scholarly journals Macroscopic folding and replication of the homogeneously staining region in late S phase leads to the appearance of replication bands in mitotic chromosomes

2004 ◽  
Vol 117 (22) ◽  
pp. 5303-5312 ◽  
Author(s):  
N. Shimizu
Keyword(s):  
S Phase ◽  
Mitotic Chromosomes ◽  
Replication Bands

scholarly journals Chromosome Banding in Amphibia. XXXII. The Genus Xenopus (Anura, Pipidae)

2015 ◽  
Vol 145 (3-4) ◽  
pp. 201-217 ◽  
Author(s):  
Michael Schmid ◽  
Claus Steinlein
Keyword(s):  
Chromosome Pair ◽  
Repetitive Sequences ◽  
5S Rdna ◽  
Mitotic Chromosomes ◽  
Banding Patterns ◽  
Single Chromosome ◽  
Replication Banding ◽  
Rdna Sequences ◽  
High Degree ◽  
Replication Bands

Mitotic chromosomes of 16 species of the frog genus Xenopus were prepared from kidney and lung cell cultures. In the chromosomes of 7 species, high-resolution replication banding patterns could be induced by treating the cultures with 5-bromodeoxyuridine (BrdU) and deoxythymidine (dT) in succession, and in 6 of these species the BrdU/dT-banded chromosomes could be arranged into karyotypes. In the 3 species of the clade with 2n = 20 and 4n = 40 chromosomes (X. tropicalis, X. epitropicalis, X. new tetraploid 1), as well as in the 3 species with 4n = 36 chromosomes (X. laevis, X. borealis, X. muelleri), the BrdU/dT-banded karyotypes show a high degree of homoeology, though differences were detected between these groups. Translocations, inversions, insertions or sex-specific replication bands were not observed. Minor replication asynchronies found between chromosomes probably involve heterochromatic regions. BrdU/dT replication banding of Xenopus chromosomes provides the landmarks necessary for the exact physical mapping of genes and repetitive sequences. FISH with an X. laevis 5S rDNA probe detected multiple hybridization sites at or near the long-arm telomeric regions in most chromosomes of X. laevis and X. borealis, whereas in X. muelleri, the 5S rDNA sequences are located exclusively at the long-arm telomeres of a single chromosome pair. Staining with the AT base pair-specific fluorochrome quinacrine mustard revealed brightly fluorescing heterochromatic regions in the majority of X. borealis chromosomes which are absent in other Xenopus species.

MICROCHROMOSOMES OF THE ONTARIO RED FOX (VULPES VULPES): AN ATTEMPT AT CHARACTERIZATION

1980 ◽  
Vol 22 (4) ◽  
pp. 553-567 ◽  
Author(s):  
J. A. Ellenton ◽  
P. K. Basrur
Keyword(s):  
Electron Microscopy ◽  
Silver Nitrate ◽  
Vulpes Vulpes ◽  
Red Fox ◽  
Light And Electron Microscopy ◽  
Testicular Tissue ◽  
S Phase ◽  
Mitotic Chromosomes ◽  
Autoradiographic Analysis ◽  
Ammoniacal Silver

Characterization of the microchromosomes of the red fox, Vulpes vulpes Linn., was attempted through the examination of mitotic chromosomes using Giemsa banding, quinacrine banding, the silver nitrate-ammoniacal silver technique for staining nucleolar organizers, and autoradiographic procedures. Pachytene cells were examined in air-dried and squash meiotic preparations and in testicular tissue sectioned for light and electron microscopy. The results of banding procedures on mitotic chromosomes and the staining properties of the microchromosomes at pachytene indicated that the microchromosomes likely contain both heterochromatin and euchromatin. Autoradiographic analysis showed that the microchromosomes replicate during mid S phase while the Y chromosome, which is in the size range of the microchromosomes, replicates during late S phase. From these observations, it would appear that the microchromosomes may not be exclusively heterochromatic as hypothesized previously. With the use of the silver nitrate-ammoniacal silver technique, the presence of nucleolar regions were detected on specific macrochromosomes but not on any of the microchromosomes. Examination of pachytene chromosomes in air-dried and squash preparations, and of testicular tissue sectioned for light and electron microscopy, also indicated that the microchromosomes may not be involved in the organization of the nucleolus in the red fox.

scholarly journals Phosphorylation Regulates Binding of the Human Papillomavirus Type 8 E2 Protein to Host Chromosomes

2012 ◽  
Vol 86 (18) ◽  
pp. 10047-10058 ◽  
Author(s):  
Vandana Sekhar ◽  
Alison A. McBride
Keyword(s):  
Human Papillomavirus ◽  
Posttranslational Modifications ◽  
S Phase ◽  
Chromatin Binding ◽  
Genome Maintenance ◽  
Mitotic Chromosomes ◽  
E2 Protein ◽  
Viral Genomes ◽  
Daughter Cells ◽  
Host Nucleus

The papillomavirus E2 proteins are indispensable for the viral life cycle, and their functions are subject to tight regulation. The E2 proteins undergo posttranslational modifications that regulate their properties and roles in viral transcription, replication, and genome maintenance. During persistent infection, the E2 proteins from many papillomaviruses act as molecular bridges that tether the viral genomes to host chromosomes to retain them within the host nucleus and to partition them to daughter cells. The betapapillomavirus E2 proteins bind to pericentromeric regions of host mitotic chromosomes, including the ribosomal DNA loci. We recently reported that two residues (arginine 250 and serine 253) within the chromosome binding region of the human papillomavirus type 8 (HPV8) E2 protein are required for this binding. In this study, we show that serine 253 is phosphorylated, most likely by protein kinase A, and this modulates the interaction of the E2 protein with cellular chromatin. Furthermore, we show that this phosphorylation occurs in S phase, increases the half-life of the E2 protein, and promotes chromatin binding from S phase through mitosis.

scholarly journals CELL CYCLE-SPECIFIC CHANGES IN HISTONE PHOSPHORYLATION ASSOCIATED WITH CELL PROLIFERATION AND CHROMOSOME CONDENSATION

1974 ◽  
Vol 60 (2) ◽  
pp. 356-364 ◽  
Author(s):  
Lawrence R. Gurley ◽  
Ronald A. Walters ◽  
Robert A. Tobey
Keyword(s):  
Cell Cycle ◽  
Structural Changes ◽  
Polyacrylamide Gel Electrophoresis ◽  
Chinese Hamster ◽  
Chromosome Condensation ◽  
S Phase ◽  
Mitotic Chromosomes ◽  
Proliferating Cells ◽  
Interphase Chromosome ◽  
Histone Phosphorylation

Preparative polyacrylamide gel electrophoresis was used to examine histone phosphorylation in synchronized Chinese hamster cells (line CHO). Results showed that histone f1 phosphorylation, absent in G1-arrested and early G1-traversing cells, commences 2 h before entry of traversing cells into the S phase. It is concluded that f1 phosphorylation is one of the earliest biochemical events associated with conversion of nonproliferating cells to proliferating cells occurring on old f1 before synthesis of new f1 during the S phase. Results also showed that f3 and a subfraction of f1 were rapidly phosphorylated only during the time when cells were crossing the G2/M boundary and traversing prophase. Since these phosphorylation events do not occur in G1, S, or G2 and are reduced greatly in metaphase, it is concluded that these two specific phosphorylation events are involved with condensation of interphase chromatin into mitotic chromosomes. This conclusion is supported by loss of prelabeled 32PO4 from those specific histone fractions during transition of metaphase cells into interphase G1 cells. A model of the relationship of histone phosphorylation to the cell cycle is presented which suggests involvement of f1 phosphorylation in chromatin structural changes associated with a continuous interphase "chromosome cycle" which culminates at mitosis with an f3 and f1 phosphorylation-mediated chromosome condensation.

