Table of Contents

Volume 9, Issue 14

  July 15, 2010

  Pages 2689 - 2982

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 Issue Catalogue (MARC XML)

EDITORIALS: CELL CYCLE FEATURES

Open Access Article

RIP-in CD95-induced cell death: The control of alternative death receptors pathways by cIAPs

Peter Geserick, Mike Hupe, Maryline Moulin and Martin Leverkus
Pages 2689 - 2691
http://dx.doi.org/10.4161/cc.9.14.12379
Abstract | PDF

Comment on: Geserick P, et al. J Cell Biol 2009; 187:1037-54.

Open Access Article

Polycomb complexes—genes make sense of host defense

Martin Leeb and Anton Wutz
Pages 2692 - 2693
http://dx.doi.org/10.4161/cc.9.14.12455
Abstract | PDF

Comment on: Leeb M, et al. Genes Dev. 2010; 24:265-76.

Open Access Article

The cell cycle and pluripotency: Is there a direct link?

Michael J. Edel and Juan Carlos Izpisua Belmonte
Pages 2694 - 2695
http://dx.doi.org/10.4161/cc.9.14.12456
Abstract | PDF

Comment on: Edel MJ, et al. Genes Dev. 2010; 24:561-73.

Open Access Article

Multiple non-cell autonomous actions of α-synuclein in neurodegenerative diseases

Seung-Jae Lee, He-Jin Lee and Eliezer Masliah
Pages 2696 - 2697
http://dx.doi.org/10.4161/cc.9.14.12590
PDF

Open Access Article

Loss of inhibitory insulin receptor substrate-1 phosphorylation: An early event in endometrial hyperplasia and progression to carcinoma

Adrienne S. McCampbell, Russell R. Broaddus and Cheryl L. Walker
Pages 2698 - 2699
http://dx.doi.org/10.4161/cc.9.14.12618
PDF

Open Access Article

Emphasizing the positive: A role for histone deacetylases in transcriptional activation

Oliver M. Dovey, Charles T. Foster and Shaun M. Cowley
Pages 2700 - 2701
http://dx.doi.org/10.4161/cc.9.14.12626
Abstract | PDF

Comment on: Wang Z, et al. Cell 2009; 138:1019-1031.


Open Access Article

ORF57: Master regulator of KSHV mRNA biogenesis

James R. Boyne, Brian R. Jackson and Adrian Whitehouse
Pages 2702 - 2703
http://dx.doi.org/10.4161/cc.9.14.12627
Abstract | PDF

Comment on: Boyne JR, et al. EMBO J 2010; 29:1851-64.




CELL CYCLE NEWS & VIEWS

Open Access Article

Polycomb group proteins: New targets of anti-cancer therapy

Mo K. Kang
Pages 2704 - 2712
http://dx.doi.org/10.4161/cc.9.14.12322
Abstract | PDF

Comment on: Bommi P, et al. Cell Cycle 2010; 9:2663-73.

Open Access Article

HDAC inhibitors conquer polycomb proteins

Paul Yaswen
Pages 2713 - 2721
http://dx.doi.org/10.4161/cc.9.14.12323
Abstract | PDF

Comment on: Bommi P, et al. Cell Cycle 2010; 9:2663-73.


Open Access Article

HDAC inhibitors repress the polycomb protein BMI1

Steven Grant
Pages 2722 - 2730
http://dx.doi.org/10.4161/cc.9.14.12324
Abstract | PDF

Comment on: Bommi P, et al. Cell Cycle 2010; 9:2663-73.


Open Access Article

New functions for the Snail family of transcription factors: Two-faced proteins

Jesús Pérez-Losada and Isidro Sánchez-García
Pages 2731 - 2739
http://dx.doi.org/10.4161/cc.9.14.12326
Abstract | PDF

Comment on: Yang D, et al. Cell Cycle 2010; 9:2789-802.


Open Access Article

Kinases involved in Rec8 phosphorylation revealed

Martin Anger
Pages 2740 - 2748
http://dx.doi.org/10.4161/cc.9.14.12380
Abstract | PDF

Comment on: Rumpf C, et al. Cell Cycle 2010; 9:2657-62.

Open Access Article

Regulation of vitamin metabolism by p53 and p63 in development and cancer

Huiqing Zhou and Hans van Bokhoven
Pages 2749 - 2757
http://dx.doi.org/10.4161/cc.9.14.12591
Abstract | PDF

Comment on: Kirschner KR, et al. Cell Cycle 2010; 9:2177-88.

Open Access Article

ΔNp73ß is oncogenic in hepatocellular carcinoma by blocking apoptosis signaling via death receptors and mitochondria

Heike Bantel and Hans-Uwe Simon
Pages 2758 - 2766
http://dx.doi.org/10.4161/cc.9.14.12592
Abstract | PDF

Comment on: Schuster A, et al. Cell Cycle 2010; 9:2629-39.


