scholarly journals Replication timing of DNA sequences associated with human centromeres and telomeres.

1990 ◽  
Vol 10 (12) ◽  
pp. 6348-6355 ◽  
Author(s):  
K G Ten Hagen ◽  
D M Gilbert ◽  
H F Willard ◽  
S N Cohen
Keyword(s):  
Dna Sequences ◽  
Cell Sorting ◽  
Replication Timing ◽  
S Phase ◽  
Alpha Satellite ◽  
Chromosomal Dna ◽  
Telomeric Sequences ◽  
Alpha Satellite Dna ◽  
Satellite Sequences ◽  
Satellite Repeats

The timing of replication of centromere-associated human alpha satellite DNA from chromosomes X, 17, and 7 as well as of human telomeric sequences was determined by using density-labeling methods and fluorescence-activated cell sorting. Alpha satellite sequences replicated late in S phase; however, the alpha satellite sequences of the three chromosomes studied replicated at slightly different times. Human telomeres were found to replicate throughout most of S phase. These results are consistent with a model in which multiple initiations of replication occur at a characteristic time within the alpha satellite repeats of a particular chromosome, while the replication timing of telomeric sequences is determined by either telomeric origins that can initiate at different times during S phase or by replication origins within the flanking chromosomal DNA sequences.

scholarly journals Replication timing of DNA sequences associated with human centromeres and telomeres

1990 ◽  
Vol 10 (12) ◽  
pp. 6348-6355
Author(s):  
K G Ten Hagen ◽  
D M Gilbert ◽  
H F Willard ◽  
S N Cohen
Keyword(s):  
Dna Sequences ◽  
Cell Sorting ◽  
Replication Timing ◽  
S Phase ◽  
Alpha Satellite ◽  
Chromosomal Dna ◽  
Telomeric Sequences ◽  
Alpha Satellite Dna ◽  
Satellite Sequences ◽  
Satellite Repeats

The timing of replication of centromere-associated human alpha satellite DNA from chromosomes X, 17, and 7 as well as of human telomeric sequences was determined by using density-labeling methods and fluorescence-activated cell sorting. Alpha satellite sequences replicated late in S phase; however, the alpha satellite sequences of the three chromosomes studied replicated at slightly different times. Human telomeres were found to replicate throughout most of S phase. These results are consistent with a model in which multiple initiations of replication occur at a characteristic time within the alpha satellite repeats of a particular chromosome, while the replication timing of telomeric sequences is determined by either telomeric origins that can initiate at different times during S phase or by replication origins within the flanking chromosomal DNA sequences.

scholarly journals Dynamic organization of DNA replication in mammalian cell nuclei: spatially and temporally defined replication of chromosome-specific alpha-satellite DNA sequences.

1992 ◽  
Vol 116 (5) ◽  
pp. 1095-1110 ◽  
Author(s):  
R T O'Keefe ◽  
S C Henderson ◽  
D L Spector
Keyword(s):  
Dna Replication ◽  
Mammalian Cell ◽  
Dna Sequences ◽  
Satellite Dna ◽  
Cell Types ◽  
S Phase ◽  
Laser Scanning Microscopy ◽  
Alpha Satellite ◽  
Alpha Satellite Dna ◽  
Dense Chromatin

Five distinct patterns of DNA replication have been identified during S-phase in asynchronous and synchronous cultures of mammalian cells by conventional fluorescence microscopy, confocal laser scanning microscopy, and immunoelectron microscopy. During early S-phase, replicating DNA (as identified by 5-bromodeoxyuridine incorporation) appears to be distributed at sites throughout the nucleoplasm, excluding the nucleolus. In CHO cells, this pattern of replication peaks at 30 min into S-phase and is consistent with the localization of euchromatin. As S-phase continues, replication of euchromatin decreases and the peripheral regions of heterochromatin begin to replicate. This pattern of replication peaks at 2 h into S-phase. At 5 h, perinucleolar chromatin as well as peripheral areas of heterochromatin peak in replication. 7 h into S-phase interconnecting patches of electron-dense chromatin replicate. At the end of S-phase (9 h), replication occurs at a few large regions of electron-dense chromatin. Similar or identical patterns have been identified in a variety of mammalian cell types. The replication of specific chromosomal regions within the context of the BrdU-labeling patterns has been examined on an hourly basis in synchronized HeLa cells. Double labeling of DNA replication sites and chromosome-specific alpha-satellite DNA sequences indicates that the alpha-satellite DNA replicates during mid S-phase (characterized by the third pattern of replication) in a variety of human cell types. Our data demonstrates that specific DNA sequences replicate at spatially and temporally defined points during the cell cycle and supports a spatially dynamic model of DNA replication.

