-fragment with genes 6-12 in both orientations. Data obtained with the DNA of the latter recombinants allowed to show the correctness of the map established earlier which did not contain a full set of overlapping sequences. As a result of the experiments reported, the position of EcoRI and HindIII recognition sites in the region of genes 50-20 and 25-48 was determined and in the region of genes 25-48 BglII and XhoI restriction sites were mapped. The location of a single BamHI restriction site in the region of gene 8 was also established.
Base Sequence↗
[Ribosomal genes of the loach Misgurnus fossilis L. Isolation and restriction analysis].
The ribosomal DNA of the teleost fish--loach has been isolated from sperm DNA by CsCl density gradient centrifugation. The rDNA sediments on density gradients by two heavy satellites beta = 1.715 and greater than 1.720. The DNA of the first satellite (1.715) was separated and treated by restrictases EcoRI and BamHI. It was shown that there are two EcoRI-sites in rDNA of loach, locating in 18S and 28S rRNA coding sequences. From tandem of repeating ribosomal genes EcoRI cuts out the fragment with homogeneous length-3 megadaltons (constant fragment) and heterogeneous population of fragments 11-13 megadaltons (major) and 7-8 megadaltons (minor fraction). The constant fragment contains mostly 28S coding sequence, and the heterogeneous fragment--18S coding sequence. The data indicate that the ribosomal genes of the loach as well as other higher eucaryotes were organized in genome as tandem of repeating units with heterogeneous length (10-16 megadaltons, 14.5-24 kb) due to heterogeneity of the length of nontranscribed spacer.
Animals↗
[Cloning of bacteriophage T5 DNA fragments in the plasmid pBR322. Analysis of recombinant plasmids by the method of bonding with RNA-polymerase from Escherichia coli on nitrocellulose filters].
DNA of bacteriophage T5 was hydrolyzed with restriction endonucleases HindIII and BamHI, and subjected to the combined hydrolysis with BamHI+EcoRI and BamHI+ +HindIII. Fragments obtained were cloned in the plasmid pBR322. About 17% of T5 genome were recovered in recombinant plasmids. Cloned fragments were localized on the physical map of the phage by restriction analysis and Southern hybridization. With the aim of direct cloning of T5 promoters, PstI/HindIII fragments were inserted into pBR322 followed by selection of recombinants on ApsTCr phenotype. Binding of BsuRI and AluI fragments of hybrid plasmids with E. coli RNA polymerase was studied by nitrocellulose filter assay. The fragments, which were capable to form heparin resistant complexes were identified.
Base Sequence↗
[DNA methylation in T3 and T7 phages by DNA-adenine methylases of various types and methylase EcoK ocR+ by protein].
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Binding Sites↗
[Structural changes in influenza virus RNA during its attenuation].
Changes in structures of only two genes of influenza virus--M and NS genes were found during virus attenuation by the method of oligonucleotide mapping. Such changes were observed in virulent and attenuated viruses (passages 10-23 in chick embryos) by comparing intermediate variants of the virus (passages 11-16 in chick embryos). These results allow us to conclude the important role of these genes in virus attenuation and in connection with virulence of the virus.
Animals↗
[Heterogeneity of 5S ribosomal RNA of the loach Misgurnus fossilis L].
The fraction of low molecular weight RNAs from the unfertilized eggs and liver of the loach (Misgurnus fossilis) was analyzed by electrophoresis in polyacrylamide gel. The 5S rRNA from unfertilized eggs differs in its electrophoretic mobility from liver 5S rRNA in the presence of 7 M urea at 20 degree C. The electrophoretic mobilities of these two rRNAs are identical at 50 degree C. These data indicate that the loach, just as the amphibians and other teleost fishes, has two types of 5S rRNA, viz. the oocyte and somatic types. Since these molecules are of identical size, their different electrophoretic mobility should be ascribed to variations in their structure. The unfertilized eggs and liver of Misgurnus fossilis contain, apart from the major fraction, a minor fraction of 5S rRNA belonging to another type. The content of 5S rRNA in preparations of the ribosomes from unfertilized eggs is much lower comparing to tht of 5.8s rRNA than in preparations of the ribosomes from somatic tissues (muscles). A possible functional significance of different 5S rRNA types (oocyte and somatic) is discussed.