Open Access Article

A novel neuronal differentiation mechanism in which Slug and Escargot are major players

Masamitsu Yamaguchi
Pages 2767 - 2775
http://dx.doi.org/10.4161/cc.9.14.12593
Abstract | PDF

Comment on: Yang D, et al. Cell Cycle 2010; 9:9:2789-802.


Open Access Article

Dancing with p53: The role of p38MAPK in mitosis of p53-deficient tetraploid cells

Sheau-Yann Shieh
Pages 2776 - 2784
http://dx.doi.org/10.4161/cc.9.14.12594
Abstract | PDF

Comment on: Vitale I, et al. Cell Cycle 2010; 9:2823-9.





EXTRA VIEWS

Open Access Article

mTORC1 signaling in Parkinson disease and L-DOPA-induced dyskinesia: A sensitized matter

Emanuela Santini, Emmanuel Valjent and Gilberto Fisone
Pages 2785 - 2790
http://dx.doi.org/10.4161/cc.9.14.12180
Abstract | PDF

Parkinson's disease is caused by the progressive loss of dopamine innervation to the basal ganglia and is commonly treated with the dopamine precursor, L-DOPA. Prolonged administration of L-DOPA results in the development of severe motor complications, or dyskinesia, which seriously hamper its clinical use. Recent evidence indicates that L-DOPA-induced dyskinesia (LID) is associated with persistent activation of the mammalian target of rapamycin complex 1 (mTORC1) in the medium spiny neurons (MSNs) of the striatum, the main component of the basal ganglia. This phenomenon is secondary to the development of a strong sensitization at the level of dopamine D1 receptors, which are abundantly expressed in a subset of MSNs. Such sensitization confers to dopaminergic drugs (including L-DOPA) the ability to activate the extracellular signal-regulated protein kinases 1/2, which, in turn promote mTORC1 signaling. Using a mouse model of LID, we recently showed that administration of the allosteric mTORC1 inhibitor, rapamycin, reduces dyskinesia. This finding is discussed with respect to underlying mechanisms and potential significance for the development of future therapeutic interventions.

Open Access Article

Differential control of ATGL-mediated lipid droplet degradation by CGI-58 and G0S2

Xin Lu, Xingyuan Yang and Jun Liu
Pages 2791 - 2797
http://dx.doi.org/10.4161/cc.9.14.12181
Abstract | PDF

Lipid droplets (LDs) are intracellular storage sites for triacylglyerols (TAGs) and steryl esters, and play essential roles in energy metabolism and membrane biosynthesis. Adipose triglyceride lipase (ATGL) is the key enzyme for TAG hydrolysis (lipolysis) in adipocytes and LD degradation in nonadipocyte cells.  Lipase activity of ATGL in vivo largely depends on its C-terminal sequence as well as coactivation by CGI-58.  Here we demonstrate that the C-terminal hydrophobic domain in ATGL is required for LD targeting and CGI-58-independent LD degradation.  Overexpression of wild type ATGL causes a dramatic decrease in LD size and number, whereas a mutant lacking the hydrophobic domain fails to localize to LDs and to affect their morphology.  Interestingly, coexpression of CGI-58 is able to promote LD turnover mediated by this ATGL mutant.  Recently we have discovered that G0S2 acts as an inhibitor of ATGL activity and ATGL-mediated lipolysis.  Here we show that G0S2 binds to ATGL irrelevantly of its activity state or the presence of CGI-58.  In G0S2-expressing cells, the combined expression of CGI-58 and ATGL is incapable of stimulating LD turnover.  We propose that CGI-58 and G0S2 regulate ATGL via non-competing mechanisms.

Open Access Article

Regulation of Myc by miR-34c: A mechanism to prevent genomic instability?

Ian Cannell and Martin Bushell
Pages 2798 - 2802
http://dx.doi.org/10.4161/cc.9.14.12182
Abstract | PDF

Over the past 8 years several lines of compelling evidence have indicated that microRNAs are critical downstream effectors of classic oncogene/tumour suppressor networks. The archetypal examples of oncogene and tumour suppressor microRNAs are the miR-17-92 (oncomir 1) polycistron and miR-34 respectively. Whilst the involvement of these two opposing families of microRNAs in oncogenesis has been known for some time, the mRNA targets through which they exert their phenotypes are only just beginning to be uncovered. Moreover, several recent reports have demonstrated that the relevant physiological targets of certain individual microRNAs are actually fairly limited, with repression of just one or two major targets sufficient to explain the observed phenotype. In this review we will discuss the emerging role of microRNAs in tumourigenesis with a specific focus on miR-34c-dependent regulation of Myc.

