scholarly journals TRF2-mediated ORC recruitment underlies telomere stability upon DNA replication stress

2021 ◽  
Author(s):  
Mitsunori Higa ◽  
Yukihiro Matsuda ◽  
Jumpei Yamada ◽  
Nozomi Sugimoto ◽  
Kazumasa Yoshida ◽  
...  
Keyword(s):  
Dna Damage ◽  
Origin Recognition Complex ◽  
Biological Significance ◽  
Replication Stress ◽  
Human Cells ◽  
Telomere Maintenance ◽  
Telomeric Dna ◽  
Binding Factor ◽  
Dna Replication Stress ◽  
Mcm Complex

AbstractTelomeres are intrinsically difficult-to-replicate regions of eukaryotic chromosomes. Telomeric repeat binding factor 2 (TRF2) binds to origin recognition complex (ORC) to facilitate the loading of ORC and the replicative helicase MCM complex onto DNA at telomeres. However, the biological significance of the TRF2-ORC interaction for telomere maintenance remains largely elusive. Here, we employed a separation-of-function TRF2 mutant with mutations in two acidic acid residues (E111A and E112A) that specifically inhibited the TRF2-ORC interaction in human cells without substantially inhibiting TRF2 interactions with its other binding partners. The TRF2 mutant was impaired in ORC recruitment to telomeres and showed increased replication stress-associated telomeric DNA damage and telomere instability. Furthermore, overexpression of an ORC1 fragment (amino acids 244–511), which competitively inhibited the TRF2-ORC interaction, increased telomeric DNA damage under replication stress conditions in human cells. Taken together, these findings suggest that TRF2-mediated ORC recruitment contributes to the suppression of telomere instability.

scholarly journals Human CTC1 primarily functions in telomere maintenance/protection and promotes CHK1 phosphorylation in response to global replication stress

2020 ◽  
Author(s):  
Stephanie M. Ackerson ◽  
Caroline I. Gable ◽  
Jason A. Stewart
Keyword(s):  
Dna Damage ◽  
Cell Cycle Progression ◽  
Replication Stress ◽  
Telomere Maintenance ◽  
Telomeric Dna ◽  
G2 Arrest ◽  
Cycle Progression ◽  
Dna Damage Signaling ◽  
Genome Wide ◽  
Damage Response

ABSTRACTCST (CTC1-STN1-TEN1) is a heterotrimeric, RPA-like protein that binds to single stranded DNA (ssDNA) and functions in the replication of telomeric and non-telomeric DNA. Previous studies have shown that deletion of CTC1 results in decreased cell proliferation and telomeric DNA damage signaling. However, a detailed analysis of the consequences of conditional CTC1 knockout (KO) have not been fully elucidated. Here, we investigated the effects of CTC1 KO on cell cycle progression, genome-wide replication and activation of the DNA damage response. We find that CTC1 KO results in p53-mediated G2 arrest and increased apoptosis, but not genome-wide replication defects or DNA damage. Instead, the G2 arrest is dependent on the accumulation of telomeric RPA following CTC1 KO, suggesting that the primary function of CST is in telomere end protection and maintenance not genome-wide replication. However, despite increased RPA-ssDNA, global CHK1 phosphorylation was not detected in CTC1 KO cells. Further analysis revealed that CTC1 KO significantly inhibits CHK1 phosphorylation following hydroxyurea-induced replication stress, due to decreased levels of the ATR activator TopBP1. Overall, our results identify that telomere not genome-wide DNA damaging signaling leads to decrease proliferation following CTC1 deletion and that CST promotes ATR-CHK1 signaling through the regulation of TopBP1.

scholarly journals DNA Damage-Induced Phosphorylation of TRF2 Is Required for the Fast Pathway of DNA Double-Strand Break Repair

2009 ◽  
Vol 29 (13) ◽  
pp. 3597-3604 ◽  
Author(s):  
Nazmul Huda ◽  
Hiromi Tanaka ◽  
Marc S. Mendonca ◽  
David Gilley
Keyword(s):  
Dna Damage ◽  
Dna Damage Response ◽  
Functional Role ◽  
Strand Break ◽  
Telomere Maintenance ◽  
Telomeric Dna ◽  
Dsb Repair ◽  
Dna Double Strand Break ◽  
Damage Response ◽  
Fast Pathway

