1
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Costa A, Forte IM, Pentimalli F, Iannuzzi CA, Alfano L, Capone F, Camerlingo R, Calabrese A, von Arx C, Benot Dominguez R, Quintiliani M, De Laurentiis M, Morrione A, Giordano A. Pharmacological inhibition of CDK4/6 impairs diffuse pleural mesothelioma 3D spheroid growth and reduces viability of cisplatin-resistant cells. Front Oncol 2024; 14:1418951. [PMID: 39011477 PMCID: PMC11246887 DOI: 10.3389/fonc.2024.1418951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2024] [Accepted: 06/11/2024] [Indexed: 07/17/2024] Open
Abstract
Introduction Diffuse pleural mesothelioma (DPM) of the pleura is a highly aggressive and treatment-resistant cancer linked to asbestos exposure. Despite multimodal treatment, the prognosis for DPM patients remains very poor, with an average survival of 2 years from diagnosis. Cisplatin, a platinum-based chemotherapy drug, is commonly used in the treatment of DPM. However, the development of resistance to cisplatin significantly limits its effectiveness, highlighting the urgent need for alternative therapeutic strategies. New selective inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6) have shown promise in various malignancies by inhibiting cell cycle progression and suppressing tumor growth. Recent studies have indicated the potential of abemaciclib for DPM therapy, and a phase II clinical trial has shown preliminary encouraging results. Methods Here, we tested abemaciclib, palbociclib, and ribociclib on a panel of DPM cell lines and non-tumor mesothelial(MET-5A) cells. Results Specifically, we focused on abemaciclib, which was the mosteffective cytotoxic agent on all the DPM cell lines tested. Abemaciclib reduced DPM cell viability, clonogenic potential, and ability to grow as three-dimensional (3D) spheroids. In addition, abemaciclib induced prolonged effects, thereby impairing second-generation sphere formation and inducing G0/G1 arrest and apoptosis/ necrosis. Interestingly, single silencing of RB family members did not impair cell response to abemaciclib, suggesting that they likely complement each other in triggering abemaciclib's cytostatic effect. Interestingly, abemaciclib reduced the phosphorylation of AKT, which is hyperactive in DPM and synergized with the pharmacological AKT inhibitor (AKTi VIII). Abemaciclib also synergized with cisplatin and reduced the viability of DPM cells with acquired resistance to cisplatin. Discussion Overall, our results suggest that CDK4/6 inhibitors alone or in combination with standard of care should be further explored for DPM therapy.
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Affiliation(s)
- Aurora Costa
- Department of Medical Biotechnologies, University of Siena, Siena, Italy
| | - Iris Maria Forte
- Experimental ClinicalOncology of Breast Unit, Department of Breast and Thoracic Oncology, Istituto Nazionale Tumori IRCCS "Fondazione G. Pascale", Naples, Italy
| | - Francesca Pentimalli
- Department of Medicine and Surgery, LUM University "Giuseppe De Gennaro", Bari, Italy
| | - Carmelina Antonella Iannuzzi
- Experimental ClinicalOncology of Breast Unit, Department of Breast and Thoracic Oncology, Istituto Nazionale Tumori IRCCS "Fondazione G. Pascale", Naples, Italy
| | - Luigi Alfano
- Experimental ClinicalOncology of Breast Unit, Department of Breast and Thoracic Oncology, Istituto Nazionale Tumori IRCCS "Fondazione G. Pascale", Naples, Italy
| | - Francesca Capone
- Experimental Pharmacology Unit-Laboratories of Naples andMercogliano (AV), Istituto Nazionale Tumori IRCCS "Fondazione G. Pascale", Naples, Italy
| | - Rosa Camerlingo
- Cell Biology and Biotherapy Unit, Istituto Nazionale Tumori, IRCCS, Fondazione G. Pascale, Naples, Italy
| | - Alessandra Calabrese
- Experimental ClinicalOncology of Breast Unit, Department of Breast and Thoracic Oncology, Istituto Nazionale Tumori IRCCS "Fondazione G. Pascale", Naples, Italy
| | - Claudia von Arx
- Experimental ClinicalOncology of Breast Unit, Department of Breast and Thoracic Oncology, Istituto Nazionale Tumori IRCCS "Fondazione G. Pascale", Naples, Italy
| | - Reyes Benot Dominguez
- Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, Department of Biology, College of Science and Technology, Temple University, Philadelphia, PA, United States
| | | | - Michelino De Laurentiis
- Experimental ClinicalOncology of Breast Unit, Department of Breast and Thoracic Oncology, Istituto Nazionale Tumori IRCCS "Fondazione G. Pascale", Naples, Italy
| | - Andrea Morrione
- Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, Department of Biology, College of Science and Technology, Temple University, Philadelphia, PA, United States
| | - Antonio Giordano
- Department of Medical Biotechnologies, University of Siena, Siena, Italy
- Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, Department of Biology, College of Science and Technology, Temple University, Philadelphia, PA, United States
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2
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Kanbar JN, Ma S, Kim ES, Kurd NS, Tsai MS, Tysl T, Widjaja CE, Limary AE, Yee B, He Z, Hao Y, Fu XD, Yeo GW, Huang WJ, Chang JT. The long noncoding RNA Malat1 regulates CD8+ T cell differentiation by mediating epigenetic repression. J Exp Med 2022; 219:213232. [PMID: 35593887 DOI: 10.1084/jem.20211756] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2021] [Revised: 03/21/2022] [Accepted: 05/03/2022] [Indexed: 12/21/2022] Open
Abstract
During an immune response to microbial infection, CD8+ T cells give rise to short-lived effector cells and memory cells that provide sustained protection. Although the transcriptional programs regulating CD8+ T cell differentiation have been extensively characterized, the role of long noncoding RNAs (lncRNAs) in this process remains poorly understood. Using a functional genetic knockdown screen, we identified the lncRNA Malat1 as a regulator of terminal effector cells and the terminal effector memory (t-TEM) circulating memory subset. Evaluation of chromatin-enriched lncRNAs revealed that Malat1 grouped with trans lncRNAs that exhibit increased RNA interactions at gene promoters and gene bodies. Moreover, we observed that Malat1 was associated with increased H3K27me3 deposition at a number of memory cell-associated genes through a direct interaction with Ezh2, thereby promoting terminal effector and t-TEM cell differentiation. Our findings suggest an important functional role of Malat1 in regulating CD8+ T cell differentiation and broaden the knowledge base of lncRNAs in CD8+ T cell biology.