Open Access Article

Centriole duplication: A lesson in self-control

Andrew J. Holland, Weijie Lan and Don W. Cleveland
Pages 2803 - 2808
http://dx.doi.org/10.4161/cc.9.14.12184
Abstract | PDF

In interphase and mitosis, centrosomes play a major role in the spatial organization of the microtubule network. Alterations in centrosome number and structure are associated with genomic instability and occur in many cancers. Centrosome duplication is controlled by centriole replication. In most dividing animal cells, centrioles duplicate only once per cell cycle at a site adjacent to existing centrioles. The conserved protein kinase Polo-like kinase 4 (Plk4) has a key role in controlling centriole biogenesis. Overexpression of Plk4 drives centrosome amplification, leading to genomic instability and the formation of tumors in flies. By contrast, haploinsufficiency of Plk4 causes cytokinesis failure leading to an increased incidence of tumors in mice. Recent studies have shown that Plk4 is a low abundance protein whose stability is linked to the activity of the enzyme. We discuss how this autoregulatory feedback loop acts to limit the damaging effects caused by too much or too little Plk4.

Open Access Article

Abl promotes cadherin-dependent adhesion and signaling in myoblasts

Min Lu and Robert S. Krauss
Pages 2809 - 2813
http://dx.doi.org/10.4161/cc.9.14.12246
Abstract | PDF

Cell-cell contact promotes myogenic differentiation but the mechanisms that regulate this phenomenon are not well understood. Cdo (also known as Cdon), an Ig superfamily member, functions as a component of cell surface complexes to promote myogenic differentiation through activation of p38a/b MAP kinase. We recently showed that N-cadherin ligation activated p38a/b in a Cdo-dependent manner, whereas N-cadherin ligation-dependent activation of ERK MAP kinase was not affected by loss of Cdo. The non-receptor tyrosine kinase Abl associates with Cdo during myoblast differentiation and is necessary for full activition of p38a/b during this process. The Abl SH3 domain binds to a PxxP motif in the Cdo intracellular domain, and both these motifs are required for their promyogenic activity. Here we show that Abl is necessary for p38a/b activation initiated by N-cadherin ligation, but in contrast to Cdo, Abl is also required for N-cadherin-dependent ERK activation. Moreover, Abl is required for efficient cadherin-mediated myoblast aggregation via modulation of RhoA-ROCK signaling. Therefore, Abl regulates N-cadherin-mediated p38a/b activation by multiple mechanisms, more generally through regulation of cell-cell adhesion and specifically as a component of Cdo-containing complexes. The role of Cdo as a multifunctional coreceptor with roles in several pathways is also discussed.

Open Access Article

microRNA-451: A conditional switch controlling glioma cell proliferation and migration

Jakub Godlewski, Agnieszka Bronisz, Michal O. Nowicki, E. Antonio Chiocca and Sean Lawler
Pages 2814 - 2820
http://dx.doi.org/10.4161/cc.9.14.12248
Abstract | PDF

Glioblastoma, the most common and aggressive primary brain tumor, is rapidly growing, and highly infiltrative. Incomplete knowledge of the molecular biology, genetics, causes and cellular origin of these tumors may limit the development of improved therapeutics. A major and fundamental advance in recent years has been the identification of microRNAs as highly conserved regulators of gene expression. Here we will discuss further our recently published data on the role of miR-451 in the biology of glioblastoma. We initially identified miR-451 due to its downregulation in a glioma cell migration assay. We then found that by targeting the LKB1 kinase complex miR-451 suppresses the activity of downstream protein kinases including the major energy biosensor AMPK. MiR-451 levels are regulated by glucose; under conditions of abundant energy miR-451 expression is high, and the suppression of AMPK signaling allows cells to maintain elevated proliferation rates via unrestrained mTOR activation. Under conditions of glucose withdrawal, miR-451 downregulation is necessary for AMPK pathway activation, leading to suppressed proliferation rates, increased cell survival, and migration. We also identified a potential feedback loop between LKB1 and miR-451, which allows a sustained and robust response to glucose deprivation. This data will be discussed in the context of potential biological significance and therapeutic implications.

Open Access Article

Feedback regulators of hypoxia-inducible factors and their role in cancer biology

Anne-Theres Henze and Till Acker
Pages 2821 - 2835
http://dx.doi.org/10.4161/cc.9.14.12249
Abstract | PDF

Malignant tumors are characterized by regions of low oxygen concentration (hypoxia). The hypoxic tumor microenvironment contributes to tumor progression by activating a set of adaptive responses via the key transcriptional regulators HIF-1a and HIF-2a. These factors have been traditionally linked to an aggressive tumor phenotype by promoting processes essential for tumor growth, such as angiogenesis, glycolysis, metastasis and invasion, as well as differentiation and self renewal. Notably, the complex HIF pathway also initiates anti-tumorigenic mechanisms that lead to cell cycle arrest or cell death, indicating the need for a stringent control of the extent and the direction of the hypoxia response. The importance of this control for tumor cell survival is illustrated by the intricate regulation of HIF activity at the mRNA, protein and epigenetic level by a complex network of positive and negative feedback regulators. We propose that these feedback regulators help to flexibly adjust and adapt HIF activated responses to the fluctuating oxygen concentrations within tumors during acute and chronic hypoxia and to curtail the tumor-suppressing components of the HIF pathway. Moreover, feedback regulation of HIF induces a switch from HIF-1a to HIF-2a driven responses under chronic hypoxia which may have essential functions in the regulation of tumor cell differentiation and tumor stem cell maintenance. Given their central role in cancer biology, HIF feedback regulators may represent an attractive and novel anti-tumor therapy target to overcome cell death resistance in tumors.

