SWR1-Independent Association of H2A.Z to the LINC Complex Promotes Meiotic Chromosome Motion

ABSTRACTThe H2A.Z histone variant is deposited into chromatin by the SWR1 complex affecting multiple aspects of meiosis. Here we describe a SWR1-independent localization of H2A.Z at meiotic telomeres and the centrosome. We demonstrate that H2A.Z colocalizes and interacts with Mps3, the SUN component of the LINC complex that spans the nuclear envelope and links meiotic telomeres to the cytoskeleton promoting meiotic chromosome movement. H2A.Z also interacts with the meiosis-specific Ndj1 protein that anchors telomeres to the nuclear periphery via Mps3. Telomeric localization of H2A.Z depends on Ndj1 and the N-terminal domain of Mps3. Although telomeric attachment to the nuclear envelope is maintained in the absence of H2A.Z, the distribution of Mps3 is altered. The velocity of chromosome movement during meiotic prophase I is reduced in the htz1Δ mutant lacking H2A.Z, but it is unaffected in swr1Δ cells. We reveal that H2A.Z is an additional LINC-associated factor that contributes to promote telomere-driven chromosome motion critical for error-free gametogenesis.

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Phosphorylation of luminal region of the SUN-domain protein Mps3 promotes nuclear envelope localization during meiosis

eLife ◽

10.7554/elife.63119 ◽

2021 ◽

Vol 10 ◽

Author(s):

Hanumanthu BD Prasada Rao ◽

Takeshi Sato ◽

Kiran Challa ◽

Yurika Fujita ◽

Miki Shinohara ◽

...

Keyword(s):

Protein Kinase ◽

Nuclear Envelope ◽

Meiotic Chromosome ◽

Linc Complex ◽

Dependent Protein ◽

Domain Protein ◽

Protein Ensembles ◽

Chromosome Motion ◽

Sun Domain ◽

Luminal Region

During meiosis, protein ensembles in the nuclear envelope (NE) containing SUN- and KASH-domain proteins, called linker nucleocytoskeleton and cytoskeleton (LINC) complex, promote the chromosome motion. Yeast SUN-domain protein, Mps3, forms multiple meiosis-specific ensembles on NE, which show dynamic localisation for chromosome motion; however, the mechanism by which these Mps3 ensembles are formed during meiosis remains largely unknown. Here, we showed that the cyclin-dependent protein kinase (CDK) and Dbf4-dependent Cdc7 protein kinase (DDK) regulate meiosis-specific dynamics of Mps3 on NE, particularly by mediating the resolution of Mps3 clusters and telomere clustering. We also found that the luminal region of Mps3 juxtaposed to the inner nuclear membrane is required for meiosis-specific localisation of Mps3 on NE. Negative charges introduced by meiosis-specific phosphorylation in the luminal region of Mps3 alter its interaction with negatively charged lipids by electric repulsion in reconstituted liposomes. Phospho-mimetic substitution in the luminal region suppresses the localisation of Mps3 via the inactivation of CDK or DDK. Our study revealed multi-layered phosphorylation-dependent regulation of the localisation of Mps3 on NE for meiotic chromosome motion and NE remodelling.

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Accessorizing and anchoring the LINC complex for multifunctionality

The Journal of Cell Biology ◽

10.1083/jcb.201409047 ◽

2015 ◽

Vol 208 (1) ◽

pp. 11-22 ◽

Cited By ~ 183

Author(s):

Wakam Chang ◽

Howard J. Worman ◽

Gregg G. Gundersen

Keyword(s):

Nuclear Membrane ◽

Meiotic Chromosome ◽

Linc Complex ◽

Factors Associated ◽

Ordered Arrays ◽

Anchoring Proteins ◽

Core Components ◽

Chromosome Movements ◽

Shed Light

The linker of nucleoskeleton and cytoskeleton (LINC) complex, composed of outer and inner nuclear membrane Klarsicht, ANC-1, and Syne homology (KASH) and Sad1 and UNC-84 (SUN) proteins, respectively, connects the nucleus to cytoskeletal filaments and performs diverse functions including nuclear positioning, mechanotransduction, and meiotic chromosome movements. Recent studies have shed light on the source of this diversity by identifying factors associated with the complex that endow specific functions as well as those that differentially anchor the complex within the nucleus. Additional diversity may be provided by accessory factors that reorganize the complex into higher-ordered arrays. As core components of the LINC complex are associated with several diseases, understanding the role of accessory and anchoring proteins could provide insights into pathogenic mechanisms.

