Search

Upregulation of nuclear factor κB (NFκB) signaling is a hallmark of aging and a major cause of age‐related chronic inflammation. However, its effect on cellular senescence remains unclear. Here, we show that alteration of NFκB nuclear dynamics from oscillatory to sustained by depleting a negative feedback regulator of NFκB pathway, NFκB inhibitor alpha (IκBα), in the presence of tumor necrosis factor α (TNFα) promotes cellular senescence. Sustained NFκB activity enhanced inflammatory gene expression through increased NFκB‐DNA binding and slowed the cell cycle. IκBα protein was decreased under replicative or oxidative stress in vitro. Furthermore, a decrease in IκBα protein and an increase in DNA‐NFκB binding at the transcription start sites of age‐associated genes in aged mouse hearts suggested that nuclear NFκB dynamics may play a critical role in the progression of aging. Our study suggests that nuclear NFκB dynamics‐dependent epigenetic changes regulated over time in a living system, possibly through a decrease in IκBα, enhance the expression of inflammatory genes to advance the cells to a senescent state. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) are obligate mutualists that can enhance nutrition and growth of their plant hosts while providing protection against pathogens. AMF produce spores and hyphal networks that can carry thousands of nuclei in a continuous cytoplasm, with no evidence of sexual reproduction. This review examines the impact of genomic technologies on our view of AMF genetics and evolution. We highlight how the genetics, nuclear dynamics, and epigenetics of these prominent symbionts follow trends preserved in distant multinucleate fungal relatives. We also propose new avenues of research to improve our understanding of their nuclear biology and their intricate genetic interactions with plant hosts. [ABSTRACT FROM AUTHOR]

The DNA replication process needs to be coordinated with other DNA metabolism transactions and must eventually extend to the full genome, regardless of chromatin status, gene expression, secondary structures and DNA lesions. Completeness and accuracy of DNA replication are crucial to maintain genome integrity, limiting transformation in normal cells and offering targeting opportunities for proliferating cancer cells. DNA replication is thus tightly coordinated with chromatin dynamics and 3D genome architecture, and we are only beginning to understand the underlying molecular mechanisms. While much has recently been discovered on how DNA replication initiation is organised and modulated in different genomic regions and nuclear territories—the so-called "DNA replication program"—we know much less on how the elongation of ongoing replication forks and particularly the response to replication obstacles is affected by the local nuclear organisation. Also, it is still elusive how specific components of nuclear architecture participate in the replication stress response. Here, we review known mechanisms and factors orchestrating replication initiation, and replication fork progression upon stress, focusing on recent evidence linking genome organisation and nuclear architecture with the cellular responses to replication interference, and highlighting open questions and future challenges to explore this exciting new avenue of research. [ABSTRACT FROM AUTHOR]

Non alloyed carbon deoxidation can fundamentally solve the technical difficulty of fatigue failure of high‐quality bearing steel caused by inclusions. Herein, nonalloyed carbon deoxidation is presented with CO as a product, which can avoid the problem of residual inclusions. The thermodynamic and kinetic nucleation models of [C] deoxidation are constructed. The results suggest that a decrease in pCO strengthens the deoxidation ability of [C], and the [%O] balanced with [%C] shows multiple decreases. When pCO = 0.1 atm and [%C] = 0.5%, [%O] can be reduced to less than 10 ppm. However, from the results of the nucleation kinetic model, as pCO decreases, the critical radius r* increases, and the resistance of CO nucleation also increases. This results in difficulty of nucleation. Based on the nucleation kinetic model, the following C–O reaction mechanism is proposed: 1) [C] and [O] move to the reaction interface, 2) [C] + [O] = CO, forming a critical bubble nucleus, and 3) the newly formed CO diffuses continuously into the critical bubble, causing the bubble to grow and float away. Alternatively, the CO separates from the gas–liquid interface and enters the bubble, which floats away. [ABSTRACT FROM AUTHOR]