Induced detachment of acentric chromatin from mitotic chromosomes leads to their cytoplasmic localization at G(1) and the micronucleation by lamin reorganization at S phase

2000 ◽  
Vol 113 (4) ◽  
pp. 697-707 ◽  
Author(s):  
T. Tanaka ◽  
N. Shimizu
Keyword(s):  
Large Scale ◽  
Human Cancer ◽  
Strand Break ◽  
S Phase ◽  
Mitotic Chromosomes ◽  
Human Cancer Cells ◽  
Double Minutes ◽  
Nuclear Lamin ◽  
Hydroxyurea Treatment ◽  
Selective Incorporation

Acentric and atelomeric double minute chromatin found in human cancer cells are eliminated from cells by selective incorporation into the micronuclei. We showed previously that most of the micronuclei were formed at S phase and mediated by the nuclear bud-shaped structures that selectively entrap double minutes. In this paper, we have examined the behavior of double minutes in relation to the nuclear lamin protein in cell cycle-synchronized human COLO 320DM tumor cells. At the G(1) phase, we observed that a portion of double minutes was localized at the cytoplasm and showed no association with lamin. The frequency of this localization was increased by hydroxyurea, an inducer of micronuclei, if treated at the preceding S phase. The acentric double minutes were normally segregated to daughter cells by attaching to the mitotic chromosomes, and the hydroxyurea-treatment induced their detachment, possibly through the introduction of the double strand break. When the cells entered S phase, our data suggested that the lamin protein accumulated around the cytoplasmic double minutes at the proximity of the nucleus leading to the formation of the nuclear bud-shaped structure and the initiation of DNA replication. This association of cytoplasmic double minutes with lamin coincided with the large-scale rearrangement of the intranuclear lamin protein. The implication of these findings as well as their application to a broad spectrum of other acentric, atelomeric and autonomously replicating molecules are discussed.

Sulfhydryl bond formation is a prerequisite for proper cycling of centrosomes and chromosomes in mammalian tissue culture cells

1993 ◽  
Vol 51 ◽  
pp. 342-343
Author(s):  
Heide Schatten ◽  
Neidhard Paweletz ◽  
Ron Balczon
Keyword(s):  
Tissue Culture ◽  
Cell Cycle Progression ◽  
Group Formation ◽  
Sulfhydryl Group ◽  
Mammalian Tissue ◽  
Mitotic Chromosomes ◽  
Microtubule Network ◽  
Culture Cells ◽  
Tissue Culture Cells ◽  
Transmission Electron

To study the role of sulfhydryl group formation during cell cycle progression, mammalian tissue culture cells (PTK2) were exposed to 100¼M 2-mercaptoethanol for 2 to 6 h during their exponential phase of growth. The effects of 2-mercaptoethanol on centrosomes, chromosomes, microtubules, membranes and intermediate filaments were analyzed by transmission electron microscopy (TEM) and by immunofluorescence microscopy (IFM) methods using a human autoimmune antibody directed against centrosomes (SPJ), and a mouse monoclonal antibody directed against tubulin (E7). Chromosomes were affected most by this treatment: premature chromosome condensation was detected in interphase nuclei, and the structure in mitotic chromosomes was altered compared to control cells. This would support previous findings in dividing sea urchin cells in which chromosomes are arrested at metaphase while the centrosome splitting cycle continues. It might also support findings that certairt-sulfhydryl-blocking agents block cyclin destruction. The organization of the microtubule network was scattered probably due to a looser organization of centrosomal material at the interphase centers and at the mitotic poles.

Induction of S phase by G1 regulatory factors

10.2741/a395 ◽  
1999 ◽  
Vol 4 (4) ◽  
pp. d787-792 ◽  
Author(s):  
Jun-ya Kato
Keyword(s):  
S Phase ◽  
Regulatory Factors
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