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A molecular mechanism for LINC complex branching by structurally diverse SUN-KASH 6:6 assemblies

eLife ◽

10.7554/elife.60175 ◽

2021 ◽

Vol 10 ◽

Author(s):

Manickam Gurusaran ◽

Owen Richard Davies

Keyword(s):

Nuclear Envelope ◽

Molecular Mechanism ◽

Complex Network ◽

Meiotic Chromosome ◽

Force Distribution ◽

The Sun ◽

Linc Complex ◽

Cellular Functions ◽

Zinc Coordination ◽

Chromosome Movements

The Linker of Nucleoskeleton and Cytoskeleton (LINC) complex mechanically couples cytoskeletal and nuclear components across the nuclear envelope to fulfil a myriad of cellular functions, including nuclear shape and positioning, hearing, and meiotic chromosome movements. The canonical model is that 3:3 interactions between SUN and KASH proteins underlie the nucleocytoskeletal linkages provided by the LINC complex. Here, we provide crystallographic and biophysical evidence that SUN-KASH is a constitutive 6:6 complex in which two constituent 3:3 complexes interact head-to-head. A common SUN-KASH topology is achieved through structurally diverse 6:6 interaction mechanisms by distinct KASH proteins, including zinc-coordination by Nesprin-4. The SUN-KASH 6:6 interface provides a molecular mechanism for the establishment of integrative and distributive connections between 3:3 structures within a branched LINC complex network. In this model, SUN-KASH 6:6 complexes act as nodes for force distribution and integration between adjacent SUN and KASH molecules, enabling the coordinated transduction of large forces across the nuclear envelope.

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A molecular mechanism for LINC complex branching by structurally diverse SUN-KASH 6:6 assemblies

10.1101/2020.03.21.001867 ◽

2020 ◽

Cited By ~ 1

Author(s):

Manickam Gurusaran ◽

Owen R. Davies

Keyword(s):

Nuclear Envelope ◽

Molecular Mechanism ◽

Meiotic Chromosome ◽

Current Model ◽

Force Distribution ◽

The Sun ◽

Linc Complex ◽

Cellular Functions ◽

Zinc Coordination ◽

Chromosome Movements

SummaryThe LINC complex mechanically couples cytoskeletal and nuclear components across the nuclear envelope to fulfil a myriad of cellular functions, including nuclear shape and positioning, hearing and meiotic chromosome movements. The canonical model of the LINC complex is of individual linear nucleocytoskeletal linkages provided by 3:3 interactions between SUN and KASH proteins. Here, we provide crystallographic and biophysical evidence that SUN-KASH is a constitutive 6:6 complex in which two SUN trimers interact back-to-back. A common SUN-KASH topology is achieved through structurally diverse 6:6 interaction mechanisms by distinct KASH proteins, including zinc-coordination by Nesprin-4. The SUN-KASH 6:6 complex is incompatible with the current model of a linear LINC complex and instead suggests the formation of a branched LINC complex network. In this model, SUN-KASH 6:6 complexes act as nodes for force distribution and integration between adjacent SUN and KASH molecules, enabling the coordinated transduction of large forces across the nuclear envelope.

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Dynein-dependent processive chromosome motions promote homologous pairing in C. elegans meiosis

The Journal of Cell Biology ◽

10.1083/jcb.201106022 ◽

2012 ◽

Vol 196 (1) ◽

pp. 47-64 ◽

Cited By ~ 63

Author(s):

David J. Wynne ◽

Ofer Rog ◽

Peter M. Carlton ◽

Abby F. Dernburg

Keyword(s):

Chromosome Segregation ◽

Meiotic Chromosome ◽

Search Rate ◽

Homologous Pairing ◽

Chromosome Dynamics ◽

C Elegans ◽

Diverse Species ◽

And Function ◽

Chromosome Motion ◽

Chromosome Regions

Meiotic chromosome segregation requires homologue pairing, synapsis, and crossover recombination, which occur during meiotic prophase. Telomere-led chromosome motion has been observed or inferred to occur during this stage in diverse species, but its mechanism and function remain enigmatic. In Caenorhabditis elegans, special chromosome regions known as pairing centers (PCs), rather than telomeres, associate with the nuclear envelope (NE) and the microtubule cytoskeleton. In this paper, we investigate chromosome dynamics in living animals through high-resolution four-dimensional fluorescence imaging and quantitative motion analysis. We find that chromosome movement is constrained before meiosis. Upon prophase onset, constraints are relaxed, and PCs initiate saltatory, processive, dynein-dependent motions along the NE. These dramatic motions are dispensable for homologous pairing and continue until synapsis is completed. These observations are consistent with the idea that motions facilitate pairing by enhancing the search rate but that their primary function is to trigger synapsis. This quantitative analysis of chromosome dynamics in a living animal extends our understanding of the mechanisms governing faithful genome inheritance.

