scholarly journals Inactivation of 14-3-3ς Influences Telomere Behavior and Ionizing Radiation-Induced Chromosomal Instability

2000 ◽  
Vol 20 (20) ◽  
pp. 7764-7772 ◽  
Author(s):  
Sonu Dhar ◽  
Jeremy A. Squire ◽  
M. Prakash Hande ◽  
Raymund J. Wellinger ◽  
Tej K. Pandita
Keyword(s):  
Dna Sequences ◽  
Nuclear Matrix ◽  
Mammalian Cells ◽  
Eukaryotic Cell ◽  
Checkpoint Control ◽  
Aberrant Chromosome ◽  
M Phase ◽  
Chromosomal Breaks ◽  
Radiation Induced

ABSTRACT Telomeres are complexes of repetitive DNA sequences and proteins constituting the ends of linear eukaryotic chromosomes. While these structures are thought to be associated with the nuclear matrix, they appear to be released from this matrix at the time when the cells exit from G2 and enter M phase. Checkpoints maintain the order and fidelity of the eukaryotic cell cycle, and defects in checkpoints contribute to genetic instability and cancer. The 14-3-3ς gene has been reported to be a checkpoint control gene, since it promotes G2 arrest following DNA damage. Here we demonstrate that inactivation of this gene influences genome integrity and cell survival. Analyses of chromosomes at metaphase showed frequent losses of telomeric repeat sequences, enhanced frequencies of chromosome end-to-end associations, and terminal nonreciprocal translocations in 14-3-3ς−/− cells. These phenotypes correlated with a reduction in the amount of G-strand overhangs at the telomeres and an altered nuclear matrix association of telomeres in these cells. Since the p53-mediated G1 checkpoint is operative in these cells, the chromosomal aberrations observed occurred preferentially in G2 after irradiation with gamma rays, corroborating the role of the 14-3-3ς protein in G2/M progression. The results also indicate that even in untreated cycling cells, occasional chromosomal breaks or telomere-telomere fusions trigger a G2 checkpoint arrest followed by repair of these aberrant chromosome structures before entering M phase. Since 14-3-3ς−/− cells are defective in maintaining G2 arrest, they enter M phase without repair of the aberrant chromosome structures and undergo cell death during mitosis. Thus, our studies provide evidence for the correlation among a dysfunctional G2/M checkpoint control, genomic instability, and loss of telomeres in mammalian cells.

scholarly journals And yet, it moves: nuclear and chromatin dynamics of a heterochromatic double-strand break

2017 ◽  
Vol 372 (1731) ◽  
pp. 20160291 ◽  
Author(s):  
P. Christopher Caridi ◽  
Laetitia Delabaere ◽  
Grzegorz Zapotoczny ◽  
Irene Chiolo
Keyword(s):  
Dna Sequences ◽  
Mammalian Cells ◽  
Molecular Mechanisms ◽  
Nuclear Periphery ◽  
Strand Break ◽  
Double Strand Break ◽  
Chromatin Dynamics ◽  
Recombination Repair ◽  
The Stability

Heterochromatin is mostly composed of repeated DNA sequences prone to aberrant recombination. How cells maintain the stability of these sequences during double-strand break (DSB) repair has been a long-standing mystery. Studies in Drosophila cells revealed that faithful homologous recombination repair of heterochromatic DSBs relies on the striking relocalization of repair sites to the nuclear periphery before Rad51 recruitment and repair progression. Here, we summarize our current understanding of this response, including the molecular mechanisms involved, and conserved pathways in mammalian cells. We will highlight important similarities with pathways identified in budding yeast for repair of other types of repeated sequences, including rDNA and short telomeres. We will also discuss the emerging role of chromatin composition and regulation in heterochromatin repair progression. Together, these discoveries challenged previous assumptions that repair sites are substantially static in multicellular eukaryotes, that heterochromatin is largely inert in the presence of DSBs, and that silencing and compaction in this domain are obstacles to repair. This article is part of the themed issue ‘Chromatin modifiers and remodellers in DNA repair and signalling’.

scholarly journals Roles for Basal and Stimulated p21Cip-1/WAF1/MDA6Expression and Mitogen-activated Protein Kinase Signaling in Radiation-induced Cell Cycle Checkpoint Control in Carcinoma Cells

1999 ◽  
Vol 10 (12) ◽  
pp. 4231-4246 ◽  
Author(s):  
Jong-Sung Park ◽  
Steven Carter ◽  
Dean B. Reardon ◽  
Rupert Schmidt-Ullrich ◽  
Paul Dent ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Mapk Pathway ◽  
Mapk Signaling ◽  
Cell Cycle Checkpoint ◽  
Carcinoma Cells ◽  
Checkpoint Control ◽  
M Phase ◽  
Cycle Checkpoint ◽  
Radiation Induced ◽  
Induced Apoptosis