scholarly journals Triple-Helical DNA in Drosophila Heterochromatin

Cells ◽  
2018 ◽  
Vol 7 (12) ◽  
pp. 227 ◽  
Author(s):  
Eduardo Gorab
Keyword(s):  
Nucleic Acids ◽  
Dna Sequences ◽  
Detection Methods ◽  
Triplex Dna ◽  
Thiazole Orange ◽  
Chromosomal Dna ◽  
Mitotic Chromosomes ◽  
Satellite Repeats

Polynucleotide chains obeying Watson-Crick pairing are apt to form non-canonical complexes such as triple-helical nucleic acids. From early characterization in vitro, their occurrence in vivo has been strengthened by increasing evidence, although most remain circumstantial particularly for triplex DNA. Here, different approaches were employed to specify triple-stranded DNA sequences in the Drosophila melanogaster chromosomes. Antibodies to triplex nucleic acids, previously characterized, bind to centromeric regions of mitotic chromosomes and also to the polytene section 59E of mutant strains carrying the brown dominant allele, indicating that AAGAG tandem satellite repeats are triplex-forming sequences. The satellite probe hybridized to AAGAG-containing regions omitting chromosomal DNA denaturation, as expected, for the intra-molecular triplex DNA formation model in which single-stranded DNA coexists with triplexes. In addition, Thiazole Orange, previously described as capable of reproducing results obtained by antibodies to triple-helical DNA, binds to AAGAG repeats in situ thus validating both detection methods. Unusual phenotype and nuclear structure exhibited by Drosophila correlate with the non-canonical conformation of tandem satellite arrays. From the approaches that lead to the identification of triple-helical DNA in chromosomes, facilities particularly provided by Thiazole Orange use may broaden the investigation on the occurrence of triplex DNA in eukaryotic genomes.

scholarly journals Position effects on the timing of replication of chromosomally integrated simian virus 40 molecules in Chinese hamster cells.

1990 ◽  
Vol 10 (8) ◽  
pp. 4345-4355 ◽  
Author(s):  
D M Gilbert ◽  
S N Cohen
Keyword(s):  
Dna Sequences ◽  
Chinese Hamster ◽  
Simian Virus 40 ◽  
Replication Timing ◽  
Simian Virus ◽  
Relative Activity ◽  
T Antigen ◽  
Temperature Sensitive ◽  
Chromosomal Dna ◽  
Position Effects

Simian virus 40 (SV40) DNA molecules chromosomally integrated at different sites in three Chinese hamster lung fibroblast lines replicated during the middle portion of S phase but not precisely at the same time in all three cell lines. The time of replication was unrelated to the presence of T antigen or to its relative activity in promoting SV40 replication. SV40 sequences and chromosomal DNA sequences adjacent to the SV40 insert in one cell line expressing a temperature-sensitive T antigen showed a T-antigen-independent difference in replication timing from the homologous, allelic locus not linked to SV40. Our results indicate that the timing of replication of these integrated SV40 molecules is dependent upon the site of integration and is not determined by the level of T antigen replication-promoting activity.

Genomic organization of alpha satellite DNA on human chromosome 7: evidence for two distinct alphoid domains on a single chromosome

1987 ◽  
Vol 7 (1) ◽  
pp. 349-356
Author(s):  
J S Waye ◽  
S B England ◽  
H F Willard
Keyword(s):  
Human Genome ◽  
Dna Sequences ◽  
Satellite Dna ◽  
Repeat Unit ◽  
Higher Order ◽  
Chromosome 7 ◽  
Alpha Satellite ◽  
Single Chromosome ◽  
Alpha Satellite Dna ◽  
Repeat Structure

A complete understanding of chromosomal disjunction during mitosis and meiosis in complex genomes such as the human genome awaits detailed characterization of both the molecular structure and genetic behavior of the centromeric regions of chromosomes. Such analyses in turn require knowledge of the organization and nature of DNA sequences associated with centromeres. The most prominent class of centromeric DNA sequences in the human genome is the alpha satellite family of tandemly repeated DNA, which is organized as distinct chromosomal subsets. Each subset is characterized by a particular multimeric higher-order repeat unit consisting of tandemly reiterated, diverged alpha satellite monomers of approximately 171 base pairs. The higher-order repeat units are themselves tandemly reiterated and represent the most recently amplified or fixed alphoid sequences. We present evidence that there are at least two independent domains of alpha satellite DNA on chromosome 7, each characterized by their own distinct higher-order repeat structure. We determined the complete nucleotide sequences of a 6-monomer higher-order repeat unit, which is present in approximately 500 copies per chromosome 7, as well as those of a less-abundant (approximately 10 copies) 16-monomer higher-order repeat unit. Sequence analysis indicated that these repeats are evolutionarily distinct. Genomic hybridization experiments established that each is maintained in relatively homogeneous tandem arrays with no detectable interspersion. We propose mechanisms by which multiple unrelated higher-order repeat domains may be formed and maintained within a single chromosomal subset.