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Affiliation(s)
- Jad N Kanbar
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Shengyun Ma
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA
| | - Eleanor S Kim
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Nadia S Kurd
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Matthew S Tsai
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Tiffani Tysl
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | | | - Abigail E Limary
- Department of Medicine, University of California, San Diego, La Jolla, CA
| | - Brian Yee
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA
| | - Zhaoren He
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA
| | - Yajing Hao
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA
| | - Xiang-Dong Fu
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA
| | - Gene W Yeo
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA.,Institute for Genomic Medicine, University of California, San Diego, La Jolla, CA
| | - Wendy J Huang
- Department of Cellular and Molecular Medicine, University of California, San Diego, La Jolla, CA
| | - John T Chang
- Department of Medicine, University of California, San Diego, La Jolla, CA.,Division of Gastroenterology, VA San Diego Healthcare System, San Diego, CA
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3
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Sayaman RW, Saad M, Thorsson V, Hu D, Hendrickx W, Roelands J, Porta-Pardo E, Mokrab Y, Farshidfar F, Kirchhoff T, Sweis RF, Bathe OF, Heimann C, Campbell MJ, Stretch C, Huntsman S, Graff RE, Syed N, Radvanyi L, Shelley S, Wolf D, Marincola FM, Ceccarelli M, Galon J, Ziv E, Bedognetti D. Germline genetic contribution to the immune landscape of cancer. Immunity 2021; 54:367-386.e8. [PMID: 33567262 DOI: 10.1016/j.immuni.2021.01.011] [Citation(s) in RCA: 85] [Impact Index Per Article: 28.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 10/14/2020] [Accepted: 01/13/2021] [Indexed: 02/07/2023]
Abstract
Understanding the contribution of the host's genetic background to cancer immunity may lead to improved stratification for immunotherapy and to the identification of novel therapeutic targets. We investigated the effect of common and rare germline variants on 139 well-defined immune traits in ∼9000 cancer patients enrolled in TCGA. High heritability was observed for estimates of NK cell and T cell subset infiltration and for interferon signaling. Common variants of IFIH1, TMEM173 (STING1), and TMEM108 were associated with differential interferon signaling and variants mapping to RBL1 correlated with T cell subset abundance. Pathogenic or likely pathogenic variants in BRCA1 and in genes involved in telomere stabilization and Wnt-β-catenin also acted as immune modulators. Our findings provide evidence for the impact of germline genetics on the composition and functional orientation of the tumor immune microenvironment. The curated datasets, variants, and genes identified provide a resource toward further understanding of tumor-immune interactions.
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Affiliation(s)
- Rosalyn W Sayaman
- Department of Population Sciences, Beckman Research Institute, City of Hope Comprehensive Cancer Center, Duarte, CA 91010, USA; Department of Laboratory Medicine, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94143, USA; Biological Sciences and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
| | - Mohamad Saad
- Qatar Computing Research Institute, Hamad Bin Khalifa University, Doha, Qatar; Neuroscience Research Center, Faculty of Medical Sciences, Lebanese University, Beirut, Lebanon
| | | | - Donglei Hu
- Department of Medicine, Institute for Human Genetics, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Wouter Hendrickx
- Research Branch, Sidra Medicine, PO Box 26999 Doha, Qatar; College of Health and Life Sciences, Hamad Bin Khalifa University, Doha, Qatar
| | - Jessica Roelands
- Research Branch, Sidra Medicine, PO Box 26999 Doha, Qatar; Department of Surgery, Leiden University Medical Center, 2333 ZA Leiden, the Netherlands
| | - Eduard Porta-Pardo
- Barcelona Supercomputing Center (BSC); Josep Carreras Leukaemia Research Institute (IJC), Badalona, 08034 Barcelona, Catalonia, Spain
| | - Younes Mokrab
- Research Branch, Sidra Medicine, PO Box 26999 Doha, Qatar; College of Health and Life Sciences, Hamad Bin Khalifa University, Doha, Qatar; Weill Cornell Medicine, Doha, Qatar
| | - Farshad Farshidfar
- Department of Oncology, University of Calgary, Alberta AB T2N 4N1, Canada; Arnie Charbonneau Cancer Institute, Calgary, Alberta AB T2N 4N1, Canada; Department of Biomedical Data Science and Institute for Stem Cell Biology and Regenerative Medicine, School of Medicine, Stanford University, Stanford, CA 94305, USA; Tenaya Therapeutics, South San Francisco, CA 94080, USA
| | - Tomas Kirchhoff
- Perlmutter Cancer Center, New York University School of Medicine, New York University Langone Health, New York, NY 10016, USA
| | - Randy F Sweis
- Department of Medicine, Section of Hematology/Oncology, Committee on Clinical Pharmacology and Pharmacogenomics, Committee on Immunology, University of Chicago, Chicago, IL 60637, USA
| | - Oliver F Bathe
- Department of Oncology, University of Calgary, Alberta AB T2N 4N1, Canada; Arnie Charbonneau Cancer Institute, Calgary, Alberta AB T2N 4N1, Canada; Department of Surgery, University of Calgary, Calgary, Alberta AB T2N 4N1, Canada
| | | | - Michael J Campbell
- Department of Surgery, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Cynthia Stretch
- Department of Oncology, University of Calgary, Alberta AB T2N 4N1, Canada; Arnie Charbonneau Cancer Institute, Calgary, Alberta AB T2N 4N1, Canada
| | - Scott Huntsman
- Department of Medicine, Institute for Human Genetics, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Rebecca E Graff
- Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Najeeb Syed
- Research Branch, Sidra Medicine, PO Box 26999 Doha, Qatar; Department of Science and Technology, University of Sannio, 82100 Benevento, Italy
| | - Laszlo Radvanyi
- Ontario Institute for Cancer Research, Toronto, Ontario M5G 0A3, Canada
| | - Simon Shelley
- Department of Research and Development, Leukemia Therapeutics, LLC, Hull, MA 02045, USA
| | - Denise Wolf
- Department of Laboratory Medicine, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94143, USA
| | | | - Michele Ceccarelli
- Department of Electrical Engineering and Information Technology, University of Naples "Federico II," 80128 Naples, Italy; Istituto di Ricerche Genetiche "G. Salvatore," Biogem s.c.ar.l., 83031 Ariano Irpino, Italy
| | - Jérôme Galon
- INSERM, Laboratory of Integrative Cancer Immunology, Equipe Labellisée Ligue Contre Le Cancer, Centre de Recherche de Cordeliers, Université de Paris, Sorbonne Université, Paris, France
| | - Elad Ziv
- Department of Medicine, Institute for Human Genetics, Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, San Francisco, CA 94143, USA.
| | - Davide Bedognetti
- Research Branch, Sidra Medicine, PO Box 26999 Doha, Qatar; College of Health and Life Sciences, Hamad Bin Khalifa University, Doha, Qatar; Department of Internal Medicine and Medical Specialties (Di.M.I.), University of Genoa, 16132 Genoa, Italy.
