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Meiotic proteins Bqt1 and Bqt2 tether telomeres to promote the bouquet arrangement of chromosomes in fission yeast

ABSTRACT: In many organisms, meiotic chromosomes are bundled at their telomeres to form a bouquet arrangement. The bouquet formation plays an important role in homologous chromosome pairing and therefore progression of meiosis. As meiotic telomere clustering occurs in response to mating pheromone signaling in fission yeast, we looked for factors essential for bouquet formation among genes induced under mating pheromone signaling. This genome-wide search identified two novel proteins, Bqt1 and Bqt2, that connect telomeres to the spindle-pole body (SPB; the centrosome equivalent in fungi). Neither Bqt1 nor Bqt2 alone functions as a connector, but together the two proteins form a bridge between Rap1 (a telomere protein) and Sad1 (an SPB protein). Significantly, when both Bqt1 and Bqt2 are ectopically expressed in mitotic cells, they also form a bridge between Rap1 and Sad1. Thus, a complex including Bqt1 and Bqt2 is essential for connecting telomeres to the SPB. Keywords: Keywards: Time course, Nitrogen starvation, Mating pheromone, P-factor.

ORGANISM(S): Schizosaccharomyces pombe

PROVIDER: GSE3515 | GEO | 2006/04/20

SECONDARY ACCESSION(S): PRJNA93561

REPOSITORIES: GEO

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A genetic interaction between RAP1 and telomerase reveals an unanticipated role for RAP1 in telomere protection

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

Mutational analysis of Rap1 reveals specific vulnerability for long telomeres fusions

Project description:The conserved Rap1 protein is part of the shelterin complex that plays critical roles in chromosome end protection and telomere length homeostasis. Previous studies addressed how fission yeast Rap1 contributes to telomere length maintenance, but the mechanism by which the protein inhibits end fusions has remained elusive. Here, we use a genetic screen in combination with high throughput sequencing to identify several amino acid positions in Rap1 that have a key role in end protection. Interestingly, mutations at these sites render cells susceptible to genome instability in a conditional manner with longer telomeres being prone to undergoing end fusions, while short telomeres are sufficiently protected. The protection of long telomeres requires their nuclear envelope attachment mediated by the Rap1-Bqt4 interaction. Our data demonstrates that longer telomeres pose an additional challenge for the maintenance of genome integrity and provides an explanation for a species-specific upper limit in telomere length.

2022-08-10 | GSE190759 | GEO

ZNF524 directly binds telomeres and supports their integrity via TRF2/RAP1

Project description:Telomeres are nucleoprotein structures at the ends of linear chromosomes. In humans, they consist of TTAGGG repeats, which are bound by dedicated proteins such as the shelterin complex. This complex consists of six proteins (TRF1, TRF2, RAP1, POT1, TPP1 and TIN2) and blocks unwanted DNA damage repair at telomeres, e.g. by suppressing non-homologous end joining (NHEJ) through its subunit TRF2. While shelterin does not work autonomously, additional direct telomere binding proteins have been described to function in a supplementary role. We here describe ZNF524, a zinc finger protein that directly binds to telomeric repeats with nanomolar affinity and reveal the base-specific sequence recognition by co-crystallization with telomeric DNA. ZNF524 localizes to telomeres and specifically maintains the presence of the TRF2/RAP1 subcomplex at telomeres without affecting the other shelterin members. Loss of ZNF524 concomitantly results in an increase in DNA damage signaling and recombination events. Overall, we identified ZNF524 as a direct telomere binding protein and propose that ZNF524 is involved in the maintenance of telomere integrity by promoting TRF2/RAP1 subcomplex binding.

2023-10-22 | PXD031416 | Pride

ZNF524 directly binds telomeres and supports their integrity via TRF2/RAP1

2023-10-21 | PXD024630 | Pride

Aberrant expression and localization of the RAP1 shelterin protein contributes to age-related phenotypes [2019]

Project description:Short telomeres induce a DNA damage response (DDR) that evokes apoptosis or senescence in human cells. An extant question is the contribution of this DDR to the phenotypes observed in telomeropathies. One exemplar is RAP1, a telomere-associated protein that also controls transcription at extratelomeric regions. To distinguish these roles, we generated a knock-in mouse containing a Rap1 variant unable to bind telomeres but which did not result in eroded telomeres or a DDR. Rap1 variant MEFs exhibited decreased RAP1 expression and re-localization away from telomeres, with an increased cytosolic distribution akin to that observed in aging human fibroblasts. Rap1 knock-in mice were viable, but exhibited transcriptional alterations, proinflammatory cytokine/chemokine signaling, decreased lifespans, increased body weight/fasting blood glucose levels, increased spontaneous tumor incidence, and behavioral deficits. Taken together, our data indicate that some of the underlying mechanisms that drive telomeropathies may arise from phenotypes distinct from a telomere-induced DDR.