Animals↗
[Computerized tomography in the diagnosis of organic brain lesions in patients with schizophrenia].
The authors retrospectively analyse CT data obtained in examinations of 1745 patients divided into three groups. Of these, 832 were male and 913 female patients. Group 1 consisted of 721 patients with schizophrenia, group 2 (reference) consisted of 855 mentally normal subjects directed to computer tomographic examination with suspected organic involvement of the brain, and group 3 (control) consisted of 169 mentally and neurologically normal subjects. On the whole the incidence of various organic brain lesions was 8% in group 1, 41.5% in group 2, and 6.5% in control group, whatever the of the examinees or any other factors. Vascular diseases of the nervous system predominated in group 2 as against group 1, being 3.5 times more incident. No intracranial tumors were detected in controls; in schizophrenics computer tomographic signs of volumic brain lesions were detected in 1.5% of cases, being diagnosed more than 10 times more frequently than in group 2 patients.
Adolescent↗
[Determination and analysis of the primary structure of a genomic sequence adjacent to the 3'-end of the human tissue plasminogen activator gene].
Primary structure was determined for the recently cloned f1/BglII-fragment [19] containing 2102 b.p. of the human tissue plasminogen activator (tPA) gene 3' end and adjacent DNA region. Computer analysis has revealed an Alu-repeat 820 b.p. downstream the tPA gene; the sequence proved to have a considerable homology (86-88%) with the Alus from the 3'-untranslated regions (3'UTRs) of cytochrome P-450, lysozyme and p53 protein human mRNAs. The same homology was estimated for this Alu in reversed orientation and Alus from the 3'UTRs of some other human mRNAs. In contrast, the homology between this 3' end tPA gene flanking Alu-repeat and other Alus dispersed throughout the gene introns either direct or reversed, was less than 70%. The polyadenylation signal AATAAA downstream the Alu and two nearby signals CACAG and GTGTT resembling consensus sequences CACAG and YGTGTTYY, respectively, were also detected. The two latter motifs located close to the 3' ends in most mammalian genes are likely to regulate mature mRNA formation. The comparison of the sequenced spaser flank adjacent to the tPA gene with short homologous sequence from the same genomic region primary structure reported previously has revealed discrepancies (substitutions, deletions or insertions) in 21 nucleotide positions. The nucleotide sequence of E. coli uvrB gene fragment (980 b.p.) is also reported. This E. coli gene fragment was cloned accidentally within the f1/BglII-fragment being an artifact of the host-vector system used.
Base Sequence↗
[Inhibiting effect of S-adenosyl-L-homocysteine and its structural analogs on the process of enzymatic methylation of tRNA].
The action of S-adenosyl-l-homocysteine (S-Ado-Hcy), its four structural analogues S-Ino-Hcy, S-Guo-Hcy, S-Urd-Hcy, S-Cyd-Hcy and the five corresponding sulfoxides on tRNA methylases has been investigated. The data obtained in the study of overall incorporation of 14CH3-groups into an unfractioned tRNA preparation suggested that both the affinity of the inhibitors tested for various methylases and the type of inhibition were different. The experiments performed with unfractioned tRNA preparation permit to get an idea of the average inhibitory potency of each of the compounds. The study of their action on individual tRNA methylases by means of fractionation of minor components produced demonstrated that the affinity of the inhibitors tested for various methylases was really different. Thus, S-Ado-Hcy, S-Ino-Hcy and S-Urd-Hcy practically do not inhibit m1A methylase but have the highest affinity for m5C methylase. In an experiment with tRNAPhe which is a substrate for a single, namely m5C methylase, the type of inhibition of this methylase by S-Cyd-Hcy was revealed; it was found to be non-competitive with respect to S-Ado-Met, and the S-Cyd-Hcy concentration reducing the methylation by 50 percent was 1.2-10(-4) M.
