Chromosome pairing in meiosis usually starts in the vicinity of the telomere attachment to the nuclear membrane and congregation of telomeres in the leptotene bouquet is believed responsible for bringing homologue pairs together. In a heterozygote for an inversion of a rye (Secale cereale L.) chromosome arm in wheat, a distal segment of the normal homologue is capable of chiasmate pairing with its counterpart in the inverted arm, located near the centromere. Using 3D imaging confocal microscopy, we observed that some telomeres failed to be incorporated into the bouquet and occupied various positions throughout the entire volume of the nucleus, including the centromere pole. Rye telomeres appeared ca. 21 times more likely to fail to be included in the telomere bouquet than wheat telomeres. The frequency of the out-of-bouquet rye telomere position in leptotene was virtually identical to the frequency of telomeres deviating from Rabl's orientation in the nuclei of somatic cells, and was similar to the frequency of synapsis of the normal and inverted chromosome arms, but lower than the MI pairing frequency of segments of these two arms normally positioned across the volume of the nucleus. Out-of-position placement of the rye telomeres may be responsible for reduced MI pairing of rye chromosomes in hybrids with wheat and their disproportionate contribution to aneuploidy, but appears responsible for initiating chiasmate pairing of distantly positioned segments of homology in an inversion heterozygote.
- MeSH
- buněčné jádro genetika ultrastruktura MeSH
- centromera chemie ultrastruktura MeSH
- chiméra genetika MeSH
- chromozomální inverze * MeSH
- chromozomy rostlin chemie ultrastruktura MeSH
- druhová specificita MeSH
- heterozygot MeSH
- hybridizace in situ fluorescenční MeSH
- konfokální mikroskopie MeSH
- párování chromozomů MeSH
- počítačové zpracování obrazu statistika a číselné údaje MeSH
- profáze meiózy I * MeSH
- pšenice genetika ultrastruktura MeSH
- rostlinné buňky metabolismus ultrastruktura MeSH
- telomery chemie ultrastruktura MeSH
- žito genetika ultrastruktura MeSH
- zobrazování trojrozměrné metody MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, U.S. Gov't, Non-P.H.S. MeSH
Cellular transition to senescence is associated with extensive chromatin reorganization and changes in gene expression. Recent studies appear to imply an association of lamin B1 (LB1) reduction with chromatin rearrangement in human fibroblasts promoted to senescence, while the mechanisms and structural features of these relationships have not yet been clarified. In this work, we examined the functions of LB1 and the lamin B receptor (LBR) in human cancer cells. We found that both LB1 and LBR tend to deplete during cancer cell transfer to senescence by γ-irradiation. A functional study employing silencing of LBR by small hairpin ribonucleic acid (shRNA) constructs revealed reduced LB1 levels suggesting that the regulation of both proteins is interrelated. The reduced expression of LBR resulted in the relocation of centromeric heterochromatin (CSH) from the inner nuclear membrane (INM) to the nucleoplasm and is associated with its unfolding. This indicates that LBR tethers heterochromatin to INM in cycling cancer cells and that LB1 is an integral part of this tethering. Down-regulation of LBR and LB1 at the onset of senescence are thus necessary for the release of heterochromatin binding to lamina, resulting in changes in chromatin architecture and gene expression. However, the senescence phenotype was not manifested in cell lines with reduced LBR and LB1 expression suggesting that other factors, such as deoxyribonucleic acid (DNA) damage, are needed to trigger senescence. We conclude that the primary response of cells to various stresses leading to senescence consists of the down-regulation of LBR and LB1 to attain reversal of the chromatin architecture.
