scholarly journals Swc4 positively regulates telomere length independently of its roles in NuA4 and SWR1 complexes

2020 ◽  
Vol 48 (22) ◽  
pp. 12792-12803
Author(s):  
Jia-Cheng Liu ◽  
Qian-Jin Li ◽  
Ming-Hong He ◽  
Can Hu ◽  
Pengfei Dai ◽  
...  
Keyword(s):  
Telomere Length ◽  
Essential Gene ◽  
Telomerase Activity ◽  
Telomere Maintenance ◽  
Direct Role ◽  
Telomere Shortening ◽  
Length Regulation ◽  
Telomere Length Regulation

Abstract Telomeres at the ends of eukaryotic chromosomes are essential for genome integrality and stability. In order to identify genes that sustain telomere maintenance independently of telomerase recruitment, we have exploited the phenotype of over-long telomeres in the cells that express Cdc13-Est2 fusion protein, and examined 195 strains, in which individual non-essential gene deletion causes telomere shortening. We have identified 24 genes whose deletion results in dramatic failure of Cdc13-Est2 function, including those encoding components of telomerase, Yku, KEOPS and NMD complexes, as well as quite a few whose functions are not obvious in telomerase activity regulation. We have characterized Swc4, a shared subunit of histone acetyltransferase NuA4 and chromatin remodeling SWR1 (SWR1-C) complexes, in telomere length regulation. Deletion of SWC4, but not other non-essential subunits of either NuA4 or SWR1-C, causes significant telomere shortening. Consistently, simultaneous disassembly of NuA4 and SWR1-C does not affect telomere length. Interestingly, inactivation of Swc4 in telomerase null cells accelerates both telomere shortening and senescence rates. Swc4 associates with telomeric DNA in vivo, suggesting a direct role of Swc4 at telomeres. Taken together, our work reveals a distinct role of Swc4 in telomere length regulation, separable from its canonical roles in both NuA4 and SWR1-C.

Telomerase Activity and Telomere Length of CD4+CD25+ Regulatory T-Cells under Conditions of In Vitro and In Vivo Expansion.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3857-3857
Author(s):  
Dominik G.F. Wolf ◽  
Anna M. Wolf ◽  
Christian Koppelstaetter ◽  
Holger F. Rumpold ◽  
Gert Mayer ◽  
...  
Keyword(s):  
T Cells ◽  
Regulatory T Cells ◽  
Telomere Length ◽  
Cancer Patients ◽  
Telomerase Activity ◽  
Telomere Maintenance ◽  
Healthy Human ◽  
Telomere Shortening

Abstract The expandability of CD4+CD25+ regulatory T-cells (Treg) has been shown in vitro and in vivo. Activation of telomerase activity is a prerequisite for clonal expansion and telomere maintenance in T-cells. There is currently no data available on the expression and function of telomerase in proliferating Treg. Analyses of telomere length by flow-FISH, real-time PCR and Southern blotting revealed that Treg isolated from healthy human volunteers have significantly shortened telomeres when compared to CD4+CD25− T-cells. However, telomere length is not further shortened in Treg isolated from the peripheral blood of cancer patients, despite the observation that the regulatory T-cell pool of these patients was significantly enlarged. To gain further insight into maintenance of telomere length of Treg, we induced in vitro proliferation of Treg by stimulation with anti-CD3 and IL-2. This led to a rapid increase of telomerase activity, as determined by PCR-ELISA. However, when we focused on the proliferating fraction of Treg using a sorting strategy based on the dilution of CFSE, we could show a significant telomere shortening in Treg with high proliferative and immmuno-suppressive capacity. Of note, proliferating CFSElow Treg are characterized by high telomerase activity, which however seems to be insufficient to avoid further telomere shortening under conditions of strong in vitro stimulation. In contrast, under conditions of in vivo expansion of Treg in cancer patients, the induction of telomerase activity is likely to compensate for further telomere erosion. These data might be of importance when considering the application of in vitro expanded Treg for the treatment of GvHD or autoimmune diseases, as telomere shortening might be associated with genomic instability.