We investigated the role of the cdk inhibitor protein p21Cip-1/WAF1/MDA6 (p21) in the ability of MAPK pathway inhibition to enhance radiation-induced apoptosis in A431 squamous carcinoma cells. In carcinoma cells, ionizing radiation (2 Gy) caused both primary (0–10 min) and secondary (90–240 min) activations of the MAPK pathway. Radiation induced p21 protein expression in A431 cells within 6 h via secondary activation of the MAPK pathway. Within 6 h, radiation weakly enhanced the proportion of cells in G1 that were p21 and MAPK dependent, whereas the elevation of cells present in G2/M at this time was independent of either p21 expression or MAPK inhibition. Inhibition of the MAPK pathway increased the proportion of irradiated cells in G2/M phase 24–48 h after irradiation and enhanced radiation-induced apoptosis. This correlated with elevated Cdc2 tyrosine 15 phosphorylation, decreased Cdc2 activity, and decreased Cdc25C protein levels. Caffeine treatment or removal of MEK1/2 inhibitors from cells 6 h after irradiation reduced the proportion of cells present in G2/M phase at 24 h and abolished the ability of MAPK inhibition to potentiate radiation-induced apoptosis. These data argue that MAPK signaling plays an important role in the progression/release of cells through G2/M phase after radiation exposure and that an impairment of this progression/release enhances radiation-induced apoptosis. Surprisingly, the ability of irradiation/MAPK inhibition to increase the proportion of cells in G2/M at 24 h was found to be dependent on basal p21 expression. Transient inhibition of basal p21 expression increased the control level of apoptosis as well as the abilities of both radiation and MEK1/2 inhibitors to cause apoptosis. In addition, loss of basal p21 expression significantly reduced the capacity of MAPK inhibition to potentiate radiation-induced apoptosis. Collectively, our data argue that MAPK signaling and p21 can regulate cell cycle checkpoint control in carcinoma cells at the G1/S transition shortly after exposure to radiation. In contrast, inhibition of MAPK increases the proportion of irradiated cells in G2/M, and basal expression of p21 is required to maintain this effect. Our data suggest that basal and radiation-stimulated p21 may play different roles in regulating cell cycle progression that affect cell survival after radiation exposure.

scholarly journals RINT-1 Regulates the Localization and Entry of ZW10 to the Syntaxin 18 Complex

2006 ◽  
Vol 17 (6) ◽  
pp. 2780-2788 ◽  
Author(s):  
Kohei Arasaki ◽  
May Taniguchi ◽  
Katsuko Tani ◽  
Mitsuo Tagaya
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Trafficking ◽  
Protein Transport ◽  
Snare Complex ◽  
Checkpoint Control ◽  
Interacting Protein ◽  
Golgi Transport ◽  
Radiation Induced ◽  
And Function

RINT-1 was first identified as a Rad50-interacting protein that participates in radiation-induced G2/M checkpoint control. We have recently reported that RINT-1, together with the dynamitin-interacting protein ZW10 and others, is associated with syntaxin 18, an endoplasmic reticulum (ER)-localized SNARE involved in membrane trafficking between the ER and Golgi. To address the role of RINT-1 in membrane trafficking, we examined the effects of overexpression and knockdown of RINT-1 on Golgi morphology and protein transport from the ER. Overexpression of the N-terminal region of RINT-1, which is responsible for the interaction with ZW10, caused redistribution of ZW10. Concomitantly, ER-to-Golgi transport was blocked and the Golgi was dispersed. Knockdown of RINT-1 also disrupted membrane trafficking between the ER and Golgi. Notably, silencing of RINT-1 resulted in a reduction in the amount of ZW10 associated with syntaxin 18, concomitant with ZW10 redistribution. In contrast, no redistribution or release of RINT-1 from the syntaxin 18 complex was observed when ZW10 expression was reduced. These results taken together suggest that RINT-1 coordinates the localization and function of ZW10 by serving as a link between ZW10 and the SNARE complex comprising syntaxin 18.

scholarly journals DNA Methylation and Chromatin: Role(s) of Methyl-CpG-Binding Protein ZBTB38

2018 ◽  
Vol 11 ◽  
pp. 251686571881111 ◽  
Author(s):  
Maud de Dieuleveult ◽  
Benoit Miotto
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Transcription Factors ◽  
Dna Sequences ◽  
Mammalian Cells ◽  
Expression Patterns ◽  
Control Of Gene Expression ◽  
Methylated Dna

