Suchergebnisse

Rho guanine exchange factors (GEFs), the enzymes that stimulate Rho GTPases, are deemed as potential therapeutic targets owing to their protumorigenic functions. However, the understanding of the spectrum of their pathobiological roles in tumors is still very limited. We report here that the GEF Vav1 unexpectedly possesses tumor-suppressor functions in immature T cells. This function entails the noncatalytic nucleation of complexes between the ubiquitin ligase Cbl-b and the intracellular domain of Notch1 (ICN1) that favors ICN1 ubiquitinylation and degradation. Ablation of Vav1 promotes ICN1 signaling and the development of T cell acute lymphoblastic leukemia (T-ALL). The downregulation of Vav1 is essential for the pathogenesis of human T-ALL of the TLX+ clinical subtype, further underscoring the suppressor role of this pathway ; X.R.B. is supported by grants from the Castilla-León Government (BIO/SA01/15, CSI049U16), Spanish Ministry of Economy and Competitiveness (MINECO) (SAF2015-64556-R, RD12/0036/0002), Worldwide Cancer Research (14-1248), Ramón Areces Foundation, and Spanish Society Against Cancer. L.E. (PI13/00448), A.B. (SAF2013-40922-R, RD12/0036/0054), and M.L.T. (SAF2013-44857-R, RD12/0036/0075) are supported by MINECO grants. Spanish funding is partially supported by the European Regional Development Fund. We thank M. Blázquez for laboratory work, R. Valiente for ChIP-seq analyses, M. Dosil for comments on the manuscript, and CIC facilities' personnel for technical assistance

Genetic data indicate that abrogation of Notch-Rbpj or Wnt-β-catenin pathways results in the loss of the intestinal stem cells (ISCs). However, whether the effect of Notch is direct or due to the aberrant differentiation of the transit-amplifying cells into post-mitotic goblet cells is unknown. To address this issue, we have generated composite tamoxifen-inducible intestine-specific genetic mouse models and analyzed the expression of intestinal differentiation markers. Importantly, we found that activation of β-catenin partially rescues the differentiation phenotype of Rbpj deletion mutants, but not the loss of the ISC compartment. Moreover, we identified Bmi1, which is expressed in the ISC and progenitor compartments, as a gene that is co-regulated by Notch and β-catenin. Loss of Bmi1 resulted in reduced proliferation in the ISC compartment accompanied by p16(INK4a) and p19(ARF) (splice variants of Cdkn2a) accumulation, and increased differentiation to the post-mitotic goblet cell lineage that partially mimics Notch loss-of-function defects. Finally, we provide evidence that Bmi1 contributes to ISC self-renewal. ; This work has been supported by the Instituto de Salud Carlos III [PI10/01128], Ministerio de Ciencia e Innovación [ACI2009-0918], Agència de Gestió d'Ajuts Universitaris i de Recerca-Convocatòria Estratègica-2010-0006 and Red Temática de Investigación Cooperativa en Cáncer [RD06/0020/0098, RD12/0036/0054]. The Mar Institute of Medical Research (IMIM) Foundation financed V.R., and she is a recipient of a European Molecular Biology Organization (EMBO) short-term fellowship [ASTF 20-2010]. E.L.-A. is funded by 'Fundación la Caixa' (2010) and the Department of Education, Universities and Research of the Basque Government [BFI-2011]. L.L.E. is an investigator of the Spanish National Health System (SNS) [CES08/006]

Phosphorylated IKKalpha(p45) is a nuclear active form of the IKKalpha kinase that is induced by the MAP kinases BRAF and TAK1 and promotes tumor growth independent of canonical NF-¿B signaling. Insights into the sources of IKKalpha(p45) activation and its downstream substrates in the nucleus remain to be defined. Here, we discover that IKKalpha(p45) is rapidly activated by DNA damage independent of ATM-ATR, but dependent on BRAF-TAK1-p38-MAPK, and is required for robust ATM activation and efficient DNA repair. Abolishing BRAF or IKKalpha activity attenuates ATM, Chk1, MDC1, Kap1, and 53BP1 phosphorylation, compromises 53BP1 and RIF1 co-recruitment to sites of DNA lesions, and inhibits 53BP1-dependent fusion of dysfunctional telomeres. Furthermore, IKKalpha or BRAF inhibition synergistically enhances the therapeutic potential of 5-FU and irinotecan to eradicate chemotherapy-resistant metastatic human tumors in vivo. Our results implicate BRAF and IKKalpha kinases in the DDR and reveal a combination strategy for cancer treatment. ; This work was funded by grants from Instituto de Salud Carlos III FEDER (PIE15/00008 and PI16/00437), Generalitat de Catalunya 2017SGR135, and the "Xarxa de Bancs de Tumors" sponsored by Pla Director d'Oncologia de Catalunya (XBTC). C.C. is supported by FPI BES-2014-068451 and the EMBO Short-Term Fellowship (na7084). P.M. is supported by funding from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement #702430. The Boulton lab is supported by The Francis Crick Institute, which receives its core funding from Cancer Research UK (FC0010048), the UK Medical Research Council (FC0010048), and the Wellcome Trust (FC0010048). S.J.B. is funded by European Research Council (ERC) Advanced Investigator Grants (TelMetab) and a Wellcome Trust Senior Investigator Grant. The Centre de Regulació Genòmica/Universitat Pompeu Fabra Proteomics Unit is part of the "Plataforma de Recursos Biomoleculares y Bioinformáticos (ProteoRed)" supported by grant PT13/0001 of Instituto de Salud Carlos III from the Spanish government and "Secretaria d'Universitats i Recerca del Departament d'Economia i Coneixement de la Generalitat de Catalunya" (2014SGR678). We acknowledge support from the Spanish Ministry of Economy and Competitiveness and "Centro de Excelencia Severo Ochoa 2013-2017" (SEV-2012-0208).

Sirtuins are NAD+-dependent deacetylases that facilitate cellular stress response. They include SirT6, which protects genome stability and regulates metabolic homeostasis through gene silencing, and whose loss induces an accelerated aging phenotype directly linked to hyperactivation of the NF-κB pathway. Here we show that SirT6 binds to the H3K9me3-specific histone methyltransferase Suv39h1 and induces monoubiquitination of conserved cysteines in the PRE-SET domain of Suv39h1. Following activation of NF-κB signaling Suv39h1 is released from the IκBα locus, subsequently repressing the NF-κB pathway. We propose that SirT6 attenuates the NF-κB pathway through IκBα upregulation via cysteine monoubiquitination and chromatin eviction of Suv39h1. We suggest a mechanism based on SirT6-mediated enhancement of a negative feedback loop that restricts the NF-κB pathway. ; This work was supported by the Fundació La Marató de TV3 (20133810 to A.V.), the Spanish Ministry of Economy and competitiveness-MINECO (SAF2011-25860, SAF2014-55964R to A.V.) confunded by FEDER funds/European Regional Development Fund (ERDF)-a way to Build Europe, and the Catalan government agency AGAUR (2009-SGR-914 to A.V.) The IDIBELL Proteomics Unit belongs to ProteoRed, PRB2-ISCIII, and is supported by grant PT13/0001/0033 and Cellex Foundation. S.B.B. is the recipient of a 13FIS037 fellowship.