10 research outputs found

    Signaling networks and intrinsic mechanisms that regulate the production of ribosomes in transformed cells

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    [EN]Eukaryotic ribosomes contain four rRNAs and ~80 proteins that are assembled in two subunits of unequal sizes, the 40S and 60S subunits. The formation of the two subunits starts with the synthesis by RNA polymerase I of a pre-rRNA transcript, and is followed by the formation of the initial 40S and 60S pre-ribosomes. Those complexes then enter two separate multi-step maturation pathways that happen in the nucleolus, nucleoplasm and cytoplasm. The whole process of ribosome formation is assisted by more than 200 ribosome biogenesis factors (RBFs) that mediate the modification, folding and processing of rRNA precursors, and the incorporation of ribosomal proteins. Because ribosome synthesis is hyperactivated in many cancers there is much interest in understanding how transformed cells deregulate this process. One aspect to ascertain is which signaling pathways activate ribosome synthesis in different cell contexts. Another important aspect is to unveil all the events within the human ribosome synthesis pathway that are subject to regulation. This thesis addressed those two aspects in two separate projects. The first project focused on the study of a VAV2-mediated signaling pathway that activates ribosome production in human keratinocytes. We dissect the elements that participate in the pathway, identify the step of ribosome synthesis that is activated, and provide evidence of its deregulation and amenability to inhibition in squamous cell carcinoma. The second project was devoted to the characterization of a set of so-far undescribed intermediates of 40S subunit maturation in human cells. We define in which steps of the 40S pathway they intervene, identify a group of RBFs associated to them, and perform loss-of-function analyses to characterize their functions. Our results reveal a process that exhibits regulatory features and is required for proper production of 40S ribosomal subunits

    Functional specificity of the members of the Sos family of Ras-GEF Activators: Novel role of Sos2 in control of epidermal stem cell homeostasis

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    © 2021 by the authors.Prior reports showed the critical requirement of Sos1 for epithelial carcinogenesis, but the specific functionalities of the homologous Sos1 and Sos2 GEFs in skin homeostasis and tumorigenesis remain unclear. Here, we characterize specific mechanistic roles played by Sos1 or Sos2 in primary mouse keratinocytes (a prevalent skin cell lineage) under different experimental conditions. Functional analyses of actively growing primary keratinocytes of relevant genotypes—WT, Sos1-KO, Sos2-KO, and Sos1/2-DKO—revealed a prevalent role of Sos1 regarding transcriptional regulation and control of RAS activation and mechanistic overlapping of Sos1 and Sos2 regarding cell proliferation and survival, with dominant contribution of Sos1 to the RAS-ERK axis and Sos2 to the RAS-PI3K/AKT axis. Sos1/2-DKO keratinocytes could not grow under 3D culture conditions, but single Sos1-KO and Sos2-KO keratinocytes were able to form pseudoepidermis structures that showed disorganized layer structure, reduced proliferation, and increased apoptosis in comparison with WT 3D cultures. Remarkably, analysis of the skin of both newborn and adult Sos2-KO mice uncovered a significant reduction of the population of stem cells located in hair follicles. These data confirm that Sos1 and Sos2 play specific, cell-autonomous functions in primary keratinocytes and reveal a novel, essential role of Sos2 in control of epidermal stem cell homeostasis.The E.S. group was supported by grants from ISCIII-MCUI (FIS PI19/00934), JCyL (SA264P18-UIC 076), Areces Foundation (CIVP19A5942), Solorzano-Barruso Foundation (FS/32-2020), and by ISCIII-CIBERONC (group CB16/12/00352). Research was co-financed by FEDER funds. The J.M.P. lab is co-funded by European Regional Development Fund (FEDER) grants from Science and Innovation (SAF2015-66015-R and PID2019-110758RB-I00 to J.M.P.) and Instituto de Salud Carlos III (CIBERONC no. CB16/12/00228 to J.M.P.). The XRB lab is funded by “la Caixa” Banking Foundation (HR20-00164), the Castilla-León autonomous government (CSI252P18, CSI145P20, CLC-2017-01), the Spanish Ministry of Science and Innovation (MSI) (RTI2018-096481-B-100), and the Spanish Association against Cancer (GC16173472GARC). The CIC is supported by the Programa de Apoyo a Planes Estratégicos de Investigación de Estructuras de Investigación de Excelencia of the Castilla-León autonomous government (CLC-2017-01). L.F.L.-M. and N.F.-P. contracts have been supported by funding from the Spanish Ministry of Universities (FPU13/02923, FPU17/03912) and, in the case of L.F.L.M., by CLC-2017-01 grant

