scholarly journals LEM-3 is a midbody-tethered DNA nuclease that resolves chromatin bridges during cytokinesis

2017 ◽  
Author(s):  
Ye Hong ◽  
Remi Sonneville ◽  
Bin Wang ◽  
Viktor Scheidt ◽  
Bettina Meier ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Chromosome Structure ◽  
Cleavage Plane ◽  
Genome Integrity ◽  
Human Breast ◽  
Genome Maintenance ◽  
C Elegans ◽  
And Function ◽  
Chromatin Bridges

AbstractFaithful chromosome segregation and genome maintenance requires the removal of all DNA bridges that physically link chromosomes before cells divide. Using C. elegans embryos we show that the LEM-3/Ankle1 nuclease defines a new genome integrity mechanism by processing DNA bridges right before cells divide. LEM-3 acts at the midbody, the structure where abscission occurs at the end of cytokinesis. LEM-3 localization depends on factors needed for midbody assembly, and LEM-3 accumulation is increased and prolonged when chromatin bridges are trapped at the cleavage plane. LEM-3 locally processes chromatin bridges that arise from incomplete DNA replication, unresolved recombination intermediates or the perturbance of chromosome structure. Proper LEM-3 midbody localization and function is regulated by AIR-2/Aurora B kinase. Strikingly, LEM-3 act cooperatively with the BRC-1/BRCA1 homologous recombination factor to promote genome integrity. These findings provide a molecular basis for the suspected role of the LEM-3 orthologue Ankle1 in human breast cancer.

scholarly journals Hcp-1, a Protein Involved in Chromosome Segregation, Is Localized to the Centromere of Mitotic Chromosomes in Caenorhabditis elegans

1999 ◽  
Vol 147 (3) ◽  
pp. 471-480 ◽  
Author(s):  
Landon L. Moore ◽  
Mike Morrison ◽  
Mark B. Roth
Keyword(s):  
Caenorhabditis Elegans ◽  
Chromosome Segregation ◽  
Chromosome Structure ◽  
Sequence Database ◽  
Mitotic Chromosomes ◽  
Expression Screening ◽  
C Elegans ◽  
Genome Sequence Database ◽  
And Function ◽  
Embryonic Arrest

To learn more about holocentric chromosome structure and function, we generated a monoclonal antibody (mAb), 6C4, that recognizes the poleward face of mitotic chromosomes in Caenorhabditis elegans. Early in mitosis, mAb 6C4 stains dots throughout the nucleoplasm. Later in prophase, mAb 6C4 stains structures on opposing faces of chromosomes which orient towards the centrosomes at metaphase. Colocalization with an antibody against a centromeric histone H3–like protein and the MPM-2 antibody, which identifies a kinetochore-associated phosphoepitope present in a variety of organisms, shows that the mAb 6C4 staining is present adjacent to the centromere. Expression screening using mAb 6C4 identified a protein in C. elegans that we named HCP-1 (for holocentric protein 1). We also identified a second protein from the C. elegans genome sequence database, HCP-2, that is 54% similar to HCP-1. When expression of HCP-1 is reduced by RNA interference (RNAi), staining with mAb 6C4 is eliminated, indicating that hcp-1 encodes the major mAb 6C4 antigen. RNAi with hcp-1 and hcp-2 together results in aberrant anaphases and embryonic arrest at ∼100 cells with different amounts of DNA in individual nuclei. These results suggest that HCP-1 is a centromere-associated protein that is involved in the fidelity of chromosome segregation.

scholarly journals The Last Chance Saloon

2021 ◽  
Vol 9 ◽  
Author(s):  
Ye Hong ◽  
Hongtao Zhang ◽  
Anton Gartner
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Chromosome Segregation ◽  
Cell Cycle Progression ◽  
Genome Instability ◽  
Genome Integrity ◽  
Cycle Progression ◽  
Chromosome Fragmentation ◽  
C Elegans ◽  
Chromatin Bridges

