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31.
Novak I Wang H Revenkova E Jessberger R Scherthan H Höög C 《The Journal of cell biology》2008,180(1):83-90
Meiotic chromosomes consist of proteinaceous axial structures from which chromatin loops emerge. Although we know that loop density along the meiotic chromosome axis is conserved in organisms with different genome sizes, the basis for the regular spacing of chromatin loops and their organization is largely unknown. We use two mouse model systems in which the postreplicative meiotic chromosome axes in the mutant oocytes are either longer or shorter than in wild-type oocytes. We observe a strict correlation between chromosome axis extension and a general and reciprocal shortening of chromatin loop size. However, in oocytes with a shorter chromosome axis, only a subset of the chromatin loops is extended. We find that the changes in chromatin loop size observed in oocytes with shorter or longer chromosome axes depend on the structural maintenance of chromosomes 1β (Smc1β), a mammalian chromosome–associated meiosis-specific cohesin. Our results suggest that in addition to its role in sister chromatid cohesion, Smc1β determines meiotic chromatin loop organization. 相似文献
32.
Hannah M��ller David Schmidt Sandra Steinbrink Ekaterina Mirgorodskaya Verena Lehmann Karin Habermann Felix Dreher Niklas Gustavsson Thomas Kessler Hans Lehrach Ralf Herwig Johan Gobom Aspasia Ploubidou Michael Boutros Bodo M H Lange 《The EMBO journal》2010,29(19):3344-3357
Regulation of centrosome structure, duplication and segregation is integrated into cellular pathways that control cell cycle progression and growth. As part of these pathways, numerous proteins with well‐established non‐centrosomal localization and function associate with the centrosome to fulfill regulatory functions. In turn, classical centrosomal components take up functional and structural roles as part of other cellular organelles and compartments. Thus, although a comprehensive inventory of centrosome components is missing, emerging evidence indicates that its molecular composition reflects the complexity of its functions. We analysed the Drosophila embryonic centrosomal proteome using immunoisolation in combination with mass spectrometry. The 251 identified components were functionally characterized by RNA interference. Among those, a core group of 11 proteins was critical for centrosome structure maintenance. Depletion of any of these proteins in Drosophila SL2 cells resulted in centrosome disintegration, revealing a molecular dependency of centrosome structure on components of the protein translation machinery, actin‐ and RNA‐binding proteins. In total, we assigned novel centrosome‐related functions to 24 proteins and confirmed 13 of these in human cells. 相似文献
33.
Zakrzewski F Weisshaar B Fuchs J Bannack E Minoche AE Dohm JC Himmelbauer H Schmidt T 《Chromosoma》2011,120(4):409-422
Sugar beet (Beta vulgaris) chromosomes consist of large heterochromatic blocks in pericentromeric, centromeric, and intercalary regions comprised of
two different highly abundant DNA satellite families. To investigate DNA methylation at single base resolution at heterochromatic
regions, we applied a method for strand-specific bisulfite sequencing of more than 1,000 satellite monomers followed by statistical
analyses. As a result, we uncovered diversity in the distribution of different methylation patterns in both satellite families.
Heavily methylated CG and CHG (H=A, T, or C) sites occur more frequently in intercalary heterochromatin, while CHH sites,
with the exception of CAA, are only sparsely methylated, in both intercalary and pericentromeric/centromeric heterochromatin.
We show that the difference in DNA methylation intensity is correlated to unequal distribution of heterochromatic histone
H3 methylation marks. While clusters of H3K9me2 were absent from pericentromeric heterochromatin and restricted only to intercalary
heterochromatic regions, H3K9me1 and H3K27me1 were observed in all types of heterochromatin. By sequencing of a small RNA
library consisting of 6.76 million small RNAs, we identified small interfering RNAs (siRNAs) of 24 nucleotides in size which
originated from both strands of the satellite DNAs. We hypothesize an involvement of these siRNAs in the regulation of DNA
and histone methylation for maintaining heterochromatin. 相似文献
34.
The regulation of pH in the apoplast, cytosol and chloroplasts of intact leaves was studied by means of fluorescent pH indicators
and as a response of photosynthesis to acid stress. The apoplastic pH increased under anaerobiosis. Aeration reversed this
effect. Apoplastic responses to CO2, HCl or NH3 differed considerably. Whereas HCl and ammonia caused rapid acidification or alkalinization, the return to initial pH values
was slow after cessation of fumigation. Addition of CO2 either did not produce the acidification expected on the basis of known apoplastic buffering or even caused some alkalinization.