    Cover contact graphs

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    We study problems that arise in the context of covering certain geometric objects called seeds (e.g., points or disks) by a set of other geometric objects called cover (e.g., a set of disks or homothetic triangles). We insist that the interiors of the seeds and the cover elements are pairwise disjoint, respectively, but they can touch. We call the contact graph of a cover a cover contact graph (CCG). We are interested in three types of tasks, both in the general case and in the special case of seeds on a line: (a) deciding whether a given seed set has a connected CCG, (b) deciding whether a given graph has a realization as a CCG on a given seed set, and (c) bounding the sizes of certain classes of CCG’s. Concerning (a) we give efficient algorithms for the case that seeds are points and show that the problem becomes hard if seeds and covers are disks. Concerning (b) we show that this problem is hard even for point seeds and disk covers (given a fixed correspondence between graph vertices and seeds). Concerning (c) we obtain upper and lower bounds on the number of CCG’s for point seeds

    Cover Contact Graphs

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    Es una ponencia presentada al 15th International Symposium on Graph Drawing (2007)We study problems that arise in the context of covering certain geometric objects (so-called seeds, e.g., points or disks) by a set of other geometric objects (a so-called cover, e.g., a set of disks or homothetic triangles). We insist that the interiors of the seeds and the cover elements are pairwise disjoint, but they can touch. We call the contact graph of a cover a cover contact graph (CCG). We are interested in two types of tasks: (a) deciding whether a given seed set has a connected CCG, and (b) deciding whether a given graph has a realization as a CCG on a given seed set. Concerning task (a) we give efficient algorithms for the case that seeds are points and covers are disks or triangles. We show that the problem becomes NP-hard if seeds and covers are disks. Concerning task (b) we show that it is even NP-hard for point seeds and disk covers (given a fixed correspondence between vertices and seeds).German Research Foundation WO 758/4-

    VAV2 signaling promotes regenerative proliferation in both cutaneous and head and neck squamous cell carcinoma

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    Regenerative proliferation capacity and poor differentiation are histological features usually linked to poor prognosis in head and neck squamous cell carcinoma (hnSCC). However, the pathways that regulate them remain ill-characterized. Here, we show that those traits can be triggered by the RHO GTPase activator VAV2 in keratinocytes present in the skin and oral mucosa. VAV2 is also required to maintain those traits in hnSCC patient-derived cells. This function, which is both catalysis- and RHO GTPase-dependent, is mediated by c-Myc- and YAP/TAZ-dependent transcriptomal programs associated with regenerative proliferation and cell undifferentiation, respectively. High levels of VAV2 transcripts and VAV2-regulated gene signatures are both associated with poor hnSCC patient prognosis. These results unveil a druggable pathway linked to the malignancy of specific SCC subtypes. The Rho signalling pathway is frequently activated in squamous carcinomas. Here, the authors find that the Rho GEF VAV2 is over expressed in both cutaneous and head and neck squamous cell carcinomas and that at the molecular level VAV2 promotes a pro-tumorigenic stem cell-like signalling programme

    VAV2 orchestrates the interplay between regenerative proliferation and ribogenesis in both keratinocytes and oral squamous cell carcinoma

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    Abstract VAV2 is an activator of RHO GTPases that promotes and maintains regenerative proliferation-like states in normal keratinocytes and oral squamous cell carcinoma (OSCC) cells. Here, we demonstrate that VAV2 also regulates ribosome biogenesis in those cells, a program associated with poor prognosis of human papilloma virus-negative (HPV−) OSCC patients. Mechanistically, VAV2 regulates this process in a catalysis-dependent manner using a conserved pathway comprising the RAC1 and RHOA GTPases, the PAK and ROCK family kinases, and the c-MYC and YAP/TAZ transcription factors. This pathway directly promotes RNA polymerase I activity and synthesis of 47S pre-rRNA precursors. This process is further consolidated by the upregulation of ribosome biogenesis factors and the acquisition of the YAP/TAZ-dependent undifferentiated cell state. Finally, we show that RNA polymerase I is a therapeutic Achilles’ heel for both keratinocytes and OSCC patient-derived cells endowed with high VAV2 catalytic activity. Collectively, these findings highlight the therapeutic potential of modulating VAV2 and the ribosome biogenesis pathways in both preneoplastic and late progression stages of OSCC

