SURF2 is a MDM2 antagonist in triggering the nucleolar stress response
Ontology highlight
ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE267134 | GEO | 2024/09/10
REPOSITORIES: GEO
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Project description:Cancer cells are addicted to strong ribosome production to sustain their proliferation rate. Many chemotherapies impede ribosome production which is perceived by cells as "nucleolar stress" (NS), triggering TP53-dependent and independent response pathways leading to cell cycle arrest and/or apoptosis. The 5S RNP particle, a sub-ribosomal particle, is instrumental to NS response. Upon ribosome assembly defects, the 5S RNP accumulate as free form. This free form is able to sequester and inhibit MDM2, thus promoting TP53 stabilization. To investigate how cancer cells could resist to NS, we purified free-5S RNP and uncovered a new partner, SURF2. Functional characterization of this protein shows that SURF2 depletion increases cells sensitivity to NS, while its overexpression promotes their resistance to it. Consistently, SURF2 expression level negatively correlates with the overall survival in some cancers. Our data demonstrate that SURF2 can buffer free-5S RNP particles, and modulate their activity. SURF2 appears as a new regulator of NS response and a key player in both ribosomopathies and oncogenic mechanisms.
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Project description:In eukaryotes, three of the four ribosomal RNAs (rRNAs), the 5.8S, 18S and 25S/28S rRNAs, are processed from a single pre-rRNA transcript and assembled into ribosomes. The fourth rRNA, the 5S rRNA, is transcribed by RNA polymerase III and is assembled into the 5S ribonucleoprotein particle (5S RNP), containing ribosomal proteins Rpl5/uL18 and Rpl11/uL5, prior to its incorporation into pre-ribosomes. In mammals the 5S RNP is also central regulator of the homeostasis of the tumour suppressor p53. The nucleolar localisation of the 5S RNP and its assembly into pre-ribosomes is performed by a specialised complex composed of Rpf2 and Rrs1 in yeast or Bxdc1 and hRrs1 in humans. Here we report the structural and functional characterisation of the Rpf2-Rrs1 complex alone, in complex with the 5S RNA and within pre-60S ribosomes. We show that the Rpf2-Rrs1 complex contains a specialised 5S RNA E loop binding module, contacts the Rpl5 protein and also contacts the ribosome assembly factor Rsa4 and the 25S RNA. We propose that the Rpf2-Rrs1 complex establishes a network of interactions that guide the incorporation of the 5S RNP in pre-ribosomes in the initial conformation prior to its rotation to form the central protuberance found in the mature large ribosomal subunit.
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Project description:The 5S RNP is assembled from its three components (5S rRNA, Rpl5/uL18, and Rpl11/uL5) before being incorporated into the pre-60S subunit. However, when ribosome synthesis is disturbed, a free 5S RNP can enter the MDM2–p53 pathway to regulate cell cycle and apoptotic signaling. Here we reconstitute and determine the cryo-EM structure of the conserved hexameric 5S RNP with fungal or human factors. This reveals how the nascent 5S rRNA associates with the initial nuclear import complex Syo1–uL18–uL5, and upon further recruitment of two nucleolar factors Rpf2–Rrs1 develops into the 5S RNP precursor that can assemble into the pre-ribosome. In addition, we elucidate the structure of another 5S RNP intermediate, carrying the human ubiquitin ligase Mdm2, which unraveled how this enzyme can be sequestered from its target substrate p53. Our data provide molecular insight into how the 5S RNP can mediate between ribosome biogenesis and cell proliferation.