Accurate chromosome segregation requires the removal of all chromatin bridges, which link chromosomes before cell division. When chromatin bridges fail to be removed, cell cycle progression may halt, or cytokinesis failure and ensuing polyploidization may occur. Conversely, the inappropriate severing of chromatin bridges leads to chromosome fragmentation, excessive genome instability at breakpoints, micronucleus formation, and chromothripsis. In this mini-review, we first describe the origins of chromatin bridges, the toxic processing of chromatin bridges by mechanical force, and the TREX1 exonuclease. We then focus on the abscission checkpoint (NoCut) which can confer a transient delay in cytokinesis progression to facilitate bridge resolution. Finally, we describe a recently identified mechanism uncovered in C. elegans where the conserved midbody associated endonuclease LEM-3/ANKLE1 is able to resolve chromatin bridges generated by various perturbations of DNA metabolism at the final stage of cell division. We also discuss how LEM-3 dependent chromatin bridge resolution may be coordinated with abscission checkpoint (NoCut) to achieve an error-free cleavage, therefore acting as a “last chance saloon” to facilitate genome integrity and organismal survival.

scholarly journals TRPV channel OCR-2 is distributed along C. elegans chemosensory cilia by diffusion in a local interplay with intraflagellar transport

2020 ◽  
Author(s):  
Jaap van Krugten ◽  
Noémie Danné ◽  
Erwin J.G. Peterman
Keyword(s):  
Single Molecule ◽  
Transmembrane Proteins ◽  
Intraflagellar Transport ◽  
Single Molecule Tracking ◽  
C Elegans ◽  
Normal Diffusion ◽  
Cellular Signal ◽  
Underlying Mechanisms ◽  
And Function

AbstractSensing and reacting to the environment is essential for survival and procreation of most organisms. Caenorhabditis elegans senses soluble chemicals with transmembrane proteins (TPs) in the cilia of its chemosensory neurons. Development, maintenance and function of these cilia relies on intraflagellar transport (IFT), in which motor proteins transport cargo, including sensory TPs, back and forth along the ciliary axoneme. Here we use live fluorescence imaging to show that IFT machinery and the sensory TP OCR-2 reversibly redistribute along the cilium after exposure to repellant chemicals. To elucidate the underlying mechanisms, we performed single-molecule tracking experiments and found that OCR-2 distribution depends on an intricate interplay between IFT-driven transport, normal diffusion and subdiffusion that depends on the specific location in the cilium. These insights in the role of IFT on the dynamics of cellular signal transduction contribute to a deeper understanding of the regulation of sensory TPs and chemosensing.

scholarly journals Heterochromatin: Guardian of the Genome

2018 ◽  
Vol 34 (1) ◽  
pp. 265-288 ◽  
Author(s):  
Aniek Janssen ◽  
Serafin U. Colmenares ◽  
Gary H. Karpen
Keyword(s):  
Chromosome Segregation ◽  
Genome Stability ◽  
Constitutive Heterochromatin ◽  
Repetitive Sequences ◽  
Genome Integrity ◽  
Chromatin Domain ◽  
Cellular Processes ◽  
Eukaryotic Nucleus ◽  
And Function ◽  
Heterochromatin Structure

Constitutive heterochromatin is a major component of the eukaryotic nucleus and is essential for the maintenance of genome stability. Highly concentrated at pericentromeric and telomeric domains, heterochromatin is riddled with repetitive sequences and has evolved specific ways to compartmentalize, silence, and repair repeats. The delicate balance between heterochromatin epigenetic maintenance and cellular processes such as mitosis and DNA repair and replication reveals a highly dynamic and plastic chromatin domain that can be perturbed by multiple mechanisms, with far-reaching consequences for genome integrity. Indeed, heterochromatin dysfunction provokes genetic turmoil by inducing aberrant repeat repair, chromosome segregation errors, transposon activation, and replication stress and is strongly implicated in aging and tumorigenesis. Here, we summarize the general principles of heterochromatin structure and function, discuss the importance of its maintenance for genome integrity, and propose that more comprehensive analyses of heterochromatin roles in tumorigenesis will be integral to future innovations in cancer treatment.

