Telomere-Mediated Chromosome Healing

1997 ◽  
Vol 148 (3) ◽  
pp. 293
Author(s):  
P. Slijepcevic ◽  
P. E. Bryant
Keyword(s):  
Chromosome Healing

scholarly journals Homolog-Dependent Repair Following Dicentric Chromosome Breakage in Drosophila melanogaster

Genetics ◽  
2019 ◽  
Vol 212 (3) ◽  
pp. 615-630 ◽  
Author(s):  
Jayaram Bhandari ◽  
Travis Karg ◽  
Kent G. Golic
Keyword(s):  
Drosophila Melanogaster ◽  
Chromosome Breakage ◽  
Dicentric Chromosome ◽  
Sequence Information ◽  
Dna Breaks ◽  
Chromosome Healing ◽  
Double Strand Dna Breaks ◽  
Reduced Rate ◽  
Pif1 Helicase ◽  
Break Induced Replication

Double-strand DNA breaks are repaired by one of several mechanisms that rejoin two broken ends. However, cells are challenged when asked to repair a single broken end and respond by: (1) inducing programmed cell death; (2) healing the broken end by constructing a new telomere; (3) adapting to the broken end and resuming the mitotic cycle without repair; and (4) using information from the sister chromatid or homologous chromosome to restore a normal chromosome terminus. During one form of homolog-dependent repair in yeast, termed break-induced replication (BIR), a template chromosome can be copied for hundreds of kilobases. BIR efficiency depends on Pif1 helicase and Pol32, a nonessential subunit of DNA polymerase δ. To date, there is little evidence that BIR can be used for extensive chromosome repair in higher eukaryotes. We report that a dicentric chromosome broken in mitosis in the male germline of Drosophila melanogaster is usually repaired by healing, but can also be repaired in a homolog-dependent fashion, restoring at least 1.3 Mb of terminal sequence information. This mode of repair is significantly reduced in pif1 and pol32 mutants. Formally, the repaired chromosomes are recombinants. However, the absence of reciprocal recombinants and the dependence on Pif1 and Pol32 strongly support the hypothesis that BIR is the mechanism for restoration of the chromosome terminus. In contrast to yeast, pif1 mutants in Drosophila exhibit a reduced rate of chromosome healing, likely owing to fundamental differences in telomeres between these organisms.

scholarly journals Telomerase-dependent and -independent chromosome healing in mouse embryonic stem cells

DNA Repair ◽  
2008 ◽  
Vol 7 (8) ◽  
pp. 1233-1249 ◽  
Author(s):  
Qing Gao ◽  
Gloria E. Reynolds ◽  
Andrew Wilcox ◽  
Douglas Miller ◽  
Peggie Cheung ◽  
...  
Keyword(s):  
Stem Cells ◽  
Embryonic Stem Cells ◽  
Embryonic Stem ◽  
Mouse Embryonic Stem Cells ◽  
Chromosome Healing

scholarly journals Developmentally Regulated Telomerase Activity Is Correlated with Chromosomal Healing during Chromatin Diminution inAscaris suum

1999 ◽  
Vol 19 (5) ◽  
pp. 3457-3465 ◽  
Author(s):  
Laurent Magnenat ◽  
Heinz Tobler ◽  
Fritz Müller
Keyword(s):  
Telomerase Activity ◽  
Embryonic Cell ◽  
Chromosomal Breakage ◽  
Chromatin Diminution ◽  
Developmentally Regulated ◽  
Cell Stage ◽  
Chromosome Healing ◽  
Cell Extracts ◽  
Dna Elimination

ABSTRACT Telomerase is the ribonucleoprotein complex responsible for the maintenance of the physical ends, or telomeres, of most eukaryotic chromosomes. In this study, telomerase activity has been identified in cell extracts from the nematode Ascaris suum. This parasitic nematode is particularly suited as a model system for the study of telomerase, because it shows the phenomenon of chromatin diminution, consisting of developmentally programmed chromosomal breakage, DNA elimination, and new telomere formation. In vitro, the A. suum telomerase is capable of efficiently recognizing and elongating nontelomeric primers with nematode-specific telomere repeats by using limited homology at the 3′ end of the DNA to anneal with the putative telomerase RNA template. The activity of this enzyme is developmentally regulated, and it correlates temporally with the phenomenon of chromatin diminution. It is up-regulated during the first two rounds of embryonic cell divisions, to reach a peak in 4-cell-stage embryos, when three presomatic blastomeres prepare for chromatin diminution. The activity remains high until the beginning of gastrulation, when the last of the presomatic cells undergoes chromatin diminution, and then constantly decreases during further development. In summary, our data strongly argue for a role of this enzyme in chromosome healing during the process of chromatin diminution.