Open Access Article

Interdependent regulation of p53 and miR-34a in chronic lymphocytic leukemia

Olaf Merkel, Daniela Asslaber, Josefina Pinon, Alexander Egle and Richard Greil
Pages 2836 - 2840
http://dx.doi.org/10.4161/cc.9.14.12267
Abstract | PDF

Chronic lymphocytic leukemia (CLL) has an incidence 4/100 000 people in the western world and is one of the first cancers reported to be associated with deregulated miRNA expression. microRNAs are small non coding RNAs that are important regulators of protein expression through binding to their untranslated 3'-UTR region. The miR-34 family was demonstrated to be induced by the tumor suppressor p53 and to elicit p53-like responses like senescence, cell cycle arrest and apoptosis depending on the cell type. We have shown in a recent paper that miR-34a is severely increased in the TCL1-mouse model of CLL. This finding was reflected in human CLL. Moreover, it is demonstrated that its expression is dependent on the presence of the SNP309 in the intronic promoter of the MDM2 gene. In addition, low miR-34a expression was associated with shorter time to treatment (log-rank P = 0.003) in CLL. When reintroduced into CLL cells, miR-34a was able to induce apoptosis. Interestingly, this was dependent on an intact p53 pathway. Here, we present data showing that knockdown of p53 in HCT-116 cells severely reduces miR-34a induced apoptosis. In conclusion, miR-34a is proposed as a marker for the activity of the p53 pathway in CLL.

Open Access Article

Signaling pathways in the epithelial origins of pulmonary fibrosis

William D. Hardie, James S. Hagood, Vrushank Dave, Anne-Karina T. Perl, Anne-Karina T. Perl, Jeffrey A. Whitsett, Thomas R. Korfhagen and Stephan Glasser
Pages 2841 - 2848
http://dx.doi.org/10.4161/cc.9.14.12268
Abstract | PDF

Pulmonary fibrosis complicates a number of disease processes and leads to substantial morbidity and mortality. Idiopathic pulmonary fibrosis (IPF) is perhaps the most pernicious and enigmatic form of the greater problem of lung fibrogenesis with a median survival of three years from diagnosis in affected patients. In this review, we will focus on the pathology of IPF as a model of pulmonary fibrotic processes, review possible cellular mechanisms, review current treatment approaches and review two transgenic mouse models of lung fibrosis to provide insight into processes that cause lung fibrosis. We will also summarize the potential utility of signaling pathway inhibitors as a future treatment in pulmonary fibrosis. Finally, we will present data demonstrating a minimal contribution of epithelial-mesenchymal transition in the development of fibrotic lesions in the transforming growth factor-alpha transgenic model of lung fibrosis.


Open Access Article

Gene regulation and tumor suppression by the bromodomain-containing protein BRD7

Fiamma Mantovani, Jarno Drost, P. Mathijs Voorhoeve, Giannino Del Sal and Reuven Agami
Pages 2849 - 2853
http://dx.doi.org/10.4161/cc.9.14.12309
Abstract | PDF

Oncogene-induced senescence (OIS) is a cellular defense mechanism against excessive mitogenic signaling and tumorigenesis. One of the major pathways required for OIS is the p53 tumor suppressor pathway. Consequently, many human tumors harbor p53 mutations while others show a dysfunctional p53 pathway, frequently by unknown mechanisms. We recently identified BRD7 as a potential tumor suppressor gene acting as a transcriptional cofactor for p53, affecting histone acetylation, p53 acetylation, and promoter activity on a subset of p53 target genes. We further found low BRD7 expression specifically in a subgroup of human breast tumors harboring wild-type, but not mutant, p53 and showed that one of the responsible mechanisms is deletion of the BRD7 gene locus. Here we further discuss the role of BRD7 as a cofactor in transcriptional regulation and highlight its role as a tumor suppressor via association with p53 and other tumor suppressor proteins.




REVIEW

Open Access Article

Pathways of oncogene-induced senescence in human melanocytic cells

Rajat Bansal and Mikhail A. Nikiforov
Pages 2854 - 2860
http://dx.doi.org/10.4161/cc.9.14.12251
Abstract | PDF

No Abstract.