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Project description:Nucleolar stress (NS) kills cells by p53-dependent and independent manners. To investigate the mechanisms of p53-indendendent toxicity, we here used (PR)n arginine-rich peptides as inducers of NS, which are found in patients of some neurodegenerative diseases. Although these peptides generate NS, how this translates to toxicity is poorly understood. We here reveal that whereas (PR)n expression leads to an overall decrease in protein abundance for the majority of the proteome, this occurs concomitant to an accumulation of free ribosomal proteins in the cytoplasm, which is a hallmark of ribosomopathies. Conversely, cells with acquired resistance to (PR)n peptides present a global downregulation of ribosomal proteins and low levels of mTOR signaling. In mice, systemic expression of (PR)97 drives widespread NS and accelerated ageing, associated to an increased expression of ribosomal proteins and mTOR hyperactivation. Furthermore, the progeroid phenotype of (PR)97-expressing mice is alleviated by rapamycin. Importantly, we show that the generalized accumulation of free ribosomal proteins is not restricted to (PR)n peptides, but is a common outcome in response to chemical or genetic perturbations that generate NS such as Actinomycin D, TIF-IA depletion or the expression or mutant HMGB1 forms recently associated to rare human diseases. Together, our study provides in vivo evidence for the role of NS as a driver of ageing in mammals, and describes a general model to understand the mechanisms behind p53-independent cell toxicity caused by NS.
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Project description:Nucleolar stress (NS) kills cells by p53-dependent and independent manners. To investigate the mechanisms of p53-indendendent toxicity, we here used (PR)n arginine-rich peptides as inducers of NS, which are found in patients of some neurodegenerative diseases. Although these peptides generate NS, how this translates to toxicity is poorly understood. We here reveal that whereas (PR)n expression leads to an overall decrease in protein abundance for the majority of the proteome, this occurs concomitant to an accumulation of free ribosomal proteins in the cytoplasm, which is a hallmark of ribosomopathies. Conversely, cells with acquired resistance to (PR)n peptides present a global downregulation of ribosomal proteins and low levels of mTOR signaling. In mice, systemic expression of (PR)97 drives widespread NS and accelerated ageing, associated to an increased expression of ribosomal proteins and mTOR hyperactivation. Furthermore, the progeroid phenotype of (PR)97-expressing mice is alleviated by rapamycin. Importantly, we show that the generalized accumulation of free ribosomal proteins is not restricted to (PR)n peptides, but is a common outcome in response to chemical or genetic perturbations that generate NS such as Actinomycin D, TIF-IA depletion or the expression or mutant HMGB1 forms recently associated to rare human diseases. Together, our study provides in vivo evidence for the role of NS as a driver of ageing in mammals, and describes a general model to understand the mechanisms behind p53-independent cell toxicity caused by NS.
2024-03-08 | PXD046380 | Pride
Project description:Nucleolar stress (NS) kills cells by p53-dependent and independent manners. To investigate the mechanisms of p53-indendendent toxicity, we here used (PR)n arginine-rich peptides as inducers of NS, which are found in patients of some neurodegenerative diseases. Although these peptides generate NS, how this translates to toxicity is poorly understood. We here reveal that whereas (PR)n expression leads to an overall decrease in protein abundance for the majority of the proteome, this occurs concomitant to an accumulation of free ribosomal proteins in the cytoplasm, which is a hallmark of ribosomopathies. Conversely, cells with acquired resistance to (PR)n peptides present a global downregulation of ribosomal proteins and low levels of mTOR signaling. In mice, systemic expression of (PR)97 drives widespread NS and accelerated ageing, associated to an increased expression of ribosomal proteins and mTOR hyperactivation. Furthermore, the progeroid phenotype of (PR)97-expressing mice is alleviated by rapamycin. Importantly, we show that the generalized accumulation of free ribosomal proteins is not restricted to (PR)n peptides, but is a common outcome in response to chemical or genetic perturbations that generate NS such as Actinomycin D, TIF-IA depletion or the expression or mutant HMGB1 forms recently associated to rare human diseases. Together, our study provides in vivo evidence for the role of NS as a driver of ageing in mammals, and describes a general model to understand the mechanisms behind p53-independent cell toxicity caused by NS.
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Project description:The 120-nt long 5S rRNA, is an indispensable component of cytoplasmic ribosomes in all living organisms. The functions of 5S rRNA and the reasons for its evolutionary preservation as an independent molecule remain unclear. Here we used ribosome engineering to investigate whether maintaining 5S rRNA as an independent molecule is critical for ribosome function and cell survival. By fusing circularly permutated 5S rRNA (cp5S) with 23S rRNA and deleting all wild type 5S rRNA genes, we generated an Escherichia coli strain completely devoid of free 5S rRNA. Viability of the engineered cells demonstrates that autonomous 5S rRNA is not required for cell growth at 37°C and is unlikely to have essential functions outside the ribosome. The fully-assembled ribosomes carrying 23S-cp5S hybrid rRNA and lacking free 5S rRNA are highly active in translation. However, the engineered cells accumulate aberrant 50S subunits that are unable to form stable 70S ribosomes. Cryo-EM analysis revealed a dramatically malformed peptidyl transferase center in the misassembled 50S subunits. The results of our experiments argue that the key evolutionary force preserving the autonomous nature of the smallest rRNA is its role in ribosome biogenesis.
