• MeSH
• Chromosomes MeSH
• Heterochromatin MeSH

• MeSH
• Heterochromatin MeSH
• Humans MeSH
• Chromosome Mapping MeSH
• Breast Neoplasms genetics   MeSH
• Ovarian Neoplasms genetics   MeSH
• Check Tag
• Humans MeSH
• Female MeSH

• MeSH
• Biomedical Research MeSH
• Heterochromatin MeSH
• Chromosomes, Human MeSH
• Publication type
• Comparative Study MeSH

Recent studies have shown that histone code dictates the type and structure of chromatin. Bearing in mind the importance of A-type lamins for chromatin arrangement, we studied the effect of trichostatin A (TSA)-induced histone hyperacetylation in lamin A/C-deficient (LMNA-/-) fibroblasts. Lamin A/C deficiency caused condensation of chromosome territories and the nuclear reorganization of centromeric heterochromatin, which was accompanied by the appearance of a chain-like morphology of HP1beta foci. Conversely, histone deacetylase (HDAC) inhibition induced de-condensation of chromosome territories, which compensated the effect of lamin A/C deficiency on chromosome regions. The amount of heterochromatin in the area associated with the nuclear membrane was significantly reduced in LMNA-/- cells when compared with lamin A/C-positive (LMNA+/+) fibroblasts. TSA also decreased the amount of peripheral heterochromatin, similarly as lamin A/C deficiency. In both LMNA+/+ and LMNA-/- cells, physically larger chromosomes were positioned more peripherally as compared with the smaller ones, even after TSA treatment. Our observations indicate that lamin A/C deficiency causes not only reorganization of chromatin and some chromatin-associated domains, but also has an impact on the extent of chromosome condensation. As HDAC inhibition can compensate the lamin A/C-dependent chromatin changes, the interaction between lamins and specifically modified histones may play an important role in higher-order chromatin organization, which influences transcriptional activity.

• MeSH
• Acetylation drug effects   MeSH
• Cell Nucleus metabolism   MeSH
• Centromere metabolism   MeSH
• Chromatin metabolism   drug effects   MeSH
• Fibroblasts metabolism   MeSH
• Financing, Organized MeSH
• Heterochromatin metabolism   MeSH
• Enzyme Inhibitors pharmacology   MeSH
• Histone Deacetylase Inhibitors MeSH
• Nuclear Proteins metabolism   MeSH
• Hydroxamic Acids pharmacology   MeSH
• Lamin Type A genetics   metabolism   deficiency   MeSH
• Lamin Type B metabolism   MeSH
• Mice MeSH
• Chromatin Assembly and Disassembly drug effects   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH

Anchoring of heterochromatin to the nuclear envelope appears to be an important process ensuring the spatial organization of the chromatin structure and genome function in eukaryotic nuclei. Proteins of the inner nuclear membrane (INM) mediating these interactions are able to recognize lamina-associated heterochromatin domains (termed LAD) and simultaneously bind either lamin A/C or lamin B1. One of these proteins is the lamin B receptor (LBR) that binds lamin B1 and tethers heterochromatin to the INM in embryonic and undifferentiated cells. It is replaced by lamin A/C with specific lamin A/C binding proteins at the beginning of cell differentiation and in differentiated cells. Our functional experiments in cancer cell lines show that heterochromatin in cancer cells is tethered to the INM by LBR, which is downregulated together with lamin B1 at the onset of cell transition to senescence. The downregulation of these proteins in senescent cells leads to the detachment of centromeric repetitive sequences from INM, their relocation to the nucleoplasm, and distension. In cells, the expression of LBR and LB1 is highly coordinated as evidenced by the reduction of both proteins in LBR shRNA lines. The loss of the constitutive heterochromatin structure containing LADs results in changes in chromatin architecture and genome function and can be the reason for the permanent loss of cell proliferation in senescence.

• Publication type
• Journal Article MeSH
• Review MeSH

Cellular senescence, an irreversible proliferation arrest evoked by stresses such as oncogene activation, telomere dysfunction, or diverse genotoxic insults, has been implicated in tumor suppression and aging. Primary human fibroblasts undergoing oncogene-induced or replicative senescence are known to form senescence-associated heterochromatin foci (SAHF), nuclear DNA domains stained densely by DAPI and enriched for histone modifications including lysine9-trimethylated histone H3. While cellular senescence occurs also in premalignant human lesions, it is unclear how universal is SAHF formation among various cell types, under diverse stresses, and whether SAHF occur in vivo. Here, we report that human primary fibroblasts (BJ and MRC-5) and primary keratinocytes undergoing replicative senescence, or premature senescence induced by oncogenic H-Ras, diverse chemotherapeutics and bacterial cytolethal distending toxin, show differential capacity to form SAHF. Whereas all tested cell types formed SAHF in response to activated H-Ras, only MRC-5, but not BJ fibroblasts or keratinocytes, formed SAHF under senescence induced by etoposide, doxorubicin, hydroxyurea, bacterial intoxication or telomere attrition. In addition, DAPI-defined SAHF were detected on paraffin sections of Ras-transformed cultured fibroblasts, but not human lesions at various stages of tumorigenesis. Overall, our results indicate that unlike the widely present DNA damage response marker γH2AX, SAHF is not a common feature of cellular senescence. Whereas SAHF formation is shared by diverse cultured cell types under oncogenic stress, SAHF are cell-type-restricted under genotoxin-induced and replicative senescence. Furthermore, while the DNA/DAPI-defined SAHF formation in cultured cells parallels enhanced expression of p16(ink4a) , such 'prototypic' SAHF are not observed in tissues, including premalignant lesions, irrespective of enhanced p16(ink4a) and other features of cellular senescence.