REPORTS

Open Access Article

Slug, mammalian homologue gene of Drosophila escargot, promotes neuronal-differentiation through suppression of HEB/daughterless

Dong-Jin Yang, Ji-Youn Chung, Su-Jin Lee, So-Young Park, Jung-Hoon Pyo, Nam-Chul Ha, Mi-Ae Yoo and Bum-Joon Park
Pages 2861 - 2874
http://dx.doi.org/10.4161/cc.9.14.12247
Abstract | PDF

At the neuron developmental stage, neuron-precursor cells can be differentiated into neuron or glia cells. However, precise molecular mechanism to determine the cell fate has not been clearly demonstrated. In this study, we reveal that Drosophila esgarcot and its mammalian homologue genes, Snail and Slug, play a key role in neuronal differentiation. In Drosophila model system, overexpression of Esg, like as Wingless, suppresses the bristle formation. In contrast, elimination of Esg though RNAi promotes double bristle phenotype. We can also observe the similar phenotype in Snail-overexpression system. In mammalian system, overexpression of Slug or Snail can induce neuronal differentiation. Esg and its mammalian homologue gene Slug directly interact with Daughtherless and its mammalian homologue HEB and eliminate them through siah-1 mediated protein degradation. Thus, overexpression of siah-1 can promote neuron cell differentiation, whereas si-siah-1 blocks the Slug-induced HEB suppression. In fact, Drosophila SINA, Siah-1 homologue, has been also known to be involved in bristle formation and Neuronal differentiation. In addition, it has been revealed that CK1 is involved in Esg or Snail stability and Neuronal differentiation. However, Snail is regulated only by CK1 but not by Siah. Considering the fact that Slug mutations have been found in human genetic disease, waardenberg syndrome, major symptoms of which is loss of hearing neuron and odd eye, our result implies that Slug/Snail system is required for proper neuronal differentiation, like as Esg in Drosophila.

Open Access Article

FM19G11: A new modulator of HIF that links mTOR activation with the DNA damage checkpoint pathways

Francisco Javier Rodríguez-Jiménez, Victoria Moreno-Manzano, Pablo Mateos-Gregorio, Inmaculada Royo, Slaven Erceg, José Ramón Murguia and Jose María Sánchez-Puelles
Pages 2875 - 2885
http://dx.doi.org/10.4161/cc.9.14.12250
Abstract | PDF

The network consisting of mTOR and p53 pathways is crucial to understanding a wide variety of physiological and pathological events, including cancer and aging. In addition, the HIF1α protein, a downstream target of mTOR, is a hallmark of different tumor types and was the desired strategy of many drug discovery efforts. Here we present the novel chemical entity FM19G11, a new modulator of HIF1a expression, which was used as a molecular tool to dissect and further characterize the cross-talk between these signaling cascades in human colon carcinoma cell lines. To our knowledge, FM19G11 is the first drug that triggers a DNA damage response (DDR) associated with G1/S-phase arrest in a p53-dependent manner, due to rapid hyper-activation of the growth signaling pathway through mTOR. Assessment of colonies demonstrated that FM19G11 decreases the clonogenicity of HT29, HCT116/p53+/+ and HCT116/p53-/- cells. Moreover, FM19G11 causes significant lower colony growth in soft agar of p53-proficient human colon cancer cells. Consequently, p53 sensitizes human colon cancer cells to FM19G11 by significant reduction of their viability, lessening their colony formation capability and shrinking their anchorage-independent growth. Cell signaling studies served to assign a new mode of action to FM19G11, whose tumor-suppressant activity compromises the survival of functional p53 malignant cells.

Open Access Article

Loss of ATM positively regulates the expression of hypoxia inducible factor 1 (HIF-1) through oxidative stress: Role in the physiopathology of the disease

Marielle Ousset, Fanny Bouquet, Frédérique Fallone, Denis Biard, Cedric Dray, Philippe Valet, Bernard Salles and Catherine Muller
Pages 2886 - 2894
http://dx.doi.org/10.4161/cc.9.14.12253
Abstract | PDF

Ataxia Telangiectasia (AT) is an autosomal recessive disorder characterized by a wide variety of progressive clinical symptoms. This includes neuronal degeneration, oculocutaneous telangiectasias, diabetes mellitus, immunodeficiency, increased risk of cancer and sensitivity to ionizing radiation. The gene mutated in this disease, ATM (Ataxia Telangiectasia Mutated), encodes a protein kinase involved in DNA double strand breaks signalling and repair. ATM deficient cells also display an increase in oxidative stress, by poorly characterized mechanism(s), which clearly contributes to the neurodegenerative aspect of the disease. Despite these advances, the occurrence of the vascular abnormalities, glucose intolerance and insulin resistance remains poorly understood. In different cellular models where ATM expression was disrupted, we demonstrated that the absence of ATM leads to an increased expression of both subunits of the transcription factor Hypoxia Inducible Factor 1 (HIF-1). We also observed enhanced trans-activating functions of HIF-1. HIF-1 is the central regulator of responses to hypoxia which induces the transcription of genes involved in angiogenesis (e.g VEGF -Vascular Endothelial Growth Factor) and cellular metabolism (e.g GLUT-1). Interestingly, we demonstrated that ATM disruption positively regulates both expression and function of the basal glucose transporter GLUT-1 as well as the proangiogenic factor, VEGF. In addition, our results suggest that the absence of ATM increases HIF-1 proteins biosynthesis, and this effect is dependant on the oxidative stress existing in ATM deficient cells. Our compelling results highlight a new link between ATM deficiency and the clinical features of the disease and provide a molecular link between ATM down-regulation and the increase in tumor angiogenesis observed in human breast cancers.

