LAP2α and BAF transiently localize to telomeres and specific regions on chromatin during nuclear assembly

Dechat, Thomas; Gajewski, Andreas; Korbei, Barbara; Gerlich, Daniel W.; Daigle, Nathalie; Haraguchi, Tokuko; Furukawa, Kazuhiro; Ellenberg, Jan; Foisner, Roland

doi:10.1242/jcs.01529

Cited by 188 publications

(227 citation statements)

References 82 publications

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“…In support of this, it has been shown that lamins interact with mitotic chromosomes (32)(33)(34) and that their assembly at the surface of chromosomes is crucial for postmitotic nuclear formation (35,36). It is also possible that the E145K mutation interferes with the lamin binding to matrix attachment regions of DNA (37) or interactions with other chromatin associated lamin-binding proteins such as histones, LAP2␣, BAF (33), and/or SUN2 (38). Even though we do not know the exact mechanisms responsible for the impact of the E145K mutation, the results of this study provide important insights into the role of lamins in the spatial and temporal organization of chromosomes throughout the cell cycle.…”

Section: Discussionmentioning

confidence: 82%

“…Therefore, the expression of LA/C with the E145K mutation inhibits the normal reorganization of interphase chromosome territories in daughter cells in early G1, most likely due to the formation of an abnormal lamina structure. In support of this, it has been shown that lamins interact with mitotic chromosomes (32)(33)(34) and that their assembly at the surface of chromosomes is crucial for postmitotic nuclear formation (35,36). It is also possible that the E145K mutation interferes with the lamin binding to matrix attachment regions of DNA (37) or interactions with other chromatin associated lamin-binding proteins such as histones, LAP2␣, BAF (33), and/or SUN2 (38).…”

Section: Discussionmentioning

confidence: 97%

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A progeria mutation reveals functions for lamin A in nuclear assembly, architecture, and chromosome organization

Taimen

Pfleghaar²,

Shimi

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

195

215

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Numerous mutations in the humancomprising the major structural components of the nuclear lamina, the fibrous meshwork underlying the inner nuclear membrane (1). They are major determinants of nuclear size and shape and are involved in essential functions such as DNA replication and transcription (1). Lamins A (LA) and C (LC) are alternatively spliced products of the LMNA gene, whereas lamins LB1 and LB2 are encoded by LMNB1 and LMNB2. Structurally, the lamins have a conserved central ␣-helical rod domain flanked by globular head and tail domains. The central rod is responsible for the formation of in-parallel and in-register coiled-coil dimers, the building blocks of lamin polymers. In vitro, lamin dimers form head-to-tail chains, which further interact laterally in an anti-parallel orientation to form highly ordered paracrystals (PCs) (2). However, little is known about the assembly of lamins into higher order structures in vivo.There are Ͼ250 mutations in human LMNA causing a wide range of diseases [for detail, see http//www.umd.be/LMNA/ and (3)]. Among these is the rare premature aging disease, Hutchinson-Gilford progeria syndrome (HGPS). HGPS children typically appear normal at birth, but show growth retardation before the age of 2 years. Further manifestations include loss of hair, lipodystrophy, sclerodermatous skin, osteolysis, and progressive atherosclerosis leading to death at an average age of 13 years due to myocardial infarcts and strokes (4). Most HGPS patients carry the 1824CϾT mutation (G608G), which activates a cryptic splice site resulting in the expression of LA with 50 amino acids deleted near its C terminus (LA⌬50/progerin) (5). As a result, LA⌬50/ progerin remains permanently farnesylated (6, 7), and its accumulation in patients' cells is correlated with the loss of heterochromatin and changes in histone methylation (1).In addition to 1824CϾT, there are 21 other LMNA mutations causing progeria (http://www.umd.be/LMNA/). Some of these are located in the central rod domain, where they could directly impact the assembly of lamins into dimers and higher order structures. Here, we have studied the alterations in nuclear architecture and chromatin organization in one of these mutations, 433GϾA (E145K), located in segment 1B of the central rod domain of LA/C (5). A patient bearing this mutation showed earlier onset cardiovascular defects, only partial loss of hair and ample s.c. fat (5). We show that fibroblasts derived from an E145K patient have severely misshapen nuclei and multiple defects in chromatin organization as reflected by centromere clustering and an abnormal distribution of telomeres throughout the cell cycle. These abnormalities are established during cell division as nuclei assemble in daughter cells. The results demonstrate that the nuclear changes in E145K progeria cells are significantly different from those seen in cells expressing LA⌬50/ progerin, and they also emphasize the essential role of lamins in establishing and maintaining nuclear architecture.