- MeSH
- centromera metabolismus účinky záření ultrastruktura MeSH
- heterochromatin metabolismus účinky záření ultrastruktura MeSH
- jaderný obal metabolismus účinky záření ultrastruktura MeSH
- lamin typ B genetika metabolismus MeSH
- lidé MeSH
- malá interferující RNA genetika metabolismus MeSH
- MFC-7 buňky MeSH
- nádorové buněčné linie MeSH
- osteoblasty metabolismus patologie účinky záření MeSH
- receptory cytoplazmatické a nukleární antagonisté a inhibitory genetika metabolismus MeSH
- regulace genové exprese u nádorů * MeSH
- signální transdukce MeSH
- stárnutí buněk účinky záření MeSH
- záření gama MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
The frequency of cells containing micronuclei (MN) and the presence of centromeres in these MN were analyzed in lymphocytes of 98 men from Southern Bohemia. Forty-six of them had worked at the uranium processing plant 'MAPE Mydlovary' which was closed in 1991, and 52 men were controls from the same area. FISH using human pan-centromeric chromosome paint was employed to detect centromere-positive (CEN+) and -negative (CEN-) MN. A total of 1,000 binucleated cells (BNC) per participant were analyzed after cytochalasin B treatment. All BNC with MN (CEN+ or CEN-) were recorded. No differences were found between formerly exposed workers and the control group, neither in the total frequency of cells with MN per 1,000 BNC (mean levels ± SD, 9.1 ± 3.1 and 9.8 ± 2.5, respectively) nor in the percentage of CEN- MN, which were equal (50 ± 18 and 49 ± 17, respectively). Also, there was no difference between individuals living in the 3 villages closest to the uranium processing plant and those living further away. Considering the fact that effective doses of the workers at MAPE Mydlovary were overall similar to those of former uranium miners in whom higher frequencies of CEN- MN have been found more than 10 years after they had finished working underground, these results are somewhat surprising. A more detailed analysis of the exposures indicates that uranium miners received a greater percentage of their effective dose from the inhalation of radon and its daughters, whereas uranium processing workers received it from the incorporation of long-lived radioactive nuclides such as uranium. If, as has been suggested before, the higher level of DNA damage in miners is due to induced genomic instability, then this phenomenon may be related to radon exposure rather than exposure to uranium.
- MeSH
- centromera účinky léků ultrastruktura MeSH
- cytochalasin B farmakologie MeSH
- hornictví * MeSH
- hybridizace in situ fluorescenční MeSH
- lidé středního věku MeSH
- lidé MeSH
- lymfocyty účinky léků ultrastruktura MeSH
- mikrojaderné testy MeSH
- mikrojádra chromozomálně defektní statistika a číselné údaje MeSH
- pracovní expozice * MeSH
- radiometrie MeSH
- radon toxicita MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- uran toxicita MeSH
- Check Tag
- lidé středního věku MeSH
- lidé MeSH
- mužské pohlaví MeSH
- senioři nad 80 let MeSH
- senioři MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Geografické názvy
- Česká republika MeSH
A new repeated DNA from Microtus thomasi, Mth-Alu2.2, was cloned and characterized and is presented here for the first time. Digestion of genomic DNA from M. thomasi with AluI restriction enzyme revealed a 2.2-kb repetitive DNA sequence with a high AT content (69%). This sequence consists of a tandemly repeated nonanucleotide of the consensus sequence CACAATGTA, which constitutes approximately 93-95% of the total unit length. The location of the Mth-Alu2.2 sequence in the karyotype was determined by FISH, demonstrating strong hybridization signals in the pericentromeric regions of all chromosomes and in the heterochromatin blocks of several X chromosome variants. In addition, the distribution of the 4 pericentromeric repeat sequences Msat-160, Mth-Alu900, Mth-Alu2.2, and interstitial telomeric repeats was analyzed by in situ hybridization in M. thomasi, in order to shed light on the complex composition of the chromosomal pericentromeric regions in this species. The order and organization of these sequences in the pericentromeric regions are conserved, with slight variations in both the degree of overlapping and the amount of each repeated DNA in the chromosomes. Specifically, Mth-Alu2.2 is localized in the terminal regions of the chromosomes, with Msat-160 occupying the immediately inner region, partially intermixed with Mth-Alu2.2. The sequence Mth-Alu900 is found in internal positions below Msat-160, and the interstitial telomeric repeats are located close to the long-arm euchromatin of the chromosomes.
- MeSH
- Arvicolinae genetika metabolismus MeSH
- buněčný rodokmen MeSH
- centromera ultrastruktura MeSH
- centrozom ultrastruktura MeSH
- DNA chemie MeSH
- fenotyp MeSH
- heterochromatin chemie MeSH
- hybridizace in situ fluorescenční MeSH
- karyotypizace MeSH
- křížení genetické MeSH
- repetitivní sekvence nukleových kyselin MeSH
- telomery ultrastruktura MeSH
- zvířata MeSH
- Check Tag
- mužské pohlaví MeSH
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