Open Access Article

Involvement of p38α in the mitotic progression of p53^-/- tetraploid cells

Ilio Vitale, Mohamed Jemaá, Laura Senovilla, Lorenzo Galluzzi, Santiago Rello-Varona, Didier Métivier, Hugues Ripoche, Vladimir Lazar, Philippe Dessen, Maria Castedo and Guido Kroemer
Pages 2895 - 2901
http://dx.doi.org/10.4161/cc.9.14.12254
Abstract | PDF

The tumor suppressor protein p53 plays a major role in preserving genomic stability. p53 suppresses a pathway leading from normal diploidy to neoplastic aneuploidy (via an intermediate metastable stage of tetraploidy) at two levels: first by preventing the generation/survival of tetraploid cells, and second by repressing their aberrant multipolar division. Here, we report the characterization of p53^-/- tetraploid cells, which - at difference with both their p53^-/- diploid and their p53^+/+ tetraploid counterparts - manifest a marked hyperphosporylation of the mitogen-activated protein kinase MAPK14 (best known as p38α) that is particularly strong during mitosis. In p53^-/- tetraploid cells, phosphorylated p38α accumulated at centrosomes during the metaphase and at midbodies during the telophase. Selective knockdown or pharmacological inhibition of p38α had a dramatic effect on p53^-/- (but not p53^+/+) tetraploids, causing the activation of the spindle assembly checkpoint, an arrest during the metaphase, a major increase in abnormal bipolar and monopolar mitoses, as well as an increment in the generation of multinuclear cells. We conclude that the mitotic progression of p53^-/- (but not p53^+/+) tetraploids heavily relies on p38α, revealing a novel function for this protein in the context of aneuploidizing cell divisions.

Open Access Article

In vivo depletion of T lymphocyte-specific transcription factors by RNA interference

Antoine Tesniere, Nassera Abermil, Frederic Schlemmer, Noelia Casares, Oliver Kepp, Marie Pequignot, Mickael Michaud, Isabelle Martins, Laura Senovilla, Laurence Zitvogel and Guido Kroemer
Pages 2902 - 2907
http://dx.doi.org/10.4161/cc.9.14.12256
Abstract | PDF

The generation of specific T lymphocyte subsets is under the strict control of specific transcription factors, as this has been shown by knockout experiments in mice. Here, we show that siRNAs that specifically target the transcription factor Gata3 (which is required for the development of T helper 1 cells) or T-Bet (which is required for the development of T helper 2 cells) can be effective in vivo. Thus, the intraperitoneal injection of siRNAs specific for Gata3 or t-Bet leads to the specific depletion of their target gene products in vivo, in the spleen and in the lymph nodes from mice. The immunomodulatory action of these siRNAs was validated in a model of anti-tumor vaccination in which colorectal cancer cells that succumb to anthracyclin-induced immunogenic cell death were injected subcutaneously into one flank, in the absence of any adjuvant, and live tumor cells were injected simultaneously in the opposite flank of immunocompetent mice. In this setting, the siRNA targeting t-Bet was able to accelerate tumor growth while the siRNA targeting Gata3 significantly reduced the proliferation of cancer cells in vivo. These effects were dependent on the immune response elicited by dying tumor cells because both siRNAs failed to modulate the growth of tumors in non-vaccinated mice. The immune response-dependent anticancer effect of the Gata3-specific siRNA was not due to the induction of class I interferons and could be fully abolished by co-injection of t-Bet-specific siRNA. These results demonstrate the possibility to use siRNAs for immunomodulaton in vivo and illustrate the antagonistic implication of distinct T helper populations in anti-cancer immune responses.

Open Access Article

Fatty acids trigger mitochondrion-dependent necrosis

Patrick Rockenfeller, Julia Ring, Vera Muschett, Andreas Beranek, Sabrina Büttner, Didac Carmona-Gutierrez, Tobias Eisenberg, Chamel Khoury, Gerald Rechberger, Sepp D. Kohlwein, Guido Kroemer and Frank Madeo
Pages 2908 - 2914
http://dx.doi.org/10.4161/cc.9.14.12346
Abstract | PDF

Obesity is characterized by lipid accumulation in non-adipose tissues, leading to organ degeneration and a wide range of diseases, including diabetes, heart attack, and liver cirrhosis. Free fatty acids (FFA) are believed to be the principal toxic triggers mediating the adverse cellular effects of lipids. Here, we show that various cooking oils used in human nutrition cause cell death in yeast in the presence of a triacylglycerol lipase, mimicking the physiological microenvironment of the small intestine. Combining genetic and cell death assays, we demonstrate that elevated FFA concentrations lead to necrotic cell death, as evidenced by loss of membrane integrity and release of nuclear HMGB1. FFA-mediated necrosis depends on functional mitochondria and leads to the accumulation of reactive oxygen species. We conclude that lipotoxicity is executed via a mitochondrial necrotic pathway, challenging the dogma that the adverse effects of lipid stress are exclusively apoptotic.

