scholarly journals NOL12 Repression Induces Nucleolar Stress-Driven Cellular Senescence and Is Associated with Normative Aging

2019 ◽  
Vol 39 (12) ◽  
Author(s):  
Marta Pinho ◽  
Joana C. Macedo ◽  
Elsa Logarinho ◽  
Paulo S. Pereira
Keyword(s):  
Stress Responses ◽  
Ribosome Biogenesis ◽  
Human Fibroblasts ◽  
Rrna Synthesis ◽  
Dependent Manner ◽  
Chronological Aging ◽  
Complex Processes ◽  
Nucleolar Stress ◽  
Primary Fibroblasts ◽  
Nucleolar Number

ABSTRACT The nucleolus is a subnuclear compartment with key roles in rRNA synthesis and ribosome biogenesis, complex processes that require hundreds of proteins and factors. Alterations in nucleolar morphology and protein content have been linked to the control of cell proliferation and stress responses and, recently, further implicated in cell senescence and ageing. In this study, we report the functional role of NOL12 in the nucleolar homeostasis of human primary fibroblasts. NOL12 repression induces specific changes in nucleolar morphology, with increased nucleolar area but reduced nucleolar number, along with nucleolar accumulation and increased levels of fibrillarin and nucleolin. Moreover, NOL12 repression leads to stabilization and activation of p53 in an RPL11-dependent manner, which arrests cells at G2 phase and ultimately leads to senescence. Importantly, we found NOL12 repression in association with nucleolar stress-like responses in human fibroblasts from elderly donors, disclosing it as a biomarker in human chronological aging.

scholarly journals Senescence induction in human fibroblasts and hematopoietic progenitors by leukemogenic fusion proteins

Blood ◽  
2010 ◽  
Vol 115 (24) ◽  
pp. 5057-5060 ◽  
Author(s):  
Narendra Wajapeyee ◽  
Shu-Zong Wang ◽  
Ryan W. Serra ◽  
Peter D. Solomon ◽  
Arvindhan Nagarajan ◽  
...  
Keyword(s):  
Fusion Proteins ◽  
Mapk Pathway ◽  
Human Fibroblasts ◽  
Hematologic Malignancies ◽  
Dependent Manner ◽  
Epigenetic Alterations ◽  
Hematopoietic Progenitors ◽  
Damage Response ◽  
Primary Fibroblasts ◽  
Senescence Program

Abstract Hematologic malignancies are typically associated with leukemogenic fusion proteins, which are required to maintain the oncogenic state. Previous studies have shown that certain oncogenes that promote solid tumors, such as RAS and BRAF, can induce senescence in primary cells, which is thought to provide a barrier to tumorigenesis. In these cases, the activated oncogene elicits a DNA damage response (DDR), which is essential for the senescence program. Here we show that 3 leukemogenic fusion proteins, BCR-ABL, CBFB-MYH11, and RUNX1-ETO, can induce senescence in primary fibroblasts and hematopoietic progenitors. Unexpectedly, we find that senescence induction by BCR-ABL and CBFB-MYH11 occurs through a DDR-independent pathway, whereas RUNX1-ETO induces senescence in a DDR-dependent manner. All 3 fusion proteins activate the p38 MAPK pathway, which is required for senescence induction. Our results reveal diverse pathways for oncogene-induced senescence and further suggest that leukemias harbor genetic or epigenetic alterations that inactivate senescence induction genes.

scholarly journals Pol I Transcription and Pre-rRNA Processing Are Coordinated in a Transcription-dependent Manner in Mammalian Cells

2007 ◽  
Vol 18 (2) ◽  
pp. 394-403 ◽  
Author(s):  
K. Kopp ◽  
J. Z. Gasiorowski ◽  
D. Chen ◽  
R. Gilmore ◽  
J. T. Norton ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Ribosome Biogenesis ◽  
Rrna Synthesis ◽  
Dependent Manner ◽  
Rrna Processing ◽  
Rdna Transcription ◽  
Pol I ◽  
Active Transcription ◽  
Key Steps ◽  
Processing Factors

Pre-rRNA synthesis and processing are key steps in ribosome biogenesis. Although recent evidence in yeast suggests that these two processes are coupled, the nature of their association is unclear. In this report, we analyze the coordination between rDNA transcription and pre-rRNA processing in mammalian cells. We found that pol I transcription factor UBF interacts with pre-rRNA processing factors as analyzed by immunoprecipitations, and the association depends on active rRNA synthesis. In addition, injections of plasmids containing the human rDNA promoter and varying lengths of 18S rDNA into HeLa nuclei show that pol I transcription machinery can be recruited to rDNA promoters regardless of the product that is transcribed, whereas subgroups of pre-rRNA processing factors are recruited to plasmids only when specific pre-rRNA fragments are produced. Our observations suggest a model for sequential recruitment of pol I transcription factors and pre-rRNA processing factors to elongating pre-rRNA on an as-needed basis rather than corecruitment to sites of active transcription.