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4
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Abstract
Several recent studies in a number of model systems including zebrafish, Arabidopsis, and mouse have revealed phenotypic differences between knockouts (i.e., mutants) and knockdowns (e.g., antisense-treated animals). These differences have been attributed to a number of reasons including off-target effects of the antisense reagents. An alternative explanation was recently proposed based on a zebrafish study reporting that genetic compensation was observed in egfl7 mutant but not knockdown animals. Dosage compensation was first reported in Drosophila in 1932, and genetic compensation in response to a gene knockout was first reported in yeast in 1969. Since then, genetic compensation has been documented many times in a number of model organisms; however, our understanding of the underlying molecular mechanisms remains limited. In this review, we revisit studies reporting genetic compensation in higher eukaryotes and outline possible molecular mechanisms, which may include both transcriptional and posttranscriptional processes.
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Affiliation(s)
- Mohamed A. El-Brolosy
- Department of Developmental Genetics, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Didier Y. R. Stainier
- Department of Developmental Genetics, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
- * E-mail:
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5
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Song Y, Sullivan T, Klarmann K, Gilbert D, O’Sullivan TN, Lu L, Wang S, Haines DC, Van Dyke T, Keller JR. RB inactivation in keratin 18 positive thymic epithelial cells promotes non-cell autonomous T cell hyperproliferation in genetically engineered mice. PLoS One 2017; 12:e0171510. [PMID: 28158249 PMCID: PMC5291521 DOI: 10.1371/journal.pone.0171510] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 01/20/2017] [Indexed: 11/25/2022] Open
Abstract
Thymic epithelial cells (TEC), as part of thymic stroma, provide essential growth factors/cytokines and self-antigens to support T cell development and selection. Deletion of Rb family proteins in adult thymic stroma leads to T cell hyperplasia in vivo. To determine whether deletion of Rb specifically in keratin (K) 18 positive TEC was sufficient for thymocyte hyperplasia, we conditionally inactivated Rb and its family members p107 and p130 in K18+ TEC in genetically engineered mice (TgK18GT121; K18 mice). We found that thymocyte hyperproliferation was induced in mice with Rb inactivation in K18+ TEC, while normal T cell development was maintained; suggesting that inactivation of Rb specifically in K18+ TEC was sufficient and responsible for the phenotype. Transplantation of wild type bone marrow cells into mice with Rb inactivation in K18+ TEC resulted in donor T lymphocyte hyperplasia confirming the non-cell autonomous requirement for Rb proteins in K18+ TEC in regulating T cell proliferation. Our data suggests that thymic epithelial cells play an important role in regulating lymphoid proliferation and thymus size.
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Affiliation(s)
- Yurong Song
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
| | - Teresa Sullivan
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
| | - Kimberly Klarmann
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
- Basic Science Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland, United States of America
| | - Debra Gilbert
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
| | - T. Norene O’Sullivan
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
| | - Lucy Lu
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
| | - Sophie Wang
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
| | - Diana C. Haines
- Pathology/ Histotechnology Laboratory, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland, United States of America
| | - Terry Van Dyke
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
| | - Jonathan R. Keller
- Mouse Cancer Genetics Program, Center for Cancer Research, National Cancer Institute, Frederick, Maryland, United States of America
- Basic Science Program, Leidos Biomedical Research, Inc., Frederick National Laboratory for Cancer Research, Frederick, Maryland, United States of America
- * E-mail:
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6
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Dong OX, Tong M, Bonardi V, El Kasmi F, Woloshen V, Wünsch LK, Dangl JL, Li X. TNL-mediated immunity in Arabidopsis requires complex regulation of the redundant ADR1 gene family. THE NEW PHYTOLOGIST 2016; 210:960-973. [PMID: 27074399 DOI: 10.1111/nph.13821] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 11/24/2015] [Indexed: 06/05/2023]
Abstract
Nucleotide-binding leucine-rich repeat proteins (NLRs) serve as intracellular immune receptors in animals and plants. Sensor NLRs perceive pathogen-derived effector molecules and trigger robust host defense. Recent studies revealed the role of three coiled-coil-type NLRs (CNLs) of the ADR1 family - ADR1, ADR1-L1 and ADR1-L2 - as redundant helper NLRs, whose function is required for defense mediated by multiple sensor NLRs. From a mutant snc1-enhancing (MUSE) forward genetic screen in Arabidopsis targeted to identify negative regulators of snc1 that encodes a TIR-type NLR (TNL), we isolated two alleles of muse15, both carrying mutations in ADR1-L1. Interestingly, loss of ADR1-L1 also enhances immunity-related phenotypes in other autoimmune mutants including cpr1, bal and lsd1. This immunity-enhancing effect is not mediated by increased SNC1 protein stability, nor is it fully dependent on the accumulation of the defense hormone salicylic acid (SA). Transcriptional analysis revealed an upregulation of ADR1 and ADR1-L2 in the adr1-L1 background, which may overcompensate the loss of ADR1-L1, resulting in enhanced immunity. Interestingly, autoimmunity of snc1 and chs2, which encode typical TNLs, is fully suppressed by the adr1 triple mutant, suggesting that the ADRs are required for TNL downstream signaling. This study extends our knowledge on the interplay among ADRs and reveals their complexity in defense regulation.