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MLKS2 is an ARM domain and F-actin-associated KASH protein that functions in stomatal complex development and meiotic chromosome segregation

10.1101/609594 ◽

2019 ◽

Author(s):

Hardeep K. Gumber ◽

Joseph F. McKenna ◽

Andrea F. Tolmie ◽

Alexis M. Jalovec ◽

Andre C. Kartick ◽

...

Keyword(s):

Chromosome Segregation ◽

Meiotic Chromosome ◽

Pollen Viability ◽

Expression System ◽

Nuclear Periphery ◽

Grass Species ◽

Cell Cortex ◽

Linc Complex ◽

Stomatal Complex ◽

Complex Development

AbstractThe linker of nucleoskeleton and cytoskeleton (LINC) complex is an essential multi-protein structure spanning the eukaryotic nuclear envelope. The LINC complex functions to maintain nuclear architecture, positioning, and mobility, along with specialized functions in meiotic prophase and chromosome segregation. Members of the LINC complex were recently identified in maize, an important scientific and agricultural grass species. Here we characterized Maize LINC KASH AtSINE-like2, MLKS2, which encodes a highly conserved SINE-group plant KASH protein with characteristic N-terminal armadillo repeats (ARM). Using a heterologous expression system, we showed that actively expressed GFP-MLKS2 is targeted to the nuclear periphery and colocalizes with F-actin and the endoplasmic reticulum, but not microtubules in the cell cortex. Expression of GFP-MLKS2, but not GFP-MLKS2ΔARM, resulted in nuclear anchoring. Genetic analysis of transposon-insertion mutations, mlks2-1 and mlks2-2, showed that the mutant phenotypes were pleiotropic, affecting root hair nuclear morphology, stomatal complex development, multiple aspects of meiosis, and pollen viability. In male meiosis, the mutants showed defects for bouquet-stage telomere clustering, nuclear repositioning, perinuclear actin accumulation, dispersal of late prophase bivalents, and meiotic chromosome segregation. These findings support a model in which the nucleus is connected to cytoskeletal F-actin through the ARM-domain, predicted alpha solenoid structure of MLKS2. Functional conservation of MLKS2 was demonstrated through genetic rescue of the misshapen nuclear phenotype of an Arabidopsis (triple-WIP) KASH mutant. This study establishes a role for the SINE-type KASH proteins in affecting the dynamic nuclear phenomena required for normal plant growth and fertility.

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Stage-resolved Hi-C analyses reveal meiotic chromosome organizational features influencing homolog alignment

Nature Communications ◽

10.1038/s41467-021-26033-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Wu Zuo ◽

Guangming Chen ◽

Zhimei Gao ◽

Shuai Li ◽

Yanyan Chen ◽

...

Keyword(s):

Meiotic Prophase ◽

Chromosome Structure ◽

Meiotic Chromosome ◽

Chromosome Length ◽

Linc Complex ◽

3D Genome ◽

Homolog Pairing ◽

Genomic Regions ◽

Organizational Features ◽

Chromosome Axis

AbstractDuring meiosis, chromosomes exhibit dramatic changes in morphology and intranuclear positioning. How these changes influence homolog pairing, alignment, and recombination remain elusive. Using Hi-C, we systematically mapped 3D genome architecture throughout all meiotic prophase substages during mouse spermatogenesis. Our data uncover two major chromosome organizational features varying along the chromosome axis during early meiotic prophase, when homolog alignment occurs. First, transcriptionally active and inactive genomic regions form alternating domains consisting of shorter and longer chromatin loops, respectively. Second, the force-transmitting LINC complex promotes the alignment of ends of different chromosomes over a range of up to 20% of chromosome length. Both features correlate with the pattern of homolog interactions and the distribution of recombination events. Collectively, our data reveal the influences of transcription and force on meiotic chromosome structure and suggest chromosome organization may provide an infrastructure for the modulation of meiotic recombination in higher eukaryotes.

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