Lacertid lizards are a widely radiated group of squamate reptiles with long-term stable ZZ/ZW sex chromosomes. Despite their family-wide homology of Z-specific gene content, previous cytogenetic studies revealed significant variability in the size, morphology, and heterochromatin distribution of their W chromosome. However, there is little evidence about the accumulation and distribution of repetitive content on lacertid chromosomes, especially on their W chromosome. In order to expand our knowledge of the evolution of sex chromosome repetitive content, we examined the topology of telomeric and microsatellite motifs that tend to often accumulate on the sex chromosomes of reptiles in the karyotypes of 15 species of lacertids by fluorescence in situ hybridization (FISH). The topology of the above-mentioned motifs was compared to the pattern of heterochromatin distribution, as revealed by C-banding. Our results show that the topologies of the examined motifs on the W chromosome do not seem to follow a strong phylogenetic signal, indicating independent and species-specific accumulations. In addition, the degeneration of the W chromosome can also affect the Z chromosome and potentially also other parts of the genome. Our study provides solid evidence that the repetitive content of the degenerated sex chromosomes is one of the most evolutionary dynamic parts of the genome.

• Klíčová slova
• C-banding, FISH, GATA, evolution, heterochromatin, karyotype, microsatellites, sex chromosomes, telomeres,
• MeSH
• chromozomy genetika   MeSH
• druhová specificita MeSH
• fylogeneze MeSH
• heterochromatin genetika   ultrastruktura   MeSH
• hybridizace in situ fluorescenční MeSH
• ještěři genetika   MeSH
• karyotyp MeSH
• mikrosatelitní repetice genetika   MeSH
• molekulární evoluce * MeSH
• nukleotidové motivy MeSH
• pohlavní chromozomy genetika   MeSH
• pruhování chromozomů MeSH
• repetitivní sekvence nukleových kyselin MeSH
• telomery genetika   MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• srovnávací studie MeSH
• Názvy látek
• heterochromatin 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
• receptor laminu B 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
• práce podpořená grantem MeSH
• Názvy látek
• heterochromatin MeSH
• lamin typ B MeSH
• malá interferující RNA MeSH
• receptory cytoplazmatické a nukleární MeSH

Although it is well known that chromosomes are non-randomly organized during interphase, it is not completely clear whether higher-order chromatin structure is transmitted from mother to daughter cells. Therefore, we addressed the question of how chromatin is rearranged during interphase and whether heterochromatin pattern is transmitted after mitosis. We additionally tested the similarity of chromatin arrangement in sister interphase nuclei. We noticed a very active cell rotation during interphase, especially when histone hyperacetylation was induced or transcription was inhibited. This natural phenomenon can influence the analysis of nuclear arrangement. Using photoconversion of Dendra2-tagged core histone H4 we showed that the distribution of chromatin in daughter interphase nuclei differed from that in mother cells. Similarly, the nuclear distribution of heterochromatin protein 1β (HP1β) was not completely identical in mother and daughter cells. However, identity between mother and daughter cells was in many cases evidenced by nucleolar composition. Moreover, morphology of nucleoli, HP1β protein, Cajal bodies, chromosome territories, and gene transcripts were identical in sister cell nuclei. We conclude that the arrangement of interphase chromatin is not transmitted through mitosis, but the nuclear pattern is identical in naturally synchronized sister cells. It is also necessary to take into account the possibility that cell rotation and the degree of chromatin condensation during functionally specific cell cycle phases might influence our view of nuclear architecture.

• MeSH
• buněčné jadérko účinky léků   genetika   ultrastruktura   MeSH
• buněčné linie MeSH
• Cajalova tělíska účinky léků   genetika   ultrastruktura   MeSH
• chromozomální proteiny, nehistonové genetika   metabolismus   MeSH
• daktinomycin farmakologie   MeSH
• fluorescenční barviva MeSH
• fluorescenční mikroskopie MeSH
• fotochemické procesy MeSH
• heterochromatin účinky léků   genetika   ultrastruktura   MeSH
• histony genetika   metabolismus   MeSH
• homolog proteinu s chromoboxem 5 MeSH
• inhibitory histondeacetylas farmakologie   MeSH
• inhibitory syntézy proteinů farmakologie   MeSH
• interfáze účinky léků   genetika   MeSH
• kyseliny hydroxamové farmakologie   MeSH
• lidé MeSH
• messenger RNA biosyntéza   MeSH
• mitóza účinky léků   genetika   MeSH
• myši MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• CBX1 protein, human MeSH Prohlížeč
• Cbx1 protein, mouse MeSH Prohlížeč
• chromozomální proteiny, nehistonové MeSH
• daktinomycin MeSH
• fluorescenční barviva MeSH
• heterochromatin MeSH
• histony MeSH
• homolog proteinu s chromoboxem 5 MeSH
• inhibitory histondeacetylas MeSH
• inhibitory syntézy proteinů MeSH
• kyseliny hydroxamové MeSH
• messenger RNA MeSH
• trichostatin A MeSH Prohlížeč