• MeSH
• Bacterial Toxins pharmacology   MeSH
• Cell Line MeSH
• Genes, ras MeSH
• Heterochromatin chemistry   MeSH
• Cyclin-Dependent Kinase Inhibitor p16 genetics   metabolism   physiology   MeSH
• Humans MeSH
• DNA Damage MeSH
• Cell Proliferation MeSH
• Cellular Senescence drug effects   genetics   physiology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

• MeSH
• Epigenesis, Genetic MeSH
• Gene Expression Regulation MeSH
• Publication type
• Monograph MeSH

• Conspectus
• Biotechnologie. Genetické inženýrství
• NML Fields
• genetika, lékařská genetika

Hybridization of closely related plant species is frequently connected to endosperm arrest and seed failure, for reasons that remain to be identified. In this study, we investigated the molecular events accompanying seed failure in hybrids of the closely related species pair Capsella rubella and C. grandiflora. Mapping of QTL for the underlying cause of hybrid incompatibility in Capsella identified three QTL that were close to pericentromeric regions. We investigated whether there are specific changes in heterochromatin associated with interspecific hybridizations and found a strong reduction of chromatin condensation in the endosperm, connected with a strong loss of CHG and CHH methylation and random loss of a single chromosome. Consistent with reduced DNA methylation in the hybrid endosperm, we found a disproportionate deregulation of genes located close to pericentromeric regions, suggesting that reduced DNA methylation allows access of transcription factors to targets located in heterochromatic regions. Since the identified QTL were also associated with pericentromeric regions, we propose that relaxation of heterochromatin in response to interspecies hybridization exposes and activates loci leading to hybrid seed failure.

• MeSH
• Capsella classification   genetics   MeSH
• Centromere genetics   MeSH
• Chromatin genetics   metabolism   MeSH
• Chromosome Aberrations MeSH
• Species Specificity MeSH
• Endosperm genetics   MeSH
• Heterochromatin genetics   metabolism   MeSH
• Hybridization, Genetic * MeSH
• Quantitative Trait Loci genetics   MeSH
• DNA Methylation MeSH
• Gene Expression Regulation, Plant MeSH
• Genes, Plant genetics   MeSH
• Seeds genetics   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

In this work, we have studied the structural and functional linkage between lamin A/C, nuclear actin, and organization of chromosome territories (CTs) in mammary carcinoma MCF-7 cells. Selective down-regulation of lamin A/C expression led to disruption of the lamin A/C perinuclear layer and disorganization of lamin-bound emerin complexes at the inner nuclear membrane. The silencing of lamin A/C expression resulted in a decrease in the volume and surface area of chromosome territories, especially in chromosomes with high heterochromatin content. Inhibition of actin polymerization led to relaxation of the structure of chromosome territories, and an increase in the volumes and surface areas of the chromosome territories of human chromosomes 1, 2 and 13. The results show an important role of polymeric actin in the organization of the nuclei and the chromosome territories.

• MeSH
• Actins metabolism   MeSH
• Cell Nucleus metabolism   MeSH
• Down-Regulation MeSH
• Financing, Organized MeSH
• Genome, Human genetics   MeSH
• Microscopy, Confocal MeSH
• Lamin Type A metabolism   MeSH
• Humans MeSH
• Chromosomes, Human metabolism   MeSH
• Cell Line, Tumor MeSH
• Cell Shape MeSH
• Check Tag
• Humans MeSH

The bighead carps of the genus Hypophthalmichthys (H. molitrix and H. nobilis) are important aquaculture species. They were subjected to extensive multidisciplinary research, but with cytogenetics confined to conventional protocols only. Here, we employed Giemsa-/C-/CMA3- stainings and chromosomal mapping of multigene families and telomeric repeats. Both species shared (i) a diploid chromosome number 2n = 48 and the karyotype structure, (ii) low amount of constitutive heterochromatin, (iii) the absence of interstitial telomeric sites (ITSs), (iv) a single pair of 5S rDNA loci adjacent to one major rDNA cluster, and (v) a single pair of co-localized U1/U2 snDNA tandem repeats. Both species, on the other hand, differed in (i) the presence/absence of remarkable interstitial block of constitutive heterochromatin on the largest acrocentric pair 11 and (ii) the number of major (CMA3-positive) rDNA sites. Additionally, we applied here, for the first time, the conventional cytogenetics in H. harmandi, a species considered extinct in the wild and/or extensively cross-hybridized with H. molitrix. Its 2n and karyotype description match those found in the previous two species, while silver staining showed differences in distribution of major rDNA. The bighead carps thus represent another case of taxonomic diversity not associated with gross karyotype differentiation, where 2n and karyotype structure cannot help in distinguishing between genomes of closely related species. On the other hand, we demonstrated that two cytogenetic characters (distribution of constitutive heterochromatin and major rDNA) may be useful for diagnosis of pure species. The universality of these markers must be further verified by analyzing other pure populations of bighead carps.

• MeSH
• Cell Differentiation genetics   MeSH
• Cytogenetics methods   MeSH
• Phylogeny * MeSH
• Genetic Variation genetics   MeSH
• Heterochromatin genetics   MeSH
• In Situ Hybridization, Fluorescence MeSH
• Carps genetics   MeSH
• Karyotype * MeSH
• Karyotyping methods   MeSH
• Chromosome Mapping MeSH
• DNA, Ribosomal genetics   MeSH
• Tandem Repeat Sequences genetics   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH