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RNA-DNA hybrids prevent resection at dysfunctional telomeres

ABSTRACT: At critically short telomeres TERRA RNA-DNA hybrids become stabilized and drive homology-directed repair (HDR) to delay replicative senescence. However, even at long- and intermediate-length telomeres, not subject to HDR, transient TERRA RNA-DNA hybrids form, suggestive of additional roles. Here, we report that hybrids at telomeres prevent resection by the Exo1 nuclease when telomeres become non-functional. We employed the well-characterized cdc13-1 allele, where telomere resection can be induced in a temperature dependent manner, to demonstrate that ssDNA generation at telomeres is either prevented or augmented when RNA-DNA hybrids are stabilized or destabilized, respectively. The viability of cdc13-1 cells is affected by the presence or absence of hybrids accordingly. These results give insights into an additional role of TERRA at dysfunctional telomeres suggesting that it not only affects replicative senescence rates through HDR activation at critically short telomeres, but may also affect resection rates at intermediate length telomeres in pre-senescent cells.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Saccharomyces Cerevisiae (baker's Yeast)

SUBMITTER: F Butter

LAB HEAD: Falk Butter

PROVIDER: PXD034986 | Pride | 2023-01-18

REPOSITORIES: Pride

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Npl3 stabilizes R-loops at telomeres to prevent accelerated replicative senescence

Project description:Telomere shortening rates must be regulated to prevent premature replicative senescence. TERRA R-loops become stabilized at critically short telomeres to promote their elongation through homology-directed repair (HDR), thereby counteracting senescence onset. Using a non-bias proteomic approach to identify telomere binding factors, we identified Npl3, an RNA-binding protein previously implicated in multiple RNA biogenesis processes. Using Chromatin- and RNA immunoprecipitation, we demonstrate that Npl3 interacts with TERRA and telomeres. Furthermore, we show that Npl3 associates to telomeres in an R-loop dependent manner, as changes in R-loop levels, e.g. at short telomeres, modulate the recruitment of Npl3 to chromosome ends. Through a series of genetic and biochemical approaches we demonstrate that Npl3 binds to TERRA and stabilizes R-loops at short telomeres, which in turn promotes HDR and prevents premature replicative senescence onset. This may have implications for diseases associated with excessive telomere shortening.

2020-01-31 | PXD016772 | Pride

RAD51AP1 regulates ALT-HDR through chromatin-directed homeostasis of TERRA

Project description:Alternative lengthening of telomeres (ALT) is a homology-directed repair (HDR) mechanism of telomere elongation that controls proliferation in subsets of highly aggressive cancer. Recent studies have revealed that TERRA (telomere repeat-containing RNA) acts to initiate ALT-associated HDR (ALT-HDR). Here we report that RAD51AP1, a crucial ALT factor, interacts with TERRA and utilizes it to generate D- and R- loop HR intermediates. We also show that RAD51AP1 binds to and may generate and potentially stabilize TERRA-containing R-loops as RAD51AP1 depletion reduces R-loop formation at telomere DNA breaks. Proteomic analyses uncover a new role for RAD51AP1 mediated TERRA R-loop homeostasis in a mechanism of chromatin-directed suppression of TERRA and prevention of transcription-replication collisions during ALT-HDR. Intriguingly, we find that both TERRA binding and this non-canonical function of RAD51AP1 require its intrinsic SUMO-SIM regulatory axis. These findings provide new insights into the multi-contextual functions of RAD51AP1 within the ALT mechanism and regulation of TERRA.

2024-01-26 | PXD035943 | Pride

TERRA interactome in human ALT cancer cells identified by iDRiP-MS method

Project description:Alternative Lengthening of Telomeres (ALT) cancer cells are a subset of cancers that depend on the homologous recombination mechanism to extend their telomere length independent of telomerase. ALT cells contain elevated levels of the telomeric-repeat containing long noncoding RNA (TERRA), which is an RNA transcribed by RNA polymerase II and can form RNA:DNA (R-loops) hybrids at telomeres. Lines of evidence have shown that the formation of R-loops at telomeres could be one of the mechanisms to trigger DNA repair to lengthen telomeres. We perform iDRiP-MS, a method to capture specific RNA interacting protein by UV light crosslinking using antisense probe capture (Chu et al., 2017a; Minajigi et al., 2015), to explore the TERRA interactomes in human ALT cancer cell. Our TERRA interactome data reveals that TERRA interacts with an extensive subset of DNA repair proteins in ALT cells including the endonuclease XPF, suggesting that TERRA R-loops activate DDR via XPF to promote homologous recombination and telomere replication to drive ALT.

2022-09-28 | PXD028882 | Pride

Functional characterization of the TERRA transcriptome at damaged telomeres

Project description:We characterize the TERRA transcriptome at normal and TRF2-depleted telomeres by RNA-seq and we demonstrate that TERRA upregulation is occurring at all transcribed telomeres upon depletion of TRF2. RNA-sequencing of HeLa mRNA, 4 samples: with or without TERRA enrichment by IP (respectively "IP" and "input"), with or without TFR-2 knock-down (respectively "_T" and "_EV").

2014-10-31 | E-GEOD-56727 | biostudies-arrayexpress

Decrease in Rnase HII and accumulation of lncRNAs/DNA hybrids: a causal implication in psoriasis?

