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Results for “Chromatin Dynamics”

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At least 37 records · Page 2Linked to original sources
PubMed1993

Interphase genome as the active space: chromatin dynamics during chick embryo chondrogenesis.

The rearrangement of the chromatin that takes place during cytodifferentiation was studied using TV image analysis in chick limb bud cartilage stained for DNA. The redistribution of the chromatin was compatible with the Rabl orientation: chromatin was extended radially from the centromeric ring to the telomere pole in young chondroblasts, and contracted back in ageing chondrocytes. The direction and gradient of this redistribution correlate with the changes in DNA content within the chromocentres formed by pericentromeric heterochromatin. In turn, intercalary heterochromatin regulates the condensation of the adjacent euchromatin depending upon the position in this radial-polar gradient.

Animals↗
PubMed2002

Chromatin remodeling enzymes: taming the machines. Third in review series on chromatin dynamics.

Members of the ATP-dependent family of chromatin remodeling enzymes play key roles in the regulation of transcription, development, DNA repair and cell cycle. Each of these enzymes are multi-subunit assemblies that hydrolyze thousands of molecules of ATP in order to change nucleosome positions, disrupt DNA-histone interactions and perhaps destabilize chromatin folding. Here I review recent studies that suggest these potent machines can be 'tamed' by one of several mechanisms: targeting their activity to localized regions, blocking their chromatin binding activity or inhibiting their remodeling activity.

Adenosine Triphosphate↗
PubMed2005

Biology of chromatin dynamics.

During the development of a multicellular organism, cell differentiation involves activation and repression of transcription programs that must be stably maintained during subsequent cell divisions. Chromatin remodeling plays a crucial role in regulating chromatin states that conserve transcription programs and provide a mechanism for chromatin states to be maintained as cells proliferate, a process referred to as epigenetic inheritance. A large number of factors and protein complexes are now known to be involved in regulating the dynamic states of chromatin structure. Their biological functions and molecular mechanisms are beginning to be revealed.

Chromatin↗
PubMed2025

Conserved HSFA1-dependent chromatin dynamics drive heat stress responses in plants.

Eukaryotic organisms remodel chromatin landscapes to regulate gene expression in response to environmental stress. In plants, heat stress (HS) induces widespread chromatin changes, yet the role of heat shock transcription factors (HSFs) in chromatin remodeling and their evolutionary conservation remains unclear. Using Marchantia polymorpha Mphsf mutants and Arabidopsis thaliana Athsfa1s mutants, we identify HSFA1 as a key regulator of HS-induced cis-regulatory element (CRE) accessibility, a mechanism conserved across land plants, mice, and humans. Gene regulatory network modeling reveals parallel transcription factor subnetworks, with MpWRKY10 and MpABI5B acting as indirect and negative HS regulators. We further showed that ABA modulates gene expression in an HSFA1-dependent manner without inducing chromatin remodeling. Finally, we develop a machine learning framework integrating chromatin accessibility and CRE information to predict gene expression across species, revealing stress-responsive regulatory logic at the transcriptional level. These findings provide insights into how TFs coordinate chromatin architecture to drive stress adaptation.

Heat-Shock Response↗
PubMed2003

Chromatin dynamics and DNA repair.

Packing of the eukaryotic genome into chromatin poses an accessibility problem for the DNA repair machinery. Chromatin structure has to be changed for the repair to occur, and we are beginning to discover how different chromatin modifying mechanisms facilitate DNA repair in the chromatin context. On the other hand, the repair-related changes in chromatin should be transient, and a particular chromatin state should be able to survive the repair process. Defects in the proper maintenance of chromatin states after repair could be a factor in the aging process, as well as in other pathologies.

Animals↗
PubMed2004

Chromatin dynamics at DNA replication, transcription and repair.

During DNA replication, transcription and DNA repair in eukaryotes, the cellular machineries performing these tasks need to gain access to the DNA that is packaged into chromatin in the nucleus. Chromatin is a dynamic structure that modulates the access of regulatory factors to the genetic material. A precise coordination and organization of events in opening and closing of the chromatin is crucial to ensure that the correct spatial and temporal epigenetic code is maintained within the eukaryotic genome. This review will summarize the current knowledge of how chromatin remodeling and histone modifying complexes cooperate to break and remake chromatin during nuclear processes on the DNA template.

Acetyltransferases↗
PubMed2002

When repair meets chromatin. First in series on chromatin dynamics.

In eukaryotic cells, the inheritance of both the DNA sequence and its organization into chromatin is critical to maintain genome stability. This maintenance is challenged by DNA damage. To fully understand how the cell can tolerate genotoxic stress, it is necessary to integrate knowledge of the nature of DNA damage, its detection and its repair within the chromatin environment of a eukaryotic nucleus. The multiplicity of the DNA damage and repair processes, as well as the complex nature of chromatin, have made this issue difficult to tackle. Recent progress in each of these areas enables us to address, both at a molecular and a cellular level, the importance of inter-relationships between them. In this review we revisit the 'access, repair, restore' model, which was proposed to explain how the conserved process of nucleotide excision repair operates within chromatin. Recent studies have identified factors potentially involved in this process and permit refinement of the basic model. Drawing on this model, the chromatin alterations likely to be required during other processes of DNA damage repair, particularly double-strand break repair, are discussed and recently identified candidates that might perform such alterations are highlighted.

Chromatin↗
PubMed2005

Dynamic chromatin: concerted nucleosome remodelling and acetylation.