scholarly journals Telomeres and Cancer

Life ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1405
Author(s):  
Hueng-Chuen Fan ◽  
Fung-Wei Chang ◽  
Jeng-Dau Tsai ◽  
Kao-Min Lin ◽  
Chuan-Mu Chen ◽  
...  
Keyword(s):  
Telomere Length ◽  
Molecular Mechanisms ◽  
Telomere Maintenance ◽  
Cancer Development ◽  
Telomere Elongation ◽  
Metabolism Pathway ◽  
Length Regulation ◽  
Telomere Length Regulation ◽  
Genome Protection

Telomeres cap the ends of eukaryotic chromosomes and are indispensable chromatin structures for genome protection and replication. Telomere length maintenance has been attributed to several functional modulators, including telomerase, the shelterin complex, and the CST complex, synergizing with DNA replication, repair, and the RNA metabolism pathway components. As dysfunctional telomere maintenance and telomerase activation are associated with several human diseases, including cancer, the molecular mechanisms behind telomere length regulation and protection need particular emphasis. Cancer cells exhibit telomerase activation, enabling replicative immortality. Telomerase reverse transcriptase (TERT) activation is involved in cancer development through diverse activities other than mediating telomere elongation. This review describes the telomere functions, the role of functional modulators, the implications in cancer development, and the future therapeutic opportunities.

scholarly journals Chromosome specific telomere lengths and the minimal functional telomere revealed by nanopore sequencing

2021 ◽  
Author(s):  
Samantha L. Sholes ◽  
Kayarash Karimian ◽  
Ariel Gershman ◽  
Thomas J. Kelly ◽  
Winston Timp ◽  
...  
Keyword(s):  
Telomere Length ◽  
Clonal Variation ◽  
Nanopore Sequencing ◽  
Biological Mechanisms ◽  
Specific Chromosome ◽  
Telomere Shortening ◽  
Long Read ◽  
Length Regulation ◽  
Telomere Length Regulation

We developed a method to tag telomeres and measure telomere length by nanopore sequencing in the yeast S. cerevisiae. Nanopore allows long read sequencing through the telomere, subtelomere and into unique chromosomal sequence, enabling assignment of telomere length to a specific chromosome end. We observed chromosome end specific telomere lengths that were stable over 120 cell divisions. These stable chromosome specific telomere lengths may be explained by stochastic clonal variation or may represent a new biological mechanism that maintains equilibrium unique to each chromosomes end. We examined the role of RIF1 and TEL1 in telomere length regulation and found that TEL1 is epistatic to RIF1 at most telomeres, consistent with the literature. However, at telomeres that lack subtelomeric Y' sequences, tel1Δ rif1Δ double mutants had a very small, but significant, increase in telomere length compared to the tel1Δ single mutant, suggesting an influence of Y' elements on telomere length regulation. We sequenced telomeres in a telomerase-null mutant (est2Δ) and found the minimal telomere length to be around 75bp. In these est2Δ mutants there were many apparent telomere recombination events at individual telomeres before the generation of survivors, and these events were significantly reduced in est2Δ rad52Δ double mutants. The rate of telomere shortening in the absence of telomerase was similar across all chromosome ends at about 5 bp per generation. This new method gives quantitative, high resolution telomere length measurement at each individual chromosome end, suggests possible new biological mechanisms regulating telomere length, and provides capability to test new hypotheses.

scholarly journals Chromosome-specific telomere lengths and the minimal functional telomere revealed by nanopore sequencing

2021 ◽  
pp. gr.275868.121
Author(s):  
Samantha L. Sholes ◽  
Kayarash Karimian ◽  
Ariel Gershman ◽  
Thomas J. Kelly ◽  
Winston Timp ◽  
...  
Keyword(s):  
Telomere Length ◽  
Clonal Variation ◽  
Nanopore Sequencing ◽  
Biological Mechanisms ◽  
Specific Chromosome ◽  
Telomere Shortening ◽  
Long Read ◽  
Length Regulation ◽  
Telomere Length Regulation

We developed a method to tag telomeres and measure telomere length by nanopore sequencing in the yeast S. cerevisiae. Nanopore allows long-read sequencing through the telomere, subtelomere and into unique chromosomal sequence, enabling assignment of telomere length to a specific chromosome end. We observed chromosome end specific telomere lengths that were stable over 120 cell divisions. These stable chromosome-specific telomere lengths may be explained by slow clonal variation or may represent a new biological mechanism that maintains equilibrium unique to each chromosome end. We examined the role of RIF1 and TEL1 in telomere length regulation and found that TEL1 is epistatic to RIF1 at most telomeres, consistent with the literature. However, at telomeres that lack subtelomeric Y’ sequences, tel1Δ rif1Δ double mutants had a very small, but significant, increase in telomere length compared to the tel1Δ single mutant, suggesting an influence of Y’ elements on telomere length regulation. We sequenced telomeres in a telomerase-null mutant (est2Δ) and found the minimal telomere length to be around 75 bp. In these est2Δ mutants there were apparent telomere recombination events at individual telomeres before the generation of survivors, and these events were significantly reduced in est2Δ rad52Δ double mutants. The rate of telomere shortening in the absence of telomerase was similar across all chromosome ends at about 5 bp per generation. This new method gives quantitative, high resolution telomere length measurement at each individual chromosome end, and suggests possible new biological mechanisms regulating telomere length.

scholarly journals Cdc13 N-Terminal Dimerization, DNA Binding, and Telomere Length Regulation

2010 ◽  
Vol 30 (22) ◽  
pp. 5325-5334 ◽  
Author(s):  
Meghan T. Mitchell ◽  
Jasmine S. Smith ◽  
Mark Mason ◽  
Sandy Harper ◽  
David W. Speicher ◽  
...  
Keyword(s):  
Dna Binding ◽  
Telomere Length ◽  
Functional Characterization ◽  
Point Mutations ◽  
Telomeric Dna ◽  
Dna Binding Domains ◽  
Binding Domains ◽  
Length Regulation ◽  
Telomere Length Regulation

ABSTRACT The essential yeast protein Cdc13 facilitates chromosome end replication by recruiting telomerase to telomeres, and together with its interacting partners Stn1 and Ten1, it protects chromosome ends from nucleolytic attack, thus contributing to genome integrity. Although Cdc13 has been studied extensively, the precise role of its N-terminal domain (Cdc13N) in telomere length regulation remains unclear. Here we present a structural, biochemical, and functional characterization of Cdc13N. The structure reveals that this domain comprises an oligonucleotide/oligosaccharide binding (OB) fold and is involved in Cdc13 dimerization. Biochemical data show that Cdc13N weakly binds long, single-stranded, telomeric DNA in a fashion that is directly dependent on domain oligomerization. When introduced into full-length Cdc13 in vivo, point mutations that prevented Cdc13N dimerization or DNA binding caused telomere shortening or lengthening, respectively. The multiple DNA binding domains and dimeric nature of Cdc13 offer unique insights into how it coordinates the recruitment and regulation of telomerase access to the telomeres.

scholarly journals Regulating telomere length from the inside out: The replication fork model

2016 ◽  
Author(s):  
Carol W Greider
Keyword(s):  
Telomere Length ◽  
Alternative Model ◽  
Replication Fork ◽  
Molecular Level ◽  
Origin Firing ◽  
Length Regulation ◽  
Telomere Length Regulation ◽  
Inside Out ◽  
Counting Model

Telomere length is regulated around an equilibrium set point. Telomeres shorten during replication and are lengthened by telomerase. Disruption of the length equilibrium leads to disease, thus it is important to understand the mechanisms that regulate length at the molecular level. The prevailing protein counting model for regulating telomerase access to elongate the telomere does not explain accumulating evidence of a role of DNA replication in telomere length regulation. Here I present an alternative model: the replication fork model that can explain how passage of a replication fork and regulation of origin firing affect telomere length.

scholarly journals SIRT1 contributes to telomere maintenance and augments global homologous recombination

2010 ◽  
Vol 191 (7) ◽  
pp. 1299-1313 ◽  
Author(s):  
Jose A. Palacios ◽  
Daniel Herranz ◽  
Maria Luigia De Bonis ◽  
Susana Velasco ◽  
Manuel Serrano ◽  
...  
Keyword(s):  
Homologous Recombination ◽  
Telomerase Activity ◽  
Histone Deacetylation ◽  
Telomere Maintenance ◽  
Loss Of Function ◽  
Entire Genome ◽  
Telomere Shortening ◽  
Telomere Biology ◽  
Sir Complex

Yeast Sir2 deacetylase is a component of the silent information regulator (SIR) complex encompassing Sir2/Sir3/Sir4. Sir2 is recruited to telomeres through Rap1, and this complex spreads into subtelomeric DNA via histone deacetylation. However, potential functions at telomeres for SIRT1, the mammalian orthologue of yeast Sir2, are less clear. We studied both loss of function (SIRT1 deficient) and gain of function (SIRT1super) mouse models. Our results indicate that SIRT1 is a positive regulator of telomere length in vivo and attenuates telomere shortening associated with aging, an effect dependent on telomerase activity. Using chromatin immunoprecipitation assays, we find that SIRT1 interacts with telomeric repeats in vivo. In addition, SIRT1 overexpression increases homologous recombination throughout the entire genome, including telomeres, centromeres, and chromosome arms. These findings link SIRT1 to telomere biology and global DNA repair and provide new mechanistic explanations for the known functions of SIRT1 in protection from DNA damage and some age-associated pathologies.

scholarly journals Essential roles for Pot1b in HSC self-renewal and survival

Blood ◽  
2011 ◽  
Vol 118 (23) ◽  
pp. 6068-6077 ◽  
Author(s):  
Yang Wang ◽  
Mei-Feng Shen ◽  
Sandy Chang
Keyword(s):  
Progenitor Cell ◽  
Essential Role ◽  
Dyskeratosis Congenita ◽  
Telomere Maintenance ◽  
Wild Type ◽  
Telomere Shortening ◽  
Damage Response ◽  
First Time

Abstract Maintenance of mammalian telomeres requires both the enzyme telomerase and shelterin, which protect telomeres from inappropriately activating DNA damage response checkpoints. Dyskeratosis congenita is an inherited BM failure syndrome disorder because of defects in telomere maintenance. We have previously shown that deletion of the shelterin component Pot1b in the setting of telomerase haploinsufficiency results in rapid telomere shortening and fatal BM failure in mice, eliciting phenotypes that strongly resemble human syskeratosis congenita. However, it was unclear why BM failure occurred in the setting of Pot1b deletion. In this study, we show that Pot1b plays an essential role in HSC survival. Deletion of Pot1b results in increased apoptosis, leading to severe depletion of the HSC reserve. BM from Pot1bΔ/Δ mice cannot compete with BM from wild-type mice to provide multilineage reconstitution, indicating that there is an intrinsic requirement for Pot1b the maintenance of HSC function in vivo. Elimination of the p53-dependent apoptotic function increased HSC survival and significantly extended the lifespan of Pot1b-null mice deficient in telomerase function. Our results document for the first time the essential role of a component of the shelterin complex in the maintenance of HSC and progenitor cell survival.

scholarly journals The Role of Rif1 in telomere length regulation is separable from its role in origin firing

2020 ◽  
Author(s):  
Calla B. Shubin ◽  
Carol W. Greider
Keyword(s):  
Telomere Length ◽  
Protein Phosphatase ◽  
Protein Phosphatase 1 ◽  
Origin Firing ◽  
Replication Complex ◽  
Telomere Elongation ◽  
Length Regulation ◽  
Telomere Length Regulation ◽  
Telomere Lengthening

AbstractTo examine the established link between DNA replication and telomere length, we tested whether firing of telomeric origins would cause telomere lengthening. We found that RIF1 mutants that block Protein Phosphatase 1 (PP1) binding activated telomeric origins but did not elongate telomeres. In a second approach, we found overexpression of ΔN-Dbf4 and Cdc7 increased DDK activity and activated telomeric origins, yet telomere length was unchanged. We tested a third mechanism to activate origins using the sld3-A mcm5-bob1 mutant that deregulates the pre-replication complex, and again saw no change in telomere length. Finally, we tested whether mutations in RIF1 that cause telomere elongation would affect origin firing. We found that neither rif1-Δ1322 nor rif1HOOK affected firing of telomeric origins. We conclude that telomeric origin firing does not cause telomere elongation, and the role of Rif1 in regulating origin firing is separable from its role in regulating telomere length.

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