Lamins, the nuclear intermediate filaments, are important regulators of nuclear structural integrity as well as nuclear functional processes such as DNA transcription, replication and repair, and epigenetic regulations. A portion of phosphorylated lamin A/C localizes to the nuclear interior in interphase, forming a lamin A/C pool with specific properties and distinct functions. Nucleoplasmic lamin A/C molecular functions are mainly dependent on its binding partners; therefore, revealing new interactions could give us new clues on the lamin A/C mechanism of action. In the present study, we show that lamin A/C interacts with nuclear phosphoinositides (PIPs), and with nuclear myosin I (NM1). Both NM1 and nuclear PIPs have been previously reported as important regulators of gene expression and DNA damage/repair. Furthermore, phosphorylated lamin A/C forms a complex with NM1 in a phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2)-dependent manner in the nuclear interior. Taken together, our study reveals a previously unidentified interaction between phosphorylated lamin A/C, NM1, and PI(4,5)P2 and suggests new possible ways of nucleoplasmic lamin A/C regulation, function, and importance for the formation of functional nuclear microdomains.

• Klíčová slova
• NM1, PI(4,5)P2, cell nucleus, lamin A/C, nuclear lamina, nuclear myosin 1, nucleoplasm, phosphoinositides, phosphorylation,
• MeSH
• buněčné jádro * metabolismus   MeSH
• interfáze MeSH
• intermediární filamenta metabolismus   MeSH
• lamin typ A * metabolismus   MeSH
• lidé MeSH
• nádorové buněčné linie MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• lamin typ A * 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
• aktiny metabolismus   MeSH
• buněčné jádro metabolismus   MeSH
• down regulace MeSH
• genom lidský genetika   MeSH
• konfokální mikroskopie MeSH
• lamin typ A metabolismus   MeSH
• lidé MeSH
• lidské chromozomy metabolismus   MeSH
• nádorové buněčné linie MeSH
• tvar buňky MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• aktiny MeSH
• lamin C MeSH Prohlížeč
• lamin typ A MeSH

The nuclear lamina is a dense network of intermediate filaments beneath the inner nuclear membrane. Composed of A-type lamins (lamin A/C) and B-type lamins (lamins B1 and B2), the nuclear lamina provides a scaffold for the nuclear envelope and chromatin, thereby maintaining the structural integrity of the nucleus. A-type lamins are also found inside the nucleus where they interact with chromatin and participate in gene regulation. Viruses replicating in the cell nucleus have to overcome the nuclear envelope during the initial phase of infection and during the nuclear egress of viral progeny. Here, we focused on the role of lamins in the replication cycle of a dsDNA virus, mouse polyomavirus. We detected accumulation of the major capsid protein VP1 at the nuclear periphery, defects in nuclear lamina staining and different lamin A/C phosphorylation patterns in the late phase of mouse polyomavirus infection, but the nuclear envelope remained intact. An absence of lamin A/C did not affect the formation of replication complexes but did slow virus propagation. Based on our findings, we propose that the nuclear lamina is a scaffold for replication complex formation and that lamin A/C has a crucial role in the early phases of infection with mouse polyomavirus.

• Klíčová slova
• VP1, lamin A/C, lamin B, mouse polyomavirus, viral replication centres,
• MeSH
• buněčné jádro metabolismus   virologie   MeSH
• fosforylace MeSH
• infekce onkogenními viry virologie   patologie   metabolismus   genetika   MeSH
• jaderná lamina * metabolismus   virologie   MeSH
• jaderný obal metabolismus   virologie   MeSH
• lamin typ A * metabolismus   genetika   MeSH
• lamin typ B metabolismus   genetika   MeSH
• myši MeSH
• polyomavirové infekce * virologie   metabolismus   genetika   patologie   MeSH
• Polyomavirus * genetika   patogenita   fyziologie   MeSH
• replikace viru * MeSH
• virové plášťové proteiny metabolismus   genetika   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• lamin typ A * MeSH
• lamin typ B MeSH
• virové plášťové proteiny MeSH
• VP1 protein, polyomavirus MeSH Prohlížeč

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
• acetylace účinky léků   MeSH
• buněčné jádro metabolismus   MeSH
• centromera metabolismus   MeSH
• chromatin účinky léků   metabolismus   MeSH
• fibroblasty metabolismus   MeSH
• heterochromatin metabolismus   MeSH
• homolog proteinu s chromoboxem 5 MeSH
• inhibitory enzymů farmakologie   MeSH
• inhibitory histondeacetylas * MeSH
• jaderné proteiny metabolismus   MeSH
• kyseliny hydroxamové farmakologie   MeSH
• lamin typ A nedostatek   genetika   metabolismus   MeSH
• lamin typ B metabolismus   MeSH
• myši MeSH
• restrukturace chromatinu účinky léků   MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• CBX1 protein, human MeSH Prohlížeč
• chromatin MeSH
• heterochromatin MeSH
• homolog proteinu s chromoboxem 5 MeSH
• inhibitory enzymů MeSH
• inhibitory histondeacetylas * MeSH
• jaderné proteiny MeSH
• kyseliny hydroxamové MeSH
• lamin typ A MeSH
• lamin typ B MeSH
• LMNA protein, human MeSH Prohlížeč
• trichostatin A MeSH Prohlížeč