Open Access Article

MCL-1 localizes to sites of DNA damage and regulates DNA damage response

Sarwat Jamil, Cezar Stoica, Tillie-Louise Hackett and Vincent Duronio
Pages 2915 - 2927
http://dx.doi.org/10.4161/cc.9.14.12354
Abstract | PDF

MCL-1, a pro-survival member of the BCL-2 family, was previously shown to have functions in ATR-dependent Chk1 phosphorylation following DNA damage. To further delineate these functions, we explored possible differences in DNA damage response caused by lack of MCL-1 in mouse embryo fibroblasts (MEFs). As expected, Mcl-1^-/- MEFs had delayed Chk1 phosphorylation following etoposide treatment, compared to wild type MEFs. However, their response to hydroxyurea, which causes a G1/S checkpoint response, was not significantly different. In addition, appearance of g-H2AX was delayed in the Mcl-1^-/- MEFs treated with etoposide. We next investigated whether MCL-1 is present, together with other DNA damage response proteins, at the sites of DNA damage. Immunoprecipitation of etoposide-treated extracts with anti-MCL-1 antibody showed association of MCL-1 with g-H2AX as well as NBS1. Immunofluorescent staining for MCL-1 further showed increased co-staining of MCL-1 and NBS1 following DNA damage. By using a system that creates DNA double strand breaks at specific sites in the genome, we demonstrated that MCL-1 is recruited directly adjacent to the sites of damage. Finally, in a direct demonstration of the importance of MCL-1 in allowing proper repair of DNA damage, we found that treatment for two brief exposures to etoposide over several days, which mimics the clinical situation of etoposide use, resulted in many more chromosomal abnormalities in the MEFs that lacked MCL-1. Together, these data indicate an important role for MCL-1 in coordinating DNA damage mediated checkpoint response, and have broad implications for the importance of MCL-1 in maintenance of genome integrity.

Open Access Article

MAD2 downregulation in hypoxia is independent of promoter hypermethylation

Maria Prencipe, Aloysius McGoldrick, Antoinette S Perry, Anthony O’Grady, Sine Phelan, Barbara McGrogan, Patricia Fitzpatrick, Jenny A Watson, Fiona Furlong, Donal J Brennan, Mark Lawler, Elaine Kay and Amanda McCann
Pages 2928 - 2937
http://dx.doi.org/10.4161/cc.9.14.12362
Abstract | PDF

Aberrant expression of the MAD2 protein has been linked to chromosomal instability, malignant transformation and chemoresistance. Although reduced MAD2 expression is well recognised in human cancer cell lines, the mechanism(s) underlying its down-regulation remain elusive.

Open Access Article

ATM regulates Mre11-dependent DNA end-degradation and microhomology-mediated end joining

Elias A. Rahal, Leigh A. Henricksen, Yuling Li, R. Scott Williams, John A. Tainer and Kathleen Dixon
Pages 2938 - 2949
http://dx.doi.org/10.4161/cc.9.14.12363
Abstract | PDF

The human disorder ataxia telangiectasia (AT), which is characterized by genetic instability and neurodegeneration, results from mutation of the ataxia telangiectasia mutated (ATM) kinase.   The loss of ATM leads to cell-cycle checkpoint deficiencies and other DNA damage signaling defects that do not fully explain all pathologies associated with A-T including neuronal loss.  In addressing this enigma, we find here that ATM suppresses DNA double-strand break (DSB) repair by microhomology-mediated end joining (MMEJ). We show that ATM repression of DNA end-degradation is dependent on its kinase activities and that Mre11 is the major nuclease behind increased DNA end-degradation and MMEJ repair in A-T. Assessment of MMEJ by an in vivo reporter assay system reveals decreased levels of MMEJ repair in Mre11-knockdown cells and in cells treated with Mre11-nuclease inhibitor mirin. Structure-based modeling of Mre11 dimer engaging DNA ends suggests the 5' ends of a bridged DSB are juxtaposed such that DNA unwinding and 3'-5' exonuclease activities may collaborate to facilitate simultaneous pairing of extended 5' termini and exonucleolytic degradation of the 3' ends in MMEJ. Together our results provide an integrated understanding of ATM and Mre11 in MMEJ: ATM has a critical regulatory function in controlling DNA end-stability and error-prone DSB repair and Mre11 nuclease plays a major role in initiating MMEJ in mammalian cells.  These functions of ATM and Mre11 could be particularly important in neuronal cells, which are post-mitotic and therefore depend on mechanisms other than homologous recombination between sister chromatids to repair DSBs.