Pericentromeric heterochromatin is mostly composed of repetitive DNA sequences prone to aberrant recombination. Cells have developed highly specialized mechanisms to enable 'safe' homologous recombination (HR) repair while preventing aberrant recombination in this domain. Understanding heterochromatin repair responses is essential to understanding the critical mechanisms responsible for genome integrity and tumor suppression. Here, we review the tools, approaches, and methods currently available to investigate double-strand break (DSB) repair in pericentromeric regions, and also suggest how technologies recently developed for euchromatin repair studies can be adapted to characterize responses in heterochromatin. With this ever-growing toolkit, we are witnessing exciting progress in our understanding of how the 'dark matter' of the genome is repaired, greatly improving our understanding of genome stability mechanisms. [ABSTRACT FROM AUTHOR]

The eukaryotic nucleus shows organized structures of chromosomes, transcriptional components and their associated proteins. It has been believed that such a dense nuclear environment prevents the formation of a cytoskeleton-like network of protein filaments. However, accumulating evidence suggests that the cell nucleus also possesses structural filamentous components to support nuclear organization and compartments, which are referred to as nucleoskeleton proteins. Nucleoskeleton proteins including lamins and actin influence nuclear dynamics including transcriptional regulation, chromatin organization and DNA damage responses. Furthermore, these nucleoskeleton proteins play a pivotal role in cellular differentiation and animal development. In this commentary, we discuss how nucleoskeleton-based regulatory mechanisms orchestrate nuclear dynamics. [ABSTRACT FROM AUTHOR]

[Display omitted] • Viruses can modulate intracellular microenvironments, including membraneless organelles (MLOs). • HIV-1 infection induces the formation of nuclear CPSF6 condensates. • HIV-1 capsid and CPSF6 coexist inside HIV-MLOs and probably trigger their formation. • HIV-1 induced MLOs play key functions in the early steps of the viral life cycle. Viruses are obligate parasites that rely on their host's cellular machinery for replication. To facilitate their replication cycle, many viruses have been shown to remodel the cellular architecture by inducing the formation of membraneless organelles (MLOs). Eukaryotic cells have evolved MLOs that are highly dynamic, self-organizing microenvironments that segregate biological processes and increase the efficiency of reactions by concentrating enzymes and substrates. In the context of viral infections, MLOs can be utilized by viruses to complete their replication cycle. This review focuses on the pathway used by the HIV-1 virus to remodel the nuclear landscape of its host, creating viral/host niches that enable efficient viral replication. Specifically, we discuss how the interaction between the HIV-1 capsid and the cellular factor CPSF6 triggers the formation of nuclear MLOs that support nuclear reverse transcription and viral integration in favored regions of the host chromatin. This review compiles current knowledge on the origin of nuclear HIV-MLOs and their role in early post-nuclear entry steps of the HIV-1 replication cycle. [ABSTRACT FROM AUTHOR]

To investigate the mitotic dynamics of an appressorium, we used live-cell confocal imaging of a fluorescence-based mitotic reporter strain of Magnaporthe oryzae . We present evidence that the M. oryzae appressorium remains viable and mitotically active well after host penetration. These results suggest the potential roles of the appressorium during post-penetration proliferation of invasive hyphae. Our studies also revealed that a mitotic appressorial nucleus undergoes extreme constriction and elongation as it migrates through the penetration peg in a manner analogous to mitosis during cell-to-cell movement of invasive hyphae. Understanding the mechanisms underlying these pathogen-specific nuclear dynamics may provide new targets for disease control. [ABSTRACT FROM AUTHOR]

The structural organization of the nucleus and its content has drawn increasing interest in recent years, as it is has become evident that the spatial and temporal arrangement of the genome and associated structures plays a crucial role in transcriptional regulation and numerous other functions. Shining light on the dynamic nature of this organization, along with the processes controlling it, were the topics of the Wenner-Gren Foundations international symposium "Nuclear Dynamics: Design (and) Principles." The meeting, organized by Piorgiogio Percipalle, Maria Vartiainen, Neus Visa, and Ann-Kristin Östlund-Farrants, brought over 60 participants, including 20 international speakers, to Stockholm, Sweden from August 19–22, 2015 to share the latest developments in the field. Given the unpublished nature of many of the talks, we have focused on covering the discussed topics and highlighting the latest trends in this exciting and rapidly evolving field. [ABSTRACT FROM PUBLISHER]

