scholarly journals BRCa1 participates in XIST RNa localization on inactive x chromosome

2019 ◽  
Vol 18 (2) ◽  
pp. 21-26
Author(s):  
E. A. Shestakova ◽  
T. A. Bogush
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Confocal Microscopy ◽  
X Chromosome ◽  
Fluorescent Microscopy ◽  
S Phase ◽  
Immunofluorescent Staining ◽  
Heterochromatin Protein ◽  
Inactive X Chromosome ◽  
Xist Rna

Introduction . Inactive X chromosome (Xi) is associated with noncoding XIST RNA, series of proteins and contains multiple epigenetic modifications that altogether determine a silence of the most of X-linked genes. Recently the data were obtained that tumor suppressor BRCA1 is also associated with Xi. The purpose of this study was to reveal the colocalization of BRCA1 and XIST RNA and precise spatial organization on Xi with the high resolution of confocal microscopy.Materials and methods . The object of the study is IMR90hTERT diploid immortalized fibroblast cell line. For BRCA1 and XIST RNA colocalization analysis on Xi the method of fluorescent hybridization in situ associated with immunofluorescent cell staining (immunoFISH) and confocal microscopy were used. For BRCA1 and heterochromatin protein-1 colocalization study the method of double immunofluorescent staining and common fluorescent microscopy were applied. Results . The study using confocal fluorescent microscopy with higher resolution has demonstrated at first the colocalization of BRCA1 with XIST RNA region of Xi revealed with XIST RNA probes and with replicating Xi and autosomes revealed with BrdU in late S-phase of cell cycle. Altogether, the data obtained suggest the involvement of BRCA1 in the inhibition of gene expression on Xi due to the regulation of XIST RNA association with Xi. Moreover, according to the results of confocal microscopy, BRCA1 also colocalizes with replicating Xi and autosomes revealed with BrdU in late S-phase of cell cycle. This indicates a possible involvement of this protein in the replication of pericentromeric repeats in cellular chromosomes. Colocalization of BRCA1 with heterochromatin protein-1α presented in pericentromeric regions of all chromosomes supports this suggestion.Conclusions . Altogether, the data obtained in this study suggest the involvement of BRCA1 in the inhibition of gene expression on Xi due to the association with noncoding inhibiting XIST RNA and in replication of heterochromatin regions. 

scholarly journals Cell cycle–dependent localization of macroH2A in chromatin of the inactive X chromosome

2002 ◽  
Vol 157 (7) ◽  
pp. 1113-1123 ◽  
Author(s):  
Brian P. Chadwick ◽  
Huntington F. Willard
Keyword(s):  
Cell Cycle ◽  
X Chromosome ◽  
Degradation Pathway ◽  
S Phase ◽  
Histone H2a ◽  
The Core ◽  
Inactive X Chromosome ◽  
Inactivation Center ◽  
Chromatin Proteins ◽  
Cycle Dependent

One of several features acquired by chromatin of the inactive X chromosome (Xi) is enrichment for the core histone H2A variant macroH2A within a distinct nuclear structure referred to as a macrochromatin body (MCB). In addition to localizing to the MCB, macroH2A accumulates at a perinuclear structure centered at the centrosome. To better understand the association of macroH2A1 with the centrosome and the formation of an MCB, we investigated the distribution of macroH2A1 throughout the somatic cell cycle. Unlike Xi-specific RNA, which associates with the Xi throughout interphase, the appearance of an MCB is predominantly a feature of S phase. Although the MCB dissipates during late S phase and G2 before reforming in late G1, macroH2A1 remains associated during mitosis with specific regions of the Xi, including at the X inactivation center. This association yields a distinct macroH2A banding pattern that overlaps with the site of histone H3 lysine-4 methylation centered at the DXZ4 locus in Xq24. The centrosomal pool of macroH2A1 accumulates in the presence of an inhibitor of the 20S proteasome. Therefore, targeting of macroH2A1 to the centrosome is likely part of a degradation pathway, a mechanism common to a variety of other chromatin proteins.

Autonomous gene expression on the human inactive X chromosome

1980 ◽  
Vol 6 (3) ◽  
pp. 309-323 ◽  
Author(s):  
Brenda Kahan ◽  
Robert DeMars
Keyword(s):  
Gene Expression ◽  
X Chromosome ◽  
Inactive X Chromosome

Morphology and behaviour of dinoflagellate chromosomes during the cell cycle and mitosis

2000 ◽  
Vol 113 (7) ◽  
pp. 1231-1239 ◽  
Author(s):  
Y. Bhaud ◽  
D. Guillebault ◽  
J. Lennon ◽  
H. Defacque ◽  
M.O. Soyer-Gobillard ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cell Cycle ◽  
Confocal Microscopy ◽  
Nuclear Envelope ◽  
Chromosome Segregation ◽  
Morphological Changes ◽  
S Phase ◽  
Chromosome Behaviour ◽  
Double Number ◽  
Do So