Project description:Long functional non-coding RNAs (lncRNAs) have been in the limelight in aging research because short telomeres are associated with higher levels of TERRA (Telomeric Repeat containing RNA). The genomic instability caused in Immune-mediated inflammatory diseases (IMID) especially in patients with psoriasis, which lead to short telomeres in psoriasis lesions, is a mechanism leading to cell aging. Research on the fraction of TERRA in hybrid with DNA offers avenues for new strategies. Skin samples were fractionated to obtain the RNA associated with DNA as a R-loop structure. TERRA analysis was performed by RT-qPCR and RNA-seq analysis. The higher amount of TERRA levels attached with each chromosome end was found with psoriasis patients. The increased levels of TERRA linked with telomeres correlate with the decrease in the RNase-HII transcript which means the unresolved DNA/RNA hybrids may ultimately facilitate the formation of skin lesions. LncRNAs have multiple molecular functions, including the regulation of heterochromatin, which controls genome stability and epigenome shaping and may be used as a trans-generational prognostic marker in patients with psoriasis. The signal of the lncRNAs is higher as DNA/RNAs hybrid (R-Loop) in patients with psoriasis in lesional tissues and above all, already in non-lesional tissues; -lncRNAs such as TERRA are found at higher levels at the end of each chromosome in patients with psoriasis, resulting in telomeres shortening; - and more importantly the idea that higher levels of lncRNAs attached to the genome lead to phenotypic changes

2022-03-30 | GSE188763 | GEO

Functional characterization of the TERRA transcriptome at damaged telomeres

2014-10-31 | GSE56727 | GEO

TERRA RNA antagonizes ATRX and protects telomeres

Project description:Through an integration of genomic and proteomic approaches to advance understanding of long noncoding RNAs, we investigate the function of the telomeric transcript, TERRA. By identifying thousands of TERRA target sites in the mouse genome, we demonstrate that TERRA can bind both in cis to telomeres and in trans to genic targets. We then define a large network of interacting proteins, including epigenetic factors, telomeric proteins, and the RNA helicase, ATRX. TERRA and ATRX share hundreds of target genes and are functionally antagonistic at these loci: whereas TERRA activates, ATRX represses gene expression. At telomeres, TERRA competes with telomeric DNA for ATRX binding, suppresses ATRX localization, and ensures telomeric stability. Depleting TERRA increases telomerase activity and induces telomeric pathologies, including formation of telomere-induced DNA damage foci and loss or duplication of telomeric sequences. We conclude that TERRA functions as an epigenomic modulator in trans and as an essential regulator of telomeres in cis.

2017-06-29 | GSE79180 | GEO

Expression data by telomere elongation in xenograft.

Project description:Telomere erosion causes cell mortality, suggesting that longer telomeres allow greater number of cell division. In telomerase-positive human cancer cells, however, telomeres are often kept shorter than the surrounding normal tissues. Recently, we have shown that telomere elongation in cancer cells represses innate immune genes and promotes their differentiation in vivo. This implies that short telomeres contribute to cancer malignancy, but it is unclear how such genetic repression is caused by long telomeres. Here we report that telomeric repeat-containing RNA (TERRA) induces genome-wide alteration of gene expression in telomere-elongated cancer cells in vivo. Using three different cell lines, we found that telomere elongation upregulates TERRA and downregulates innate immune genes in vivo xenograft tumors. Most of the suppressed genes belonged to innate immune system categories and were upregulated in various cancers. We propose that TERRA G4 counteracts cancer malignancy through suppression of innate immune genes. Four samples are telomere-elongated cells (PC3/LhTERTL, PC3/LhTERTL/cre, HBC4/hTERT and MKN74/hTERT), and the other four samples are control cell lines.

2015-02-05 | E-GEOD-56177 | biostudies-arrayexpress

Expression data by telomere elongation in xenograft.

2015-02-05 | GSE56177 | GEO

Expression data by G-quadruplex (G4) forming oligonucleotides transfection in 3D culture.

Project description:Telomere erosion causes cell mortality, suggesting that longer telomeres allow greater number of cell division. In telomerase-positive human cancer cells, however, telomeres are often kept shorter than the surrounding normal tissues. Recently, we have shown that telomere elongation in cancer cells represses innate immune genes and promotes their differentiation in vivo. This implies that short telomeres contribute to cancer malignancy, but it is unclear how such genetic repression is caused by long telomeres. Here we report that telomeric repeat-containing RNA (TERRA) induces genome-wide alteration of gene expression in telomere-elongated cancer cells in vivo. Using three different cell lines, we found that G4 forming oligonucleotide repressed innate immune genes in vivo 3D culture conditions. Most of the suppressed genes belonged to innate immune system categories and were upregulated in various cancers. We propose that TERRA G4 counteracts cancer malignancy through suppression of innate immune genes. Six samples are G4 oligo-transfected cells (PC-3/(uuaggg)^4, PC-3/AS1411, HBC4/(uuaggg)^4, HBC4/AS1411, MKN74/(uuaggg)^4 and MKN74/AS1411), and the other six samples are control oligo-transfected cells.

2015-02-05 | E-GEOD-56239 | biostudies-arrayexpress

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