DNA methylation plays an essential role in the control of gene expression during early stages of development as well as in disease. Although many transcription factors are sensitive to this modification of the DNA, we still do not clearly understand how it contributes to the establishment of proper gene expression patterns. We discuss here the recent findings regarding the biological and molecular function(s) of the transcription factor ZBTB38 that binds methylated DNA sequences in vitro and in cells. We speculate how these findings may help understand the role of DNA methylation and DNA methylation–sensitive transcription factors in mammalian cells.

scholarly journals Mechanistic insights into KDM4A driven genomic instability

2021 ◽  
Author(s):  
Nicolas L. Young ◽  
Ruhee Dere
Keyword(s):  
Genomic Instability ◽  
Methylation Status ◽  
Histone H3 ◽  
Checkpoint Control ◽  
Cellular Processes ◽  
Chromosomal Breaks ◽  
Transcriptional Modulation ◽  
Epigenetic Signatures ◽  
Mitotic Disturbances

Alterations in global epigenetic signatures on chromatin are well established to contribute to tumor initiation and progression. Chromatin methylation status modulates several key cellular processes that maintain the integrity of the genome. KDM4A, a demethylase that belongs to the Fe-II dependent dioxygenase family that uses α-ketoglutarate and molecular oxygen as cofactors, is overexpressed in several cancers and is associated with an overall poor prognosis. KDM4A demethylates lysine 9 (H3K9me2/3) and lysine 36 (H3K36me3) methyl marks on histone H3. Given the complexity that exists with these marks on chromatin and their effects on transcription and proliferation, it naturally follows that demethylation serves an equally important role in these cellular processes. In this review, we highlight the role of KDM4A in transcriptional modulation, either dependent or independent of its enzymatic activity, arising from the amplification of this demethylase in cancer. KDM4A modulates re-replication of distinct genomic loci, activates cell cycle inducers, and represses proteins involved in checkpoint control giving rise to proliferative damage, mitotic disturbances and chromosomal breaks, ultimately resulting in genomic instability. In parallel, emerging evidence of non-nuclear substrates of epigenetic modulators emphasize the need to investigate the role of KDM4A in regulating non-nuclear substrates and evaluate their contribution to genomic instability in this context. The existence of promising KDM-specific inhibitors makes these demethylases an attractive target for therapeutic intervention in cancers.

scholarly journals Identification of Mammalian Sds3 as an Integral Component of the Sin3/Histone Deacetylase Corepressor Complex

2002 ◽  
Vol 22 (8) ◽  
pp. 2743-2750 ◽  
Author(s):  
Leila Alland ◽  
Gregory David ◽  
Hong Shen-Li ◽  
Jason Potes ◽  
Rebecca Muhle ◽  
...  
Keyword(s):  
Histone Deacetylase ◽  
Cell Biology ◽  
Mammalian Cells ◽  
Chromatin Modification ◽  
Eukaryotic Cell ◽  
Hdac Activity ◽  
Corepressor Complex ◽  
Local Recruitment

ABSTRACT Silencing of gene transcription involves local chromatin modification achieved through the local recruitment of large multiprotein complexes containing histone deacetylase (HDAC) activity. The mammalian corepressors mSin3A and mSin3B have been shown to play a key role in this process by tethering HDACs 1 and 2 to promoter-bound transcription factors. Similar mechanisms appear to be operative in yeast, in which epistasis experiments have established that the mSin3 and HDAC orthologs (SIN3 and RPD3), along with a novel protein, SDS3, function in the same repressor pathway. Here, we report the identification of a component of the mSin3-HDAC complex that bears homology to yeast SDS3, physically associates with mSin3 proteins in vivo, represses transcription in a manner that is partially dependent on HDAC activity, and enables HDAC1 catalytic activity in vivo. That key physical and functional properties are also shared by yeast SDS3 underscores the central role of the Sin3-HDAC-Sds3 complex in eukaryotic cell biology, and the discovery of mSds3 in mammalian cells provides a new avenue for modulating the activity of this complex in human disease.

Verteilung und enzymatische Hypermethylierung invers repetitiver DNA-Sequenzen in verschiedenen Mäuse-und menschlichen Zellen / Distribution and Enzymic Hypermethylation of Inverted DNA Repeats in Different Murine and Human Cells

1979 ◽  
Vol 34 (7-8) ◽  
pp. 558-564 ◽  
Author(s):  
Thomas L. J. Boehm ◽  
Dusan Drahovsky
Keyword(s):  
Dna Sequences ◽  
Mammalian Cells ◽  
Nuclear Dna ◽  
Repetitive Sequences ◽  
Specific Class ◽  
Dna Repeats ◽  
Quantitative Analyses ◽  
Chang Cells ◽  
P815 Mouse

