DNA constancy and chromatin structure in some cell nuclei ofAmphiuma

1972 ◽  
Vol 4 (3) ◽  
pp. 181-192 ◽  
Author(s):  
J. James
Keyword(s):  
Chromatin Structure ◽  
Cell Nuclei

scholarly journals DNA Replication in Quiescent Cell Nuclei: Regulation by the Nuclear Envelope and Chromatin Structure

1999 ◽  
Vol 10 (12) ◽  
pp. 4091-4106 ◽  
Author(s):  
Zhi Hong Lu ◽  
Hongzhi Xu ◽  
Gregory H. Leno
Keyword(s):  
Dna Replication ◽  
Nuclear Envelope ◽  
Chromatin Structure ◽  
Cell Nuclei ◽  
Free System ◽  
Replication Complex ◽  
Linker Histones ◽  
Egg Extract ◽  
Initiation Of Replication ◽  
Stable Association

Quiescent nuclei from differentiated somatic cells can reacquire pluripotence, the capacity to replicate, and reinitiate a program of differentiation after transplantation into amphibian eggs. The replication of quiescent nuclei is recapitulated in extracts derived from activated Xenopus eggs; therefore, we have exploited this cell-free system to explore the mechanisms that regulate initiation of replication in nuclei from terminally differentiatedXenopus erythrocytes. We find that these nuclei lack many, if not all, pre-replication complex (pre-RC) proteins. Pre-RC proteins from the extract form a stable association with the chromatin of permeable nuclei, which replicate in this system, but not with the chromatin of intact nuclei, which do not replicate, even though these proteins cross an intact nuclear envelope. During extract incubation, the linker histones H1 and H10 are removed from erythrocyte chromatin by nucleoplasmin. We show that H1 removal facilitates the replication of permeable nuclei by increasing the frequency of initiation most likely by promoting the assembly of pre-RCs on chromatin. These data indicate that initiation in erythrocyte nuclei requires the acquisition of pre-RC proteins from egg extract and that pre-RC assembly requires the loss of nuclear envelope integrity and is facilitated by the removal of linker histone H1 from chromatin.

scholarly journals Distribution of ABL and BCR Genes in Cell Nuclei of Normal and Irradiated Lymphocytes

Blood ◽  
1997 ◽  
Vol 89 (12) ◽  
pp. 4537-4545 ◽  
Author(s):  
S. Kozubek ◽  
E. Lukášová ◽  
L. Rýznar ◽  
M. Kozubek ◽  
A. Lišková ◽  
...  
Keyword(s):  
Chromatin Structure ◽  
Human Fibroblasts ◽  
Physical Distance ◽  
Gene Arrangement ◽  
Cell Nuclei ◽  
Interphase Nuclei ◽  
Γ Radiation ◽  
Shortest Distance ◽  
G0 Phase

Abstract Using dual-color fluorescence in situ hybridization (FISH) combined with two-dimensional (2D) image analysis, the locations of ABL and BCR genes in cell nuclei were studied. The center of nucleus-to-gene and mutual distances of ABL and BCR genes in interphase nuclei of nonstimulated and stimulated lymphocytes as well as in lymphocytes stimulated after irradiation were determined. We found that, after stimulation, the ABL and BCR genes move towards the membrane, their mutual distances increase, and the shortest distance between heterologous ABL and BCR genes increases. The distribution of the shortest distances between ABL and BCR genes in the G0 phase of lymphocytes corresponds to the theoretical distribution calculated by the Monte-Carlo simulation. Interestingly, the shortest ABL-BCR distances in G1 and S(G2 ) nuclei are greater in experiment as compared with theory. This result suggests the existence of a certain regularity in the gene arrangement in the G1 and S(G2 ) nuclei that keeps ABL and BCR genes at longer than random distances. On the other hand, in about 2% to 8% of lymphocytes, the ABL and BCR genes are very close to each other (the distance is less than ∼0.2 to 0.3 μm). For comparison, we studied another pair of genes, c-MYC and IgH, that are critical for the induction of t(8; 14) translocation that occurs in the Burkitt's lymphoma. We found that in about 8% of lymphocytes, c-MYC and IgH are very close to each other. Similar results were obtained for human fibroblasts. γ-Radiation leads to substantial changes in the chromatin structure of stimulated lymphocytes: ABL and BCR genes are shifted to the nuclear center, and mutual ABL-BCR distances become much shorter in the G1 and S(G2 ) nuclei. Therefore, we hypothesize that the changes of chromatin structure in the irradiated lymphocytes might increase the probability of a translocation during G1 and S(G2 ) stages of the cell cycle. The fact that the genes involved in the t(8; 14) translocation are also located close together in a certain fraction of cells substantiates the hypothesis that physical distance plays an important role in the processes leading to the translocations that are responsible for oncogenic transformation of cells.