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Affiliation(s)
- Oliver Xiaoou Dong
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
- Department of Botany, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Meixuezi Tong
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
- Department of Botany, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Vera Bonardi
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599-3280, USA
| | - Farid El Kasmi
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599-3280, USA
| | - Virginia Woloshen
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
- Department of Botany, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Lisa K Wünsch
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599-3280, USA
| | - Jeffery L Dangl
- Department of Biology, University of North Carolina, Chapel Hill, NC, 27599-3280, USA
- Howard Hughes Medical Institute, University of North Carolina, Chapel Hill, NC, 27599-3280, USA
| | - Xin Li
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
- Department of Botany, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
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7
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Abstract
Mammalian DREAM is a conserved protein complex that functions in cellular quiescence. DREAM contains an E2F, a retinoblastoma (RB)-family protein, and the MuvB core (LIN9, LIN37, LIN52, LIN54, and RBBP4). In mammals, MuvB can alternatively bind to BMYB to form a complex that promotes mitotic gene expression. Because BMYB-MuvB is essential for proliferation, loss-of-function approaches to study MuvB have generated limited insight into DREAM function. Here, we report a gene-targeted mouse model that is uniquely deficient for DREAM complex assembly. We have targeted p107 (Rbl1) to prevent MuvB binding and combined it with deficiency for p130 (Rbl2). Our data demonstrate that cells from these mice preferentially assemble BMYB-MuvB complexes and fail to repress transcription. DREAM-deficient mice show defects in endochondral bone formation and die shortly after birth. Micro-computed tomography and histology demonstrate that in the absence of DREAM, chondrocytes fail to arrest proliferation. Since DREAM requires DYRK1A (dual-specificity tyrosine phosphorylation-regulated protein kinase 1A) phosphorylation of LIN52 for assembly, we utilized an embryonic bone culture system and pharmacologic inhibition of (DYRK) kinase to demonstrate a similar defect in endochondral bone growth. This reveals that assembly of mammalian DREAM is required to induce cell cycle exit in chondrocytes.
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8
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Diss G, Ascencio D, DeLuna A, Landry CR. Molecular mechanisms of paralogous compensation and the robustness of cellular networks. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2013; 322:488-99. [PMID: 24376223 DOI: 10.1002/jez.b.22555] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 11/26/2013] [Indexed: 11/10/2022]
Abstract
Robustness is the ability of a system to maintain its function despite environmental or genetic perturbation. Genetic robustness is a key emerging property of living systems and is achieved notably by the presence of partially redundant parts that result from gene duplication. Functional overlap between paralogs allows them to compensate for each other's loss, as commonly revealed by aggravating genetic interactions. However, the molecular mechanisms linking the genotype (loss of function of a gene) to the phenotype (genetic buffering by a paralog) are still poorly understood and the molecular aspects of this compensation are rarely addressed in studies of gene duplicates. Here, we review molecular mechanisms of functional compensation between paralogous genes, many of which from studies that were not meant to study this phenomenon. We propose a standardized terminology and, depending on whether or not the molecular behavior of the intact gene is modified in response to the deletion of its paralog, we classify mechanisms of compensation into passive and active events. We further describe three non-exclusive mechanisms of active paralogous compensation for which there is evidence in the literature: changes in abundance, in localization, and in protein interactions. This review will serve as a framework for the genetic and molecular analysis of paralogous compensation, one of the universal features of genetic systems.
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Affiliation(s)
- Guillaume Diss
- Département de Biologie, Institut de Biologie Intégrative et des Systèmes, PROTEO, Pavillon Charles-Eugène-Marchand, Québec, QC, Canada
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9
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Costa C, Paramio JM, Santos M. Skin Tumors Rb(eing) Uncovered. Front Oncol 2013; 3:307. [PMID: 24381932 PMCID: PMC3865458 DOI: 10.3389/fonc.2013.00307] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 12/04/2013] [Indexed: 11/23/2022] Open
Abstract
The Rb1 gene was the first bona fide tumor suppressor identified and cloned more than 25 years ago. Since then, a plethora of studies have revealed the functions of pRb and the existence of a sophisticated and strictly regulated pathway that modulates such functional roles. An emerging paradox affecting Rb1 in cancer connects the relatively low number of mutations affecting Rb1 gene in specific human tumors, compared with the widely functional inactivation of pRb in most, if not in all, human cancers. The existence of a retinoblastoma family of proteins pRb, p107, and p130 and their potential unique and overlapping functions as master regulators of cell cycle progression and transcriptional modulation by similar processes, may provide potential clues to explain such conundrum. Here, we will review the development of different genetically engineered mouse models, in particular those affecting stratified epithelia, and how they have offered new avenues to understand the roles of the Rb family members and their targets in the context of tumor development and progression.
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Affiliation(s)
- Clotilde Costa
- Molecular Oncology Unit, Department of Basic Research, Centro de Investigaciones Energéticas Medioambientales y Teconológicas (ed70A) , Madrid , Spain
| | - Jesús M Paramio
- Molecular Oncology Unit, Department of Basic Research, Centro de Investigaciones Energéticas Medioambientales y Teconológicas (ed70A) , Madrid , Spain
| | - Mirentxu Santos
- Molecular Oncology Unit, Department of Basic Research, Centro de Investigaciones Energéticas Medioambientales y Teconológicas (ed70A) , Madrid , Spain
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10
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The retinoblastoma family of proteins and their regulatory functions in the mammalian cell division cycle. Cell Div 2012; 7:10. [PMID: 22417103 PMCID: PMC3325851 DOI: 10.1186/1747-1028-7-10] [Citation(s) in RCA: 183] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Accepted: 03/14/2012] [Indexed: 12/15/2022] Open
Abstract
The retinoblastoma (RB) family of proteins are found in organisms as distantly related as humans, plants, and insects. These proteins play a key role in regulating advancement of the cell division cycle from the G1 to S-phases. This is achieved through negative regulation of two important positive regulators of cell cycle entry, E2F transcription factors and cyclin dependent kinases. In growth arrested cells transcriptional activity by E2Fs is repressed by RB proteins. Stimulation of cell cycle entry by growth factor signaling leads to activation of cyclin dependent kinases. They in turn phosphorylate and inactivate the RB family proteins, leading to E2F activation and additional cyclin dependent kinase activity. This propels the cell cycle irreversibly forward leading to DNA synthesis. This review will focus on the basic biochemistry and cell biology governing the regulation and activity of mammalian RB family proteins in cell cycle control.
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11
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Talluri S, Isaac CE, Ahmad M, Henley SA, Francis SM, Martens AL, Bremner R, Dick FA. A G1 checkpoint mediated by the retinoblastoma protein that is dispensable in terminal differentiation but essential for senescence. Mol Cell Biol 2010; 30:948-60. [PMID: 20008551 PMCID: PMC2815577 DOI: 10.1128/mcb.01168-09] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2009] [Revised: 09/23/2009] [Accepted: 12/07/2009] [Indexed: 11/20/2022] Open
Abstract
Terminally differentiated cell types are needed to live and function in a postmitotic state for a lifetime. Cellular senescence is another type of permanent arrest that blocks the proliferation of cells in response to genotoxic stress. Here we show that the retinoblastoma protein (pRB) uses a mechanism to block DNA replication in senescence that is distinct from its role in permanent cell cycle exit associated with terminal differentiation. Our work demonstrates that a subtle mutation in pRB that cripples its ability to interact with chromatin regulators impairs heterochromatinization and repression of E2F-responsive promoters during senescence. In contrast, terminally differentiated nerve and muscle cells bearing the same mutation fully exit the cell cycle and block E2F-responsive gene expression by a different mechanism. Remarkably, this reveals that pRB recruits chromatin regulators primarily to engage a stress-responsive G(1) arrest program.