Abstract A specific class of DNA sequences, the inverted repetitive sequences, forms a double-stranded structure within a single linear polynucleotide chain in denatured DNA. The reassociation process is unimolecular and occurs very fast. Quantitative analyses have shown that these sequences com-E rise about 4-5% of the nuclear DNA of various mammalian cells (P815 mouse mastocytoma, Hela, L cells, Raji and Chang cells, and human embryonic hepatocytes) and are interspersed within sequences of other degrees of repetitiveness.After labeling the cells with L-[Metnyl-3H]methionine and [14C]deoxycytidine, relative rates of enzymic DNA methylation were computed on the basis of 3H and 14C radioactivities found in py­ rimidine residues of the nuclear DNA. The results indicate that DNA of inverted repetitive sequences is methylated to a level about 50% higher than the ordinary repetitive sequences and to about 300% higher than the unique and intermediary sequences.The biological function of the inverted repeats as well as the role of their enzymic hypermethyl­ ation is unknown.

scholarly journals DNA polymerase ζ in DNA replication and repair

2019 ◽  
Vol 47 (16) ◽  
pp. 8348-8361 ◽  
Author(s):  
Sara K Martin ◽  
Richard D Wood
Keyword(s):  
Dna Replication ◽  
Dna Polymerase ◽  
Dna Sequences ◽  
Mammalian Cells ◽  
Translesion Synthesis ◽  
Dna Lesions ◽  
Replication Forks ◽  
Dna Replication And Repair ◽  
Radiation Induced ◽  
Break Induced Replication

Abstract Here, we survey the diverse functions of DNA polymerase ζ (pol ζ) in eukaryotes. In mammalian cells, REV3L (3130 residues) is the largest catalytic subunit of the DNA polymerases. The orthologous subunit in yeast is Rev3p. Pol ζ also includes REV7 subunits (encoded by Rev7 in yeast and MAD2L2 in mammalian cells) and two subunits shared with the replicative DNA polymerase, pol δ. Pol ζ is used in response to circumstances that stall DNA replication forks in both yeast and mammalian cells. The best-examined situation is translesion synthesis at sites of covalent DNA lesions such as UV radiation-induced photoproducts. We also highlight recent evidence that uncovers various roles of pol ζ that extend beyond translesion synthesis. For instance, pol ζ is also employed when the replisome operates sub-optimally or at difficult-to-replicate DNA sequences. Pol ζ also participates in repair by microhomology mediated break-induced replication. A rev3 deletion is tolerated in yeast but Rev3l disruption results in embryonic lethality in mice. Inactivation of mammalian Rev3l results in genomic instability and invokes cell death and senescence programs. Targeting of pol ζ function may be a useful strategy in cancer therapy, although chromosomal instability associated with pol ζ deficiency must be considered.

scholarly journals DNA Damage Triggers p21WAF1-dependent Emi1 Down-Regulation That Maintains G2 Arrest

2009 ◽  
Vol 20 (7) ◽  
pp. 1891-1902 ◽  
Author(s):  
Jinho Lee ◽  
Jin Ah Kim ◽  
Valerie Barbier ◽  
Arun Fotedar ◽  
Rati Fotedar
Keyword(s):  
Dna Damage ◽  
Cell Cycle Progression ◽  
Control Cell ◽  
Anaphase Promoting Complex ◽  
Checkpoint Control ◽  
G2 Arrest ◽  
Down Regulation ◽  
Cycle Progression ◽  
M Phase

Several regulatory proteins control cell cycle progression. These include Emi1, an anaphase-promoting complex (APC) inhibitor whose destruction controls progression through mitosis to G1, and p21WAF1, a cyclin-dependent kinase (CDK) inhibitor activated by DNA damage. We have analyzed the role of p21WAF1 in G2-M phase checkpoint control and in prevention of polyploidy after DNA damage. After DNA damage, p21+/+ cells stably arrest in G2, whereas p21−/− cells ultimately progress into mitosis. We report that p21 down-regulates Emi1 in cells arrested in G2 by DNA damage. This down-regulation contributes to APC activation and results in the degradation of key mitotic proteins including cyclins A2 and B1 in p21+/+ cells. Inactivation of APC in irradiated p21+/+ cells can overcome the G2 arrest. siRNA-mediated Emi1 down-regulation prevents irradiated p21−/− cells from entering mitosis, whereas concomitant down-regulation of APC activity counteracts this effect. Our results demonstrate that Emi1 down-regulation and APC activation leads to stable p21-dependent G2 arrest after DNA damage. This is the first demonstration that Emi1 regulation plays a role in the G2 DNA damage checkpoint. Further, our work identifies a new p21-dependent mechanism to maintain G2 arrest after DNA damage.

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