Removal of CO2 shifted the apoplastic pH into the alkaline range before the pH returned to initial steady-state levels. In the presence
of vanadate, the alkaline shift was absent and the apoplastic pH returned slowly to the initial level when CO2 was removed from the atmosphere. In contrast to the response of the apoplast, anaerobiosis acidified the cytosol or, in some
species, had little effect on its pH. Acidification was rapidly reversed upon re-admission of oxygen. The CO2-dependent pH changes were very fast in the cytosol. Considerable alkalinization was observed after removal of CO2 under aerobic, but not under anaerobic conditions. Rates of the re-entry of protons into the cytosol during recovery from
CO2 stress increased in the presence of oxygen with the length of previous exposure to high CO2. Effective pH regulation in the chloroplasts was indicated by the recovery of photosynthesis after the transient inhibition
of photosynthetic electron flow when CO2 was increased from 0.038% to 16% in air. As photosynthesis became inhibited under high CO2, reduction of the electron transport chain increased transiently. The time required for recovery of photosynthesis from inhibition
during persistent CO2 stress was similar to the time required for establishing steady-state pH values in the cytosol under acid stress. The high
capacity of leaf cells for the rapid re-attainment of pH homeostasis in the apoplast and the cytoplasm under acid or alkaline
stress suggested the rapid activation or deactivation of membrane-localised proton-transporting enzymes and corresponding
ion channel regulation for co-transport of anions or counter-transport of cations together with proton fluxes. Acidification
of the cytoplasm appeared to activate energy-dependent proton export primarily into the vacuoles whereas apoplastic alkalinization
resulted in the pumping of protons into the apoplast. Proton export rates from the cytosol into the apoplast after anaerobiosis
were about 100 nmol (m2 leaf area)−1 s−1 or less. Proton export under acid stress into the vacuole was about 1200 nmol m−2 s−1. The kinetics of pH responses to the addition or withdrawal of CO2 indicated the presence of carbonic anhydrase in the cytosol, but not in the apoplast.
Received: 19 July 1999 / Accepted: 29 December 1999 相似文献
35.
Membrane preparations, capable of high rates of respiration-linked ATP synthesis, have been obtained from a gram-positive methylotrophic bacterium Bacillus sp. MGA3. NADH, succinate, reduced TMPD and methanol were shown to be suitable substrates for the oxidative phosphorylation. Esterification of orthophosphate was dependent on electron transfer, as evidenced by the requirement for both substrate and oxygen. Phosphorylation was also dependent on ADP and was destroyed by boiling the membrane preparation. The phosphorylation was markedly uncoupled by carbonyl cyanide p-(trichloromethoxy)-phenylhydrazone (CCCP) and was inhibited by N,N-dicyclohexylcarbodiimide (DCCD). KCN caused strong inhibition of substrate oxidation as well as phosphorylation for all substrates tested. Rotenone, amytal and antimycin A caused inhibition when NADH or methanol were used as substrates. Antimycin A inhibited respiration and ATP synthesis with succinate as substrate and had no effect on ascorbate —N,N,N,N-tetramethyl-p-phenylenediimide (TMPD) oxidation by membrane preparations of Bacillus sp. MGA3. P/O ratios determined were 2.4 with NADH, 1.7 with succinate and 0.8 with reduced TMPD. The measured P/O ratio with methanol-oxidizing system was similar to that with NADH (about 2.4).Abbreviations CCCP
Carbonyl cyanide p-(trichloromethoxy)-phenylhydrazone
- DCCD
N,N-dicyclohexylcarbodiimide
- TMPD
N,N,N,N-tetramethyl-p-phenylenediimide
- Q
ubiquinone Q 相似文献
36.