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Affiliation(s)
- Srikanth Talluri
- London Regional Cancer Program, Children's Health Research Institute, Department of Biochemistry, University of Western Ontario, London, Ontario, Canada, Genetics and Development Division, Toronto Western Research Institute, Department of Ophthalmology and Visual Science, Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Christian E. Isaac
- London Regional Cancer Program, Children's Health Research Institute, Department of Biochemistry, University of Western Ontario, London, Ontario, Canada, Genetics and Development Division, Toronto Western Research Institute, Department of Ophthalmology and Visual Science, Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Mohammad Ahmad
- London Regional Cancer Program, Children's Health Research Institute, Department of Biochemistry, University of Western Ontario, London, Ontario, Canada, Genetics and Development Division, Toronto Western Research Institute, Department of Ophthalmology and Visual Science, Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Shauna A. Henley
- London Regional Cancer Program, Children's Health Research Institute, Department of Biochemistry, University of Western Ontario, London, Ontario, Canada, Genetics and Development Division, Toronto Western Research Institute, Department of Ophthalmology and Visual Science, Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Sarah M. Francis
- London Regional Cancer Program, Children's Health Research Institute, Department of Biochemistry, University of Western Ontario, London, Ontario, Canada, Genetics and Development Division, Toronto Western Research Institute, Department of Ophthalmology and Visual Science, Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Alison L. Martens
- London Regional Cancer Program, Children's Health Research Institute, Department of Biochemistry, University of Western Ontario, London, Ontario, Canada, Genetics and Development Division, Toronto Western Research Institute, Department of Ophthalmology and Visual Science, Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Rod Bremner
- London Regional Cancer Program, Children's Health Research Institute, Department of Biochemistry, University of Western Ontario, London, Ontario, Canada, Genetics and Development Division, Toronto Western Research Institute, Department of Ophthalmology and Visual Science, Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
| | - Frederick A. Dick
- London Regional Cancer Program, Children's Health Research Institute, Department of Biochemistry, University of Western Ontario, London, Ontario, Canada, Genetics and Development Division, Toronto Western Research Institute, Department of Ophthalmology and Visual Science, Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada
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12
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Abstract
The
mechanisms controlling organismal aging have yet to be clearly defined. In
our recent paper [1], we revealed
thatTAp63, the p53 family member, is a critical gene in
preventing organismal aging by controlling the maintenance of dermal and
epidermal precursor and stem cells critical for wound healing and hair
growth. In the absence of TAp63, dermal stem cells (skin-derived
precursors or SKPs) in young mice are hyperproliferative. As early as one
month of age, SKPs and epidermal precursor cells exhibit signs of premature
aging including a marked increase in senescence, DNA damage, and genomic
instability resulting in an exhaustion of these cells and an overall
acceleration in aging. Here, we discuss our findings and its relevance to
longevity, regenerative medicine, and tumorigenesis.
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Affiliation(s)
- Xiaohua Su
- Department of Molecular and Cellular Oncology, Graduate School of Biomedical Sciences, The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, USA
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13
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Harb G, Vasavada RC, Cobrinik D, Stewart AF. The retinoblastoma protein and its homolog p130 regulate the G1/S transition in pancreatic beta-cells. Diabetes 2009; 58:1852-62. [PMID: 19509021 PMCID: PMC2712776 DOI: 10.2337/db08-0759] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE The retinoblastoma protein family (pRb, p130, p107) plays a central role in the regulation of cell cycle progression. Surprisingly, loss of pRb in the beta-cell has no discernible effect on cell cycle control. Therefore, we explored the effects of individual loss of either p130 or p107 in addition to the simultaneous loss of both pRb/p130 on the beta-cell. RESEARCH DESIGN AND METHODS Adult mice deficient in either p130 or p107 or both pRb/p130 were examined for effects on beta-cell replication, function, and survival. The Cre-Lox system was also used to inactivate pRb in wild-type and p130-deficient beta-cells in vitro. RESULTS In vivo loss of either p107 or p130 did not affect beta-cell replication or function. Combined pRb/p130 loss, however, resulted in dramatically accelerated proliferation as well as apoptotic cell death. Pancreas and beta-cell mass were significantly reduced in double mutants. Despite this, overall glucose tolerance was normal, except for mild postprandial hyperglycemia. Ex vivo, acute deletion of pRb in p130-deficient beta-cells also caused a striking increase in proliferation. The combined deletion of pRb/p130 upregulated islet expression of E2F2 but not E2F1. CONCLUSIONS These studies define an essential role for the pocket proteins in controlling the G(1)/S transition in beta-cells. When deficient in both pRb and p130, beta-cells undergo unrestrained cell cycle reentry and activation of apoptosis. These studies underscore the central role of the pRb pathway in controlling beta-cell turnover and provide new cellular targets for beta-cell regeneration.
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Affiliation(s)
- George Harb
- Division of Endocrinology and Metabolism, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Rupangi C. Vasavada
- Division of Endocrinology and Metabolism, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - David Cobrinik
- Margaret M. Dyson Vision Research Institute, Weill Medical College of Cornell University, New York, New York
| | - Andrew F. Stewart
- Division of Endocrinology and Metabolism, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
- Corresponding author: Andrew F. Stewart,
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14
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Ho VM, Schaffer BE, Karnezis AN, Park KS, Sage J. The retinoblastoma gene Rb and its family member p130 suppress lung adenocarcinoma induced by oncogenic K-Ras. Oncogene 2009; 28:1393-9. [PMID: 19151761 DOI: 10.1038/onc.2008.491] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Mutations of the retinoblastoma tumor suppressor gene RB are frequently observed in human cancers, but rarely in non-small cell lung carcinomas (NSCLCs). Emerging evidence also suggests that the RB-related gene p130 is inactivated in a subset of human NSCLCs. To directly test the specific tumor suppressor roles of RB and p130 in NSCLC, we crossed Rb and p130 conditional mutant mice to mice carrying a conditional oncogenic K-Ras allele. In this model, controlled oncogenic K-Ras activation leads to the development of adenocarcinoma, a major subtype of NSCLC. We found that loss of p130 accelerated the death of mice, providing direct evidence in vivo that p130 is a tumor suppressor gene, albeit a weak one in this context. Loss of Rb increased the efficiency of lung cancer initiation and resulted in the development of high-grade adenocarcinomas and rapid death. Thus, despite the low frequency of RB mutations in human NSCLCs and reports that K-Ras activation and loss of RB function are rarely found in the same human tumors, loss of Rb clearly cooperates with activation of oncogenic K-Ras in lung adenocarcinoma development in mice.
