Transgenic Tobacco plants expressing bacterial genes encoded the thermostable glucanases

It is shown that bacterial genes for thermostable beta-glucanases are expressed retaining their activity and substrate specificity. The leader peptide of the carrot extensin exerts effective secretion of the bacterial enzymes into the intercellular space of the plant tissue. Expression of the bacterial gene for beta-1,3-glucanase in plant tissues alters their morphogenetic potential. Regeneration of shoots from the calli of these plant lines requires a six- to eightfold increase in cytokinin (6-BAP) concentration in comparison with the control lines and the transgenic lines expressing beta-1,3-1,4-glucanase. Rooting of transgenic plants expressing the bacterial gene for beta-1,3-glucanase occurs much faster. The transgenic plants obtained in the study are proposed as model objects for investigating the role of glucanases in plants.     

Russian genofond. Genogeography of surnames

Surnames are traditionally used in population genetics as "quasi-genetic" markers (i.e., analogs of genes) when studying the structure of the gene pool and the factors of its microevolution. In this study, spatial variation of Russian surnames was analyzed with the use of computer-based gene geography. Gene geography of surnames was demonstrated to be promising for population studies on the total Russian gene pool. Frequencies of surnames were studied in 64 sel'sovets (rural communities; a total of 33 thousand persons) of 52 raions (districts) of 22 oblasts (regions) of the European part of Russia. For each of 75 widespread surnames, an electronic map of its frequency was constructed. Summary maps of principal components were drawn based on all maps of individual surnames. The first 5 of 75 principal components accounted for half of the total variance, which indicates high resolving power of surnames. The map of the first principal component exhibits a trend directed from the northwestern to the eastern regions of the area studied. The trend of the second component was directed from the southwestern to the northern regions of the area studied, i.e., it was close to latitudinal. This trend almost coincided with the latitudinal trend of principal components for three sets of data (genetic, anthropological, and dermatoglyphical). Therefore, the latitudinal trend may be considered the main direction of variation of the Russian gene pool. The similarity between the main scenarios for the genetic and quasi-genetic markers demonstrates the effectiveness of the use of surnames for analysis of the Russian gene pool. In view of the dispute between R. Sokal and L.L. Cavalli-Sforza about the effects of false correlations, the maps of principal components of Russian surnames were constructed by two methods: through analysis of maps and through direct analysis of original data on the frequencies of surnames. An almost complete coincidence of these maps (correlation coefficient rho = 0.96) indicates that, taking into account the reliability of the data, the resultant maps of principal components have no errors of false correlations.     

The Russian gene pool. Frequency of genetic markers

Frequency distribution of several genetic markers was studied in ethnic Russians from the Moscow, Bryansk, Ryazan', Kostroma, Novgorod, Arkhangel'sk, and Sverdlovsk oblasts and Udmurtiya. Systems AB0, RH, HP, TF, GC, PI, C'3, ACP1, PGM1, ESD, GLO1, 6PGD, and AK were analyzed in most samples. New data on informative polymorphic genetic loci showed that the Russian gene pool mostly displays Caucasoid features. In addition, Y-chromosomal short tandem repeats (STRs) DYS19, DYS390, and YCAII were analyzed in the Russian samples. STRs of the chromosome are particularly valuable for elucidating ethnogenetic processes in Eastern Europe. Frequency distributions of the Y-chromosomal markers in Russians were intermediate between those of West European populations and eastern Finno-Ugric ethnoses of the Volga region. A marked longitudinal gradient was revealed for frequencies of several molecular markers.     

Distributions of circular DNA according its topological states

A distinctive feature of closed circular DNA molecules is their particular topological state, which cannot be altered by any conformational rearrangement short of breaking at least one strand. This topological constraint opens unique possibilities for experimental studies of the distributions of topological states created in different ways. Primarily, the equilibrium distributions of topological properties are considered in the review. It is described how such distributions can be obtained and measured experimentally, and how they can be computed. Comparison of the calculated and measured equilibrium distributions over the linking number of complementary strands, equilibrium fractions of knots and links formed by circular molecules has provided much valuable information about the properties of the double helix. Study of the steady-state fraction of knots and links created by type II DNA topoisomerases has revealed a surprising property of the enzymes: their ability to reduce these fractions considerably below the equilibrium level.     