ABSTRACT Protein kinases of the phosphatidylinositol 3-kinase-like kinase family, originally known to act in maintaining genomic integrity via DNA repair pathways, have been shown to also function in telomere maintenance. Here we focus on the functional role of DNA damage-induced phosphorylation of the essential mammalian telomeric DNA binding protein TRF2, which coordinates the assembly of the proteinaceous cap to disguise the chromosome end from being recognized as a double-stand break (DSB). Previous results suggested a link between the transient induction of human TRF2 phosphorylation at threonine 188 (T188) by the ataxia telangiectasia mutated protein kinase (ATM) and the DNA damage response. Here, we report evidence that X-ray-induced phosphorylation of TRF2 at T188 plays a role in the fast pathway of DNA DSB repair. These results connect the highly transient induction of human TRF2 phosphorylation to the DNA damage response machinery. Thus, we find that a protein known to function in telomere maintenance, TRF2, also plays a functional role in DNA DSB repair.

scholarly journals G-quadruplex Stabilization Fuels the ALT Pathway in ALT-positive Osteosarcoma Cells

Genes ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 304 ◽  
Author(s):  
Roberta Amato ◽  
Martina Valenzuela ◽  
Francesco Berardinelli ◽  
Erica Salvati ◽  
Carmen Maresca ◽  
...  
Keyword(s):  
Dna Damage ◽  
Sister Chromatid Exchanges ◽  
Telomere Maintenance ◽  
Osteosarcoma Cell ◽  
Telomeric Dna ◽  
Replicative Stress ◽  
Alternative Lengthening ◽  
G Quadruplex ◽  
Reduce Cell Proliferation ◽  
The Impact

Most human tumors maintain telomere lengths by telomerase, whereas a portion of them (10–15%) uses a mechanism named alternative lengthening of telomeres (ALT). The telomeric G-quadruplex (G4) ligand RHPS4 is known for its potent antiproliferative effect, as shown in telomerase-positive cancer models. Moreover, RHPS4 is also able to reduce cell proliferation in ALT cells, although the influence of G4 stabilization on the ALT mechanism has so far been poorly investigated. Here we show that sensitivity to RHPS4 is comparable in ALT-positive (U2OS; SAOS-2) and telomerase-positive (HOS) osteosarcoma cell lines, unlinking the telomere maintenance mechanism and RHPS4 responsiveness. To investigate the impact of G4 stabilization on ALT, the cardinal ALT hallmarks were analyzed. A significant induction of telomeric doublets, telomeric clusterized DNA damage, ALT-associated Promyelocytic Leukaemia-bodies (APBs), telomere sister chromatid exchanges (T-SCE) and c-circles was found exclusively in RHPS4-treated ALT cells. We surmise that RHPS4 affects ALT mechanisms through the induction of replicative stress that in turn is converted in DNA damage at telomeres, fueling recombination. In conclusion, our work indicates that RHPS4-induced telomeric DNA damage promotes overactivation of telomeric recombination in ALT cells, opening new questions on the therapeutic employment of G4 ligands in the treatment of ALT positive tumors.

scholarly journals Protective Mechanisms Against DNA Replication Stress in the Nervous System

Genes ◽  
2020 ◽  
Vol 11 (7) ◽  
pp. 730
Author(s):  
Clara Forrer Charlier ◽  
Rodrigo A. P. Martins
Keyword(s):  
Dna Damage ◽  
Nervous System ◽  
Dna Replication ◽  
Neurological Diseases ◽  
Replication Stress ◽  
Nervous System Development ◽  
Stress Generation ◽  
Genome Replication ◽  
Cns Development ◽  
Dna Replication Stress

The precise replication of DNA and the successful segregation of chromosomes are essential for the faithful transmission of genetic information during the cell cycle. Alterations in the dynamics of genome replication, also referred to as DNA replication stress, may lead to DNA damage and, consequently, mutations and chromosomal rearrangements. Extensive research has revealed that DNA replication stress drives genome instability during tumorigenesis. Over decades, genetic studies of inherited syndromes have established a connection between the mutations in genes required for proper DNA repair/DNA damage responses and neurological diseases. It is becoming clear that both the prevention and the responses to replication stress are particularly important for nervous system development and function. The accurate regulation of cell proliferation is key for the expansion of progenitor pools during central nervous system (CNS) development, adult neurogenesis, and regeneration. Moreover, DNA replication stress in glial cells regulates CNS tumorigenesis and plays a role in neurodegenerative diseases such as ataxia telangiectasia (A-T). Here, we review how replication stress generation and replication stress response (RSR) contribute to the CNS development, homeostasis, and disease. Both cell-autonomous mechanisms, as well as the evidence of RSR-mediated alterations of the cellular microenvironment in the nervous system, were discussed.