Tatiana Egorova Nikita Biziaev Alexey Shuvalov Elizaveta Sokolova Sabina Mukba Konstantin Evmenov Maria Zotova Artem Kushchenko Ekaterina Shuvalova Elena Alkalaeva 《Nucleic acids research》2021,49(19):11181
eIF3j is one of the eukaryotic translation factors originally reported as the labile subunit of the eukaryotic translation initiation factor eIF3. The yeast homolog of this protein, Hcr1, has been implicated in stringent AUG recognition as well as in controlling translation termination and stop codon readthrough. Using a reconstituted mammalian in vitro translation system, we showed that the human protein eIF3j is also important for translation termination. We showed that eIF3j stimulates peptidyl-tRNA hydrolysis induced by a complex of eukaryotic release factors, eRF1-eRF3. Moreover, in combination with the initiation factor eIF3, which also stimulates peptide release, eIF3j activity in translation termination increases. We found that eIF3j interacts with the pre-termination ribosomal complex, and eRF3 destabilises this interaction. In the solution, these proteins bind to each other and to other participants of translation termination, eRF1 and PABP, in the presence of GTP. Using a toe-printing assay, we determined the stage at which eIF3j functions – binding of release factors to the A-site of the ribosome before GTP hydrolysis. Based on these data, we assumed that human eIF3j is involved in the regulation of translation termination by loading release factors into the ribosome. 相似文献
37.
38.
Michel Dion Daniel Charlier Haifeng Wang Daniel Gigot Alexey Savchenko Jean-Noël Hallet Nicolas Glansdorff & Vehary Sakanyan 《Molecular microbiology》1997,25(2):385-398
We report here the cloning of the arginine repressor gene argR of Bacillus stearothermophilus and the characterization and purification to homogeneity of its product. The deduced amino acid sequence of the 16.8-kDa ArgR subunit shares 72% identity with its mesophilic homologue AhrC of Bacilus subtilis . Sequence analysis of B. stearothermophilus ArgR and comparisons with mesophilic arginine repressors suggest that the thermostable repressor comprises an N-terminal DNA-binding and a C-terminal oligomerization and arginine-binding region. B. stearothermophilus ArgR has been overexpressed in E. coli and purified as a 48.0-kDa trimeric protein. The repressor inhibits the expression of a B. stearothermophilus argC–lacZ fusion in E. coli cells. In the presence of arginine, the purified protein binds tightly and specifically to the argC operator, which largely overlaps the argC promoter. The purified B. stearothermophilus repressor proved to be very thermostable with a half-life of approximately 30 min at 90°C, whereas B. subtilis AhrC was largely inactivated at 65°C. Moreover, ArgR operator complexes were found to be remarkably thermostable and could be formed efficiently at up to 85°C, well above the optimal growth temperature of the moderate thermophile B. stearothermophilus . This pronounced resistance of the repressor–operator complexes to heat treatment suggests that the same type of regulatory mechanism could operate in extreme thermophiles. 相似文献
39.
Three closely related species of the genus Probles Förster, P. fulgida
sp. n., P. korusa
sp. n. and P. rukora
sp. n., belong to the subgenus Euporizon Horstmann and differ from other Palearctic species of the genus by a combination of long and apically weakly sinuate ovipositor and short temple. These three species are assigned to a newly designated fulgida species-group, and a portion of the key for identification of this species-group is provided. Based on the shape of the ovipositor apex, the fulgida species-group resemble members of the subgenus Microdiaparsis Horstmann but are distinct in having a much shorter temple. 相似文献
40.
Natalia Pozdnyakova Ekaterina Dubrovskaya Marina Chernyshova Oleg Makarov Sergey Golubev Svetlana Balandina Olga Turkovskaya 《Fungal biology》2018,122(5):363-372
The degradation of two isomeric three-ringed polycyclic aromatic hydrocarbons by the white rot fungus Pleurotus ostreatus D1 and the litter-decomposing fungus Agaricus bisporus F-8 was studied. Despite some differences, the degradation of phenanthrene and anthracene followed the same scheme, forming quinone metabolites at the first stage. The further fate of these metabolites was determined by the composition of the ligninolytic enzyme complexes of the fungi. The quinone metabolites of phenanthrene and anthracene produced in the presence of only laccase were observed to accumulate, whereas those formed in presence of laccase and versatile peroxidase were metabolized further to form products that were further included in basal metabolism (e.g. phthalic acid). Laccase can catalyze the initial attack on the PAH molecule, which leads to the formation of quinones, and that peroxidase ensures their further oxidation, which eventually leads to PAH mineralization.A. bisporus, which produced only laccase, metabolized phenanthrene and anthracene to give the corresponding quinones as the dominant metabolites. No products of further utilization of these compounds were detected. Thus, the fungi's affiliation with different ecophysiological groups and their cultivation conditions affect the composition and dynamics of production of the ligninolytic enzyme complex and the completeness of PAH utilization. 相似文献