2022-11-04 | GSE193523 | GEO

Aberrant expression and localization of the RAP1 shelterin protein contributes to age-related phenotypes [2017]

2022-11-04 | GSE193520 | GEO

Genome-wide analysis reveals that budding yeast Rif1 binds to replication origins and at blocked replication forks to protect nascent DNA

Project description:This experiment details ChIP sequencing to decipher the binding sites of the Rif1 protein in budding yeast. Rif1 binds most strongly to telomeres where its binding is mediated by Rap1. To reduce telomere binding and help reveal Rap1-independent binding sites, a truncation mutant of Rif1 lacking the Rap1 interaction domain was constructed and analysed. Binding was examined at various cell-cycle stages to elucidate the role of Rif1 in DNA replication and other chromosome transactions.

2018-12-31 | E-MTAB-6736 | biostudies-arrayexpress

TEBP-1 and TEBP-2 are double-stranded telomere binders required for fertility

Project description:Telomeres are the ends of linear chromosomes and consist of repetitive double- and single-stranded DNA sequences. Telomeres are bound by dedicated protein complexes, such as shelterin in mammals. In the nematode Caenorhabditis elegans, a comprehensive understanding of the proteins interacting with the telomere sequence is lacking. Here, we harnessed a quantitative proteomics approach to screen for proteins binding to C. elegans telomeres, and identified TEBP-1 and TEBP-2, two paralogs that associate to telomeres in vitro and in vivo. TEBP-1 and TEBP-2 form a telomeric complex with the known single-stranded telomere-binding proteins POT-1, POT-2, and MRT-1. tebp-1 and tebp-2 mutants display strikingly distinct phenotypes: tebp-1 mutants have longer telomeres than wild-type animals, while tebp 2 mutants display shorter telomeres and a mortal germline, a phenotype characterized by transgenerational germline deterioration. Notably, tebp 1;tebp-2 double mutant animals are synthetic sterile, with germlines showing signs of severe mitotic and meiotic arrest. These results define the first telomere-binding complex of C. elegans, including TEBP-1 and TEBP-2, two double-stranded telomere binders required for fertility.

2021-03-09 | PXD019241 | Pride

RNA sequencing of pheromone stimulated and unstimulated MATa and MATα Saccharomyces cerevisiae

Project description:Haploid budding yeast has two mating types, defined by the alleles of the MAT locus, MATa and MATα. Mating occurs when two haploid cells of opposite mating types signal to each other using reciprocal pheromones and receptors, polarize and grow towards each other, and eventually fuse to form a single diploid cell. The pheromones and receptors are necessary and sufficient to define a mating type, but other mating type-specific proteins make mating more efficient. We examined the role of these proteins by genetically engineering “transvestite” cells that swap the pheromone, pheromone receptor, and pheromone processing factors of one mating type for another. These cells can mate with each other, but their mating is inefficient. By characterizing their mating defects and examining their transcriptomes, we found Afb1 (a-factor barrier), a novel MATα-specific protein that interferes with a-factor, the pheromone secreted by MATa cells. We show that strong pheromone secretion is essential for efficient mating and that the weak mating of transvestites can be improved by boosting their pheromone production. Using synthetic biology, it is possible to characterize the factors that control efficiency in biological processes. In the case of budding yeast mating, selection for increased mating efficiency is likely to have continually boosted pheromone levels and the ability to discriminate between partners who make more (potentially fitter) and less (potentially less fit) pheromones. This sensitivity to which partner makes more pheromone comes at a cost: it means mating is not robust in situations where all potential partners make less pheromone.

2014-01-07 | GSE49372 | GEO

Genome-wide gene expression in response to mating pheromones in S. pombe

Project description:Fission yeast cells undergo sexual differentiation in response to nitrogen starvation. In this process haploid M and P cells first mate to form diploid zygotes, which subsequently enter meiosis and sporulate. Prior to mating, M cells secrete M-factor and P-cells secrete P-factor, and these diffusible mating pheromone can activate a signal transduction pathway in the opposite cell type. The pheromone response orchestrates mating and is also required for entry into meiosis. Here we use DNA microarrays to identify genes that are induced by M-factor in P cells and by P-factor in M-cells. The use of a cyr1 genetic background allowed us to study pheromone stimulation independently of nitrogen starvation. We identified a total of 163 genes that were consistently induced more than two-fold by pheromone stimulation. As expected, there was a substantial overlap between the genes induced by M- and P-factor. Surprisingly, we found that pheromone control extended to genes fulfilling their function well beyond the point of entry into meiosis, including numerous genes required for meiotic recombination. A direct comparison of the M- and P-factor induced expression pattern allowed us to identify cell-type specific transcripts, including three new M-specific genes and one new P-specific gene. Finally, our results support the notion that Ste11 is the key transcription factor activated by pheromone signalling. Keywords: dose response

2007-08-22 | GSE5323 | GEO

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