Cells sense physical cues at the level of focal adhesions and transduce them to the nucleus by biochemical and mechanical pathways. While the molecular intermediates in the mechanical links have been well studied, their dynamic coupling is poorly understood. In this study, fibroblast cells were adhered to micropillar arrays to probe correlations in the physical coupling between focal adhesions and nucleus. For this, we used novel imaging setup to simultaneously visualize micropillar deflections and EGFP labeled chromatin structure at high spatial and temporal resolution. We observed that micropillar deflections, depending on their relative positions, were positively or negatively correlated to nuclear and heterochromatin movements. Our results measuring the time scales between micropillar deflections and nucleus centroid displacement are suggestive of a strong elastic coupling that mediates differential force transmission to the nucleus. [ABSTRACT FROM AUTHOR]

Only a limited number of studies exist on the life cycles of nonmodel ciliates such as Chilodonella uncinata (Cl: Phyllopharyngea). The handful of papers on this taxon indicate the presence of a heteromeric macronucleus, marked by separate DNA-rich and DNA-poor regions. Here, we study the life cycle of C. uncinata using confocal laser scanning microscopy with 4′,6-diamidino-2-phenylindole staining, which allows us to differentiate nuclear dynamics of the micronucleus and the macronucleus during life-cycle stages. We photo-documented various stages and confirmed aspects of the development of the new macronucleus previously characterized by electron microscopy. We further reveal the heteromeric structure of the macronucleus with Z-stacks and three-dimensional (3D) reconstructions. We find no evidence for the presence of an endosome at the center of the macronucleus during vegetative growth. In addition to illustrating the life cycle of this ciliate, the approaches developed for this study will enable additional comparative analyses of nuclear dynamics using fluorescence microscopy. [ABSTRACT FROM AUTHOR]

DM1 (myotonic dystrophy type 1) is caused by elongation of a CTG repeat in the DMPK (dystrophia myotonica-protein kinase) gene. mRNA transcripts containing these CUGexp (CUG expansion) repeats form accumulations, or foci, in the nucleus of the cell. The pathogenesis of DM1 is proposed to result from inappropriate patterns of alternative splicing caused by sequestration of the developmentally regulated alternative splicing factor MBNL1 (muscleblind-like 1) by these foci. Since eye lens cataract is a common feature of DM1 we have examined the distribution and dynamics of MBNL1 in lens epithelial cell lines derived from patients with DM1. The results of the present study demonstrate that only a small proportion of nuclear MBNL1 accumulates in CUGexp pre-mRNA foci. MBNL1 is, however, highly mobile and changes localization in response to altered transcription and splicing activity. Moreover, immunolocalization studies in lens sections suggest that a change in MBNL1 distribution is important during lens growth and differentiation. Although these data suggest that the loss of MBNL1 function due to accumulation in foci is an unlikely explanation for DM1 symptoms in the lens, they do demonstrate a strong relationship between the subcellular MBNL1 localization and pathways of cellular differentiation, providing an insight into the sensitivity of the lens to changes in MBNL1 distribution. [ABSTRACT FROM AUTHOR]

Abstract: We summarize our development of instrumentation for the study of liquids, aqueous solutions, and liquid/solid interfaces using resonant inelastic soft X-ray scattering (RIXS) and illustrate the value of the experimental approach with a few instructional examples. Using a high-transmission, high-resolution soft X-ray spectrometer, we are able to measure complete RIXS maps, i.e., record the soft X-ray emission intensity as a function of emission and absorption energy. As a first example, we show that a comparison of RIXS maps of “normal” and deuterated liquid and gas-phase water allows us to identify dissociation processes on the time scale of the oxygen 1 s core-hole lifetime. Similar dissociation effects are found for aqueous solutions of ammonia and amino acids. For the latter, the pH value has a strong influence on the nitrogen K emission spectra, which can thus be used to identify protonation and deprotonation processes in the solution. Finally, we review the investigation of the interface between liquid water and a CuIn(S,Se)2 thin-film solar cell absorber, demonstrating the power of the technique to study liquid–solid interfaces in real-world systems. Under X-ray irradiation, the formation of sulfate on the absorber surface can be found. [Copyright &y& Elsevier]

