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2.
Genes Dev ; 2021 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-34764137

RESUMO

The mammalian telomeric shelterin complex-comprised of TRF1, TRF2, Rap1, TIN2, TPP1, and POT1-blocks the DNA damage response at chromosome ends and interacts with telomerase and the CST complex to regulate telomere length. The evolutionary origins of shelterin are unclear, partly because unicellular organisms have distinct telomeric proteins. Here, we describe the evolution of metazoan shelterin, showing that TRF1 emerged in vertebrates upon duplication of a TRF2-like ancestor. TRF1 and TRF2 diverged rapidly during vertebrate evolution through the acquisition of new domains and interacting factors. Vertebrate shelterin is also distinguished by the presence of an HJRL domain in the split C-terminal OB fold of POT1, whereas invertebrate POT1s carry inserts of variable nature. Importantly, the data reveal that, apart from the primate and rodent POT1 orthologs, all metazoan POT1s are predicted to have a fourth OB fold at their N termini. Therefore, we propose that POT1 arose from a four-OB-fold ancestor, most likely an RPA70-like protein. This analysis provides insights into the biology of shelterin and its evolution from ancestral telomeric DNA-binding proteins.

3.
Nat Commun ; 12(1): 2093, 2021 04 07.
Artigo em Inglês | MEDLINE | ID: mdl-33828097

RESUMO

Telomere crisis contributes to cancer genome evolution, yet only a subset of cancers display breakage-fusion-bridge (BFB) cycles and chromothripsis, hallmarks of experimental telomere crisis identified in previous studies. We examine the spectrum of structural variants (SVs) instigated by natural telomere crisis. Eight spontaneous post-crisis clones did not show prominent patterns of BFB cycles or chromothripsis. Their crisis-induced genome rearrangements varied from infrequent simple SVs to more frequent and complex SVs. In contrast, BFB cycles and chromothripsis occurred in MRC5 fibroblast clones that escaped telomere crisis after CRISPR-controlled telomerase activation. This system revealed convergent evolutionary lineages altering one allele of chromosome 12p, where a short telomere likely predisposed to fusion. Remarkably, the 12p chromothripsis and BFB events were stabilized by independent fusions to chromosome 21. The data establish that telomere crisis can generate a wide spectrum of SVs implying that a lack of BFB patterns and chromothripsis in cancer genomes does not indicate absence of past telomere crisis.


Assuntos
Cromotripsia , Neoplasias/genética , Telômero/química , Linhagem Celular , Instabilidade Cromossômica , Fibroblastos , Genoma , Instabilidade Genômica , Humanos , Pulmão , Metáfase , Modelos Biológicos , Telômero/ultraestrutura
4.
Elife ; 92020 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-33258446

RESUMO

Telomere shortening is a presumed tumor suppressor pathway that imposes a proliferative barrier (the Hayflick limit) during tumorigenesis. This model predicts that excessively long somatic telomeres predispose to cancer. Here, we describe cancer-prone families with two unique TINF2 mutations that truncate TIN2, a shelterin subunit that controls telomere length. Patient lymphocyte telomeres were unusually long. We show that the truncated TIN2 proteins do not localize to telomeres, suggesting that the mutations create loss-of-function alleles. Heterozygous knock-in of the mutations or deletion of one copy of TINF2 resulted in excessive telomere elongation in clonal lines, indicating that TINF2 is haploinsufficient for telomere length control. In contrast, telomere protection and genome stability were maintained in all heterozygous clones. The data establish that the TINF2 truncations predispose to a tumor syndrome. We conclude that TINF2 acts as a haploinsufficient tumor suppressor that limits telomere length to ensure a timely Hayflick limit.