scholarly journals Uniform Widespread Nuclear Phosphorylation of Histone H2AX Is an Indicator of Lethal DNA Replication Stress

Cancers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 355 ◽  
Author(s):  
Eric Moeglin ◽  
Dominique Desplancq ◽  
Sascha Conic ◽  
Mustapha Oulad-Abdelghani ◽  
Audrey Stoessel ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cell Death ◽  
Cancer Cells ◽  
Drug Efficacy ◽  
Replication Stress ◽  
Strand Break ◽  
Histone H2ax ◽  
C Terminus ◽  
Dna Replication Stress ◽  
Stressed Cells

Phosphorylated histone H2AX (γ-H2AX), a central player in the DNA damage response (DDR), serves as a biomarker of DNA double-strand break repair. Although DNA damage is generally visualized by the formation of γ-H2AX foci in injured nuclei, it is unclear whether the widespread uniform nuclear γ-H2AX (called pan-nuclear) pattern occurring upon intense replication stress (RS) is linked to DDR. Using a novel monoclonal antibody that binds exclusively to the phosphorylated C-terminus of H2AX, we demonstrate that H2AX phosphorylation is systematically pan-nuclear in cancer cells stressed with RS-inducing drugs just before they die. The pan-nuclear γ-H2AX pattern is abolished by inhibition of the DNA-PK kinase. Cell death induction of cancer cells treated with increasing combinations of replication and kinase (ATR and Chk1) inhibitory drugs was proportional to the appearance of pan-nuclear γ-H2AX pattern. Delivery of labeled anti-γ-H2AX Fabs in stressed cells demonstrated at a single cell level that pan-nuclear γ-H2AX formation precedes irreversible cell death. Moreover, we show that H2AX is not required for RS-induced cell death in HeLa cells. Thus, the nuclear-wide formation of γ-H2AX is an incident of RS-induced cell death and, thus, the pan nuclear H2AX pattern should be regarded as an indicator of lethal RS-inducing drug efficacy.

scholarly journals Telomeric Double Strand Breaks in G1 Human Cells Facilitate Formation of 5′ C-Rich Overhangs and Recruitment of TERRA

2021 ◽  
Vol 12 ◽  
Author(s):  
Christopher B. Nelson ◽  
Taghreed M. Alturki ◽  
Jared J. Luxton ◽  
Lynn E. Taylor ◽  
David G. Maranon ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cellular Response ◽  
Human Cells ◽  
Double Strand Breaks ◽  
End Joining ◽  
Telomeric Dna ◽  
Strand Breaks ◽  
Alternative Lengthening ◽  
Non Homologous End Joining ◽  
G1 Cells

Telomeres, repetitive nucleoprotein complexes that protect chromosomal termini and prevent them from activating inappropriate DNA damage responses (DDRs), shorten with cell division and thus with aging. Here, we characterized the human cellular response to targeted telomeric double-strand breaks (DSBs) in telomerase-positive and telomerase-independent alternative lengthening of telomere (ALT) cells, specifically in G1 phase. Telomeric DSBs in human G1 cells elicited early signatures of a DDR; however, localization of 53BP1, an important regulator of resection at broken ends, was not observed at telomeric break sites. Consistent with this finding and previously reported repression of classical non-homologous end-joining (c-NHEJ) at telomeres, evidence for c-NHEJ was also lacking. Likewise, no evidence of homologous recombination (HR)-dependent repair of telomeric DSBs in G1 was observed. Rather, and supportive of rapid truncation events, telomeric DSBs in G1 human cells facilitated formation of extensive tracks of resected 5′ C-rich telomeric single-stranded (ss)DNA, a previously proposed marker of the recombination-dependent ALT pathway. Indeed, induction of telomeric DSBs in human ALT cells resulted in significant increases in 5′ C-rich (ss)telomeric DNA in G1, which rather than RPA, was bound by the complementary telomeric RNA, TERRA, presumably to protect these exposed ends so that they persist into S/G2 for telomerase-mediated or HR-dependent elongation, while also circumventing conventional repair pathways. Results demonstrate the remarkable adaptability of telomeres, and thus they have important implications for persistent telomeric DNA damage in normal human G1/G0 cells (e.g., lymphocytes), as well as for therapeutically relevant targets to improve treatment of ALT-positive tumors.

scholarly journals Human SKI is a telomere-associated complex involved in DNA-RNA hybrid control and telomere stability