Abstract: Ultrafast dissociation following core–shell excitation into an antibonding orbital led to the early observation in HBr of atomic Auger lines associated to the decay of dissociated excited atoms. The purpose of this article is to review the very large variety of systems where such a situation has been encountered, extending from simple diatomic molecules toward more complex systems like polyatomics, clusters, or adsorbed molecules. Interestingly, this phenomenon has revealed an extremely rich and powerful tool for probing nuclear dynamics and its subtle interplay with electron relaxation occurring on a comparable time scale. Consequently this review covers a surprisingly large period, starting in 1986 and still ongoing. [Copyright &y& Elsevier]

This study focuses on the two C1s-to-LUMO (lowest unoccupied molecular orbital) excitations of the iso-dichloroethylene (H2C=CCl2) and the subsequent Auger decay. We investigate the effect of the two different carbon core excitations on the population of the cation produced after electronic relaxation. The resonant Auger spectra are interpreted by comparison to the valence shells photoionization spectrum and with the help of theoretical calculations. Several consequences of the core-hole localization on the electronic decay are observed. In particular, the resonant excitation of the C1s(CH2) to the LUMO leads to a large intensity increase in the region of the first satellite state, whereas no dramatic changes are observed for the C1s(CCl2) excitation. [ABSTRACT FROM AUTHOR]

It is becoming increasingly clear that defects in RNA metabolism can lead to disease. Spinal muscular atrophy (SMA), a leading genetic cause of infant mortality, results from insufficient amounts of survival motor neuron (SMN) protein. SMN is required for the biogenesis of small nuclear ribonucleoproteins (snRNPs): essential components of the spliceosome. Splicing abnormalities have been detected in models of SMA but it is unclear how lowered SMN affects the fidelity of pre-mRNA splicing. We have examined the dynamics of mature snRNPs in cells depleted of SMN and demonstrated that SMN depletion increases the mobility of mature snRNPs within the nucleus. To dissect the molecular mechanism by which SMN deficiency affects intranuclear snRNP mobility, we employed a panel of inhibitors of different stages of pre-mRNA processing. This in vivo modelling demonstrates that snRNP mobility is altered directly as a result of impaired snRNP maturation. Current models of nuclear dynamics predict that subnuclear structures, including the spliceosome, form by self-organization mediated by stochastic interactions between their molecular components. Thus, alteration of the intranuclear mobility of snRNPs provides a molecular mechanism for splicing defects in SMA. [ABSTRACT FROM AUTHOR]

Linker histone H1 is a fundamental chromosomal protein involved in the maintenance of higher-ordered chromatin organization. The exchange dynamics of histone H1 correlates well with chromatin plasticity. A variety of core histone chaperones involved in core histone dynamics has been identified, but the identity of the linker histone chaperone in the somatic cell nucleus has been a longstanding unanswered question. Here we show that Template Activating Factor-I (TAF-I, also known as protein SET) is involved in histone H1 dynamics as a linker histone chaperone. Among previously identified core histone chaperones and linker histone chaperone candidates, only TAF-I was found to be associated specifically with histone H1 in mammalian somatic cell nuclei. TAF-I showed linker histone chaperone activity in vitro. Fluorescence recovery after photobleaching analyses revealed that TAF-I is involved in the regulation of histone H1 dynamics in the nucleus. Therefore, we propose that TAF-I is a key molecule that regulates linker histone-mediated chromatin assembly and disassembly. [ABSTRACT FROM AUTHOR]

Nonadiabatic events, in which the Born-Oppenheimer approximation breaks down, are ubiquitous in chemistry and biology. It is now widely accepted that they are facilitated by conical intersections (CIs), actual degeneracies between electronic states. We review the basic theory of CIs and how they can be studied using modern quantum chemistry and nuclear dynamics. We highlight their importance by presenting their role in radiationless decay pathways present in the building blocks of DNA and proteins. The presence of CIs may contribute to the photostability of these important biomolecules. [ABSTRACT FROM AUTHOR]