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Affiliation(s)
- V M Ho
- Department of Pediatrics and Genetics, Stanford Medical School, Stanford, CA 94305-5149, USA
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15
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Burkhart DL, Viatour P, Ho VM, Sage J. GFP reporter mice for the retinoblastoma-related cell cycle regulator p107. Cell Cycle 2008; 7:2544-52. [PMID: 18719374 DOI: 10.4161/cc.7.16.6441] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The RB tumor suppressor gene is mutated in a broad range of human cancers, including pediatric retinoblastoma. Strikingly, however, Rb mutant mice develop tumors of the pituitary and thyroid glands, but not retinoblastoma. Mouse genetics experiments have demonstrated that p107, a protein related to pRB, is capable of preventing retinoblastoma, but not pituitary tumors, in Rb-deficient mice. Evidence suggests that the basis for this compensatory function of p107 is increased transcription of the p107 gene in response to Rb inactivation. To begin to address the context-dependency of this compensatory role of p107 and to follow p107 expression in vivo, we have generated transgenic mice carrying an enhanced GFP (eGFP) reporter inserted into a bacterial artificial chromosome (BAC) containing the mouse p107 gene. Expression of the eGFP transgene parallels that of p107 in these transgenic mice and identifies cells with a broad range of expression level for p107, even within particular organs or tissues. We also show that loss of Rb results in the upregulation of p107 transcription in specific cell populations in vivo, including subpopulations of hematopoietic cells. Thus, p107 BAC-eGFP transgenic mice serve as a useful tool to identify distinct cell types in which p107 is expressed and may have key functions in vivo, and to characterize changes in cellular networks accompanying Rb deficiency.
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Affiliation(s)
- Deborah L Burkhart
- Department of Pediatrics and Genetics, Cancer Biology Program, Stanford Medical School, Stanford, California, USA
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16
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Hu XT. TGFbeta-mediated formation of pRb-E2F complexes in human myeloid leukemia cells. Biochem Biophys Res Commun 2008; 369:277-80. [PMID: 18294958 DOI: 10.1016/j.bbrc.2008.02.051] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Accepted: 02/14/2008] [Indexed: 10/22/2022]
Abstract
TGFbeta is well known for its inhibitory effect on cell cycle G1 checkpoint kinases. However, its role in the control of pRb-E2F complexes is not well established. TGFbeta inhibits phosphorylation of pRb at several serine and threonine residues and regulates the association of E2F transcription factors with pRb family proteins. Recent studies found that predominantly E2F-4, p130, and histone deacetylase (HDAC) are found to bind to corresponding E2F-responsive promoters in G0/G1 phase. As cells progress through mid-G1, p130-E2F4 complex are replaced by p107-E2F4 followed by activators E2F1, 2, and 3. pRb was not detectable in the promoters containing the E2F-responsive site in cycling cells but was associated with E2F4-p130 complexes or E2F4-p107 complexes during G0/G1 phase. In human myeloid leukemia cell line, MV4-11, TGFbeta upregulated pRb-E2F-4 and p130-E2F-4, and downregulated p107-E2F-4 complexes. However, pRB-E2F1 and pRb-E2F3 complexes were found in proliferating cells but not in TGFbeta arrested G1 cells. In addition, electrophoretic gel mobility shift assay (EMSA) could not detect pRb-E2F DNA-binding activities either in S or G1 phase but exhibited the existence of p107-E2F4 in proliferating cells and p130-E2F4 complexes in TGFbeta-arrested G1 cells, respectively. Our data suggest that p107 and p130, but not pRb, and the repressor E2F, but not activator E2Fs, play a critical role in regulating E2F-responsive gene expression in TGFbeta-mediated cell cycle control in human myeloid leukemia cells.
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Affiliation(s)
- Xiao Tang Hu
- School of Natural and Health Science, Barry University, 11300 Northeast Second Avenue, Miami Shores, FL 33161, USA
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17
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Normal development is an integral part of tumorigenesis in T cell-specific PTEN-deficient mice. Proc Natl Acad Sci U S A 2008; 105:2022-7. [PMID: 18250301 DOI: 10.1073/pnas.0712059105] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
PTEN is a tumor suppressor gene but whether cancer can develop in all PTEN-deficient cells is not known. In T cell-specific PTEN-deficient (tPTEN-/-) mice, which suffer from mature T cell lymphomas, we found that premalignancy, as defined by elevated AKT and senescence pathways, starts in immature T cell precursors and surprisingly not in mature T cells. Premalignancy only starts in 6-week-old mice and becomes much stronger in 9-week-old mice although PTEN is lost since birth. tPTEN-/- immature T cells do not become tumors, and senescence has no role in this model because these cells exist in a novel cell cycle state, expressing proliferating proteins but not proliferating to any significant degree. Instead, the levels of p27(kip1), which is lower in tPTEN-/- immature T cells and almost nonexistent in tPTEN-/- mature T cells, correlate with the proliferation capability of these cells. Interestingly, transient reduction of these cancer precursor cells in adult tPTEN-/- mice within a crucial time window significantly delayed lymphomas and mouse lethality. Thus, loss of PTEN alone is not sufficient for cells to become cancerous, therefore other developmental events are necessary for tumor formation.
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18
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Wang Y, Ray SK, Hinds PW, Leiter AB. The retinoblastoma protein, RB, is required for gastrointestinal endocrine cells to exit the cell cycle, but not for hormone expression. Dev Biol 2007; 311:478-86. [PMID: 17936268 DOI: 10.1016/j.ydbio.2007.08.052] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2007] [Revised: 07/26/2007] [Accepted: 08/28/2007] [Indexed: 11/26/2022]
Abstract
Important functions of the RB family proteins include inhibition of cell cycle progression and regulation of terminal differentiation. We have examined the role of RB and the related protein, p107, in regulating cell cycle activity and differentiation of gastrointestinal endocrine cells, a relatively quiescent cell population, by conditionally disrupting the RB gene in neurogenin3 (Ngn3)-expressing cells in both p107(+/+) and p107(-/-) mice. Endocrine cells in the small intestine, colon, pancreas, and stomach were present in normal numbers in RB and RB-p107 mutants except for an increase in serotonin cells and decrease in ghrelin cells in the antral stomach. Deletion of RB resulted in a dramatic increase in proliferating serotonin cells in the antral stomach and intestine, whereas other enteroendocrine cell types exhibited much lower cell cycle activity or remained quiescent. The related p107 protein appears dispensable for enteroendocrine differentiation and does not functionally compensate for the loss of RB. Our results suggest that RB is required for enteroendocrine cells, particularly serotonin cells, to undergo cell cycle arrest as they terminally differentiate. RB has relatively subtle effects on enteroendocrine cell differentiation and is not required for the expression of the normal repertoire of hormones in the gastrointestinal tract.