scholarly journals Evolutionary History of Alpha Satellite DNA Repeats Dispersed within Human Genome Euchromatin

2020 ◽  
Vol 12 (11) ◽  
pp. 2125-2138
Author(s):  
Isidoro Feliciello ◽  
Željka Pezer ◽  
Dušan Kordiš ◽  
Branka Bruvo Mađarić ◽  
Đurđica Ugarković
Keyword(s):  
Satellite Dna ◽  
Evolutionary History ◽  
Genomic Sequence ◽  
Sequence Divergence ◽  
Dna Repeats ◽  
Alpha Satellite ◽  
Alpha Satellite Dna ◽  
Satellite Repeats ◽  
Number Variation ◽  
History Of

Abstract Major human alpha satellite DNA repeats are preferentially assembled within (peri)centromeric regions but are also dispersed within euchromatin in the form of clustered or short single repeat arrays. To study the evolutionary history of single euchromatic human alpha satellite repeats (ARs), we analyzed their orthologous loci across the primate genomes. The continuous insertion of euchromatic ARs throughout the evolutionary history of primates starting with the ancestors of Simiformes (45–60 Ma) and continuing up to the ancestors of Homo is revealed. Once inserted, the euchromatic ARs were stably transmitted to the descendant species, some exhibiting copy number variation, whereas their sequence divergence followed the species phylogeny. Many euchromatic ARs have sequence characteristics of (peri)centromeric alpha repeats suggesting heterochromatin as a source of dispersed euchromatic ARs. The majority of euchromatic ARs are inserted in the vicinity of other repetitive elements such as L1, Alu, and ERV or are embedded within them. Irrespective of the insertion context, each AR insertion seems to be unique and once inserted, ARs do not seem to be subsequently spread to new genomic locations. In spite of association with (retro)transposable elements, there is no indication that such elements play a role in ARs proliferation. The presence of short duplications at most of ARs insertion sites suggests site-directed recombination between homologous motifs in ARs and in the target genomic sequence, probably mediated by extrachromosomal circular DNA, as a mechanism of spreading within euchromatin.

scholarly journals CENP-C binds the alpha-satellite DNA in vivo at specific centromere domains

2002 ◽  
Vol 115 (11) ◽  
pp. 2317-2327 ◽  
Author(s):  
Valeria Politi ◽  
Giovanni Perini ◽  
Stefania Trazzi ◽  
Artem Pliss ◽  
Ivan Raska ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Satellite Dna ◽  
Alpha Satellite ◽  
Alpha Satellite Dna ◽  
Human Centromere ◽  
Ultrastructural Characterization ◽  
First Time

CENP-C is a fundamental component of the centromere, highly conserved among species and necessary for the proper assembly of the kinetochore structure and for the metaphase-anaphase transition. Although CENP-C can bind DNA in vitro,the identification of the DNA sequences associated with it in vivo and the significance of such an interaction have been, until now, elusive. To address this problem we took advantage of a chromatin-immunoprecipitation procedure and applied this technique to human HeLa cells. Through this approach we could establish that: (1) CENP-C binds the alpha-satellite DNA selectively; (2) the CENP-C region between amino acids 410 and 537, previously supposed to contain a DNA-binding domain, is indeed required to perform such a function in vivo;and (3) the profile of the alpha-satellite DNA associated with CENP-C is essentially identical to that recognized by CENP-B. However, further biochemical and ultrastructural characterization of CENP-B/DNA and CENP-C/DNA complexes, relative to their DNA components and specific spatial distribution in interphase nuclei, surprisingly reveals that CENP-C and CENP-B associate with the same types of alpha-satellite arrays but in distinct non-overlapping centromere domains. Our results, besides extending previous observations on the role of CENP-C in the formation of active centromeres, show, for the first time, that CENP-C can associate with the centromeric DNA sequences in vivo and, together with CENP-B, defines a highly structured organization of the alpha-satellite DNA within the human centromere.

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