Advances in Molecular Biology / Moleküler Biyolojide Gelişmeler

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Browsing Advances in Molecular Biology / Moleküler Biyolojide Gelişmeler by Author "Alexandrova, Margarita V."

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    PublicationOpen Access
    39 spatial arrangement of the animal male germ cell genome: II. 2d-3d Simulation and visualization of spatial configuration of major chromosome 2 in Drosophila sperm
    (İstanbul Kültür Üniversitesi, 2007-09) Alexandrov, Igor D.; Stepanenko, Victor A.; Alexandrova, Margarita V.
    Data on the non-random distribution of radiationinduced inversion breakpoints were used as genetic markers for 2D and 3D modeling of the largescale architecture of the chromosome 2 in Drosophila sperm genome at the time of irradiation. During modeling, Gmax program with application of splines, the additional objects and operations as well as the methods of visualization of macromolecular biostructures were employed. A specific megarosette-loop model of spatial arrangement of chromatin fiber in the haploid sperm nucleus can account well for the experimental data.
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    PublicationOpen Access
    Spatial arrangement of the animal male germ cell genome: I. Non-random pattern of radiation-induced inversions involving the vestigial region in autosome 2 of Drosophila melanogaster
    (İstanbul Kültür Üniversitesi, 2007-03) Alexandrov, Igor; Alexandrova, Margarita V.; Korablinova, Svetlana V.; Korovina, Larisa N.
    At present, given a bulk of models for higher-order chromatin structure in interphase nuclei of animal somatic cells, little is known about the spatial chromosome organization in animal male germ cells mainly due to the lack suitable methods for detailed observation and analysis without disruption of the existing organization. We pioneered in the study of this issue via analysis of radiation-induced inversion patterns in Drosophila male germ cell genome taking into account the fact that the formation of inversion requires the spatial proximity and contact of its ends. Analysis of 72 γ- ray- or neutron-induced vg inversions in which the first break is invariantly associated with the vestigial (vg) gene in the middle of 2R autosome shows the second inversion breakpoints that highly non-randomly distributed over the entire second chromosome clustering at the three autosome 2 “hot” chromosome areas. These findings show that the polar Rabl-configuration of interphase chromosomes in various somatic cells is not typical for the haploid genome of Drosophila mature sperms. The specific megarosetteloopstructure of haploid chromosome in the mature animal sperms is proposed and justified.
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    PublicationOpen Access
    Spatial arrangement of the animal male germ cell genome: III. A new experimental evidences in support of the Megarosette-loop model of spatial organization of chromosomes in Drosophila sperm genome
    (İstanbul Kültür Üniversitesi, 2008) Alexandrov, Igor; Alexandrova, Margarita V.; Stepanenko, Victor A.; Korablinova, Svetlana V.; Korovina, Larisa N.; Stetsenko, Stanislav G.
    The data on the non-random pattern of induction of the black (b) inversions in autosome 2 after action of γ-rays of 60Co or 0.85 MeV fission neutrons on Drosophila mature spermatozoa were described and 2D model of spatial arrangement of this autosome in sperm nucleus at the time of irradiation based on these data was presented. The main features of this model found to be entirely consistent with the chromosome macroarchitecture proposed earlier on the basis of data for the vestigial (vg) inversions at the same autosome. A general 2D and 3D models for the specific megarosette-loop structure of autosome in question with both sets of the inversion data were constructed validity of which was independently confirmed by the induction patterns of inversions not associated with the locus-specific mutations under study. It is stated that there are all reasons to believe that all other chromosomes in sperm genome have the same spatial macroarchitecture as the most compact and suitable one to pass on the genetic information from one generation to another. It is particularly emphasized that large-scale chromosome geometry proposed is fundamentally unlike Rabl’s configuration of interphase chromosomes in animal somatic cells. The conversion of Rabl’s configuration to megarosetteloop structure is presumed to keep pace with protein remodeling of chromatin in late spermiogenesis.
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    PublicationOpen Access
    Spatial arrangement of the animal male germ cell genome: IV. Radiation-induced locus-specific translocations (2;3) and large-scale organization of Drosophila sperm nucleus
    (İstanbul Kültür Üniversitesi, 2009) Alexandrov, Igor D.; Stepanenko, Victor A.; Alexandrova, Margarita V.; Korablinova, Svetlana V.; Korovina, Larisa N.
    At the previous papers (Alexandrov et al., 2007b, 2008), the specific megarosette-loop organization (but not polar-linear Rabl-configuration) of major haploid autosome 2 in Drosophila sperm nucleus has been proposed and experimentally substantiated by analysis of radiation-induced locus-specific inversions showing highly nonrandomly distribution of the second inversion breakpoints over the entire autosome. We have speculated that spatial organization of the other major chromosomes in Drosophila sperm nucleus must be the same. To test this expectations, the nature and frequency of radiation-induced interchromosomal exchanges (reciprocal translocations) between autosomes 2 and 3 with the first breaks invariantly associated with the same genetic loci (black or vestigial) on the autosome 2 were studied and, at once, the distribution patterns of the second translocation breakpoints over the entire autosome 3 were detected. Analysis of 23 translocations scored has shown that both black and vestigial loci highly non-randomly interact with certain, including pericentromeric heterochromatin, “hot” areas of autosome 3. Surprisingly, positioning of these areas found to be co-linear with that of “hot” areas for inversion breakpoints on the autosome 2 if both euchromatic arms and pericentromeric heterochromatic regions of two major autosomes arrange in parallel to each other, showing thereby that spatial organization of both autosomes 2 and 3 goes on concurrently with space and time. Using these data, 2D and 3D models of spatial arrangement of autosome 3 in Drosophila haploid sperm nucleus were constructed the principle features of which found to be well consistent with the megarosette-loop configuration proposed for the second chromosome. Independent reciprocal translocations (2;3) scored in the genome of the eight radiation-induced “point” black or vestigial mutants turned out to have the breakpoints within the autosomes 2 and 3 areas proximity of which is predetermined by the megarosette-loop configuration of these major chromosomes. These results show that approaches of the classical radiation cytogenetics and genetics employed in our genomic investigations may be useful strategy to assist in the elucidation of the other conceptual point in the dynamics of sperm nucleus as a self-organizing system, namely, whether the chromatic protein remodeling (histon -to- protamine transition) in late spermatids is coupled with the structural reorganization of primary polar-linear Rabl’s state of chromosomes in the early post-meiotic spermatids into the compact megarosette-loop structures in the fully mature spermatozoa.