Assuntos
Genes Supressores de Tumor , Encurtamento do Telômero/genética , Proteínas de Ligação a Telômeros/fisiologia , Telômero/genética , Linhagem Celular , Feminino , Células HEK293 , Heterozigoto , Humanos , Mutação com Perda de Função , Masculino , Neoplasias/genética , Telômero/patologia , Proteínas de Ligação a Telômeros/genética , Proteína 1 de Ligação a Repetições Teloméricas/metabolismo , Proteínas Supressoras de Tumor
5.
Cell ; 183(1): 197-210.e32, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-33007263

RESUMO

Cancer genomes often harbor hundreds of somatic DNA rearrangement junctions, many of which cannot be easily classified into simple (e.g., deletion) or complex (e.g., chromothripsis) structural variant classes. Applying a novel genome graph computational paradigm to analyze the topology of junction copy number (JCN) across 2,778 tumor whole-genome sequences, we uncovered three novel complex rearrangement phenomena: pyrgo, rigma, and tyfonas. Pyrgo are "towers" of low-JCN duplications associated with early-replicating regions, superenhancers, and breast or ovarian cancers. Rigma comprise "chasms" of low-JCN deletions enriched in late-replicating fragile sites and gastrointestinal carcinomas. Tyfonas are "typhoons" of high-JCN junctions and fold-back inversions associated with expressed protein-coding fusions, breakend hypermutation, and acral, but not cutaneous, melanomas. Clustering of tumors according to genome graph-derived features identified subgroups associated with DNA repair defects and poor prognosis.


Assuntos
Variação Estrutural do Genoma/genética , Genômica/métodos , Neoplasias/genética , Inversão Cromossômica/genética , Cromotripsia , Variações do Número de Cópias de DNA/genética , Rearranjo Gênico/genética , Genoma Humano/genética , Humanos , Mutação/genética , Sequenciamento Completo do Genoma/métodos
6.
Genes Dev ; 34(19-20): 1392-1405, 2020 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-32883681

RESUMO

TRF1 facilitates the replication of telomeric DNA in part by recruiting the BLM helicase, which can resolve G-quadruplexes on the lagging-strand template. Lagging-strand telomeres lacking TRF1 or BLM form fragile telomeres-structures that resemble common fragile sites (CFSs)-but how they are formed is not known. We report that analogous to CFSs, fragile telomeres in BLM-deficient cells involved double-strand break (DSB) formation, in this case by the SLX4/SLX1 nuclease. The DSBs were repaired by POLD3/POLD4-dependent break-induced replication (BIR), resulting in fragile telomeres containing conservatively replicated DNA. BIR also promoted fragile telomere formation in cells with FokI-induced telomeric DSBs and in alternative lengthening of telomeres (ALT) cells, which have spontaneous telomeric damage. BIR of telomeric DSBs competed with PARP1-, LIG3-, and XPF-dependent alternative nonhomologous end joining (alt-NHEJ), which did not generate fragile telomeres. Collectively, these findings indicate that fragile telomeres can arise from BIR-mediated repair of telomeric DSBs.


Assuntos
Sítios Frágeis do Cromossomo/genética , Quebras de DNA de Cadeia Dupla , Replicação do DNA , RecQ Helicases/genética , RecQ Helicases/metabolismo , Telômero/patologia , Animais , Linhagem Celular , Células Cultivadas , Reparo do DNA , Endodesoxirribonucleases/genética , Endodesoxirribonucleases/metabolismo , Fibroblastos , Humanos , Camundongos , Recombinases/genética , Recombinases/metabolismo
7.
Nat Genet ; 52(9): 884-890, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32719516

RESUMO

Chromothripsis and kataegis are frequently observed in cancer and may arise from telomere crisis, a period of genome instability during tumorigenesis when depletion of the telomere reserve generates unstable dicentric chromosomes1-5. Here we examine the mechanism underlying chromothripsis and kataegis by using an in vitro telomere crisis model. We show that the cytoplasmic exonuclease TREX1, which promotes the resolution of dicentric chromosomes4, plays a prominent role in chromothriptic fragmentation. In the absence of TREX1, the genome alterations induced by telomere crisis primarily involve breakage-fusion-bridge cycles and simple genome rearrangements rather than chromothripsis. Furthermore, we show that the kataegis observed at chromothriptic breakpoints is the consequence of cytosine deamination by APOBEC3B. These data reveal that chromothripsis and kataegis arise from a combination of nucleolytic processing by TREX1 and cytosine editing by APOBEC3B.