scholarly journals Effect of polyamine depletion on chromatin structure in U-87 MG human brain tumour cells

1992 ◽  
Vol 282 (3) ◽  
pp. 723-727 ◽  
Author(s):  
H S Basu ◽  
M C J M Sturkenboom ◽  
J G Delcros ◽  
P P Csokan ◽  
J Szollosi ◽  
...  
Keyword(s):  
Human Brain ◽  
Brain Tumour ◽  
Chromatin Structure ◽  
Cell Cycle Progression ◽  
Tumour Cells ◽  
Micrococcal Nuclease ◽  
Cell Nuclei ◽  
Growth Inhibitory ◽  
Kinetics Of ◽  
In Cells

The chromatin structure of polyamine-depleted U-87 MG human brain tumour cells was studied by following the kinetics of digestion of cell nuclei by micrococcal nuclease and bovine pancreatic DNAase I. Cells growing in monolayers were treated with either alpha-difluoromethylornithine (DFMO), to deplete putrescine and spermidine, or N1,N14-bis(ethyl)homospermine (BE-4-4-4), to deplete putrescine, spermidine and spermine. BE-4-4-4 increased the initial rates of digestion and the magnitudes of limit digest by both enzymes; DFMO increased the limit digests without affecting initial digestion rates. Addition of 1 mM-putrescine 1 day after addition of DFMO reversed the effect of DFMO on limit digests. (Because polyamine uptake is low in cells treated with BE-4-4-4, and because putrescine does not reverse the growth-inhibitory effects of BE-4-4-4, reversal of the effects of BE-4-4-4 with putrescine was not attempted.) The increases in initial rates and limit digests did not result from changes in the lengths of nucleosomal or linker DNA, from blocks in cell-cycle progression, or from growth inhibition caused by DFMO or BE-4-4-4. Thus, because the limit digest is highest in cells with the lowest polyamine levels, it seems clear that the enhanced enzymic digestion of nuclei is caused by polyamine depletion and its possible effect on chromatin structure.

Chromatin Structure in Neuronal and Neuroglial Cell Nuclei as a Function of Age

1983 ◽  
Vol 41 (2) ◽  
pp. 516-523 ◽  
Author(s):  
Ellen M. Berkowitz ◽  
Anne C. Sanborn ◽  
Deborah W. Vaughan
Keyword(s):  
Chromatin Structure ◽  
Cell Nuclei ◽  
Neuroglial Cell

scholarly journals Super-resolution visualization and modeling of human chromosomal regions reveals cohesin-dependent loop structures

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Xian Hao ◽  
Jyotsana J. Parmar ◽  
Benoît Lelandais ◽  
Andrey Aristov ◽  
Wei Ouyang ◽  
...  
Keyword(s):  
Single Molecule ◽  
Chromatin Structure ◽  
Spatial Information ◽  
Low Cost ◽  
Single Cells ◽  
Regulation Of Gene Expression ◽  
Fluorescence Labeling ◽  
Cell Nuclei ◽  
Invasive Approach ◽  
Chromatin Loops

Abstract Background The 3D organization of the chromatin fiber in cell nuclei plays a key role in the regulation of gene expression. Genome-wide techniques to score DNA-DNA contacts, such as Hi-C, reveal the partitioning of chromosomes into epigenetically defined active and repressed compartments and smaller “topologically associated” domains. These domains are often associated with chromatin loops, which largely disappear upon removal of cohesin. Because most Hi-C implementations average contact frequencies over millions of cells and do not provide direct spatial information, it remains unclear whether and how frequently chromatin domains and loops exist in single cells. Results We combine 3D single-molecule localization microscopy with a low-cost fluorescence labeling strategy that does not denature the DNA, to visualize large portions of single human chromosomes in situ at high resolution. In parallel, we develop multi-scale, whole nucleus polymer simulations, that predict chromatin structures at scales ranging from 5 kb up to entire chromosomes. We image chromosomes in G1 and M phase and examine the effect of cohesin on interphase chromatin structure. Depletion of cohesin leads to increased prevalence of loose chromatin stretches, increased gyration radii, and reduced smoothness of imaged chromatin regions. By comparison to model predictions, we estimate that 6–25 or more purely cohesin-dependent chromatin loops coexist per megabase of DNA in single cells, suggesting that the vast majority of the genome is enclosed in loops. Conclusion Our results provide new constraints on chromatin structure and showcase an affordable non-invasive approach to study genome organization in single cells.

Chromatin Structure and its Cell Cycle Kinetics in Intact and Irradiated Cell Nuclei

1999 ◽  
pp. 231-242
Author(s):  
S. Kozubek ◽  
E. Lukášová ◽  
L. Rýznar ◽  
M. Kozubek ◽  
A. Lišková ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Chromatin Structure ◽  
Cell Nuclei ◽  
Cell Cycle Kinetics
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