The APC/C cofactor Cdh1 prevents replicative stress and p53-dependent cell death in neural progenitors

The E3-ubiquitin ligase APC/C-Cdh1 is essential for endoreduplication but its relevance in the mammalian mitotic cell cycle is still unclear. Here we show that genetic ablation of Cdh1 in the developing nervous system results in hypoplastic brain and hydrocephalus. These defects correlate with enhanced levels of Cdh1 substrates and increased entry into the S phase in neural progenitors. However, cell division is prevented in the absence of Cdh1 due to hyperactivation of cyclin-dependent kinases, replicative stress, induction of p53, G2 arrest and apoptotic death of these progenitor cells. Concomitant ablation of p53 rescues apoptosis but not replicative stress, resulting in the presence of damaged neurons throughout the adult brain. These data indicate that the inactivation of Cdh1 in vivo results in replicative stress, cell cycle arrest and cell death, supporting recent therapeutic proposals aimed to inhibit the APC/C in tumours.M.E. was supported by the Spanish Ministry of Economy and Competitiveness (MINECO). This work was funded by grants from the Foundation Ramón Areces and MINECO SAF2012-38215 to M.M.). The Cell Division and Cancer Group of the CNIO are supported by the OncoCycle Programme (S2010/BMD-2470) from the Comunidad de Madrid, the OncoBIO Consolider-Ingenio 2010 Programme (MINECO, CSD2007-00017) and the European Union Seventh Framework Programme (MitoSys project; HEALTH-F5-2010-241548).Peer Reviewe

Targeting Mitotic Exit Leads to Tumor Regression In Vivo: Modulation by Cdk1, Mastl, and the PP2A/B55α,δ Phosphatase

SummaryTargeting mitotic exit has been recently proposed as a relevant therapeutic approach against cancer. By using genetically engineered mice, we show that the APC/C cofactor Cdc20 is essential for anaphase onset in vivo in embryonic or adult cells, including progenitor/stem cells. Ablation of Cdc20 results in efficient regression of aggressive tumors, whereas current mitotic drugs display limited effects. Yet, Cdc20 null cells can exit from mitosis upon inactivation of Cdk1 and the kinase Mastl (Greatwall). This mitotic exit depends on the activity of PP2A phosphatase complexes containing B55α or B55δ regulatory subunits. These data illustrate the relevance of critical players of mitotic exit in mammals and their implications in the balance between cell death and mitotic exit in tumor cells

Therapeutic relevance of the PP2A-B55 inhibitory kinase MASTL/Greatwall in breast cancer.

PP2A is a major tumor suppressor whose inactivation is frequently found in a wide spectrum of human tumors. In particular, deletion or epigenetic silencing of genes encoding the B55 family of PP2A regulatory subunits is a common feature of breast cancer cells. A key player in the regulation of PP2A/B55 phosphatase complexes is the cell cycle kinase MASTL (also known as Greatwall). During cell division, inhibition of PP2A-B55 by MASTL is required to maintain the mitotic state, whereas inactivation of MASTL and PP2A reactivation is required for mitotic exit. Despite its critical role in cell cycle progression in multiple organisms, its relevance as a therapeutic target in human cancer and its dependence of PP2A activity is mostly unknown. Here we show that MASTL overexpression predicts poor survival and shows prognostic value in breast cancer patients. MASTL knockdown or knockout using RNA interference or CRISPR/Cas9 systems impairs proliferation of a subset of breast cancer cells. The proliferative function of MASTL in these tumor cells requires its kinase activity and the presence of PP2A-B55 complexes. By using a new inducible CRISPR/Cas9 system in breast cancer cells, we show that genetic ablation of MASTL displays a significant therapeutic effect in vivo. All together, these data suggest that the PP2A inhibitory kinase MASTL may have both prognostic and therapeutic value in human breast cancer

Control de la salida de mitosis en mamíferos

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid. Facultad de Medicina. Departamento de Bioquímica. Fecha de lectura: 2 de Marzo de 2011

Cdc14b regulates mammalian RNA polymerase II and represses cell cycle transcription