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Affiliation(s)
- Yang Wang
- Division of Gastroenterology, GRASP Digestive Disease Center, Tufts-New England Medical Center, Boston, MA 02111, USA
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19
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Andreu-Vieyra C, Chen R, Matzuk MM. Effects of granulosa cell-specific deletion of Rb in Inha-alpha null female mice. Endocrinology 2007; 148:3837-49. [PMID: 17510234 DOI: 10.1210/en.2006-1590] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Our laboratory is interested in the gonadal growth regulatory properties of inhibins, members of the TGFbeta superfamily. We have previously shown that female mice lacking inhibins (Inha(-/-)) develop granulosa cell tumors and that concurrent loss of p27 accelerates tumor development. It has also been shown that the retinoblastoma protein RB regulates the G(1) to S phase transition of the cell cycle by controlling the activity of transcription factors and stabilizing the levels of the cell cycle inhibitor P27. Based on these data, we hypothesized that concurrent loss of Rb and inhibins in the ovary will exacerbate tumor formation. To test this hypothesis, we generated an ovarian granulosa cell conditional knockout (cKO) of Rb using the Cre/lox recombination system in the background of Inha(-/-) mice. Inha(-/-)/Rb cKO females show a modest increase in mortality rates compared with Inha(-/-) females. Although histologically similar to Inha(-/-) ovarian tumors, tumors from Inha(-/-)/Rb cKO females show increased number of mitotic figures and apoptotic rates. Interestingly, P27 levels are decreased in Inha(-/-)/Rb cKO ovarian tumors, likely due to the combined effect of Rb loss and increased Skp2 expression, which targets P27 to the proteosome. We propose that Rb loss may cause cell cycle delay or arrest, followed by apoptosis and that increases in p107 and p130 levels may compensate for Rb loss. These findings confirm the importance of P27 as a cell cycle regulator in granulosa cells and suggest functional compensation between RB-like proteins in ovarian tumorigenesis.
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Affiliation(s)
- Claudia Andreu-Vieyra
- Baylor College of Medicine, Department of Pathology, One Baylor Plaza, Smith Building S217, Houston, Texas 77030, USA
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20
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Cosgrove RA, Philpott A. Cell cycling and differentiation do not require the retinoblastoma protein during early Xenopus development. Dev Biol 2007; 303:311-24. [PMID: 17188261 DOI: 10.1016/j.ydbio.2006.11.015] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2006] [Revised: 11/03/2006] [Accepted: 11/08/2006] [Indexed: 11/23/2022]
Abstract
The retinoblastoma protein (pRb) is a central regulator of the cell cycle, controlling passage through G1 phase. Moreover, pRb has also been shown to play a direct role in the differentiation of multiple tissues, including nerve and muscle. Rb null mice display embryonic lethality, although recent data have indicated that at least some of these defects are due to placental insufficiency. To investigate this further, we have examined the role of pRb in early development of the frog Xenopus laevis, which develops without the need for a placenta. Surprisingly, we see that loss of pXRb has no effect on either cell cycling or differentiation of neural or muscle tissue, while overexpression of pXRb similarly has no effects. We demonstrate that, in fact, pXRb is maintained in a hyperphosphorylated and therefore inactive state early in development. Therefore, Rb protein is not required for cell cycle control or differentiation in early embryos, indicating unusual control of these G1/G0 events at this developmental stage.
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Affiliation(s)
- Ruth A Cosgrove
- Department of Oncology, University of Cambridge, Hutchison/MRC Research Centre, Addenbrookes Hospital, Hills Road, Cambridge CB2 0XZ, UK
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21
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Kirienko NV, Fay DS. Transcriptome profiling of the C. elegans Rb ortholog reveals diverse developmental roles. Dev Biol 2007; 305:674-84. [PMID: 17368442 PMCID: PMC2680605 DOI: 10.1016/j.ydbio.2007.02.021] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Accepted: 02/14/2007] [Indexed: 11/25/2022]
Abstract
LIN-35 is the single C. elegans ortholog of the mammalian pocket protein family members, pRb, p107, and p130. To gain insight into the roles of pocket proteins during development, a microarray analysis was performed with lin-35 mutants. Stage-specific regulation patterns were revealed, indicating that LIN-35 plays diverse roles at distinct developmental stages. LIN-35 was found to repress the expression of many genes involved in cell proliferation in larvae, an activity that is carried out in conjunction with E2F. In addition, LIN-35 was found to regulate neuronal genes during embryogenesis and targets of the intestinal-specific GATA transcription factor, ELT-2, at multiple developmental stages. Additional findings suggest that LIN-35 functions in cell cycle regulation in embryos in a manner that is independent of E2F. A comparison of LIN-35-regulated genes with known fly and mammalian pocket protein targets revealed a high degree of overlap, indicating strong conservation of pocket protein functions in diverse phyla. Based on microarray results and our refinement of the C. elegans E2F consensus sequence, we were able to generate a comprehensive list of putative E2F-regulated genes in C. elegans. These results implicate a large number of genes previously unconnected to cell cycle control as having potential roles in this process.
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Affiliation(s)
| | - David S. Fay
- To whom correspondence should be addressed. David S. Fay, Telephone: (307) 766-4961, Fax: (307) 766-5098,
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22
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Cobrinik D, Francis RO, Abramson DH, Lee TC. Rb induces a proliferative arrest and curtails Brn-2 expression in retinoblastoma cells. Mol Cancer 2006; 5:72. [PMID: 17163992 PMCID: PMC1764425 DOI: 10.1186/1476-4598-5-72] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2006] [Accepted: 12/12/2006] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Retinoblastoma is caused by loss of the Rb protein in early retinal cells. Although numerous Rb functions have been identified, Rb effects that specifically relate to the suppression of retinoblastoma have not been defined. RESULTS In this study, we examined the effects of restoring Rb to Y79 retinoblastoma cells, using novel retroviral and lentiviral vectors that co-express green fluorescent protein (GFP). The lentiviral vector permitted transduction with sufficient efficiency to perform biochemical analyses. Wild type Rb (RbWT) and to a lesser extent the low penetrance mutant Rb661W induced a G0/G1 arrest associated with induction of p27KIP1 and repression of cyclin E1 and cyclin E2. Microarray analyses revealed that in addition to down-regulating E2F-responsive genes, Rb repressed expression of Brn-2 (POU3F2), which is implicated as an important transcriptional regulator in retinal progenitor cells and other neuroendocrine cell types. The repression of Brn-2 was a specific Rb effect, as ectopic p27 induced a G0/G1 block, but enhanced, rather than repressed, Brn-2 expression. CONCLUSION In addition to Rb effects that occur in many cell types, Rb regulates a gene that selectively governs the behavior of late retinal progenitors and related cells.