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Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 97%

A progeria mutation reveals functions for lamin A in nuclear assembly, architecture, and chromosome organization

Taimen

Pfleghaar²,

Shimi

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

195

215

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“…Oligomeric Complexes in Vivo-Our previous studies revealed the formation of stable, chromatin-associated LAP2␣ structures during early nuclear assembly stages (14,17), indicating oligomerization of the protein. To analyze oligomeric LAP2␣ structures in vivo and to determine the domain of LAP2␣ responsible for oligomerization, either full-length LAP2␣ or the LAP2␣-specific C-terminal domain, LAP2␣-(188 -693), fused to the C terminus of monomeric red fluorescent protein 1 (mRFP1) (Fig.…”

Section: The C Terminus Of Lap2␣ Is Involved In the Formation Ofmentioning

confidence: 95%

“…The LAP2␣-lamin A/C-pRb complex is thought to regulate cell proliferation and differentiation in adult stem cells (3,12). During mitosis, LAP2␣ dissociates from chromosomes in a phosphorylation-dependent manner and is redistributed throughout the mitotic cytoplasm, like most nuclear lamina components (14,15). However, during anaphase, LAP2␣ associates with the telomeres of separated sister chromatids and subsequently forms stable structures associated with decondensing chromatin before the nuclear envelope is formed (14).…”

mentioning

confidence: 99%

“…During mitosis, LAP2␣ dissociates from chromosomes in a phosphorylation-dependent manner and is redistributed throughout the mitotic cytoplasm, like most nuclear lamina components (14,15). However, during anaphase, LAP2␣ associates with the telomeres of separated sister chromatids and subsequently forms stable structures associated with decondensing chromatin before the nuclear envelope is formed (14). Although LAP2␣ can interact with BAF and DNA via its common LEM and LEM-like motifs, its C terminus was shown to be essential and sufficient for chromatin association during mitosis (16,17).…”

mentioning

confidence: 99%

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Lamina-associated Polypeptide 2-α Forms Homo-trimers via Its C Terminus, and Oligomerization Is Unaffected by a Disease-causing Mutation