Actinomycetales↗
[Isolation and characteristics of DNA fragments for the region of the tissue plasminogen activator genes and areas adjacent to it in the human genome].
Fragments overlapping the tPA gene and its 5'- and 3'-flanking regions were isolated from human liver DNA library cloned in lambda Charon4A vector. A BglII fragment comprising the 3' end and the adjacent genomic region (total length 3.7 kb) was subcloned in plasmid pUC19 and its restriction map was determined. The nucleotide sequence of the 5' region of this fragment was compared with the 3' end region of the tPA gene and the corresponding regions of five published variants of tPA mRNA cDNA from different tissues; discrepancies in seven positions were revealed, which might be caused by intragenomic polymorphism.
Base Sequence↗
Use of the method of mixed substrates to study the specificity of tRNA methylases.
The absence of summation of the rate of methylation of positionally analogous cytidine residues in tRNA1Val, tRNAPhe, and tRNAMet in the case of simultaneous presence of two substrates in the incubation mixture was demonstrated by the method of mixed substrates. The same result was also obtained in the methylation of A19 (counting from the 3' end of the molecule) in tRNA1Val, tRNAPhe, tRNAfMet, tRNASer, and tRNAGlu individually and in the case of their mixing in pairs. These data are evidence that positionally analogous nucleotides in different RNAs are attacked by the same enzyme. Yeast tRNASer, already possessing a methyl group at the cytidine residue studied, proved to be an effective inhibitor of methylase, forming m5C with valine and phenylalanine tRNAs. The results obtained are evidence that differences in the primary and secondary structures at the site of methylation are not the deciding factors in the interaction of tRNA with methylases.
Base Sequence↗
Effect of change in structure of cohesive ends on aggregating ability and biological activity of bacteriophage lambda DNA.
The effect of different types of buildup of the cohesive ends on the ability of phage lambda DNA molecules to form cyclic and concatemeric forms and on their biological activity in two infection systems--transfection and transformation--was investigated with the aid of E. coli DNA polymerase. A change in the structure of the cohesive ends leads to a change in the aggregating ability of the phage lambda DNA molecules up to an almost complete loss of this ability. The infectious activity of phage lambda DNA in the transfection system is very sensitive to a change in structure of the cohesive ends. It is suggested that phage development in this system requires retention of the ability to form cyclic or concatemeric forms. In the transformation system molecules with any of the modifications of the cohesive ends differ insignificantly from one another in infectivity. This can be attributed to the important role of recombination processes, which can save the defective DNA markers. DNAs with completely normal cohesive ends behave in the transformation system like phage lambda DNA fragments from internal parts of the molecule. No polarity of the cohesive ends is found when phage lambda develops in systems with or without a helper phage.
Base Sequence↗
[Recombinant murine cell lines, transformed by various vectors based on bovine type 1 papillomavirus and expressing human tissue plasminogen activator. II. Analysis of cell lines, producing recombinant tissue plasminogen activator].
We have characterized a number of recombinant cell lines established with BPV1 and Lx1 (containing duplication of LCR-E6-E7 sequence) vectors on the basis of C127 cells. It had been shown that Lx1 based vectors possess the higher number of intracellular copies than analogous vectors on the basis of wtBPV, and most part of them is integrated into the host genome. Using various concentrations of heavy metal salts we have developed the optimized procedure for induction of recombinant tPA synthesis which is controlled by the mouse MT1 promoter. A 8-fold increase of rtPA concentration was reached in the course of induction. It had been shown that native and non-glucosylated forms of recombinant and human tPA are identical in their properties.
Animals↗
[The Russian human genome program].
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Base Sequence↗