The nuclear arrangement of the ABL, c-MYC, and RB1 genes was quantitatively investigated in human undifferentiated HL-60 cells and in a terminally differentiated population of human granulocytes. The ABL gene was expressed in both cell types, the c-MYC gene was active in HL-60 cells and down-regulated in granulocytes, and expression of the RB1 gene was undetectable in HL-60 cells but up-regulated in granulocytes. The distances of these genes to the nuclear center (membrane), to the center of the corresponding chromosome territory, and to the nearest centromere were determined. During granulopoesis, the majority of selected genetic structures were repositioned closer to the nuclear periphery. The nuclear reposition of the genes studied did not correlate with the changes of their expression. In both cell types, the c-MYC and RB1 genes were located at the periphery of the chromosome territories regardless of their activity. The centromeres of chromosomes 8 and 13 were always positioned more centrally within the chromosome territory than the studied genes. Close spatial proximity of the c-MYC and RB1 genes with centromeric heterochromatin, forming the chromocenters, correlated with gene activity, although the nearest chromocenter of the silenced RB1 gene did not involve centromeric heterochromatin of chromosome 13 where the given gene is localized. In addition, the role of heterochromatin in gene silencing was studied in retinoblastoma cells. In these differentiated tumor cells, one copy of the RB1 gene was positioned near the heterochromatic chromosome X, and reduced RB1 gene activity was observed. In the experiments presented here, we provide evidence that the regulation of gene activity during important cellular processes such as differentiation or carcinogenesis may be realized through heterochromatin-mediated gene silencing.

• MeSH
• buněčná diferenciace MeSH
• buněčná membrána metabolismus   MeSH
• buněčné jádro chemie   metabolismus   MeSH
• G0 fáze MeSH
• G1 fáze MeSH
• geny abl genetika   MeSH
• heterochromatin metabolismus   ultrastruktura   MeSH
• HL-60 buňky MeSH
• hybridizace in situ fluorescenční MeSH
• lidé MeSH
• lidské chromozomy X MeSH
• lidské chromozomy, pár 13 MeSH
• lidské chromozomy, pár 8 MeSH
• metylace DNA MeSH
• nádorové buňky kultivované MeSH
• polymerázová řetězová reakce s reverzní transkripcí MeSH
• protoonkogenní proteiny c-abl biosyntéza   MeSH
• protoonkogenní proteiny c-myc biosyntéza   genetika   MeSH
• retinoblastomový protein biosyntéza   genetika   MeSH
• translokace genetická MeSH
• umlčování genů MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, P.H.S. MeSH
• Názvy látek
• heterochromatin MeSH
• protoonkogenní proteiny c-abl MeSH
• protoonkogenní proteiny c-myc MeSH
• retinoblastomový protein MeSH

Fluorescence in situ hybridization (FISH) combined with high-resolution cytometry was used to determine the topographic characteristics of the centromeric heterochromatin (of the chromosomes 6, 8, 9, 17) and the tumor suppressor gene TP53 (which is located on chromosome 17) in cells of the human leukemia cell lines ML-1 and U937. Analysis was performed on cells that were either untreated or irradiated with gamma rays and incubated for different intervals after exposure. Compared to untreated cells, homologous centromeres and the TP53 genes were found closer to each other and also closer to the nuclear center 2 h after irradiation. The spatial relationship between genetic elements returned to that of the unirradiated controls during the next 2-3 h. Statistical evaluation of our experimental results shows that homologous centromeres and the homologous genes are positioned closer to each other 2 h after irradiation because they are localized closer to the center of the nucleus (probably due to more pronounced decondensation of the chromatin related to repair). This radial movement of genetic loci, however, is not connected with repair of DSBs by processes involving homologous recombination, because the angular distribution of homologous sequences remains random after irradiation.

• MeSH
• buněčné jádro chemie   účinky záření   ultrastruktura   MeSH
• centromera chemie   účinky záření   ultrastruktura   MeSH
• geny účinky záření   MeSH
• heterochromatin chemie   účinky záření   ultrastruktura   MeSH
• hybridizace in situ fluorescenční MeSH
• leukemie genetika   patologie   MeSH
• lidé MeSH
• lidské chromozomy chemie   účinky záření   ultrastruktura   MeSH
• nádorové kmenové buňky chemie   účinky záření   ultrastruktura   MeSH
• oprava DNA MeSH
• počítačové zpracování obrazu MeSH
• poškození DNA MeSH
• rekombinace genetická MeSH
• U937 buňky chemie   účinky záření   ultrastruktura   MeSH
• záření gama MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• heterochromatin MeSH

• MeSH
• chromozom Y ultrastruktura   MeSH
• heterochromatin ultrastruktura   MeSH
• lidé MeSH
• lidské chromozomy, 1-3 ultrastruktura   MeSH
• lidské chromozomy, 16-18 ultrastruktura   MeSH
• lidské chromozomy, 6-12 a X ultrastruktura   MeSH
• pruhování chromozomů * MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• heterochromatin MeSH