The morphology and behaviour of the chromosomes of dinoflagellates during the cell cycle appear to be unique among eukaryotes. We used synchronized and aphidicolin-blocked cultures of the dinoflagellate Crypthecodinium cohnii to describe the successive morphological changes that chromosomes undergo during the cell cycle. The chromosomes in early G(1) phase appeared to be loosely condensed with numerous structures protruding toward the nucleoplasm. They condensed in late G(1), before unwinding in S phase. The chromosomes in cells in G(2) phase were tightly condensed and had a double number of arches, as visualised by electron microscopy. During prophase, chromosomes elongated and split longitudinally, into characteristic V or Y shapes. We also used confocal microscopy to show a metaphase-like alignment of the chromosomes, which has never been described in dinoflagellates. The metaphase-like nucleus appeared flattened and enlarged, and continued to do so into anaphase. Chromosome segregation occurred via binding to the nuclear envelope surrounding the cytoplasmic channels and microtubule bundles. Our findings are summarized in a model of chromosome behaviour during the cell cycle.

scholarly journals macroH2A1 Histone Variants Are Depleted on Active Genes but Concentrated on the Inactive X Chromosome

2006 ◽  
Vol 26 (12) ◽  
pp. 4410-4420 ◽  
Author(s):  
Lakshmi N. Changolkar ◽  
John R. Pehrson
Keyword(s):  
X Chromosome ◽  
Distribution Patterns ◽  
Detailed Examination ◽  
Histone Variants ◽  
Heterochromatin Protein ◽  
Inactive X Chromosome ◽  
Preferential Localization ◽  
Intergenic Regions ◽  
Liver Chromatin ◽  
Active Genes

ABSTRACT Using a novel thiol affinity chromatography approach to purify macroH2A1-containing chromatin fragments, we examined the distribution of macroH2A1 histone variants in mouse liver chromatin. We found that macroH2A1 was depleted on the transcribed regions of active genes. This depletion was observed on all of the 20 active genes that we probed, with only one site showing a small amount of enrichment. In contrast, macroH2A1 was concentrated on the inactive X chromosome, consistent with our previous immunofluorescence studies. This preferential localization was seen on genes that are active in liver, genes that are inactive in liver, and intergenic regions but was absent from four regions that escape X inactivation. These results support the hypothesis that macroH2As function as transcriptional repressors. Also consistent with this hypothesis is our finding that the heterochromatin protein HP1β copurifies with the macroH2A1-containing chromatin fragments. This study presents the first detailed examination of the distribution of macroH2A1 variants on specific sequences. Our results indicate that macroH2As have complex distribution patterns that are influenced by both local factors and long-range mechanisms.

scholarly journals Identification of DHX9 as a cell cycle regulated nucleolar recruitment factor for CIZ1

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Urvi Thacker ◽  
Tekle Pauzaite ◽  
James Tollitt ◽  
Maria Twardowska ◽  
Charlotte Harrison ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Cell Cycle Progression ◽  
Zinc Finger Protein ◽  
S Phase ◽  
Cycle Progression ◽  
Inactive X Chromosome ◽  
Functional Characterisation ◽  
Interaction Partners

Abstract CIP1-interacting zinc finger protein 1 (CIZ1) is a nuclear matrix associated protein that facilitates a number of nuclear functions including initiation of DNA replication, epigenetic maintenance and associates with the inactive X-chromosome. Here, to gain more insight into the protein networks that underpin this diverse functionality, molecular panning and mass spectrometry are used to identify protein interaction partners of CIZ1, and CIZ1 replication domain (CIZ1-RD). STRING analysis of CIZ1 interaction partners identified 2 functional clusters: ribosomal subunits and nucleolar proteins including the DEAD box helicases, DHX9, DDX5 and DDX17. DHX9 shares common functions with CIZ1, including interaction with XIST long-non-coding RNA, epigenetic maintenance and regulation of DNA replication. Functional characterisation of the CIZ1-DHX9 complex showed that CIZ1-DHX9 interact in vitro and dynamically colocalise within the nucleolus from early to mid S-phase. CIZ1-DHX9 nucleolar colocalisation is dependent upon RNA polymerase I activity and is abolished by depletion of DHX9. In addition, depletion of DHX9 reduced cell cycle progression from G1 to S-phase in mouse fibroblasts. The data suggest that DHX9-CIZ1 are required for efficient cell cycle progression at the G1/S transition and that nucleolar recruitment is integral to their mechanism of action.

scholarly journals Growth factor, steroid, and steroid antagonist regulation of cyclin gene expression associated with changes in T-47D human breast cancer cell cycle progression.