scholarly journals Fanconi anemia A protein participates in nucleolar homeostasis maintenance and ribosome biogenesis

2021 ◽  
Vol 7 (1) ◽  
pp. eabb5414
Author(s):  
Anna Gueiderikh ◽  
Frédérique Maczkowiak-Chartois ◽  
Guillaume Rouvet ◽  
Sylvie Souquère-Besse ◽  
Sébastien Apcher ◽  
...  
Keyword(s):  
Dna Damage ◽  
Fanconi Anemia ◽  
Stress Responses ◽  
Ribosome Biogenesis ◽  
Bone Marrow Failure ◽  
Loss Of Function ◽  
Independent Manner ◽  
Ribosomal Subunits ◽  
Nucleolar Proteins ◽  
Nucleolar Stress

Fanconi anemia (FA), the most common inherited bone marrow failure and leukemia predisposition syndrome, is generally attributed to alterations in DNA damage responses due to the loss of function of the DNA repair and replication rescue activities of the FANC pathway. Here, we report that FANCA deficiency, whose inactivation has been identified in two-thirds of FA patients, is associated with nucleolar homeostasis loss, mislocalization of key nucleolar proteins, including nucleolin (NCL) and nucleophosmin 1 (NPM1), as well as alterations in ribosome biogenesis and protein synthesis. FANCA coimmunoprecipitates with NCL and NPM1 in a FANCcore complex–independent manner and, unique among the FANCcore complex proteins, associates with ribosomal subunits, influencing the stoichiometry of the translational machineries. In conclusion, we have identified unexpected nucleolar and translational consequences specifically associated with FANCA deficiency that appears to be involved in both DNA damage and nucleolar stress responses, challenging current hypothesis on FA physiopathology.

scholarly journals SMN protein promotes membrane compartmentalization of ribosomal protein S6 transcript in human fibroblasts

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Francesca Gabanella ◽  
Annalisa Onori ◽  
Massimo Ralli ◽  
Antonio Greco ◽  
Claudio Passananti ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Ribosome Biogenesis ◽  
Potential Role ◽  
Muscular Atrophy ◽  
Human Fibroblasts ◽  
Membrane Dynamics ◽  
Translation Efficiency ◽  
Dependent Manner ◽  
Smn Protein

Abstract Alterations of RNA homeostasis can lead to severe pathological conditions. The Survival of Motor Neuron (SMN) protein, which is reduced in Spinal Muscular Atrophy, impacts critical aspects of the RNA life cycle, such as splicing, trafficking, and translation. Increasing evidence points to a potential role of SMN in ribosome biogenesis. Our previous study revealed that SMN promotes membrane-bound ribosomal proteins (RPs), sustaining activity-dependent local translation. Here, we suggest that plasma membrane domains could be a docking site not only for RPs but also for their encoding transcripts. We have shown that SMN knockdown perturbs subcellular localization as well as translation efficiency of RPS6 mRNA. We have also shown that plasma membrane-enriched fractions from human fibroblasts retain RPS6 transcripts in an SMN-dependent manner. Furthermore, we revealed that SMN traffics with RPS6 mRNA promoting its association with caveolin-1, a key component of membrane dynamics. Overall, these findings further support the SMN-mediated crosstalk between plasma membrane dynamics and translation machinery. Importantly, our study points to a potential role of SMN in the ribosome assembly pathway by selective RPs synthesis/localization in both space and time.

scholarly journals Role of uL3 in the Crosstalk between Nucleolar Stress and Autophagy in Colon Cancer Cells

2020 ◽  
Vol 21 (6) ◽  
pp. 2143 ◽  
Author(s):  
Annalisa Pecoraro ◽  
Pietro Carotenuto ◽  
Brunella Franco ◽  
Rossella De Cegli ◽  
Giulia Russo ◽  
...  
Keyword(s):  
Colon Cancer ◽  
Cancer Cells ◽  
Ribosome Biogenesis ◽  
Chemotherapeutic Agents ◽  
Rrna Synthesis ◽  
Autophagic Flux ◽  
Colon Cancer Cells ◽  
Nucleolar Stress ◽  
Autophagic Process