scholarly journals Propensity of undulatory swimmers, such as worms, to go against the flow

2015 ◽  
Vol 112 (12) ◽  
pp. 3606-3611 ◽  
Author(s):  
Jinzhou Yuan ◽  
David M. Raizen ◽  
Haim H. Bau
Keyword(s):  
Control Strategies ◽  
Aquatic Organisms ◽  
Life Cycles ◽  
Environmental Cues ◽  
Mechanical Forces ◽  
C Elegans ◽  
The Subject ◽  
And Function ◽  
First Time

The ability to orient oneself in response to environmental cues is crucial to the survival and function of diverse organisms. One such orientation behavior is the alignment of aquatic organisms with (negative rheotaxis) or against (positive rheotaxis) fluid current. The questions of whether low-Reynolds-number, undulatory swimmers, such as worms, rheotax and whether rheotaxis is a deliberate or an involuntary response to mechanical forces have been the subject of conflicting reports. To address these questions, we use Caenorhabditis elegans as a model undulatory swimmer and examine, in experiment and theory, the orientation of C. elegans in the presence of flow. We find that when close to a stationary surface the animal aligns itself against the direction of the flow. We elucidate for the first time to our knowledge the mechanisms of rheotaxis in worms and show that rheotaxis can be explained solely by mechanical forces and does not require sensory input or deliberate action. The interaction between the flow field induced by the swimmer and a nearby surface causes the swimmer to tilt toward the surface and the velocity gradient associated with the flow rotates the animal to face upstream. Fluid mechanical computer simulations faithfully mimic the behavior observed in experiments, supporting the notion that rheotaxis behavior can be fully explained by hydrodynamics. Our study highlights the important role of hydrodynamics in the behavior of small undulating swimmers and may assist in developing control strategies to affect the animals’ life cycles.

scholarly journals Dissecting the cell to nucleus, perinucleus and cytosol

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
Tattym E. Shaiken ◽  
Antone R. Opekun
Keyword(s):  
Regulation Of Gene Expression ◽  
Genome Integrity ◽  
Perinuclear Region ◽  
Isolation Method ◽  
Total Proteins ◽  
Isolation Technique ◽  
Unknown Composition ◽  
And Function ◽  
P53 Tumor Suppressor Protein

Abstract Cells have been described under the microscope as organelles containing cytoplasm and the nucleus. However, an unnoted structure exists between the cytoplasm and the nucleoplasm of eukaryotic cells. In addition to the nuclear envelope, there exists a perinuclear region (PNR or perinucleus) with unknown composition and function. Until now, an investigation of the role of the perinucleus has been restricted by the absence of a PNR isolation method. This manuscript describes a perinucleus isolation technique on the basis of its unique compact organization. The perinucleus was found to contain approximately 15 to 18% of the total proteins of the mammalian cell, almost half of the proteins of nuclei. Using four different normal and cancer cell lines, it was shown that the composition of PNR is highly dynamic. Application of the method showed that translocation of the p53 tumor-suppressor protein to the perinucleus in immortalized MEF cells is correlated with the translocation of p53-stabilizing protein, nucleophosmin (B23), to the PNR. Herein, the concept of the perinuclear region is advanced as a formal, identifiable structure. The roles of the perinucleus in maintaining genome integrity, regulation of gene expression and understanding of malignant transformation are discussed.

scholarly journals The yeast core spliceosome maintains genome integrity through R-loop prevention and α-tubulin expression

2018 ◽  
Author(s):  
Annie S. Tam ◽  
Veena Mathew ◽  
Tianna S. Sihota ◽  
Anni Zhang ◽  
Peter C. Stirling
Keyword(s):  
Gene Expression ◽  
Dna Replication ◽  
Chromosome Segregation ◽  
Genome Stability ◽  
Spindle Assembly Checkpoint ◽  
Genome Instability ◽  
Genome Integrity ◽  
Genome Maintenance ◽  
Maintenance Factors ◽  
Spindle Assembly Checkpoint Protein

To achieve genome stability cells must coordinate the action of various DNA transactions including DNA replication, repair, transcription and chromosome segregation. How transcription and RNA processing enable genome stability is only partly understood. Two predominant models have emerged: one involving changes in gene expression that perturb other genome maintenance factors, and another in which genotoxic DNA:RNA hybrids, called R-loops, impair DNA replication. Here we characterize genome instability phenotypes in a panel yeast splicing factor mutants and find that mitotic defects, and in some cases R-loop accumulation, are causes of genome instability. Genome instability in splicing mutants is exacerbated by loss of the spindle-assembly checkpoint protein Mad1. Moreover, removal of the intron from the α-tubulin gene TUB1 restores genome integrity. Thus, while R-loops contribute in some settings, defects in yeast splicing predominantly lead to genome instability through effects on gene expression.

scholarly journals Mitotic chromosome condensation requires phosphorylation of the centromeric protein KNL-2 in C. elegans

2021 ◽  
Author(s):  
Joanna M Wenda ◽  
Reinier F Prosée ◽  
Caroline Gabus ◽  
Florian A Steiner
Keyword(s):  
Chromosome Segregation ◽  
Mitotic Chromosome ◽  
Chromosome Condensation ◽  
Embryonic Lethality ◽  
Phosphorylation Sites ◽  
C Elegans ◽  
Microtubule Attachment ◽  
Centromeric Protein ◽  
Mitotic Chromosome Condensation

Centromeres are chromosomal regions that serve as sites for kinetochore formation and microtubule attachment, processes that are essential for chromosome segregation during mitosis. Centromeres are almost universally defined by the histone variant CENP-A. In the holocentric nematode C. elegans, CENP-A deposition depends on the loading factor KNL-2. Depletion of either CENP-A or KNL-2 results in defects in centromere maintenance, chromosome condensation and kinetochore formation, leading to chromosome segregation failure. Here, we show that KNL-2 is phosphorylated by CDK-1, and that mutation of three C-terminal phosphorylation sites causes chromosome segregation defects and an increase in embryonic lethality. In strains expressing phosphodeficient KNL-2, CENP-A and kinetochore proteins are properly localised, indicating that the role of KNL-2 in centromere maintenance is not affected. Instead, the mutant embryos exhibit reduced mitotic levels of condensin II on chromosomes and significant chromosome condensation impairment. Our findings separate the functions of KNL-2 in CENP-A loading and chromosome condensation and demonstrate that KNL-2 phosphorylation regulates the cooperation between centromeric regions and the condensation machinery in C. elegans.

scholarly journals Caenorhabditis elegans nuclear RNAi factor SET-32 deposits the transgenerational histone modification, H3K23me3

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Lianna Schwartz-Orbach ◽  
Chenzhen Zhang ◽  
Simone Sidoli ◽  
Richa Amin ◽  
Diljeet Kaur ◽  
...  
Keyword(s):  
Chromatin Modification ◽  
Epigenetic Inheritance ◽  
Rnai Pathway ◽  
C Elegans ◽  
And Function ◽  
Nuclear Rnai ◽  
Factor Set

Nuclear RNAi provides a highly tractable system to study RNA-mediated chromatin changes and epigenetic inheritance. Recent studies have indicated that the regulation and function of nuclear RNAi-mediated heterochromatin are highly complex. Our knowledge of histone modifications and the corresponding histonemodifying enzymes involved in the system remains limited. In this study, we show that the heterochromatin mark, H3K23me3, is induced by nuclear RNAi at both exogenous and endogenous targets in C. elegans. In addition, dsRNA-induced H3K23me3 can persist for multiple generations after the dsRNA exposure has stopped. We demonstrate that the histone methyltransferase SET-32, methylates H3K23 in vitro. Both set-32 and the germline nuclear RNAi Argonaute, hrde-1, are required for nuclear RNAi-induced H3K23me3 in vivo. Our data poise H3K23me3 as an additional chromatin modification in the nuclear RNAi pathway and provides the field with a new target for uncovering the role of heterochromatin in transgenerational epigenetic silencing.

Sign in / Sign up

Export Citation Format

Share Document