1993 ◽  
Vol 13 (6) ◽  
pp. 3577-3587 ◽  
Author(s):  
E A Musgrove ◽  
J A Hamilton ◽  
C S Lee ◽  
K J Sweeney ◽  
C K Watts ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Gene Expression ◽  
Cell Cycle ◽  
Cyclin D1 ◽  
Cancer Cell ◽  
Breast Cancer Cell ◽  
Cell Cycle Progression ◽  
S Phase ◽  
G1 Phase ◽  
Cycle Progression

Cyclins and proto-oncogenes including c-myc have been implicated in eukaryotic cell cycle control. The role of cyclins in steroidal regulation of cell proliferation is unknown, but a role for c-myc has been suggested. This study investigated the relationship between regulation of T-47D breast cancer cell cycle progression, particularly by steroids and their antagonists, and changes in the levels of expression of these genes. Sequential induction of cyclins D1 (early G1 phase), D3, E, A (late G1-early S phase), and B1 (G2 phase) was observed following insulin stimulation of cell cycle progression in serum-free medium. Transient acceleration of G1-phase cells by progestin was also accompanied by rapid induction of cyclin D1, apparent within 2 h. This early induction of cyclin D1 and the ability of delayed administration of antiprogestin to antagonize progestin-induced increases in both cyclin D1 mRNA and the proportion of cells in S phase support a central role for cyclin D1 in mediating the mitogenic response in T-47D cells. Compatible with this hypothesis, antiestrogen treatment reduced the expression of cyclin D1 approximately 8 h before changes in cell cycle phase distribution accompanying growth inhibition. In the absence of progestin, antiprogestin treatment inhibited T-47D cell cycle progression but in contrast did not decrease cyclin D1 expression. Thus, changes in cyclin D1 gene expression are often, but not invariably, associated with changes in the rate of T-47D breast cancer cell cycle progression. However, both antiestrogen and antiprogestin depleted c-myc mRNA by > 80% within 2 h. These data suggest the involvement of both cyclin D1 and c-myc in the steroidal control of breast cancer cell cycle progression.

Differentiation Profiling of Marrow Stem Cells: A Megakaryopoietic Hotspot and the Continuum Model of Hematopoiesis.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 4217-4217
Author(s):  
Gerald A. Colvin ◽  
Dooner Gerri ◽  
Delia Demers ◽  
Shiela Pascual ◽  
Samuel Chung ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
Stem Cells ◽  
S Phase ◽  
Platelet Glycoprotein ◽  
No Production ◽  
Colony Stimulating Factor ◽  
Hematopoietic Stem ◽  
Steel Factor ◽  
Stimulating Factor

Abstract Hierarchical models of hematopoiesis suppose an ordered system in which stem cells and progenitors with specific fixed differentiation potentials exist. We show here that the potential of marrow stem cells to differentiate changes reversibly with cytokine-induced cell cycle transit. This along with other data strongly suggest that stem cell regulation is not based on the classic hierarchical model, but instead more on a functional continuum We have previously shown that hematopoietic stem cells reversibly shift their engraftment phenotype with cytokine induced cell cycle transit. Further work has shown that adhesion protein, cytokine receptor, gene expression and progenitor phenotypes also shift. Evolving data indicate the phenotype of murine marrow stem cells reversible change with cell cycle transit. Murine experiments have been performed on highly purified, quiescent G0-1 lineagenegativerhodaminelowHoeschtlow (LRH) marrow stem cells. When exposed to thrombopoietin, FLT3-ligand and steel factor, they synchronously pass through cell cycle as measured by propidium iodide, cell doublings and tritiated thymidine. LRH cells enter S-phase in a synchronized fashion by 18 hours, leave S-phase at 40–42 hours and divide between 44–48 hours. The capacity of these cells to respond to a differentiation inductive signal (granulocyte colony-stimulating factor, granulocyte-macrophage colony stimulating factor and steel factor) is altered at different points in cell cycle. Megakaryocyte production is specifically focused at early to mid S-phase, this returned to baseline before the first cell division. Population based cultures after 14-days of differentiation culture produced up to 49% megakaryocytes with stem cells sub-cultured during early-mid S-phase with little to no production with colonies cultured from stem cells in G0-1 or G2 phase at time of differentiation induction signaling. Cell type was confirmed by staining cells with acetylcholinesterase, antibodies to platelet glycoprotein complex IIb/IIIa and von Willebrand’s factor. Evaluation of gene expression at this hotspot showed a marked increase in expression of CD4 with up to 464.2 fold increase above baseline. Sca-1 and transcriptional factor FOG was strikingly amplified at S-phase as well as other relevant markers. While pertinent cytokine receptors were not increased, studies on a clonal level confirm the existence of a reversible megakaryocytic hotspot. Compared with other time-points relating to cell cycle position prior to differentiation sub-culture in one experiment, 33% of clonally derived colonies that grew from early S-phase cells and 10% of colonies that grew from mid S-phase cells had megakaryocytes present two weeks after initiation of culture compared with 0% for G0-1 and G2 cells. Granulocyte differentiation also showed specific differentiation hotspots, but presentation is outside the scope of this abstract. These data indicate that marrow hematopoiesis stem cells exist in a continuum, not in a hierarchy with continuously changing windows of transcriptional opportunity.

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