The flexibility of chromatin that enables translation of environmental cues into changes in genome utilisation, relies on a battery of enzymes able to modulate chromatin structure in a highly targeted and regulated manner. The most dynamic structural changes are brought about by two kinds of enzymes with different functional principles. Changes in the acetylation status of histones modulate the folding of the nucleosomal fibre. The histone-DNA interactions that define the nucleosome itself can be disrupted by ATP-dependent remodelling factors. This review focuses on recent developments that illustrate various strategies for integrating these disparate activities into complex regulatory schemes. Synergies may be brought about by consecutive or parallel action during the stepwise process of chromatin opening or closing. Tight co-ordination may be achieved by direct interaction of (de-)acetylation enzymes and remodelling ATPases or even permanent residence within the same multi-enzyme complex. The fact that remodelling ATPases can be acetylated by histone acetyltransferases themselves suggests exciting possibilities for the co-ordinate modulation of chromatin structure and remodelling enzymes.

Acetylation↗
PubMed2005

Changing chromatin dynamics and nuclear organization during differentiation in Drosophila larval tissue.

Global changes in gene expression and exit from the cell cycle underlie differentiation. Therefore, understanding chromatin behavior in differentiating nuclei and late G1 is key to understanding this developmental event. A nuclear event that has been shown to specifically occur in late G1 is the association of two heterochromatic blocks in Drosophila. The brown(Dominant) (bw(D)) chromosome of Drosophila melanogaster contains a large block of heterochromatin near the end of 2R. This distal block associates with centric heterochromatin (2Rh), but not until at least 5 hours into G1. We used the bw(D) allele as a model for nuclear organization to determine whether its association with the heterochromatic compartment of the second chromosomes (2Rh) strictly requires differentiation or if this change is a stochastic event, its occurrence being proportional to time spent in G1/G0 phase of the cell cycle. Fluorescence in situ hybridization on eye imaginal discs showed increased association between the bw locus and 2Rh in differentiated cells. Interestingly, an increase in the number of nuclei showing bw(D)-2Rh association in the brains of developmentally delayed larvae that were compromised for differentiation was also observed. Live fluorescence imaging showed that the kinetics of chromatin movement remains unchanged in the developmentally arrested nuclei. These observations suggest that nuclear reorganization is not directly controlled by specific inductive signals during differentiation and that this nuclear reorganization can happen in a cell, regardless of differentiation state, that is arrested in the appropriate cell cycle stage. However, we did see changes that appear to be more directly correlated with differentiation. Dynamic imaging in eye imaginal discs showed that the movement of chromatin is more constrained in differentiated cells, implying that confinement of loci to a smaller nuclear space may help to maintain the changed organization and the transcription profile that accompanies differentiation.

Alleles↗
PubMed1998

Facilitation of chromatin dynamics by SARs.

Metaphase chromosome condensation is a dynamic process that must utilize cis elements to form and maintain the final structure. Likewise, cis elements must regulate the accessibility of chromatin domains to protein machines involved in processes such as transcription. Scaffold associated regions appear to play important roles in both of these dynamic processes.

Animals↗
PubMed2006

A novel role for microtubules in apoptotic chromatin dynamics and cellular fragmentation.

Dramatic changes in cellular dynamics characterise the apoptotic execution phase, culminating in fragmentation into membrane-bound apoptotic bodies. Previous evidence suggests that actin-myosin plays a dominant role in apoptotic cellular remodelling, whereas all other cytoskeletal elements dismantle. We have used fixed cells and live-cell imaging to confirm that interphase microtubules rapidly depolymerise at the start of the execution phase. Around this time, pericentriolar components (pericentrin, ninein and gamma-tubulin) are lost from the centrosomal region. Subsequently, however, extensive non-centrosomal bundles of densely packed, dynamic microtubules rapidly assemble throughout the cytoplasm in all cell lines tested. These microtubules have an important role in the peripheral relocation of chromatin in the dying cell, because nocodazole treatment restricts the dispersal of condensed apoptotic chromatin into surface blebs, and causes the withdrawal of chromatin fragments back towards the cell centre. Importantly, nocodazole and taxol are both potent inhibitors of apoptotic fragmentation in A431 cells, implicating dynamic microtubules in apoptotic body formation. Live-cell-imaging studies indicate that fragmentation is accompanied by the extension of rigid microtubule-rich spikes that project through the cortex of the dying cell. These structures enhance interactions between apoptotic cells and phagocytes in vitro, by providing additional sites for attachment to neighbouring cells.

Anisomycin↗
PubMed2006

Chromatin dynamics and the evolution of alternate promoter states.

Eucaryotic gene transcriptional switches utilize changes both in the activity and composition of soluble transcription factor complexes, and epigenetic modifications to the chromatin template. Until recently, alternate states of promoter activity have been associated with the assembly of relatively stable multiprotein complexes on target genes, with transitions in the composition of these complexes occurring on the time scale of minutes or hours. The development of living cell techniques to characterize transcription factor function in real time has led to an alternate view of highly dynamic protein/template interactions. In addition, emerging evidence suggests that energy-dependent processes contribute significantly to the rapid movement of proteins in living cells, and to the exchange of sequence-specific DNA-binding proteins with regulatory elements. Potential mechanisms involved in the unexpectedly rapid flux of factor/template interactions are discussed in the context of a "return-to-template" model for transcription factor function.

Animals↗