Nonadiabatic events, in which the Born-Oppenheimer approximation breaks down, are ubiquitous in chemistry and biology. It is now widely accepted that they are facilitated by conical intersections (CIs), actual degeneracies between electronic states. We review the basic theory of CIs and how they can be studied using modern quantum chemistry and nuclear dynamics. We highlight their importance by presenting their role in radiationless decay pathways present in the building blocks of DNA and proteins. The presence of CIs may contribute to the photostability of these important biomolecules. [ABSTRACT FROM AUTHOR]

gas electron diffraction study of PrI and GdI has been carried out in combination with mass spectrometric vapour monitoring at 1110(10) K and 1100(10) K, respectively. Up to 3 mol.% of dimeric species was observed in addition to the dominating monomeric molecules. The change of the thermal-averaged r configuration parameters of the molecules in the series LaI → LuI reflects the lanthanide contraction. A low value of the shrinkage δ(I···I) even at such a high temperatures may be considered due to vibration effects in molecule whose equilibrium geometric nuclear structure is planar and which correspond to configurationally averaged 4 f electronic state. B3LYP calculations performed in this study with large core potential for lanthanide atoms also resulted in equilibrium geometry of D symmetry. According to the quantum chemical calculations, the potential function the non-planar vibration is essentially anharmonic, which is therefore to be taken into account to correctly describe nuclear dynamics in molecules such as LnI. [ABSTRACT FROM AUTHOR]

Abstract: A first gas electron diffraction study of TbI3, DyI3, HoI3 and ErI3 has been carried out in combination with mass spectrometric vapour monitoring at 1117(10), 1117(10), 1132(10) and 1102(10)K, respectively. Up to 4mol.% of dimeric species was observed in addition to the dominating monomeric molecules. The change of the thermal-averaged r g-configuration parameters of the molecules in the series TbI3 →ErI3 reflect the lanthanide contraction. A low value of the shrinkage δ(I…I) even at such a high temperatures may be considered due to vibration effects in molecule whose equilibrium geometric nuclear structure is planar and which correspond to configurationally-averaged 4fn electronic state. B3LYP and МР2 calculations performed in this work with large core potential for lanthanide atoms also resulted in equilibrium geometry of D3h symmetry. According to the both quantum chemical methods applied the potential function the non-planar vibration is essentially anharmonic, which is therefore to be taken into account to correctly describe nuclear dynamics in molecules such as LnI3. Different models applied in this study predict the equilibrium distance r e(Ln–I) to be shorter than the thermal-averaged r g(Ln–I) distance by 0.002–0.018(1)Å. [ABSTRACT FROM AUTHOR]

Abstract: Background: The nuclear lamina provides structural support to the nucleus and has a central role in defining nuclear organization. Defects in its filamentous constituents, the lamins, lead to a class of diseases collectively referred to as laminopathies. On the cellular level, lamin mutations affect the physical integrity of nuclei and nucleo-cytoskeletal interactions, resulting in increased susceptibility to mechanical stress and altered gene expression. Methods: In this study we quantitatively compared nuclear deformation and chromatin mobility in fibroblasts from a homozygous nonsense LMNA mutation patient and a Hutchinson–Gilford progeria syndrome patient with wild type dermal fibroblasts, based on the visualization of mCitrine labeled telomere-binding protein TRF2 with light-economical imaging techniques and cytometric analyses. Results: Without application of external forces, we found that the absence of functional lamin A/C leads to increased nuclear plasticity on the hour and minute time scale but also to increased intranuclear mobility down to the second time scale. In contrast, progeria cells show overall reduced nuclear dynamics. Experimental manipulation (farnesyltransferase inhibition or lamin A/C silencing) confirmed that these changes in mobility are caused by abnormal or reduced lamin A/C expression. Conclusions: These observations demonstrate that A-type lamins affect both nuclear membrane and telomere dynamics. General significance: Because of the pivotal role of dynamics in nuclear function, these differences likely contribute to or represent novel mechanisms in laminopathy development. [Copyright &y& Elsevier]

Abstract: Studies of the two-nucleon system are essential for a profound understanding of nuclear structure and for the exploration of the limits of the effective description of atomic nuclei in terms of nucleons, mesons and isobars. In the present work, a unified description of hadronic and electromagnetic reactions on the two-nucleon system is developed in the framework of a coupled-channel -approach which is based on one general Hamiltonian and which treats the pion exchange in the hadronic baryon–baryon interaction as well as in the meson exchange currents in the exact retarded manner. Unitarity and gauge invariance are at least approximately fulfilled. Several hadronic and electromagnetic reactions in the two-nucleon sector are discussed and the role of the deuteron as an effective neutron target is considered. [Copyright &y& Elsevier]