A- and C-type lamins are intermediate filament proteins responsible for the maintenance of nuclear shape and most likely nuclear architecture. Here, we propose that pronounced invaginations of A/C-type lamins into the nuclear interior represent channels for the transport of regulatory molecules to and from nuclear and nucleolar regions. Using fluorescent protein technology and immunofluorescence, we show that A-type lamin channels interact with several nuclear components, including fibrillarin- and UBF-positive regions of nucleoli, foci of heterochromatin protein 1 β, polycomb group bodies, and genomic regions associated with DNA repair. Similar associations were observed between A/C-type lamin channels and nuclear pores, lamin-associated protein LAP2α, and promyelocytic leukemia nuclear bodies. Interestingly, regions with high levels of A/C-type lamins had low levels of B-type lamins, and vice versa. These characteristics were observed in primary and immortalized mouse embryonic fibroblasts as well as human and mouse embryonic stem cell colonies exhibiting stem cell-specific lamin positivity. Our findings indicate that internal channels formed by nuclear lamins likely contribute to normal cellular processes through association with various nuclear and nucleolar structures.

• Klíčová slova
• CHROMATIN, DNA REPAIR, ES CELLS, HP1 PROTEIN, LAMINS, NUCLEAR PORES, PML BODIES, TRANSCRIPTION,
• MeSH
• buněčné jádro genetika   MeSH
• chromozomální proteiny, nehistonové ultrastruktura   MeSH
• DNA vazebné proteiny metabolismus   ultrastruktura   MeSH
• lamin typ A ultrastruktura   MeSH
• lamin typ B ultrastruktura   MeSH
• lidé MeSH
• membránové proteiny metabolismus   ultrastruktura   MeSH
• myši MeSH
• oprava DNA genetika   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• chromozomální proteiny, nehistonové MeSH
• DNA vazebné proteiny MeSH
• fibrillarin MeSH Prohlížeč
• lamin C MeSH Prohlížeč
• lamin typ A MeSH
• lamin typ B MeSH
• lamina-associated polypeptide 2 MeSH Prohlížeč
• membránové proteiny MeSH

The molecular architecture and assembly mechanism of intermediate filaments have been enigmatic for decades. Among those, lamin filaments are of particular interest due to their universal role in cell nucleus and numerous disease-related mutations. Filament assembly is driven by specific interactions of the elementary dimers, which consist of the central coiled-coil rod domain flanked by non-helical head and tail domains. We aimed to investigate the longitudinal 'head-to-tail' interaction of lamin dimers (the so-called ACN interaction), which is crucial for filament assembly. To this end, we prepared a series of recombinant fragments of human lamin A centred around the N- and C-termini of the rod. The fragments were stabilized by fusions to heterologous capping motifs which provide for a correct formation of parallel, in-register coiled-coil dimers. As a result, we established crystal structures of two N-terminal fragments one of which highlights the propensity of the coiled-coil to open up, and one C-terminal rod fragment. Additional studies highlighted the capacity of such N- and C-terminal fragments to form specific complexes in solution, which were further characterized using chemical cross-linking. These data yielded a molecular model of the ACN complex which features a 6.5 nm overlap of the rod ends.

• Klíčová slova
• X-ray crystallography, chemical cross-linking, intermediate filaments, mass spectrometry, nuclear lamins,
• MeSH
• hmotnostní spektrometrie MeSH
• krystalografie rentgenová MeSH
• lamin typ A chemie   MeSH
• lidé MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• lamin typ A MeSH

The lamins are components of nuclear lamina and they have a profound influence on nuclear structure and functions. They are encoded by three genes, LMNA, LMNB1 and LMNB2. A genomic fragment of the porcine LMNA gene (822 bp; from exons 7 to 9) was amplified by polymerase chain reaction and comparatively sequenced. Four single nucleotide polymorphisms (SNPs) were identified in intronic sequences: G162A, G208A, T367G and C618T. The SNPs are within the restriction sites for enzymes Bsh1236I, HpaII, AluI and Bsh1236I respectively. Allele frequencies at SNPs G208A, T367G and C618T were determined by using eight pig breeds. Linkage analysis in the Hohenheim Meishan x Piétrain family placed the LMNA gene in the chromosome 4q linkage group, between MEF2D and GBA (MEF2D - 3.0 cM - LMNA - 0.2 cM - GBA). In radiation hybrid mapping LMNA was most significantly linked to SW270 on chromosome 4 (39 cR; LOD = 7.86). The LMNA gene is located in the quantitative trait loci region for some carcass traits on chromosome 4q.