2020-06-18 | PXD019058 | Pride
Project description:The role of ribosome biogenesis in erythroid development is supported by the recognition of erythroid defects in ribosomopathies in both Diamond-Blackfan anemia and 5q- syndrome. Whether ribosome biogenesis exerts a regulatory function on normal erythroid development is still unknown. In the present study, a detailed characterization of ribosome biogenesis dynamics during human and murine erythropoiesis shows that ribosome biogenesis is abruptly interrupted by the drop of rDNA transcription and the collapse of ribosomal protein neo-synthesis. Its premature arrest by RNA polI inhibitor, CX-5461 targets the proliferation of immature erythroblasts. We also show that p53 is activated spontaneously or in response to CX-5461 concomitantly to ribosome biogenesis arrest, and drives a transcriptional program in which genes involved in cell cycle arrest, negative regulation of apoptosis and DNA damage response were upregulated. RNA polI transcriptional stress results in nucleolar disruption and activation of ATR-CHK1-p53 pathway. Our results imply that the timing of ribosome biogenesis extinction and p53 activation are crucial for erythroid development. In ribosomopathies in which ribosome availability is altered by unbalanced production of ribosomal proteins, the threshold of ribosome biogenesis down-regulation could be prematurely reached and together with pathological p53 activation prevents a normal expansion of erythroid progenitors.
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Project description:The role of ribosome biogenesis in erythroid development is supported by the recognition of erythroid defects in ribosomopathies in both Diamond-Blackfan anemia and 5q- syndrome. Whether ribosome biogenesis exerts a regulatory function on normal erythroid development is still unknown. In the present study, a detailed characterization of ribosome biogenesis dynamics during human and murine erythropoiesis shows that ribosome biogenesis is abruptly interrupted by the drop of rDNA transcription and the collapse of ribosomal protein neo-synthesis. Its premature arrest by RNA polI inhibitor, CX-5461 targets the proliferation of immature erythroblasts. We also show that p53 is activated spontaneously or in response to CX-5461 concomitantly to ribosome biogenesis arrest, and drives a transcriptional program in which genes involved in cell cycle arrest, negative regulation of apoptosis and DNA damage response were upregulated. RNA polI transcriptional stress results in nucleolar disruption and activation of ATR-CHK1-p53 pathway. Our results imply that the timing of ribosome biogenesis extinction and p53 activation are crucial for erythroid development. In ribosomopathies in which ribosome availability is altered by unbalanced production of ribosomal proteins, the threshold of ribosome biogenesis down-regulation could be prematurely reached and together with pathological p53 activation prevents a normal expansion of erythroid progenitors.
2020-09-14 | GSE157208 | GEO
Project description:In ribosomopathies, perturbed expression of ribosome components leads to tissue-specific phenotypes. What accounts for such tissue-selective manifestations as a result of mutations in the ribosome, a ubiquitous cellular machine, has remained a mystery. Combining mouse genetics and in vivo ribosome profiling, we observe limb patterning phenotypes in ribosomal protein (RP) haploinsufficient embryos and uncover selective translational changes of transcripts controlling limb development. Surprisingly, both loss of p53, which is activated by RP haploinsufficiency, and augmented protein synthesis rescue these phenotypes. These findings are explained by the identification that p53 functions as a master regulator of protein synthesis, at least in part, through transcriptional activation of 4E-BP1. 4E-BP1, a key translational regulator, in turn, facilitates selective changes in the translatome downstream of p53, and thereby explains how RP haploinsufficiency may elicit specificity to gene expression. These results provide an integrative model to understand how in vivo tissue-specific phenotypes emerge in ribosomopathies.
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