The nucleolus is the site of ribosome biogenesis and has been recently described as important sensor for a variety of cellular stressors. In the last two decades, it has been largely demonstrated that many chemotherapeutics act by inhibiting early or late rRNA processing steps with consequent alteration of ribosome biogenesis and activation of nucleolar stress response. The overall result is cell cycle arrest and/or apoptotic cell death of cancer cells. Our previously data demonstrated that ribosomal protein uL3 is a key sensor of nucleolar stress activated by common chemotherapeutic agents in cancer cells lacking p53. We have also demonstrated that uL3 status is associated to chemoresistance; down-regulation of uL3 makes some chemotherapeutic drugs ineffective. Here, we demonstrate that in colon cancer cells, the uL3 status affects rRNA synthesis and processing with consequent activation of uL3-mediated nucleolar stress pathway. Transcriptome analysis of HCT 116p53−/− cells expressing uL3 and of a cell sub line stably depleted of uL3 treated with Actinomycin D suggests a new extra-ribosomal role of uL3 in the regulation of autophagic process. By using confocal microscopy and Western blotting experiments, we demonstrated that uL3 acts as inhibitory factor of autophagic process; the absence of uL3 is associated to increase of autophagic flux and to chemoresistance. Furthermore, experiments conducted in presence of chloroquine, a known inhibitor of autophagy, indicate a role of uL3 in chloroquine-mediated inhibition of autophagy. On the basis of these results and our previous findings, we hypothesize that the absence of uL3 in cancer cells might inhibit cancer cell response to drug treatment through the activation of cytoprotective autophagy. The restoration of uL3 could enhance the activity of many drugs thanks to its pro-apoptotic and anti-autophagic activity.

scholarly journals p53 induces a survival transcriptional response after nucleolar stress.

2021 ◽  
pp. mbc.E21-05-0251
Author(s):  
Han Liao ◽  
Anushri Gaur ◽  
Claire Mauvais ◽  
Catherine Denicourt
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Arrest ◽  
Ribosome Biogenesis ◽  
Rrna Synthesis ◽  
Transcriptional Program ◽  
Induce Cell Cycle Arrest ◽  
Cycle Arrest ◽  
Pol I ◽  
Nucleolar Stress ◽  
Metabolic Remodeling

Accumulating evidence indicate that increased ribosome biogenesis is a hallmark of cancer. It is well established that inhibition of any steps of ribosome biogenesis induces a nucleolar stress characterized by p53 activation and subsequent cell cycle arrest and/or cell death. However, cells derived from solid tumors have demonstrated different degree of sensitivity to ribosome biogenesis inhibition, where cytostatic effects rather than apoptosis are observed. The reason for this is not clear and the p53-specific transcriptional program induced after nucleolar stress has not been previously investigated. Here we demonstrate that blocking rRNA synthesis by depletion of essential rRNA processing factors such as LAS1L, PELP1, and NOP2 or by inhibition of RNA Pol I with the specific small molecule inhibitor CX-5461, mainly induce cell cycle arrest accompanied with autophagy in solid tumor-derived cell lines. Using gene expression analysis, we find that p53 orchestrates a transcriptional program involved in promoting metabolic remodeling and autophagy to help cells survive under nucleolar stress. Importantly, our study demonstrates that blocking autophagy significantly sensitizes cancer cells to RNA Pol I inhibition by CX-5461, suggesting that interfering with autophagy should be considered a strategy to heighten the responsiveness of ribosome biogenesis-targeted therapies in p53-positive tumors.

scholarly journals Arginine Decarboxylase Is Essential for Pneumococcal Stress Responses

Pathogens ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 286
Author(s):  
Mary Frances Nakamya ◽  
Moses B. Ayoola ◽  
Leslie A. Shack ◽  
Mirghani Mohamed ◽  
Edwin Swiatlo ◽  
...  
Keyword(s):  
Stress Responses ◽  
Critical Role ◽  
Acid Stress ◽  
Arginine Decarboxylase ◽  
Arginine Deiminase ◽  
Dependent Manner ◽  
Cellular Processes ◽  
Opportunistic Human Pathogen ◽  
Thiol Peroxidase ◽  
The Impact