• MeSH
• alely MeSH
• genetická vazba genetika   MeSH
• jednonukleotidový polymorfismus genetika   MeSH
• lamin typ A genetika   MeSH
• mapování pomocí radiačních hybridů veterinární   MeSH
• prasata genetika   MeSH
• savčí chromozomy genetika   MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• lamin typ A 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.

• Klíčová slova
• cellular senescence, centromere-specific satellite heterochromatin, constitutive heterochromatin, heterochromatin tether, lamin A/C, lamin B receptor, lamin B1,
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH

The organization of the nuclear periphery is crucial for many nuclear functions. Nuclear lamins form dense network at the nuclear periphery and play a substantial role in chromatin organization, transcription regulation and in organization of nuclear pore complexes (NPCs). Here, we show that TPR, the protein located preferentially within the nuclear baskets of NPCs, associates with lamin B1. The depletion of TPR affects the organization of lamin B1 but not lamin A/C within the nuclear lamina as shown by stimulated emission depletion microscopy. Finally, reduction of TPR affects the distribution of NPCs within the nuclear envelope and the effect can be reversed by simultaneous knock-down of lamin A/C or the overexpression of lamin B1. Our work suggests a novel role for the TPR at the nuclear periphery: the TPR contributes to the organization of the nuclear lamina and in cooperation with lamins guards the interphase assembly of nuclear pore complexes.

• Klíčová slova
• Image analysis, Lamina, Lamins, Nuclear pore complex, Nucleus, Super-resolution imaging, TPR, Translocated promoter region,
• MeSH
• HeLa buňky MeSH
• jaderná lamina metabolismus   ultrastruktura   MeSH
• jaderný obal metabolismus   ultrastruktura   MeSH
• komplex proteinů jaderného póru antagonisté a inhibitory   genetika   metabolismus   MeSH
• lamin typ A antagonisté a inhibitory   genetika   metabolismus   MeSH
• lamin typ B genetika   metabolismus   MeSH
• lidé MeSH
• malá interferující RNA genetika   metabolismus   MeSH
• molekulární zobrazování MeSH
• protoonkogenní proteiny antagonisté a inhibitory   genetika   metabolismus   MeSH
• regulace genové exprese MeSH
• signální transdukce MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• komplex proteinů jaderného póru MeSH
• lamin typ A MeSH
• lamin typ B MeSH
• LMNA protein, human MeSH Prohlížeč
• malá interferující RNA MeSH
• protoonkogenní proteiny MeSH
• TPR protein, human MeSH Prohlížeč

Nuclear lamins are major architectural elements of the mammalian cell nucleus, and they have been implicated in the functional organization of the nuclear interior, possibly by providing structural support for nuclear compartments. Colocalization studies have suggested a structural role for lamins in the formation and maintenance of pre-mRNA splicing factor compartments. Here, we have directly tested this hypothesis by analysis of embryonic fibroblasts from knock-out mice lacking A- and C-type lamins. We show that the morphology and cellular properties of splicing factor compartments are independent of A- and C-type lamins. Genetic loss of lamins A/C has no effect on the cellular distribution of several pre-mRNA splicing factors and does not affect the compartment morphology as examined by light and electron microscopy. The association of splicing factors with the nuclear matrix fraction persists in the absence of lamins A/C. Live cell microscopy demonstrates that the intranuclear positional stability of splicing factor compartments is maintained and that the exchange dynamics of SF2/ASF between the compartments and the nucleoplasm is not affected by loss of lamin A/C. Our results demonstrate that formation and maintenance of intranuclear splicing factor compartments is independent of lamins A/C, and they argue against an essential structural role of lamins A/C in splicing factor compartment morphology.

• MeSH
• buněčné jádro metabolismus   MeSH
• časové faktory MeSH
• cytoplazma metabolismus   MeSH
• elektronová mikroskopie MeSH
• fibroblasty metabolismus   MeSH
• fluorescenční mikroskopie MeSH
• fluorescenční protilátková technika nepřímá MeSH
• konfokální mikroskopie MeSH
• lamin typ A fyziologie   MeSH
• laminy chemie   MeSH
• messenger RNA metabolismus   MeSH
• myši knockoutované MeSH
• myši MeSH
• proteiny vázající RNA chemie   metabolismus   MeSH
• sestřih RNA * MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• lamin C MeSH Prohlížeč
• lamin typ A MeSH
• laminy MeSH
• messenger RNA MeSH
• proteiny vázající RNA MeSH