Snyers

Vlcek

Dechat

et al. 2007

Journal of Biological Chemistry

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The nucleoplasmic protein, Lamina-associated polypeptide (LAP) 2␣, is one of six alternatively spliced products of the LAP2gene, which share a common N-terminal region. In contrast to the other isoforms, which also share most of their C termini, LAP2␣ has a large unique C-terminal region that contains binding sites for chromatin, A-type lamins, and retinoblastoma protein. By immunoprecipitation analyses of LAP2␣ complexes from cells expressing differently tagged LAP2␣ proteins and fragments, we demonstrate that LAP2␣ forms higher order structures containing multiple LAP2␣ molecules in vivo and that complex formation is mediated by the C terminus. Solid phase binding assays using recombinant and in vitro translated LAP2␣ fragments showed direct interactions of LAP2␣ C termini. Cross-linking of LAP2␣ complexes and multiangle light scattering of purified LAP2␣ revealed the existence of stable homo-trimers in vivo and in vitro. Finally, we show that, in contrast to the LAP2␣-lamin A interaction, its self-association is not affected by a disease-linked single point mutation in the LAP2␣ C terminus.The nuclear envelope comprises the inner and outer nuclear membranes, the nuclear pore complexes, and the nuclear lamina, which underlies the inner nuclear membrane (1, 2). The nuclear lamina is the major structural framework in the nucleus of multicellular eukaryotes and is composed of a filamentous meshwork of type V intermediate filament proteins, the lamins. B-type lamins, encoded by two human genes (LMNB1 and LMNB2), are essential for cell viability. In contrast, the four A-type lamins (A, C, C2, and A⌬10), representing splicing isoforms of the LMNA gene, are dispensable for viability of individual cells but have crucial functions in tissue organization after birth (3, 4).In addition to the lamins, the nuclear lamina contains a number of integral membrane proteins of the inner nuclear membrane, the best characterized of which are the Lamin B receptor, Lamina-associated polypeptide (LAP), 4 and the three LEM domain-containing proteins LAP2␤, emerin and MAN1 (5, 6). All these proteins interact with lamin A/C and/or B and contribute to anchorage of the nuclear membrane to the lamina. The LEM domain, a conserved 40-amino-acid motif located near the N terminus of the LEM family proteins, interacts with the DNA-binding protein barrier-to-autointegration factor (BAF) and mediates the binding of these proteins to chromatin (7). In LAP2 proteins, a LEM-like segment at the very N terminus has been shown to interact with DNA directly (8).The family of LAP2 proteins includes six alternatively spliced isoforms derived from the same gene (9). Most LAP2 isoforms are closely related structurally and functionally and are localized to the inner nuclear membrane, such as LAP2␤. In contrast, LAP2␣ shares only the N-terminal 187 amino acids with the other isoforms, including the LEM and LEM-like domains, but otherwise possesses a unique 506-amino-acid C-terminal region without a transmembrane domain (see Fig. 1A), encoded by one large exon...

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A Unified Linear Viscoelastic Model of the Cell Nucleus Defines the Mechanical Contributions of Lamins and Chromatin

et al. 2020

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The cell nucleus is constantly subjected to externally applied forces. During metazoan evolution, the nucleus has been optimized to allow physical deformability while protecting the genome under load. Aberrant nucleus mechanics can alter cell migration across narrow spaces in cancer metastasis and immune response and disrupt nucleus mechanosensitivity. Uncovering the mechanical roles of lamins and chromatin is imperative for understanding the implications of physiological forces on cells and nuclei. Lamin‐knockout and ‐rescue fibroblasts and probed nucleus response to physiologically relevant stresses are generated. A minimal viscoelastic model is presented that captures dynamic resistance across different cell types, lamin composition, phosphorylation states, and chromatin condensation. The model is conserved at low and high loading and is validated by micropipette aspiration and nanoindentation rheology. A time scale emerges that separates between dominantly elastic and dominantly viscous regimes. While lamin‐A and lamin‐B1 contribute to nucleus stiffness, viscosity is specified mostly by lamin‐A. Elastic and viscous association of lamin‐B1 and lamin‐A is supported by transcriptional and proteomic profiling analyses. Chromatin decondensation quantified by electron microscopy softens the nucleus unless lamin‐A is expressed. A mechanical framework is provided for assessing nucleus response to applied forces in health and disease.

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LAP2α and BAF transiently localize to telomeres and specific regions on chromatin during nuclear assembly

Cited by 188 publications

References 82 publications

A progeria mutation reveals functions for lamin A in nuclear assembly, architecture, and chromosome organization

A progeria mutation reveals functions for lamin A in nuclear assembly, architecture, and chromosome organization

Lamina-associated Polypeptide 2-α Forms Homo-trimers via Its C Terminus, and Oligomerization Is Unaffected by a Disease-causing Mutation

A Unified Linear Viscoelastic Model of the Cell Nucleus Defines the Mechanical Contributions of Lamins and Chromatin

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