Abstract: The present review article gives a historical overview of high-resolution inner-shell coincidence spectroscopies followed by selected examples showing their scientific impact in studying molecular fragmentation dynamics. The development of such spectroscopies was intimately related to the last 20 years spectacular advances of the instrumentation. They include the construction of high-performance soft X-ray beamlines at the newest synchrotron radiation facilities, but also the remarkable improvement of charged particles analyzers and detectors and the extensive use of multidimensional coincidence techniques allowing for simultaneous recording and further correlation of several physical parameters. From the examples shown, it clearly appears the importance of using coincidence measurements in addition to pure electron spectroscopy methods in order to fully characterize the complex decay processes of inner-shell excited species leading for instance to site-selective fragmentation, vibrational motion mediated dissociation or ultrafast intramolecular recombination processes. The perspectives of the field will be briefly drawn in the end. [Copyright &y& Elsevier]

Abstract: A circularly polarized infrared (IR) laser pulse which propagates along the axis of a pre-aligned linear polyatomic molecule may excite unidirectional pseudorotations corresponding to excitation of the molecular bend and rotation of the bent molecule around that axis. This preparation and spinning a molecular top is, in part, analogous to the generation of unidirectional electron circulation in molecules by means of circularly polarized ultraviolet (UV) laser pulses [I. Barth, J. Manz, Angew. Chem. 118 (2006) 3028; Angew. Chem., Int. Ed. 45 (2006) 2962], allowing to apply similar methods for the laser driven wavepacket dynamics. It is demonstrated here by means of quantum simulations of the laser driven wavefunction of the model system , where is expanded in terms of vibrational eigenfunctions which are labeled by quantum numbers for the vibrations (v) including the symmetric stretch (s), bend (b), antisymmetric stretch (a), and for the pseudorotation (l). The corresponding vibrational and pseudorotational eigenenergies and matrix elements for the model are adapted as approximations from accurate values which have been determined previously, for simulations of high resolution IR spectra. These dipole matrix elements and related selection or propensity rules imply dominant ladder climbing or , i.e., sequential populations of the states with increasing quantum numbers for the bends and pseudorotations , where or depending on the right (+) or left circular polarization of the IR laser pulse, respectively. [Copyright &y& Elsevier]

Molecular imaging in living cells or organisms now allows us to observe macromolecular assemblies with a time resolution sufficient to address cause-and-effect relationships on specific molecules. These emerging technologies have gained much interest from the scientific community since they have been able to reveal novel concepts in cell biology, thereby changing our vision of the cell. One main paradigm is that cells stochastically vary, thus implying that population analysis may be misleading. In fact, cells should be analyzed within time-resolved single-cell experiments rather than being compared to other cells within a population. Technological imaging developments as well as the stochastic events present in gene expression have been reviewed. Here, we discuss how the structural organization of the nucleus is revealed using noninvasive single-cell approaches, which ultimately lead to the resolution required for the analysis of highly controlled molecular processes taking place within live cells. We also describe the efforts being made towards physiological approaches within the context of living organisms. [ABSTRACT FROM AUTHOR]

Fluorescence recovery after photobleaching (FRAP) has become a popular technique to investigate the behavior of proteins in living cells. Although the technique is relatively old, its application to studying endogenous intracellular proteins in living cells is relatively recent and is a consequence of the newly developed fluorescent protein-based living cell protein tags. This is particularly true for nuclear proteins, in which endogenous protein mobility has only recently been studied. Here we examine the experimental design and analysis of FRAP experiments. Mathematical modeling of FRAP data enables the experimentalist to extract information such as the association and dissociation constants, distribution of a protein between mobile and immobilized pools, and the effective diffusion coefficient of the molecule under study. As experimentalists begin to dissect the relative influence of protein domains within individual proteins, this approach will allow a quantitative assessment of the relative influences of different molecular interactions on the steady-state distribution and protein function in vivo. [Copyright &y& Elsevier]

Resonant Auger spectroscopy is used to study the molecular core-excited states with an inner-shell electron promoted to the lowest unoccupied molecular orbital. Dissociating Cl2p→σ* excitations are investigated in the HCl and Cl2 molecules, where the resonant Auger electron spectra exhibit both molecular and atomic features, depending on the time scale of the dissociation. The use of electron time-of-flight analyzers in combination with two-dimensional (in electron and photon energies) mapping technique allows to create a detailed picture of the interplay between dissociation and Auger decay. Also a Renner–Teller-split bound excited state, C1s→π* is studied in the CO2 molecule. Here, the Auger spectra recorded with high-resolution SES-200 hemispherical analyzer exhibit strong photon energy dependency across the resonance. From the analysis and semi-empirical modelling, properties of the core-excited state are derived. [Copyright &y& Elsevier]