Open Access Article

Mammosphere-forming cells from breast cancer cell lines as a tool for the identification of CSC-like- and early progenitor-targeting drugs

Mario Cioce, Simona Gherardi, Giuseppe Viglietto, Sabrina Strano, Giovanni Blandino, Paola Muti and Gennaro Ciliberto
Pages 2950 - 2959
http://dx.doi.org/10.4161/cc.9.14.12371
Abstract | PDF

Here we show that a subpopulation of MCF-7 breast cancer cells which stains pale to Toluidine Blue (Light Cells- LCs), is endowed with  features of CSCs. LCs give rise to self-renewing mammospheres and express typical CSC markers; moreover this subpopulation is chemoresistant and highly tumorigenic in vivo. LCs can be identified in several  other breast cancer cell lines, irrespectively of their histological origin (luminal vs mesenchymal vs basal) and represent an heterogeneous cell population composed mainly of CSC-like and early progenitor cells.  By a limited  in vitro drug screening assay, we identify compounds which can specifically interfere with the viability of LCs from multiple breast cancer cell lines. Analysis of the Sphere-Forming Efficiency (SFE) and  of the distribution of ALDH^bright cells within the treated cell lines suggest that one of the identified compounds acts in vitro by modulating the CSC phenotype. Interestingly, a subset of the identified compounds is known to affect directly or indirectly the NFkB pathway which is emerging as an important modulator of CSC proliferation and chemoresistance.

Open Access Article

Molecular cloning and characterization of mitogen-activated protein kinase 2 in Trypanosoma cruzi

Yi Bao, Louis M Weiss , Yan Fen Ma , Michael P. Lisanti, Herbert B Tanowitz, Bhaskar C Das, Renjian Zheng and Huan Huang
Pages 2960 - 2968
http://dx.doi.org/10.4161/cc.9.14.12372
Abstract | PDF

Mitogen-activated protein kinase (MAPK) pathways are major signal transduction systems by which eukaryotic cells convert environmental cues to intracellular events such as proliferation and differentiation.  We have identified a Trypanosoma cruzi homologue of the MAPK family that we have called TcMAPK2.  Sequence analyses demonstrates TcMAPK2 has high homology with lower eukaryotic ERK2 but has significant differences from mammalian ERK2.  Enzymatic assays of both recombinant TcMAPK2 and native protein obtained by immunoprecipitation using anti-TcMAPK2 demonstrated that both preparations of TcMAPK2 were catalytically active.  Immunofluorescence analysis of the subcellular localization of TcMAPK2 determined it is mainly cytoplasmic in epimastigotes, along the flagella in trypomastigotes and on the plasma membrane of intracellular amastigotes.  Phosphorylated TcMAPK2 was highest in trypomastigotes and lowest in amastigotes.  Recombinant TcMAPK2 was able to phosphorylate the recombinant protein of a cAMP specific phosphodiesterase.  Over-expression of TcMAPK2 in epimastigotes inhibited growth and development leading to death.  TcMAPK2 has an important role in the stress response of the parasite and may be important in regulating proliferation and differentiation.

Open Access Article

Pharicin A, a novel natural ent-kaurene diterpenoid, induces mitotic arrest and mitotic catastrophe of cancer cells by interfering with BubR1 function

Han-Zhang Xu, Ying Huang, Ying-Li Wu, Yong Zhao, Wei-Lie Xiao, Qi-Shan Lin, Han-Dong Sun, Wei Dai and Guo-Qiang Chen
Pages 2969 - 2979
http://dx.doi.org/10.4161/cc.9.14.12406
Abstract | PDF

In this study, we report the functional characterization of a new ent-kaurene diterpenoid termed pharicin A, which was originally isolated from Isodon xerophilus, a perennial shrub frequently used in Chinese folk medicine for tumor treatment. Pharicin A induces mitotic arrest in leukemia and solid tumor-derived cells identified by their morphology, DNA content, and mitotic marker analyses. Pharicin A-induced mitotic arrest is associated with unaligned chromosomes, aberrant BubR1 localization, and deregulated spindle checkpoint activation. Pharicin A directly binds to BubR1 in vitro, which is correlated with premature sister chromatid separation in vivo. Pharicin A also induces mitotic arrest in paclitaxel-resistant Jurkat and U2OS cells. Combined, our study strongly suggests that pharicin A represents a novel class of small molecule compounds capable of perturbing mitotic progression and initiating mitotic catastrophe, which merits further preclinical and clinical investigations for cancer drug development.




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Open Access Article

Cell cycle regulation via inter-nuclear communication during the early embryonic development of Drosophila melanogaster

Xuemin Lu, Jeff Drocco and Eric F. Wieschaus
Pages 2980 - 2982
http://dx.doi.org/10.4161/cc.9.14.12357
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