Elements of structural organization of the transcribed area of the ribosomal repeat (rDNA) in human peripheral blood lymphocytes

The rDNA transcribed region (TR) was tested for accessibility to RsaI recognizing 15 TR sites, DNase I, and photoinducible arylazide (N-(4-azido-2-hydroxybenzoyl)-N,N'-diaminoheptane acetate) in isolated nuclei and, with arylazide, in intact cells. Arylazide entered cells well and did not appreciably affect the chromatin structure. Its photolysis products efficiently modified DNA in accessible sites. Single-strand breaks made by DNase I were not transformed in double-stranded in rDNA TR, suggesting the necessity of denaturing electrophoresis for such an analysis. About 70% of all rDNA copies proved poorly inaccessible to endonucleases and arylazide, the accessibility being higher in their 18S and 5.8S rRNA gene regions than in the regions of the external transcribed spacers (ETSs) and the 28S rRNA gene. Proteinase K disrupted this structure, and the corresponding copies were extracted from nuclei. This explained why in situ hybridization occasionally fails to reveal rDNA in the nucleolar fibrillar center (FC) on electron microscopic preparations. In other rDNA copies, TR (excluding 5'-ETS) was accessible to nucleases and arylazide. These copies were not extracted from nuclei treated with proteinase K. Some of their RsaI sites were protected by tightly bound proteins. Seven such regions were identified in TR. Possible association of the molecular structure, nucleolar location, and functional state of rDNA is discussed.     

Study of molecular mechanisms of translation initiation in mammals using in vitro reconstruction of initiation complexes

Papers on the mechanisms of translation initiation in mammals studied by reconstruction of initiation complexes from individual components are reviewed. The author points to the constraints of this approach and to the pitfalls ignoring which one might come to erroneous conclusions and even artifacts. In addition, some methods employed in the field as well as some technical problems are discussed in the paper, together with the means of obviating them. The review could be a guidebook for newcomers into this quite labor-consuming field.     

Functional compartmentation of the translation apparatus and channeling of tRNA/aminoacyl-tRNA in cells of higher eukaryotes

Literature data and authors' results in the field of structure-function organization of the translation apparatus in higher eukaryotes are considered. Proof is presented of the channeling of tRNA/aminoacyl-tRNA in the course of eukaryotic protein synthesis. The concept of the shuttle role of elongation factor eEF1A is grounded; the factor, being in a GTP-bound form, delivers aminoacyl-tRNA to the ribosome and then, in the GDP form after hydrolysis of GTP on the ribosome, forms a complex with the deacylated tRNA and delivers it to the aminoacyl-tRNA synthetase. The notion of translational compartment is defined.     

Calculation of DNA condensation, caused by adsorption of ligands

A method for calculating the curves of DNA transition from linear to condensed state upon binding of condensing ligands has been developed. The character of the transition and ligand concentration necessary for condensation have been shown to be governed by the length of DNA molecule, energy and stoichiometry parameters of DNA-ligand complex (equilibrium constant between linear and condensed form in the absence of ligands, constants for ligand binding to linear and condensed forms, the number of base pairs covered by one ligand, etc.). The results of the calculations indicate that only slight difference in the free energies of these states in free DNA (less than 6 cal/mole(bp) for DNA of 500 bp long) is sufficient for the existence of stable linear state in the absence of ligands (in free DNA) and the formation of stable condensed state upon complexation.     

Construction of peptide mimetics of an epitope of the human immunodeficiency virus (HIV-1) gp41 protein, recognized by virus-neutralizing antibodies 2F5

A phase peptide library was screened with virus-neutralizing monoclonal antibodies (MCA) 2F5 which recognize a conserved epitope of HIV-1 gp41. Phages that expose peptides specifically binding with MCA 2F5 were selected by ELISA. Amino acid sequence analysis revealed a homology to region 662-671 of HIV-1 HB10 gp160 for most peptides. The major role in recognition was ascribed to Asp-664, Lys-665, and Trp-666. The epitope-mimicking peptides were tested for immunogenicity. Antibodies to gp41 were detected in serum of immunized rabbits.