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

One of the remarkable features of eukaryotes is the nucleus, delimited by the nuclear envelope (NE), a complex structure and home to the nuclear lamina and nuclear pore complex (NPC). For decades, these structures were believed to be mainly architectural elements and, in the case of the NPC, simply facilitating nucleocytoplasmic trafficking. More recently, the critical roles of the lamina, NPC and other NE constituents in genome organisation, maintaining chromosomal domains and regulating gene expression have been recognised. Importantly, mutations in genes encoding lamina and NPC components lead to pathogenesis in humans, while pathogenic protozoa disrupt the progression of normal development and expression of pathogenesis-related genes. Here, we review features of the lamina and NPC across eukaryotes and discuss how these elements are structured in trypanosomes, protozoa of high medical and veterinary importance, highlighting lineage-specific and conserved aspects of nuclear organisation.

• Klíčová slova
• evolutionary diversity, nuclear lamina, nuclear pore complex, nucleus, trypanosoma,
• MeSH
• aktivní transport - buněčné jádro fyziologie   MeSH
• jaderný obal MeSH
• jaderný pór genetika   metabolismus   MeSH
• komplex proteinů jaderného póru * metabolismus   MeSH
• lidé MeSH
• Trypanosoma * genetika   metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• komplex proteinů jaderného póru * MeSH

The nuclear lamina supports many functions, including maintaining nuclear structure and gene expression control, and correct spatio-temporal assembly is vital to meet these activities. Recently, multiple lamina systems have been described that, despite independent evolutionary origins, share analogous functions. In trypanosomatids the two known lamina proteins, NUP-1 and NUP-2, have molecular masses of 450 and 170 kDa, respectively, which demands a distinct architecture from the ∼60 kDa lamin-based system of metazoa and other lineages. To uncover organizational principles for the trypanosome lamina we generated NUP-1 deletion mutants to identify domains and their arrangements responsible for oligomerization. We found that both the N- and C-termini act as interaction hubs, and that perturbation of these interactions impacts additional components of the lamina and nuclear envelope. Furthermore, the assembly of NUP-1 terminal domains suggests intrinsic organizational capacity. Remarkably, there is little impact on silencing of telomeric variant surface glycoprotein genes. We suggest that both terminal domains of NUP-1 have roles in assembling the trypanosome lamina and propose a novel architecture based on a hub-and-spoke configuration.

• Klíčová slova
• Heterochromatin, Lamina, Macromolecular assembly, Nuclear organization, Trypanosomatid,
• MeSH
• buněčné jádro MeSH
• jaderná lamina * genetika   MeSH
• jaderný obal MeSH
• laminy genetika   MeSH
• telomery MeSH
• Trypanosoma * MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• laminy 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

The nuclear lamina represents a multifunctional platform involved in such diverse yet interconnected processes as spatial organization of the genome, maintenance of mechanical stability of the nucleus, regulation of transcription and replication. Most of lamina activities are exerted through tethering of lamina-associated chromatin domains (LADs) to the nuclear periphery. Yet, the lamina is a dynamic structure demonstrating considerable expansion during the cell cycle to accommodate increased number of LADs formed during DNA replication. We analyzed dynamics of nuclear growth during interphase and changes in lamina structure as a function of cell cycle progression. The nuclear lamina demonstrates steady growth from G1 till G2, while quantitative analysis of lamina meshwork by super-resolution microscopy revealed that microdomain organization of the lamina is maintained, with lamin A and lamin B microdomain periodicity and interdomain gap sizes unchanged. FRAP analysis, in contrast, demonstrated differences in lamin A and B1 exchange rates; the latter showing higher recovery rate in S-phase cells. In order to further analyze the mechanism of lamina growth in interphase, we generated a lamina-free nuclear envelope in living interphase cells by reversible hypotonic shock. The nuclear envelope in nuclear buds formed after such a treatment initially lacked lamins, and analysis of lamina formation revealed striking difference in lamin A and B1 assembly: lamin A reassembled within 30 min post-treatment, whereas lamin B1 did not incorporate into the newly formed lamina at all. We suggest that in somatic cells lamin B1 meshwork growth is coordinated with replication of LADs, and lamin A meshwork assembly seems to be chromatin-independent process.

• Klíčová slova
• Cell cycle, DNA replication, Interphase, Microdomains, Nuclear lamina, Nucleus,
• MeSH
• Cricetulus MeSH
• interfáze * MeSH
• jaderná lamina chemie   metabolismus   MeSH
• kultivované buňky MeSH
• lidé MeSH
• myši MeSH
• prasata MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH