POLIE suppresses telomerase-mediated telomere G-strand extension and helps ensure proper telomere C-strand synthesis in trypanosomes
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ABSTRACT:
PROVIDER: PRJNA758389 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR15655358_1.fastq.gz | Fastqsanger.gz | |||
| SRR15655358_2.fastq.gz | Fastqsanger.gz | |||
| SRR15655359_1.fastq.gz | Fastqsanger.gz | |||
| SRR15655359_2.fastq.gz | Fastqsanger.gz | |||
| SRR15655360_1.fastq.gz | Fastqsanger.gz |
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Project description:T. brucei regularly switches its major surface antigen, VSG, to evade the mammalian host immune response. VSGs are expressed from subtelomeric loci in a strictly monoallelic manner. We identify POLIE as an intrinsic component of the T. brucei telomere complex and examined the effect of POLIE depletion on VSG expression regulation by RNAseq.
2022-01-07 | GSE182941 | GEO
Project description:Trypanosoma brucei causes human African trypanosomiasis and sequentially expresses distinct VSGs, its major surface antigen, to achieve host immune evasion. VSGs are monoallelically expressed from subtelomeric loci, and telomere proteins regulate VSG monoallelic expression and VSG switching. T. brucei telomerase is essential for telomere maintenance, but no regulators of telomerase have been identified. T. brucei appears to lack OB fold-containing telomere-specific ssDNA binding factors that are critical for coordinating telomere G- and C-strand syntheses in higher eukaryotes. We identify POLIE as a telomere protein essential for telomere integrity. POLIE-depleted cells have more frequent VSG gene conversion-mediated VSG switching and an increased amount of telomeric circles (T-circles), indicating that POLIE suppresses DNA recombination at the telomere/subtelomere. POLIE-depletion elongates telomere 3' overhangs dramatically, indicating that POLIE is essential for coordinating DNA syntheses of the two telomere strands. POLIE depletion increases the level of telomerase-dependent telomere G-strand extension, identifying POLIE as the first T. brucei telomere protein that suppresses telomerase. Furthermore, depletion of POLIE results in an elevated telomeric C-circle level, suggesting that the telomere C-strand experiences replication stress and that POLIE may promote telomere C-strand synthesis. Therefore, T. brucei uses a novel mechanism to coordinate the telomere G- and C-strand DNA syntheses.
| S-EPMC8887473 | biostudies-literature
Project description:Background and Aims: Telomere dysfunction can increase tumor initiation by induction of chromosomal instability, but initiated tumor cells need to reactivate telomerase for genome stabilization and tumor progression. However, this concept has not been proven in vivo since appropriate mouse models were lacking. Here, we analyzed hepatocarcinogenesis (i) in a novel mouse model of inducible telomere dysfunction on a telomerase-proficient background, (ii) in telomerase knockout mice with chronic telomere dysfunction (G3 mTerc-/-), and (iii) in wild-type mice with functional telomeres and telomerase. Transient or chronic telomere dysfunction enhanced the rates of chromosomal aberrations during hepatocarcinogenesis, but only telomerase-proficient mice exhibited significantly increased rates of macroscopic tumor formation and cancer cell proliferation in response to telomere dysfunction. In contrast, telomere dysfunction resulted in pronounced accumulation of DNA damage, cell cycle arrest and apoptosis in telomerase-deficient liver tumors. Together, these data provide the first in vivo evidence that transient telomere dysfunction during early and late stages of tumorigenesis can promote chromosomal instability and carcinogenesis in telomerase-proficient mice in the absence of additional genetic checkpoint defects at germline level. RNA from liver tumors derived from from DEN treated TTD+ mice TTD- mice and RNA from normal liver 48h-72h after doxycycline induced transient telomere dysfunction in TTD+ and TTD- liver were isolated and RNA was extracted. Agilent Mouse 4x44K v2 arrays were used. DNA from liver tumors and corrresponding kidney as control derived from from DEN treated TTD+ mice, TTD- mice and mTERC-/- G3 mice was isolated and extracted using Phenol/Chloroform. Agilent Mouse 4x44K and Mouse 1x244K arrays were used.
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Project description:The end replication problem refers to the incomplete replication of parental DNA at telomeres, a process whose molecular depiction is hampered by the complex nature of telomere ends. Here we recapitulate this process using a synthetic de novo telomere in yeast and delineate distinct molecular fates of telomere ends in vivo. We show that the lagging strand telomere carries a ~10 nt 3’ overhang, while the leading strand telomere has a Yku-protected blunt end, which is prevalent on native telomeres. Moreover, we find that RNase H2 is mainly responsible for the removal of the last RNA primer. In the absence of RNase H2 activity, RNA primer retention on the lagging strand telomere attenuates telomere erosion and delays senescence in telomerase-null cells. These findings highlight incongruent end structures on telomeres and clarify that the primary culprit behind end replication problem is the incompletely replicated lagging strand telomere.
2024-12-09 | GSE283459 | GEO
Project description:Background and Aims: Telomere dysfunction can increase tumor initiation by induction of chromosomal instability, but initiated tumor cells need to reactivate telomerase for genome stabilization and tumor progression. However, this concept has not been proven in vivo since appropriate mouse models were lacking. Here, we analyzed hepatocarcinogenesis (i) in a novel mouse model of inducible telomere dysfunction on a telomerase-proficient background, (ii) in telomerase knockout mice with chronic telomere dysfunction (G3 mTerc-/-), and (iii) in wild-type mice with functional telomeres and telomerase. Transient or chronic telomere dysfunction enhanced the rates of chromosomal aberrations during hepatocarcinogenesis, but only telomerase-proficient mice exhibited significantly increased rates of macroscopic tumor formation and cancer cell proliferation in response to telomere dysfunction. In contrast, telomere dysfunction resulted in pronounced accumulation of DNA damage, cell cycle arrest and apoptosis in telomerase-deficient liver tumors. Together, these data provide the first in vivo evidence that transient telomere dysfunction during early and late stages of tumorigenesis can promote chromosomal instability and carcinogenesis in telomerase-proficient mice in the absence of additional genetic checkpoint defects at germline level.
2012-03-31 | GSE36813 | GEO
Project description:Most DNA double-strand breaks (DSBs) are harmful to genome integrity. However, some forms of DSBs are essential to biological processes, such as meiotic recombination and V(D)J recombination. DSBs are also required for programmed DNA elimination (PDE) in ciliates and nematodes. In nematodes, the DSBs are healed with telomere addition. While telomere addition sites have been well-characterized, little is known regarding the DSBs that fragment nematode chromosomes. Here, we used embryos from the nematode Ascaris to study the timing of PDE breaks and examine the DSBs and their end processing. Using END-seq, we characterize the DSB ends and demonstrate that DNA breaks are introduced before mitosis, followed by extensive end resection. The resection profile is unique for each break site, and the resection generates 3’ overhangs before the addition of telomeres. Interestingly, telomere healing occurs much more frequently on retained DSB ends than on eliminated ends. This biased repair of the DSB in Ascaris is likely due to the sequestration of the eliminated DNA into micronuclei, preventing their ends from telomere healing. Additional DNA breaks occur within the eliminated DNA in both Ascaris and Parascaris, ensuring chromosomal breakage and providing a fail-safe mechanism for nematode PDE.
2024-03-15 | GSE260958 | GEO
Project description:The Rif1 protein negatively regulates telomeric TG repeat length in the budding yeast S. cerevisiae, but how it prevents telomere over-extension is unknown. Rif1 was recently shown to control DNA replication by acting as a Protein Phosphatase 1 (PP1)-targeting subunit. Therefore we investigated whether Rif1 controls telomere length by targeting PP1 activity. We find that a Rif1 mutant that cannot interact with PP1 causes a long-telomere phenotype, similar to that of rif1∆ cells. Compromised PP1 function also causes telomere extension. Tethering PP1 at a specific telomere partially substitutes for Rif1 in limiting TG repeat length, confirming the importance of PP1 in telomere length control. Ablating Rif1-PP1 interaction leads to precocious activation of telomere-proximal replication origins and aberrantly early telomere replication. However, we find that Rif1 still limits telomere length even if nearby replication origins are deleted, indicating that effects of Rif1 on telomere length are not mediated through replication timing. Instead we find that, even at a telomere created after DNA synthesis during a mitotic block, Rif1-PP1 interaction is required to suppress telomere lengthening and prevent inappropriate recruitment of Tel1 kinase. Overall, our results show that Rif1 controls telomere length by recruiting PP1 to directly suppress telomerase-mediated TG repeat lengthening.
2018-02-14 | GSE109241 | GEO
Project description:Somatic cell nuclear transfer (SCNT) and induced pluripotent stem cells (iPSCs) represent two major approaches for somatic cell reprogramming. However, little attention has been paid to the ability of these two strategies in rejuvenating cells from donors with aging associated syndrome. Here, we utilized telomerase deficient (Terc-/-) mice to probe this question. SCNT-derived embryonic stem cells (ntESCs) and iPSCs were successfully derived from second generation (G2) and third generation (G3) of Terc-/- mice, and ntESCs showed better differentiation potential and self-renewal ability. Telomeres lengthened extensively in cloned embryos while remained or slightly increased in the process of iPSCs induction. Furthermore, G3 ntESCs exhibited improvement of telomere capping function as evidenced by decreased signal free ends and chromosome end-to-end fusion events. In contrast, there was a further decline of telomere capping function in G3 iPSCs. In addition to telomere dysfunction, mitochondria function was severely impaired in G3 iPSCs as evidenced by oxygen consumption rate (OCR) decline, reactive oxygen species (ROS) accumulation and dramatically increased mitochondria genome mutations while these deficiencies were greatly mitigated in G3 ntESCs. Our data proved the principle that SCNT-mediated reprogramming appears more superior than transcription factors induced reprogramming in terms of the resetting of telomere quality and mitochondria function, and thus, providing valuable information for further improvement of transcription factors mediated reprogramming. We compared the gene expression profile of G3 Terc-/- ntES and G3 Terc-/- iPS. Three biological repeats were included for each cell line.
2013-11-11 | E-GEOD-46860 | biostudies-arrayexpress
Project description:Telomere extension by telomerase is essential for chromosome stability and cell vitality. Here, we report the identification of a splice variant of mammalian heterogeneous nuclear ribonucleoprotein A2 (hnRNP A2), hnRNP A2*, which binds telomeric DNA and telomerase in vitro. hnRNP A2* colocalizes with telomerase in Cajal bodies and at telomeres. In vitro assays show that hnRNP A2* actively unfolds telomeric G-quadruplex DNA, exposes 5 nt of the 3' telomere tail and substantially enhances the catalytic activity and processivity of telomerase. The expression level of hnRNP A2* in tissues positively correlates with telomerase activity, and overexpression of hnRNP A2* leads to telomere elongation in vivo. Thus, hnRNP A2* plays a positive role in unfolding telomere G-quadruplexes and in enhancing telomere extension by telomerase.
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Project description:RAP1 is one of the components of mammalian shelterin, the capping complex at chromosome ends or telomeres, although its role in telomere protection has remained elusive. RAP1 binds along chromosome arms, where it regulates gene expression and has been shown to function in metabolism control. Telomerase is the enzyme that elongates telomeres and its deficiency causes a premature aging in mice. We describe an unanticipated genetic interaction between RAP1 and telomerase. While RAP1 deficiency alone does not impact in mouse survival, mice lacking both RAP1 and telomerase show a progressive decreased survival with increasing mouse generation as compared to telomerase single mutants. Telomere shortening was more pronounced in Rap1-/- Terc-/- than in Terc-/- counterparts, leading to an earlier onset of DNA damage and its consequent DNA damage response as well as accelerated degenerative pathologies in the intestines. In its turn, telomerase deficiency abolishes RAP1-mediated obesity and liver pathologies. Mouse embryonic fibroblasts with shorten telomeres present less amount of telomere-bound RAP1 but in contrast show higher numbers of RAP1 bound extratelomeric sites genomewide. Absence of RAP1 leads to deregulation of several metabolic pathways, and these changes were more pronounce in cells with short telomeres suggesting that RAP1 release from telomere foci could constitute a coordinated genomic response to telomere shortening. Our findings also demonstrate that although RAP1 is not a key factor in telomere capping under normal conditios, under stress situation such as critical telomere shortening RAP1 exerts an important function for telomere protection and justify its evolutionary conservation as a shelterin component in mammalian cells.
2016-11-16 | GSE79996 | GEO