Mechanisms and functions of nuclear envelope remodelling
01 Apr 2017-Nature Reviews Molecular Cell Biology (Nature Publishing Group)-Vol. 18, Iss: 4, pp 229-245
TL;DR: The nuclear envelope is shown to be a dynamic and highly adaptable boundary that changes composition during differentiation, deforms in response to mechanical challenges, can be repaired upon rupture and even rapidly disassembles and reforms during open mitosis.
Abstract: As a compartment border, the nuclear envelope (NE) needs to serve as both a protective membrane shell for the genome and a versatile communication interface between the nucleus and the cytoplasm. Despite its important structural role in sheltering the genome, the NE is a dynamic and highly adaptable boundary that changes composition during differentiation, deforms in response to mechanical challenges, can be repaired upon rupture and even rapidly disassembles and reforms during open mitosis. NE remodelling is fundamentally involved in cell growth, division and differentiation, and if perturbed can lead to devastating diseases such as muscular dystrophies or premature ageing.
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01 Mar 2016
TL;DR: A review of the current status of pore complex research with a focus on the functional implications of its structural and compositional heterogeneity is provided in this article, where the structural elements exhibit flexibility, which may hold a clue in understanding NPC assembly and function.
Abstract: Nuclear pore complexes (NPCs) perforate the nuclear envelope and serve as the primary transport gates for molecular exchange between nucleus and cytoplasm. Stripping the megadalton complex down to its most essential organizational elements, one can divide the NPC into scaffold components and the disordered elements attached to them that generate a selective barrier between compartments. These structural elements exhibit flexibility, which may hold a clue in understanding NPC assembly and function. Here we review the current status of NPC research with a focus on the functional implications of its structural and compositional heterogeneity.
263 citations
TL;DR: It is shown that spindle microtubules block assembly of NPCs and other non-core nuclear envelope proteins on lagging chromosomes, causing an irreversible defect in nuclear envelope assembly, which leads to spontaneous envelope disruption of micronuclei and subsequent genome instability.
Abstract: Defects in the architecture or integrity of the nuclear envelope are associated with a variety of human diseases1. Micronuclei, one common nuclear aberration, are an origin for chromothripsis2, a catastrophic mutational process that is commonly observed in cancer3–5. Chromothripsis occurs after micronuclei spontaneously lose nuclear envelope integrity, which generates chromosome fragmentation6. Disruption of the nuclear envelope exposes DNA to the cytoplasm and initiates innate immune proinflammatory signalling7. Despite its importance, the basis of the fragility of the micronucleus nuclear envelope is not known. Here we show that micronuclei undergo defective nuclear envelope assembly. Only ‘core’ nuclear envelope proteins8,9 assemble efficiently on lagging chromosomes, whereas ‘non-core’ nuclear envelope proteins8,9, including nuclear pore complexes (NPCs), do not. Consequently, micronuclei fail to properly import key proteins that are necessary for the integrity of the nuclear envelope and genome. We show that spindle microtubules block assembly of NPCs and other non-core nuclear envelope proteins on lagging chromosomes, causing an irreversible defect in nuclear envelope assembly. Accordingly, experimental manipulations that position missegregated chromosomes away from the spindle correct defective nuclear envelope assembly, prevent spontaneous nuclear envelope disruption, and suppress DNA damage in micronuclei. Thus, during mitotic exit in metazoan cells, chromosome segregation and nuclear envelope assembly are only loosely coordinated by the timing of mitotic spindle disassembly. The absence of precise checkpoint controls may explain why errors during mitotic exit are frequent and often trigger catastrophic genome rearrangements4,5. The mitotic spindle prevents normal nuclear envelope assembly on missegregated chromosomes, leading to spontaneous envelope disruption of micronuclei and subsequent genome instability.
207 citations
TL;DR: It is shown that the inner nuclear membrane is an adaptable membrane territory capable of lipid metabolism and a link between INM metabolism and genome regulation and have potential relevance for human lipodystrophy.
188 citations
Howard Hughes Medical Institute1, University of California, San Francisco2, Columbia University3, University of Massachusetts Amherst4, Massachusetts Institute of Technology5, Francis Crick Institute6, Randall Division of Cell and Molecular Biophysics7, University of North Carolina at Chapel Hill8, Donald Danforth Plant Science Center9, Laboratory of Molecular Biology10, Stowers Institute for Medical Research11, University of Kansas12, Research Institute of Molecular Pathology13, Stanford University14
TL;DR: A range of 'non-model model organisms' are highlighted as emerging systems for tackling questions across the whole spectrum of biology (and beyond), the opportunities and challenges, and the outlook for the future.
Abstract: Model organisms are widely used in research as accessible and convenient systems to study a particular area or question in biology. Traditionally only a handful of organisms have been widely studied, but modern research tools are enabling researchers to extend the set of model organisms to include less-studied and more unusual systems. This Forum highlights a range of 'non-model model organisms' as emerging systems for tackling questions across the whole spectrum of biology (and beyond), the opportunities and challenges, and the outlook for the future.