Assuntos
Citidina Desaminase/genética , Exodesoxirribonucleases/genética , Fosfoproteínas/genética , Telômero/genética , Linhagem Celular Tumoral , Cromotripsia , Citosina Desaminase/genética , Instabilidade Genômica/genética , Humanos , Mutação/genética , Neoplasias/genética , Células U937
8.
Nucleus ; 11(1): 164-177, 2020 12.
Artigo em Inglês | MEDLINE | ID: mdl-32564646

RESUMO

T-loops are thought to hide telomeres from DNA damage signaling and DSB repair pathways. T-loop formation requires the shelterin component TRF2, which represses ATM signaling and NHEJ. Here we establish that TRF2 alone, in the absence of other shelterin proteins can form t-loops. Mouse and human cells contain two isoforms of TRF2, one of which is uncharacterized. We show that both isoforms protect telomeres and form t-loops. The isoforms are not cell cycle regulated and t-loops are present in G1, S, and G2.  Using the DNA wrapping deficient TRF2 Topless mutant, we confirm its inability to form t-loops and repress ATM. However, since the mutant is also defective in repression of NHEJ and telomeric localization, the role of topological changes in telomere protection remains unclear.  Finally, we show that Rad51 does not affect t-loop frequencies or telomere protection. Therefore, alternative models for how TRF2 forms t-loops should be explored.


Assuntos
Proteína 2 de Ligação a Repetições Teloméricas/metabolismo , Animais , Sistemas CRISPR-Cas/genética , Linhagem Celular , Camundongos , Camundongos Knockout , Proteômica , Rad51 Recombinase/genética , Rad51 Recombinase/metabolismo , Proteína 2 de Ligação a Repetições Teloméricas/genética
9.
PLoS Biol ; 18(1): e3000594, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31895940

RESUMO

Alpha thalassemia/mental retardation syndrome X-linked chromatin remodeler (ATRX), a DAXX (death domain-associated protein) interacting protein, is often lost in cells using the alternative lengthening of telomeres (ALT) pathway, but it is not known how ATRX loss leads to ALT. We report that ATRX deletion from mouse cells altered the repair of telomeric double-strand breaks (DSBs) and induced ALT-like phenotypes, including ALT-associated promyelocytic leukemia (PML) bodies (APBs), telomere sister chromatid exchanges (T-SCEs), and extrachromosomal telomeric signals (ECTSs). Mechanistically, we show that ATRX affects telomeric DSB repair by promoting cohesion of sister telomeres and that loss of ATRX in ALT cells results in diminished telomere cohesion. In addition, we document a role for DAXX in the repair of telomeric DSBs. Removal of telomeric cohesion in combination with DAXX deficiency recapitulates all telomeric DSB repair phenotypes associated with ATRX loss. The data reveal that ATRX has an effect on telomeric DSB repair and that this role involves both telomere cohesion and a DAXX-dependent pathway.


Assuntos
Proteínas Correpressoras/fisiologia , Quebras de DNA de Cadeia Dupla , Reparo do DNA/genética , Chaperonas Moleculares/fisiologia , Troca de Cromátide Irmã/genética , Telômero/genética , Proteína Nuclear Ligada ao X/fisiologia , Animais , Células Cultivadas , Embrião de Mamíferos , Feminino , Células HeLa , Humanos , Masculino , Retardo Mental Ligado ao Cromossomo X/genética , Retardo Mental Ligado ao Cromossomo X/patologia , Camundongos , Camundongos Knockout , Transdução de Sinais/genética , Telômero/metabolismo , Homeostase do Telômero/genética , Talassemia alfa/genética , Talassemia alfa/patologia
10.
Genes Dev ; 34(1-2): 7-23, 2020 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-31896689

RESUMO

53BP1 is an enigmatic DNA damage response factor that gained prominence because it determines the efficacy of PARP1 inhibitory drugs (PARPi) in BRCA1-deficient cancers. Recent studies have elevated 53BP1 from its modest status of (yet another) DNA damage factor to master regulator of double-strand break (DSB) repair pathway choice. Our review of the literature suggests an alternative view. We propose that 53BP1 has evolved to avoid mutagenic repair outcomes and does so by controlling the processing of DNA ends and the dynamics of DSBs. The consequences of 53BP1 deficiency, such as diminished PARPi efficacy in BRCA1-deficient cells and altered repair of damaged telomeres, can be explained from this viewpoint. We further propose that some of the fidelity functions of 53BP1 coevolved with class switch recombination (CSR) in the immune system. We speculate that, rather than being deterministic in DSB repair pathway choice, 53BP1 functions as a DSB escort that guards against illegitimate and potentially tumorigenic recombination.


