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91.
Książczyk T Kovarik A Eber F Huteau V Khaitova L Tesarikova Z Coriton O Chèvre AM 《Chromosoma》2011,120(6):557-571
The dynamics of genome modification that occurred from the initial hybridization event to the stabilization of allopolyploid
species remains largely unexplored. Here, we studied inheritance and expression of rDNA loci in the initial generations of
Brassica napus allotetraploids (2n = 38, AACC) resynthesized from Brassica oleracea (2n = 18, CC) and B. rapa (2n = 20, AA) and compared the patterns to natural forms. Starting already from F1 generation, there was a strong uniparental
silencing of B. oleracea genes. The epigenetic reprogramming was accompanied with immediate condensation of C-genome nucleolar organizer region (NOR)
and progressive transgeneration hypermethylation of polymerase I promoters, mainly at CG sites. No such changes were observed
in the A-genome NORs. Locus loss and gains affecting mainly non-NOR loci after the first allotetraploid meiosis did not influence
established functional status of NORs. Collectively, epigenetic and genetic modifications in synthetic lines resemble events
that accompanied formation of natural allopolyploid species. 相似文献
92.
The biosynthetic origin of 9-phenylphenalenones and the sequence according to which their oxygen functionalities are introduced were studied using nuclear magnetic resonance (NMR) spectroscopy and high-resolution electrospray ionization mass spectrometry (HRESIMS). 13C-labelled precursors were administered to root cultures of Anigozanthos preissii, which were simultaneously incubated in an atmosphere of 18O2. Two major phenylphenalenones, anigorufone and hydroxyanigorufone, were isolated and analyzed by spectroscopic methods. Incorporation of 13C-labelled precursors from the culture medium and 18O from the atmosphere was detected. O-Methylation with 13C-diazomethane was used to attach 13C-labels to each hydroxyl and thereby dramatically enhance the sensitivity with which NMR spectroscopy can detect 18O by means of isotope-induced shifts of 13C signals. The isotopologue patterns inferred from NMR and HRESIMS analyses indicated that the hydroxyl group at C-2 of 9-phenylphenalenones had been introduced on the stage of a linear diarylheptanoid. The oxygen atoms of the carbonyl and lateral aryl ring originated from the hydroxyl group of the 4-coumaroyl moiety, which was incorporated as a unit. 相似文献
93.
Seemingly identical cells can differ in their biochemical state, function and fate, and this variability plays an increasingly recognized role in organism-level outcomes. Cellular heterogeneity arises in part from variation in enzyme activity, which results from interplay between biological noise and multiple cellular processes. As a result, single-cell assays of enzyme activity, particularly those that measure product formation directly, are crucial. Recent innovations have yielded a range of techniques to obtain these data, including image-, flow- and separation-based assays. Research to date has focused on easy-to-measure glycosylases and clinically-relevant kinases. Expansion of these techniques to a wider range and larger number of enzymes will answer contemporary questions in proteomics and glycomics, specifically with respect to biological noise and cellular heterogeneity. 相似文献
94.
Praper T Sonnen A Viero G Kladnik A Froelich CJ Anderluh G Dalla Serra M Gilbert RJ 《The Journal of biological chemistry》2011,286(4):2946-2955
Perforin (PFN) is a pore-forming protein produced by cytotoxic lymphocytes that aids in the clearance of tumor or virus-infected cells by a mechanism that involves the formation of transmembrane pores. The properties of PFN pores and the mechanism of their assembly remain unclear. Here, we studied pore characteristics by functional and structural methods to show that perforin forms pores more heterogeneous than anticipated. Planar lipid bilayer experiments indicate that perforin pores exhibit a broad range of conductances, from 0.15 to 21 nanosiemens. In comparison with large pores that possessed low noise and remained stably open, small pores exhibited high noise and were very unstable. Furthermore, the opening step and the pore size were dependent on the lipid composition of the membrane. The heterogeneity in pore sizes was confirmed with cryo-electron microscopy and showed a range of sizes matching that observed in the conductance measurements. Furthermore, two different membrane-bound PFN conformations were observed, interpreted as pre-pore and pore states of the protein. The results collectively indicate that PFN forms heterogeneous pores through a multistep mechanism and provide a new paradigm for understanding the range of different effects of PFN and related membrane attack complex/perforin domain proteins observed in vivo and in vitro. 相似文献
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96.
Shelly J. Krebs Sean P. McBurney Dina N. Kovarik Chelsea D. Waddell J. Pablo Jaworski William F. Sutton Michelle M. Gomes Maria Trovato Garret Waagmeester Susan J. Barnett Piergiuseppe DeBerardinis Nancy L. Haigwood 《PloS one》2014,9(12)
Developing a vaccine that overcomes the diversity of HIV-1 is likely to require a strategy that directs antibody (Ab) responses toward conserved regions of the viral Envelope (Env). However, the generation of neutralizing Abs (NAbs) targeting these regions through vaccination has proven to be difficult. One conserved region of particular interest is the membrane proximal external region (MPER) of Env located within the gp41 ectodomain. In order to direct the immune response to this region, the MPER and gp41 ectodomain were expressed separately as N-terminal fusions to the E2 protein of Geobacillus stearothermophilus. The E2 protein acts as a scaffold by self-assembling into 60-mer particles, displaying up to 60 copies of the fused target on the surface. Rabbits were immunized with E2 particles displaying MPER and/or the gp41 ectodomain in conjunction with DNA encoding full-length gp160. Only vaccines including E2 particles displaying MPER elicited MPER-specific Ab responses. NAbs were elicited after two immunizations that largely targeted the V3 loop. To overcome V3 immunodominance in the DNA component, E2 particles displaying MPER were used in conjunction with gp160 DNA lacking hypervariable regions V2, V3, or combined V1V2V3. All rabbits had HIV binding Ab responses and NAbs following the second vaccination. Using HIV-2/HIV-1 MPER chimeric viruses as targets, NAbs were detected in 12/16 rabbits after three immunizations. Low levels of NAbs specific for Tier 1 and 2 viruses were observed in all groups. This study provides evidence that co-immunizing E2 particles displaying MPER and gp160 DNA can focus Ab responses toward conserved regions of Env. 相似文献
97.
98.
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100.
Matthew C. P. Glyn Michaela Egertová Blanka Gazdova Aleš Kovarik Milan Bezdek Andrew R. Leitch 《Chromosoma》1997,106(8):485-492
This paper describes the effects of 5-azacytidine on the condensation state of rye (Secale cereale L.) chromatin introduced into the wheat genome (Triticum aestivum L. cv. Beaver). The wheat cultivar Beaver carries a translocation between the short arm of rye chromosome 1R (1RS) and the
long arm of wheat chromosome 1B (1BL/1RS). 1RS can be detected using genomic in situ hybridisation and carries a ribosomal
DNA (rDNA) locus that can be simultaneously detected using multiple labelling strategies. The rDNA locus divides 1RS into
a distal region that is gene rich and a proximal region that is gene poor and highly methylated. 1RS also carries a large
block of subtelomeric heterochromatin. The drug, which acts to inhibit DNA methylation in plants, has three pronounced effects
on interphase nuclei. (1) It induces aberrant condensation of the rye subtelomeric heterochromatin and in many cases induces
sister chromatid separation in the subtelomeric heterochromatin of G2 nuclei. (2) Nuclei trisomic for 1RS are observed at
low frequency in treated material and are probably a consequence of aberrant sister chromatid separation or condensation.
(3) The drug alters normal condensation of 1RS euchromatin. However, contrary to expectation the effect is not simply to induce
decondensation. The proximal region of the arm actually condenses at low levels of drug administration while the distal region
remains unaltered or increases its decondensation state. Increasing the concentration of 5-azacytidine induces a biphasic
response and at the highest concentration used all regions of the arm show signs of decondensation. Thus the influence of
the drug on chromatin condensation depends on the genomic structure.
Received: 14 July 1997; in revised form: 26 August 1997 / Accepted: 27 August 1997 相似文献