164 citations
Cites background from "Mechanisms and functions of nuclear..."
...Although work by many groups provided detailed insights into the mechanisms underlying NE remodeling in a number of organisms [93, 94], we understand very little about how these circuitries evolve....
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TL;DR: This study reveals that BAF-mediated changes in chromosome mechanics underlie nuclear assembly with broad implications for proper genome function.
159 citations
Cites background from "Mechanisms and functions of nuclear..."
...During interphase of the cell cycle, various transmembrane proteins link the nuclear envelope (NE) to chromatin either by direct binding to DNA or by binding to adaptor proteins like barrier-to-autointegration factor (BAF) (Ungricht and Kutay, 2017; Wandke and Kutay, 2013)....
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References
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TL;DR: It is found that one, or indeed more than one, cancer-causing lesion can emerge out of the genomic crisis, which has important implications for the origins of genomic remodeling and temporal emergence of cancer.
2,099 citations
TL;DR: Evidence of mutations in lamin A (LMNA) as the cause of Hutchinson–Gilford progeria syndrome is presented, and the discovery of the molecular basis of this disease may shed light on the general phenomenon of human ageing.
Abstract: Hutchinson-Gilford progeria syndrome (HGPS) is a rare genetic disorder characterized by features reminiscent of marked premature ageing. Here, we present evidence of mutations in lamin A (LMNA) as the cause of this disorder. The HGPS gene was initially localized to chromosome 1q by observing two cases of uniparental isodisomy of 1q-the inheritance of both copies of this material from one parent-and one case with a 6-megabase paternal interstitial deletion. Sequencing of LMNA, located in this interval and previously implicated in several other heritable disorders, revealed that 18 out of 20 classical cases of HGPS harboured an identical de novo (that is, newly arisen and not inherited) single-base substitution, G608G(GGC > GGT), within exon 11. One additional case was identified with a different substitution within the same codon. Both of these mutations result in activation of a cryptic splice site within exon 11, resulting in production of a protein product that deletes 50 amino acids near the carboxy terminus. Immunofluorescence of HGPS fibroblasts with antibodies directed against lamin A revealed that many cells show visible abnormalities of the nuclear membrane. The discovery of the molecular basis of this disease may shed light on the general phenomenon of human ageing.
1,963 citations
TL;DR: A high-resolution map of the interaction sites of the entire genome with NL components in human fibroblasts is constructed and demonstrates that the human genome is divided into large, discrete domains that are units of chromosome organization within the nucleus.
Abstract: The architecture of human chromosomes in interphase nuclei is still largely unknown. Microscopy studies have indicated that specific regions of chromosomes are located in close proximity to the nuclear lamina (NL). This has led to the idea that certain genomic elements may be attached to the NL, which may contribute to the spatial organization of chromosomes inside the nucleus. However, sequences in the human genome that interact with the NL in vivo have not been identified. Here we construct a high-resolution map of the interaction sites of the entire genome with NL components in human fibroblasts. This map shows that genome-lamina interactions occur through more than 1,300 sharply defined large domains 0.1-10 megabases in size. These lamina-associated domains (LADs) are typified by low gene-expression levels, indicating that LADs represent a repressive chromatin environment. The borders of LADs are demarcated by the insulator protein CTCF, by promoters that are oriented away from LADs, or by CpG islands, suggesting possible mechanisms of LAD confinement. Taken together, these results demonstrate that the human genome is divided into large, discrete domains that are units of chromosome organization within the nucleus.
1,762 citations
TL;DR: In this article, proteomics analyses revealed that levels of the nucleoskeletal protein lamin-A scaled with tissue elasticity, as did levels of collagens in the extracellular matrix that determine E.
Abstract: Tissues can be soft like fat, which bears little stress, or stiff like bone, which sustains high stress, but whether there is a systematic relationship between tissue mechanics and differentiation is unknown. Here, proteomics analyses revealed that levels of the nucleoskeletal protein lamin-A scaled with tissue elasticity, E, as did levels of collagens in the extracellular matrix that determine E. Stem cell differentiation into fat on soft matrix was enhanced by low lamin-A levels, whereas differentiation into bone on stiff matrix was enhanced by high lamin-A levels. Matrix stiffness directly influenced lamin-A protein levels, and, although lamin-A transcription was regulated by the vitamin A/retinoic acid (RA) pathway with broad roles in development, nuclear entry of RA receptors was modulated by lamin-A protein. Tissue stiffness and stress thus increase lamin-A levels, which stabilize the nucleus while also contributing to lineage determination.
1,563 citations
TL;DR: It is demonstrated that SIRT6 is a nuclear, chromatin-associated protein that promotes resistance to DNA damage and suppresses genomic instability in mouse cells, in association with a role in base excision repair (BER).
1,399 citations