Polyamines such as putrescine, cadaverine, and spermidine are small cationic molecules that play significant roles in cellular processes, including bacterial stress responses and host–pathogen interactions. Streptococcus pneumoniae is an opportunistic human pathogen, which causes several diseases that account for significant morbidity and mortality worldwide. As it transits through different host niches, S. pneumoniae is exposed to and must adapt to different types of stress in the host microenvironment. We earlier reported that S. pneumoniae TIGR4, which harbors an isogenic deletion of an arginine decarboxylase (ΔspeA), an enzyme that catalyzes the synthesis of agmatine in the polyamine synthesis pathway, has a reduced capsule. Here, we report the impact of arginine decarboxylase deletion on pneumococcal stress responses. Our results show that ΔspeA is more susceptible to oxidative, nitrosative, and acid stress compared to the wild-type strain. Gene expression analysis by qRT-PCR indicates that thiol peroxidase, a scavenger of reactive oxygen species and aguA from the arginine deiminase system, could be important for peroxide stress responses in a polyamine-dependent manner. Our results also show that speA is essential for endogenous hydrogen peroxide and glutathione production in S. pneumoniae. Taken together, our findings demonstrate the critical role of arginine decarboxylase in pneumococcal stress responses that could impact adaptation and survival in the host.

scholarly journals Dendritic Fibroblasts in Three-dimensional Collagen Matrices

2003 ◽  
Vol 14 (2) ◽  
pp. 384-395 ◽  
Author(s):  
Frederick Grinnell ◽  
Chin-Han Ho ◽  
Elisa Tamariz ◽  
David J. Lee ◽  
Gabriella Skuta
Keyword(s):  
Dimensional Space ◽  
Human Fibroblasts ◽  
Three Dimensional ◽  
Rho Kinase ◽  
Matrix Remodeling ◽  
Dependent Manner ◽  
Collagen Matrices ◽  
Form And Function ◽  
Metabolic Coupling ◽  
Dendritic Network

Cell motility determines form and function of multicellular organisms. Most studies on fibroblast motility have been carried out using cells on the surfaces of culture dishes. In situ, however, the environment for fibroblasts is the three-dimensional extracellular matrix. In the current research, we studied the morphology and motility of human fibroblasts embedded in floating collagen matrices at a cell density below that required for global matrix remodeling (i.e., contraction). Under these conditions, cells were observed to project and retract a dendritic network of extensions. These extensions contained microtubule cores with actin concentrated at the tips resembling growth cones. Platelet-derived growth factor promoted formation of the network; lysophosphatidic acid stimulated its retraction in a Rho and Rho kinase-dependent manner. The dendritic network also supported metabolic coupling between cells. We suggest that the dendritic network provides a mechanism by which fibroblasts explore and become interconnected to each other in three-dimensional space.

scholarly journals Repurposing cabozantinib with therapeutic potential in KIT-driven t(8;21) acute myeloid leukaemias

2021 ◽  
Author(s):  
Kuan-Wei Su ◽  
Da-Liang Ou ◽  
Yu-Hsuan Fu ◽  
Hwei-Fang Tien ◽  
Hsin-An Hou ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Ribosome Biogenesis ◽  
Kinase Inhibitor ◽  
Therapeutic Potential ◽  
Xenograft Model ◽  
Sequencing Analysis ◽  
Dependent Manner ◽  
Leukocyte Activation ◽  
Mouse Xenograft Model ◽  
Acute Myeloid

AbstractCabozantinib is an orally available, multi-target tyrosine kinase inhibitor approved for the treatment of several solid tumours and known to inhibit KIT tyrosine kinase. In acute myeloid leukaemia (AML), aberrant KIT tyrosine kinase often coexists with t(8;21) to drive leukaemogenesis. Here we evaluated the potential therapeutic effect of cabozantinib on a selected AML subtype characterised by t(8;21) coupled with KIT mutation. Cabozantinib exerted substantial cytotoxicity in Kasumi-1 cells with an IC50 of 88.06 ± 4.32 nM, which was well within clinically achievable plasma levels. The suppression of KIT phosphorylation and its downstream signals, including AKT/mTOR, STAT3, and ERK1/2, was elicited by cabozantinib treatment and associated with subsequent alterations of cell cycle- and apoptosis-related molecules. Cabozantinib also disrupted the synthesis of an AML1-ETO fusion protein in a dose- and time-dependent manner. In a mouse xenograft model, cabozantinib suppressed tumourigenesis at 10 mg/kg and significantly prolonged survival of the mice. Further RNA-sequencing analysis revealed that mTOR-mediated signalling pathways were substantially inactivated by cabozantinib treatment, causing the downregulation of ribosome biogenesis and glycolysis, along with myeloid leukocyte activation. We suggest that cabozantinib may be effective in the treatment of AML with t(8;21) and KIT mutation. Relevant clinical trials are warranted.

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