Assuntos
Quebras de DNA de Cadeia Dupla , Reparo do DNA/genética , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Evolução Molecular , Humanos , Switching de Imunoglobulina/genética , Telômero/genética , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/deficiência , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/genética
11.
Nat Rev Mol Cell Biol ; 20(4): 259, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30816301

RESUMO

In the original Fig. 2a, telomeres are erroneously depicted having blunt ends following resection and CST-mediated fill-in. Instead, telomeres retain 3' overhangs, as depicted below.

12.
Annu Rev Genet ; 52: 223-247, 2018 11 23.
Artigo em Inglês | MEDLINE | ID: mdl-30208292

RESUMO

For more than a decade, it has been known that mammalian cells use shelterin to protect chromosome ends. Much progress has been made on the mechanism by which shelterin prevents telomeres from inadvertently activating DNA damage signaling and double-strand break (DSB) repair pathways. Shelterin averts activation of three DNA damage response enzymes [the ataxia-telangiectasia-mutated (ATM) and ataxia telangiectasia and Rad3-related (ATR) kinases and poly(ADP-ribose) polymerase 1 (PARP1)], blocks three DSB repair pathways [classical nonhomologous end joining (c-NHEJ), alternative (alt)-NHEJ, and homology-directed repair (HDR)], and prevents hyper-resection at telomeres. For several of these functions, mechanistic insights have emerged. In addition, much has been learned about how shelterin maintains the telomeric 3' overhang, forms and protects the t-loop structure, and promotes replication through telomeres. These studies revealed that shelterin is compartmentalized, with individual subunits dedicated to distinct aspects of the end-protection problem. This review focuses on the current knowledge of shelterin-mediated telomere protection, highlights differences between human and mouse shelterin, and discusses some of the questions that remain.


Assuntos
Reparo do DNA/genética , Reparo de DNA por Recombinação/genética , Telômero/genética , Proteína 2 de Ligação a Repetições Teloméricas/genética , Animais , Proteínas Mutadas de Ataxia Telangiectasia/genética , Cromossomos , Quebras de DNA de Cadeia Dupla , Dano ao DNA/genética , Reparo do DNA por Junção de Extremidades , Humanos , Camundongos , Poli(ADP-Ribose) Polimerase-1/genética
13.
J Biol Chem ; 293(37): 14384-14392, 2018 09 14.
Artigo em Inglês | MEDLINE | ID: mdl-30082315

RESUMO

Comprised of telomeric TTAGGG repeats and shelterin, telomeres ensure that the natural ends of chromosomes remain impervious to the DNA damage response. Telomeres carry a long constitutive 3' overhang that can bind replication protein A (RPA) and activate the ATR Ser/Thr kinase (ATR), which induces cell cycle arrest. A single-stranded (ss) TTAGGG repeat-binding protein in mouse shelterin, POT1a, has been proposed to repress ATR signaling by preventing RPA binding. Repression of ATR at telomeres requires tethering of POT1a to the other shelterin subunits situated on the double-stranded (ds) telomeric DNA. The simplest model of ATR repression, the "tethered exclusion model," suggests that the only critical features of POT1a are its connection to shelterin and its binding to ss telomeric DNA. In agreement with the model, we show here that a shelterin-tethered variant of RPA70 (lacking the ATR recruitment domain) can repress ATR signaling at telomeres that lack POT1a. However, arguing against the tethered exclusion model, the nearly identical POT1b subunit of shelterin has been shown to be much less proficient than POT1a in repression of ATR. We now show that POT1b has the intrinsic ability to fully repress ATR but is prevented from doing so when bound to Ctc1, Stn1, Ten1 (CST), the complex needed for telomere end processing. These results establish that shelterin represses ATR with a tethered ssDNA-binding domain that excludes RPA from the 3' overhang and also reveal an unexpected effect of CST on the ability of POT1b to repress ATR.