    The Rho guanosine nucleotide exchange factors Vav2 and Vav3 modulate epidermal stem cell function

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    It is known that Rho GTPases control different aspects of the biology of skin stem cells (SSCs). However, little information is available on the role of their upstream regulators under normal and tumorigenic conditions in this process. To address this issue, we have used here mouse models in which the activity of guanosine nucleotide exchange factors of the Vav subfamily has been manipulated using both gain- and loss-of-function strategies. These experiments indicate that Vav2 and Vav3 regulate the number, functional status, and responsiveness of hair follicle bulge stem cells. This is linked to gene expression programs related to the reinforcement of the identity and the quiescent state of normal SSCs. By contrast, in the case of cancer stem cells, they promote transcriptomal programs associated with the identity, activation state, and cytoskeletal remodeling. These results underscore the role of these Rho exchange factors in the regulation of normal and tumor epidermal stem cells.The X.R.B.’s project leading to these results has received funding from Worldwide Cancer Research (14-1248), the RTI2018-096481-B-100 grant cofunded by MCIN/AEI/10.13039/501100011033 and the European Research Development Fund “A way of making Europe” of the European Union, the Spanish Association against Cancer (GC16173472GARC), the Castilla-León autonomous government (CSI252P18, CSI145P20, CLC-2017-01), and “la Caixa” Banking Foundation (HR20-00164). X.R.B.’s institution is supported by the Programa de Apoyo a Planes Estratégicos de Investigación de Estructuras de Investigación de Excelencia of the Castilla-León autonomous government (CLC-2017-01) L.F.L.-M. contract has been mostly supported by funding from the Spanish Ministry of Education, Culture and Sports (FPU13/02923) and, subsequently, by the CLC-2017-01 grant. S.R.-F. contracts was supported by the grant BES-2013-063573 funded by both the MCIN/AEI/10.13039/501100011033 and the European Social Fund “Investing in your future” of the European Union. The funding from the Castilla-León governments has been also partially supported by the European Regional Development Fund

    Higher Fluid Balance Increases the Risk of Death from Sepsis: Results from a Large International Audit∗

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    Objectives: Excessive fluid therapy in patients with sepsis may be associated with risks that outweigh any benefit. We investigated the possible influence of early fluid balance on outcome in a large international database of ICU patients with sepsis. Design: Observational cohort study. Setting: Seven hundred and thirty ICUs in 84 countries. Patients: All adult patients admitted between May 8 and May 18, 2012, except admissions for routine postoperative surveillance. For this analysis, we included only the 1,808 patients with an admission diagnosis of sepsis. Patients were stratified according to quartiles of cumulative fluid balance 24 hours and 3 days after ICU admission. Measurements and Main Results: ICU and hospital mortality rates were 27.6% and 37.3%, respectively. The cumulative fluid balance increased from 1,217 mL (-90 to 2,783 mL) in the first 24 hours after ICU admission to 1,794 mL (-951 to 5,108 mL) on day 3 and decreased thereafter. The cumulative fluid intake was similar in survivors and nonsurvivors, but fluid balance was less positive in survivors because of higher fluid output in these patients. Fluid balances became negative after the third ICU day in survivors but remained positive in nonsurvivors. After adjustment for possible confounders in multivariable analysis, the 24-hour cumulative fluid balance was not associated with an increased hazard of 28-day in-hospital death. However, there was a stepwise increase in the hazard of death with higher quartiles of 3-day cumulative fluid balance in the whole population and after stratification according to the presence of septic shock. Conclusions: In this large cohort of patients with sepsis, higher cumulative fluid balance at day 3 but not in the first 24 hours after ICU admission was independently associated with an increase in the hazard of death
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