• Some arbuscular mycorrhizal (AM) fungal strains referred as AMF dikaryons carry thousands of nuclei originating from two parental strains. • The ratio of coexisting nucleotypes in AMF dikaryons is affected by abiotic factors. • The ratio of coexisting nucleotypes in AMF dikaryons is harmonized when the mycelium encounters multiple abiotic factors simultaneously. • The observed ratios are stable across conditions. Arbuscular mycorrhizal fungi (AMF) are widespread obligate root symbionts that assist plants in obtaining nutrients and protection against environmental stresses. In the model species Rhizophagus irregularis , heterokaryotic strains (AMF dikaryons) carry thousands of nuclei originating from two parental strains whose frequency varies depending on strains and host identity. Here, using digital droplet PCR, we demonstrate that surrounding abiotic factors (temperature, phosphorus, and pH) also change the nuclear dynamics of such strains in root organ cultures. Furthermore, when spatially separated portions of the AMF mycelium grow under different abiotic conditions, all the produced spores carry highly similar nuclear ratios. Overall, these findings demonstrate that abiotic stressors impact the nuclear organization of a widespread group of multinucleate plant symbionts, and reveal remarkable mechanisms of nuclear ratio harmonization across the mycelium in these prominent symbionts. [ABSTRACT FROM AUTHOR]

Nucleus position in cells can act as a developmental cue. Mammalian oocytes position their nucleus centrally using an F-actin-mediated pressure gradient. The biological significance of nucleus centering in mammalian oocytes being unknown, we sought to assess the F-actin pressure gradient effect on the nucleus. We addressed this using a dedicated computational 3D imaging approach, biophysical analyses, and a nucleus repositioning assay in mouse oocytes mutant for cytoplasmic F-actin. We found that the cytoplasmic activity, in charge of nucleus centering, shaped the nucleus while promoting nuclear envelope fluctuations and chromatin motion. Off-centered nuclei in F-actin mutant oocytes were misshaped with immobile chromatin and modulated gene expression. Restoration of F-actin in mutant oocytes rescued nucleus architecture fully and gene expression partially. Thus, the F-actin-mediated pressure gradient also modulates nucleus dynamics in oocytes. Moreover, this study supports a mechano-transduction model whereby cytoplasmic microfilaments could modulate oocyte transcriptome, essential for subsequent embryo development. • Formin 2-nucleated F-actin impacts both oocyte nuclear position and architecture • Cytoplasmic F-actin promotes nuclear envelope fluctuations • Nuclear envelope fluctuations impact chromatin motion inside the nucleus • Cytoskeleton-induced nuclear envelope fluctuations modulate the oocyte transcriptome Almonacid et al. show that the positioning of the nucleus in the center of the oocyte is essential for proper gene expression. Actin, which positions the nucleus centrally, also ensures proper nuclear shape, and promotes nuclear envelope and chromatin movements that fine-tune gene expression. [ABSTRACT FROM AUTHOR]

Summary A key feature of Notch signaling is that it directs immediate changes in transcription via the DNA-binding factor CSL, switching it from repression to activation. How Notch generates both a sensitive and accurate response—in the absence of any amplification step—remains to be elucidated. To address this question, we developed real-time analysis of CSL dynamics including single-molecule tracking in vivo . In Notch-OFF nuclei, a small proportion of CSL molecules transiently binds DNA, while in Notch-ON conditions CSL recruitment increases dramatically at target loci, where complexes have longer dwell times conferred by the Notch co-activator Mastermind. Surprisingly, recruitment of CSL-related corepressors also increases in Notch-ON conditions, revealing that Notch induces cooperative or “assisted” loading by promoting local increase in chromatin accessibility. Thus, in vivo Notch activity triggers changes in CSL dwell times and chromatin accessibility, which we propose confer sensitivity to small input changes and facilitate timely shut-down. [ABSTRACT FROM AUTHOR]