This work is licensed under a Creative Commons Attribution-NonCommercial.Cdc14 is an essential phosphatase in yeast but its role in the mammalian cell cycle remains obscure. We report here that Cdc14b-knockout cells display unscheduled induction of multiple cell cycle regulators resulting in early entry into DNA replication and mitosis from quiescence. Cdc14b dephosphorylates Ser5 at the C-terminal domain (CTD) of RNA polymerase II, a major substrate of cyclin-dependent kinases. Lack of Cdc14b results in increased CTD-Ser5 phosphorylation, epigenetic modifications that mark active chromatin, and transcriptional induction of cell cycle regulators. These data suggest a function for mammalian Cdc14 phosphatases in the control of transcription during the cell cycle.This work was funded by grants from the Association for International Cancer Research (AICR #08-0188), Foundation Ramón Areces, and the Spanish Ministry of Science and Innovation (MICINN; BFU2008-04293 to M.S.; SAF2009-07973 to M.M.). The Cell Division and Cancer Group of the CNIO is supported by the OncoCycle Programme (S-BIO-0283-2006) from the Comunidad de Madrid, the OncoBIO Consolider-Ingenio 2010 Programme (CSD2007- 00017) from the MICINN, Madrid, and the European Union Seventh Framework Programme (MitoSys project; HEALTH-F5-2010-241548).Peer Reviewe

Targeting mitotic exit leads to tumor regression in vivo: Modulation by Cdk1, Mastl, and the PP2A/B55α,δ phosphatase

Targeting mitotic exit has been recently proposed as a relevant therapeutic approach against cancer. By using genetically engineered mice, we show that the APC/C cofactor Cdc20 is essential for anaphase onset in vivo in embryonic or adult cells, including progenitor/stem cells. Ablation of Cdc20 results in efficient regression of aggressive tumors, whereas current mitotic drugs display limited effects. Yet, Cdc20 null cells can exit from mitosis upon inactivation of Cdk1 and the kinase Mastl (Greatwall). This mitotic exit depends on the activity of PP2A phosphatase complexes containing B55α or B55δ regulatory subunits. These data illustrate the relevance of critical players of mitotic exit in mammals and their implications in the balance between cell death and mitotic exit in tumor cells. © 2010 Elsevier Inc.E.M., M.G., and M.E are supported by fellowships from the Ministerio de Ciencia e Innovación (MICINN). M.T. and H.Y. are supported by Marie Curie Cancer Care and the Association for International Cancer Research (AICR). M.M. and S.M. wish to acknowledge the Fundación Cientíica de la Asociación Española contra el Cáncer for financial support. I.G.-H. and S.M. are supported by grants BFU2008-01808, Consolider CSD2007-00015, and Junta de Castilla y León Grupo de Excelencia GR 265. The Cell Division and Cancer group of the CNIO is funded by the MICINN (SAF2009-07973), Consolider-Ingenio 2010 Programme (CSD2007-00017), Comunidad de Madrid (OncoCycle Programme; S-BIO-0283-2006), Fundación Ramón Areces, AICR (08-0188), and the MitoSys project (HEALTH-F5-2010-241548; European Union Seventh Framework Program).Peer Reviewe

Effect of carbon nanofillers on flexible polyurethane foaming from a chemical and physical perspective

The effect of carbon nanoparticles (CNPs) on the physical and chemical events taking place during the foaming evolution of flexible polyurethane (FPU) foams is analysed by in situ X-ray time-resolved imaging. The differences observed in the cellular structure and density evolution of nanocomposite foams are explained in terms of the type of nanoparticles and the functional groups on their surface. The presence of certain types of particles enhanced the bubble nucleation at the beginning of the process although some others did not. The chemical interaction seems to produce delays in the blowing reaction process and promotes coalescence events during foam evolution as regarding the cell density results obtained. This study on the kinetics of polymerisation and morphology development of reactive PU nanocomposite foams contributes to understanding the physical phenomena occurring as a consequence of the CNP-FPU chemical interaction. This journal is © the Partner Organisations 2014.Peer Reviewe

GFP induction and mKate2 expression is uniform in most organs of <i>CAGs-rtTA3</i> and <i>CAGs-RIK</i> mice.

<p>Immunofluorescence stains for GFP and mKate2 in the small intestine and pancreas of ‘no rtTA’, <i>R26-rtTA</i>, <i>CAGs-rtTA3</i> and <i>CAGs-RIK</i> mice following 1 week of doxycycline treatment. All rtTA strains show strong GFP induction in small intestine (<b>A</b>), but only <i>CAGs-rtTA3</i> and <i>CAGs-RIK</i> show robust and uniform GFP expression (and mKate2 for <i>RIK</i>) in the pancreatic acinar tissue (<b>B</b>).</p