2020 ◽  
Author(s):  
Emilia Herrera-Moyano ◽  
Rosa Maria Porreca ◽  
Lepakshi Ranjha ◽  
Roser Gonzalez-Franco ◽  
Eleni Skourti ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Mrna Decay ◽  
Hybrid Control ◽  
Replication Stress ◽  
Rna Helicase ◽  
Cell Cycle Phase ◽  
Cycle Phase ◽  
Telomeric Dna ◽  
Non Coding Rnas

SummarySuper killer (SKI) complex is a well-known cyplasmic 3’ to 5’ mRNA decay complex that functions with the exosome to degrade excessive and aberrant mRNAs. Recently, SKIV2L, the 3’ to 5’ RNA helicase of the human SKI (hSKI) complex was implicated in the degradation of nuclear non-coding RNAs escaping to the cytoplasm. Here, we show that hSKI is also present in the nucleus, on chromatin and in particular at telomeres during the G2 cell cycle phase. hSKI preferentially binds single stranded telomeric DNA and DNA-RNA hybrids, and SKIV2L interacts with telomeric Shelterin factors TRF1, TIN2, TPP1 and POT1. Loss of SKIV2L leads to telomere loss, DNA damage activation and fragility, which we attribute to replication stress caused by the accumulation of telomeric DNA-RNA hybrids. Our results reveal a nuclear function of the hSKI complex and implicate SKIV2L in averting DNA-RNA hybrid-dependent replication stress at human telomeres.

scholarly journals The deubiquitinase USP36 Regulates DNA replication stress and confers therapeutic resistance through PrimPol stabilization

2020 ◽  
Vol 48 (22) ◽  
pp. 12711-12726
Author(s):  
Yuanliang Yan ◽  
Zhijie Xu ◽  
Jinzhou Huang ◽  
Guijie Guo ◽  
Ming Gao ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Replication ◽  
Stress Response ◽  
Critical Role ◽  
Replication Stress ◽  
Regulatory Mechanisms ◽  
Therapeutic Resistance ◽  
Chemotherapy Response ◽  
Dna Replication Stress ◽  
Damage Tolerant

Abstract PrimPol has been recently identified as a DNA damage tolerant polymerase that plays an important role in replication stress response. However, the regulatory mechanisms of PrimPol are not well defined. In this study, we identify that the deubiquitinase USP36 interferes with degradation of PrimPol to regulate the replication stress response. Mechanistically, USP36 is deubiquitinated following DNA replication stress, which in turn facilitates its upregulation and interaction with PrimPol. USP36 deubiquitinates K29-linked polyubiquitination of PrimPol and increases its protein stability. Depletion of USP36 results in replication stress-related defects and elevates cell sensitivity to DNA-damage agents, such as cisplatin and olaparib. Moreover, USP36 expression positively correlates with the level of PrimPol protein and poor prognosis in patient samples. These findings indicate that the regulation of PrimPol K29-linked ubiquitination by USP36 plays a critical role in DNA replication stress and chemotherapy response.

scholarly journals Stwl Modifies Chromatin Compaction and Is Required to Maintain DNA Integrity in the Presence of Perturbed DNA Replication

2009 ◽  
Vol 20 (3) ◽  
pp. 983-994 ◽  
Author(s):  
Xia Yi ◽  
Hilda I. de Vries ◽  
Katarzyna Siudeja ◽  
Anil Rana ◽  
Willy Lemstra ◽  
...  
Keyword(s):  
Dna Damage ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Replication Stress ◽  
Epigenetic Mechanism ◽  
Dna Integrity ◽  
Silent Chromatin ◽  
Chromatin Compaction ◽  
Cycle Arrest ◽  
Dna Replication Stress

Hydroxyurea, a well-known DNA replication inhibitor, induces cell cycle arrest and intact checkpoint functions are required to survive DNA replication stress induced by this genotoxic agent. Perturbed DNA synthesis also results in elevated levels of DNA damage. It is unclear how organisms prevent accumulation of this type of DNA damage that coincides with hampered DNA synthesis. Here, we report the identification of stonewall (stwl) as a novel hydroxyurea-hypersensitive mutant. We demonstrate that Stwl is required to prevent accumulation of DNA damage induced by hydroxyurea; yet, Stwl is not involved in S/M checkpoint regulation. We show that Stwl is a heterochromatin-associated protein with transcription-repressing capacities. In stwl mutants, levels of trimethylated H3K27 and H3K9 (two hallmarks of silent chromatin) are decreased. Our data provide evidence for a Stwl-dependent epigenetic mechanism that is involved in the maintenance of the normal balance between euchromatin and heterochromatin and that is required to prevent accumulation of DNA damage in the presence of DNA replication stress.

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