scholarly journals Chromosome Healing Is Promoted by the Telomere Cap Component Hiphop in Drosophila

Genetics ◽  
2017 ◽  
Vol 207 (3) ◽  
pp. 949-959 ◽  
Author(s):  
Rebeccah L. Kurzhals ◽  
Laura Fanti ◽  
A. C. Gonzalez Ebsen ◽  
Yikang S. Rong ◽  
Sergio Pimpinelli ◽  
...  
Keyword(s):  
Chromosome Healing

Cytological and molecular analysis of centromere misdivision in maize

Genome ◽  
2002 ◽  
Vol 45 (4) ◽  
pp. 759-768 ◽  
Author(s):  
Étienne Kaszás ◽  
Akio Kato ◽  
James A Birchler
Keyword(s):  
Ring Chromosome ◽  
B Chromosome ◽  
Repeat Sequence ◽  
Telomeric Repeat ◽  
Univalent Chromosome ◽  
Telocentric Chromosome ◽  
Chromosome Healing ◽  
Centromeric Repeat ◽  
Ring Chromosomes ◽  
Pulsed Field Electrophoresis

B chromosome derivatives suffering from breaks within their centromere were examined cytologically and molecularly. We showed by high resolution FISH that misdivision of the centromere of a univalent chromosome can occur during meiosis. The breaks divide the centromere repeat sequence cluster. A telocentric chromosome formed by misdivision was found to have the addition of telomeric repeats to the broken centromere. A ring chromosome formed after misdivision occurred by fusion of the broken centromere to the telomere. Pulsed-field electrophoresis analyses were performed on the telocentric and ring chromosomes to identify fragments that hybridize to both the telomeric repeat and the B-specific centromeric repeat. We conclude that healing of broken maize centromeres can be achieved through the mechanisms of addition or fusion of telomeric repeat sequences to the broken centromere.Key words: centromere, telomere, meiosis, chromosome healing, B chromosome, Zea mays.

scholarly journals Breakage–fusion–bridge cycles and de novo telomere formation on broken chromosomes in maize callus cultures

Genome ◽  
2016 ◽  
Vol 59 (6) ◽  
pp. 367-378 ◽  
Author(s):  
Janay A. Santos-Serejo ◽  
Margarida L.R. Aguiar-Perecin
Keyword(s):  
De Novo ◽  
Chromosomal Evolution ◽  
Callus Cultures ◽  
Chromosome 7 ◽  
Telomeric Sequences ◽  
Chromosome Healing ◽  
Regenerated Plants ◽  
The Stability ◽  
Maize Callus

Breakpoints involved in chromosome alterations associated with heterochromatin have been detected in maize plants regenerated from callus culture. A cytogenetic analysis of plants regenerated from a maize callus was performed aiming to analyze the stability of a chromosome 7 bearing a deficiency-duplication (Df-Dp), which was interpreted as derived from a chromatid type breakage–fusion–bridge (BFB) cycle. The Df-Dp chromosome 7 was stable in mitotic and meiotic cells of the regenerated plants. Fluorescence in situ hybridization showed signals of telomeric sequences on the broken chromosome arm and provided evidence of de novo telomere formation. The stability of two types of altered chromosome 7 was investigated in C-banded metaphases from samples of the original callus that were collected during a period of 30–42 months after culture initiation. New alterations involving heterochromatic knobs of chromosomes 7 and 9 were observed. The aberrant chromosomes were stable in the subcultures, thus providing evidence of broken chromosome healing. The examination of anaphases showed the presence of bridges, which was consistent with the occurrence of BFB cycles. De novo telomere formation occurred in euchromatic and heterochromatic chromosome termini. The results point to events of chromosomal evolution that might occur in plants.

Chromosome healing: Spontaneous and programmedde novo telomere formation by telomerase

BioEssays ◽  
1996 ◽  
Vol 18 (4) ◽  
pp. 301-308 ◽  
Author(s):  
Meni Melek ◽  
Dorothy E. Shippen
Keyword(s):  
Chromosome Healing
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