Assuntos
Proteínas de Ligação a DNA/metabolismo , Proteína de Replicação A/metabolismo , Transdução de Sinais , Telômero , Animais , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Células Cultivadas , DNA/metabolismo , Células HEK293 , Humanos , Camundongos , Modelos Teóricos , Ligação Proteica
14.
Nature ; 560(7716): 112-116, 2018 08.
Artigo em Inglês | MEDLINE | ID: mdl-30022158

RESUMO

In DNA repair, the resection of double-strand breaks dictates the choice between homology-directed repair-which requires a 3' overhang-and classical non-homologous end joining, which can join unresected ends1,2. BRCA1-mutant cancers show minimal resection of double-strand breaks, which renders them deficient in homology-directed repair and sensitive to inhibitors of poly(ADP-ribose) polymerase 1 (PARP1)3-8. When BRCA1 is absent, the resection of double-strand breaks is thought to be prevented by 53BP1, RIF1 and the REV7-SHLD1-SHLD2-SHLD3 (shieldin) complex, and loss of these factors diminishes sensitivity to PARP1 inhibitors4,6-9. Here we address the mechanism by which 53BP1-RIF1-shieldin regulates the generation of recombinogenic 3' overhangs. We report that CTC1-STN1-TEN1 (CST)10, a complex similar to replication protein A that functions as an accessory factor of polymerase-α (Polα)-primase11, is a downstream effector in the 53BP1 pathway. CST interacts with shieldin and localizes with Polα to sites of DNA damage in a 53BP1- and shieldin-dependent manner. As with loss of 53BP1, RIF1 or shieldin, the depletion of CST leads to increased resection. In BRCA1-deficient cells, CST blocks RAD51 loading and promotes the efficacy of PARP1 inhibitors. In addition, Polα inhibition diminishes the effect of PARP1 inhibitors. These data suggest that CST-Polα-mediated fill-in helps to control the repair of double-strand breaks by 53BP1, RIF1 and shieldin.


Assuntos
Quebras de DNA de Cadeia Dupla , DNA Polimerase I/metabolismo , Complexos Multiproteicos/química , Complexos Multiproteicos/metabolismo , Proteínas de Ligação a Telômeros/metabolismo , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/metabolismo , Animais , Proteína BRCA1/deficiência , Linhagem Celular , DNA Primase/metabolismo , DNA de Cadeia Simples/genética , DNA de Cadeia Simples/metabolismo , Humanos , Camundongos , Poli(ADP-Ribose) Polimerase-1/antagonistas & inibidores , Reparo de DNA por Recombinação , Telômero/genética , Telômero/metabolismo
15.
J Biol Chem ; 293(27): 10453-10456, 2018 07 06.
Artigo em Inglês | MEDLINE | ID: mdl-29794139

RESUMO

The ASBMB 2018 Bert and Natalie Vallee award in Biomedical Sciences honors our work on shelterin, a protein complex that helps cells distinguish the chromosome ends from sites of DNA damage. Shelterin protects telomeres from all aspects of the DNA damage response, including ATM and ATR serine/threonine kinase signaling and several forms of double-strand break repair. Today, this six-subunit protein complex could easily be identified in one single proteomics step. But, it took us more than 15 years to piece together the entire shelterin complex, one protein at a time. Although we did a lot of things right, here I tell the story of shelterin's discovery with an emphasis on the things that I got wrong along the way.


Assuntos
Distinções e Prêmios , Pesquisa Biomédica , Proteínas de Ligação a Telômeros/metabolismo , Telômero/metabolismo , Dano ao DNA , Reparo do DNA , Humanos , Ligação Proteica , Proteínas de Ligação a Telômeros/genética
16.
Nat Struct Mol Biol ; 24(9): 734-742, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28805810

RESUMO

Although t-loops protect telomeres, they are at risk of cleavage by Holliday junction (HJ) resolvases if branch migration converts the three-way t-loop junction into four-way HJs. T-loop cleavage is repressed by the TRF2 basic domain, which binds three- and four-way junctions and protects HJs in vitro. By replacing the basic domain with bacterial-protein domains binding three- and four-way junctions, we demonstrated the in vivo relevance of branched-DNA binding. Branched-DNA binding also repressed PARP1, presumably by masking the PARP1 site in the t-loop junction. Although PARP1 recruits HJ resolvases and promotes t-loop cleavage, PARP1 activation alone did not result in t-loop cleavage, thus suggesting that the basic domain also prevents formation of HJs. Concordantly, removal of HJs by BLM helicase mitigated t-loop cleavage in response to loss of the basic domain. We propose that TRF2 masks and stabilizes the t-loop three-way junction, thereby protecting telomeres from detrimental deletions and PARP1 activation.


Assuntos
DNA/metabolismo , Telômero/metabolismo , Proteína 2 de Ligação a Repetições Teloméricas/química , Proteína 2 de Ligação a Repetições Teloméricas/metabolismo , Animais , Camundongos , Modelos Biológicos , Poli(ADP-Ribose) Polimerase-1/antagonistas & inibidores , Ligação Proteica
17.
Mol Cancer Res ; 15(11): 1579-1586, 2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-28811362

RESUMO

The mammalian nuclear envelope (NE) forms a stable physical barrier between the nucleus and the cytoplasm, normally breaking down only during mitosis. However, spontaneous transient NE rupture in interphase can occur when NE integrity is compromised, such as when the nucleus experiences mechanical stress. For instance, deficiencies in the nuclear lamins and their associated proteins can cause NE rupture that is promoted by forces exerted by actin filaments. NE rupture can allow cytoplasmic nucleases to access chromatin, potentially compromising genome integrity. Importantly, spontaneous NE rupture was noted in several human cancer cell lines, but the cause of this defect is not known. Here, we investigated the mechanistic contributions of two major tumor suppressors, p53 (TP53) and Rb (RB1), to the repression of NE rupture. NE rupture was induced in normal human epithelial RPE-1 cells upon impairment of either Rb or p53 achieved by shRNA knockdown and CRISPR/Cas9 gene editing. NE rupture did not involve diminished expression of NE components or greater cell motility. However, cells that underwent NE rupture displayed a larger nuclear projection area. In conclusion, the data indicate that NE rupture in cancer cells is likely due to loss of either the Rb or the p53 pathway.Implications: These findings imply that tumor suppression by Rb and p53 includes the ability to prevent NE rupture, thereby protecting against genome alterations. Mol Cancer Res; 15(11); 1579-86. ©2017 AACR.


Assuntos
Membrana Nuclear/fisiologia , Proteínas de Ligação a Retinoblastoma/genética , Estresse Mecânico , Proteína Supressora de Tumor p53/genética , Ubiquitina-Proteína Ligases/genética , Sistemas CRISPR-Cas , Linhagem Celular , Movimento Celular , Células Epiteliais/citologia , Edição de Genes , Técnicas de Silenciamento de Genes , Humanos , Mitose , Neoplasias/genética
19.
Genes Dev ; 31(6): 578-589, 2017 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-28381412

RESUMO

Telomeres are protected by shelterin, a six-subunit protein complex that represses the DNA damage response (DDR) at chromosome ends. Extensive data suggest that TRF2 in shelterin remodels telomeres into the t-loop structure, thereby hiding telomere ends from double-stranded break repair and ATM signaling, whereas POT1 represses ATR signaling by excluding RPA. An alternative protection mechanism was suggested recently by which shelterin subunits TRF1, TRF2, and TIN2 mediate telomeric chromatin compaction, which was proposed to minimize access of DDR factors. We performed superresolution imaging of telomeres in mouse cells after conditional deletion of TRF1, TRF2, or both, the latter of which results in the complete loss of shelterin. Upon removal of TRF1 or TRF2, we observed only minor changes in the telomere volume in most of our experiments. Upon codeletion of TRF1 and TRF2, the telomere volume increased by varying amounts, but even those samples exhibiting small changes in telomere volume showed DDR at nearly all telomeres. Upon shelterin removal, telomeres underwent 53BP1-dependent clustering, potentially explaining at least in part the apparent increase in telomere volume. Furthermore, chromatin accessibility, as determined by ATAC-seq (assay for transposase-accessible chromatin [ATAC] with high-throughput sequencing), was not substantially altered by shelterin removal. These results suggest that the DDR induced by shelterin removal does not require substantial telomere decompaction.


Assuntos
Dano ao DNA , Telômero/ultraestrutura , Proteína 1 de Ligação a Repetições Teloméricas/fisiologia , Proteína 2 de Ligação a Repetições Teloméricas/fisiologia , Animais , Células Cultivadas , Cromatina/fisiologia , Camundongos , Microscopia de Fluorescência , Proteína 1 de Ligação à Proteína Supressora de Tumor p53/fisiologia
20.
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