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Affiliation(s)
- David Cobrinik
- Margaret M. Dyson Vision Research Institute, Weill Medical College of Cornell University, New York, NY 10021, USA
- Department of Ophthalmology, Weill Medical College of Cornell University, New York, NY 10021, USA
| | - Richard O Francis
- Department of Pathology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
| | - David H Abramson
- Department of Ophthalmology, Weill Medical College of Cornell University, New York, NY 10021, USA
- Ophthalmic Oncology Service, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA
| | - Thomas C Lee
- Margaret M. Dyson Vision Research Institute, Weill Medical College of Cornell University, New York, NY 10021, USA
- Department of Ophthalmology, Weill Medical College of Cornell University, New York, NY 10021, USA
- Division of Ophthalmology, Department of Surgery, Childrens Hospital Los Angeles, Los Angeles, CA, USA
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23
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Macaluso M, Montanari M, Giordano A. Rb family proteins as modulators of gene expression and new aspects regarding the interaction with chromatin remodeling enzymes. Oncogene 2006; 25:5263-7. [PMID: 16936746 DOI: 10.1038/sj.onc.1209680] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The pRb family proteins (pRb1/105, p107, pRb2/p130), collectively referred to as pocket proteins, are believed to function primarily as regulators of the mammalian cell cycle progression, and suppressors of cellular growth and proliferation. In addition, different studies suggest that these pocket proteins are also involved in development and differentiation of various tissues. Several lines of evidence indicate that generally pRb-family proteins function through their effect on the transcription of E2F-regulated genes. In fact, each of Rb family proteins binds to distinct members of the E2F transcription factors, which regulate the expression of genes whose protein products are necessary for cell proliferation and to drive cell-cycle progression. Nevertheless, pocket proteins can affect the G1/S transition through E2F-independent mechanisms. More recently, a broad range of evidences indicate that pRb-family proteins associate with a wide variety of transcription factors and chromatin remodeling enzymes forming transcriptional repressor complexes that control gene expression. This review focuses on the complex regulatory mechanisms by which pRb-family proteins tell genes when to switch on and off.
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Affiliation(s)
- M Macaluso
- Sbarro Institute for Cancer Research and Molecular Medicine, Center of Biotechnology, College of Science and Technology, Temple University, Philadelphia, PA, USA
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24
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Williams JP, Stewart T, Li B, Mulloy R, Dimova D, Classon M. The retinoblastoma protein is required for Ras-induced oncogenic transformation. Mol Cell Biol 2006; 26:1170-82. [PMID: 16449633 PMCID: PMC1367176 DOI: 10.1128/mcb.26.4.1170-1182.2006] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2005] [Revised: 05/23/2005] [Accepted: 10/20/2005] [Indexed: 12/24/2022] Open
Abstract
Most human cancers involve either mutational activation of the Ras oncogenic pathway and/or inactivation of the retinoblastoma tumor suppressor (RB) pathway. Paradoxically, tumors that harbor Ras mutations almost invariably retain expression of a wild-type pRB protein. We explain this phenomenon by demonstrating that Ras-induced oncogenic transformation surprisingly depends on functional pRB protein. Cells lacking pRB are less susceptible to the oncogenic actions of H-RasV12 than wild-type cells and activated Ras has an inhibitory effect on the proliferation of pRB-deficient human tumor cells. In addition, depletion of pRB from Ras-transformed murine cells or human tumor cells that harbor Ras pathway mutations inhibits their proliferation and anchorage-independent growth. In sharp contrast to pRB-/- 3T3 cells, fibroblasts deficient in other pRB family members (p107 and p130) are more susceptible to Ras-mediated transformation than wild-type 3T3 cells. Moreover, loss of pRB in tumor cells harboring a Ras mutation results in increased expression of p107, and overexpression of p107 but not pRB strongly inhibits proliferation of these tumor cells. Together, these findings suggest that pRB and p107 have distinct roles in Ras-mediated transformation and suggest a novel tumor-suppressive role for p107 in the context of activated Ras.
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Affiliation(s)
- Jonathan P Williams
- MGH Cancer Center and Harvard Medical School, Bldg. 149, 13th St., Charlestown, MA 02129, USA
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25
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Haigis K, Sage J, Glickman J, Shafer S, Jacks T. The related retinoblastoma (pRb) and p130 proteins cooperate to regulate homeostasis in the intestinal epithelium. J Biol Chem 2005; 281:638-47. [PMID: 16258171 DOI: 10.1074/jbc.m509053200] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
pRb, p107, and p130 are related proteins that play a central role in the regulation of cell cycle progression and terminal differentiation in mammalian cells. Nevertheless, it is still largely unclear how these proteins achieve this regulation in vivo. The intestinal epithelium is an ideal in vivo system in which to study the molecular pathways that regulate proliferation and differentiation because it exists in a constant state of development throughout an animal's lifetime. We studied the phenotypic effects on the intestinal epithelium of mutating Rb and p107 or p130. Although mutating these genes singly had little or no effect, loss of pRb and p107 or p130 together produced chronic hyperplasia and dysplasia of the small intestinal and colonic epithelium. In Rb/p130 double mutants this hyperplasia was associated with defects in terminal differentiation of specific cell types and was dependent on the increased proliferation seen in the epithelium of mutant animals. At the molecular level, dysregulation of the Rb pathway led to an increase in the expression of Math1, Cdx1, Cdx2, transcription factors that regulate proliferation and differentiation in the intestinal epithelium. The absence of Cdx1 function in Rb/p130 double mutant mice partially reverted the histologic phenotype by suppressing ectopic mitosis in the epithelium. These studies implicate the Rb pathway as a regulator of epithelial homeostasis in the intestine.
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Affiliation(s)
- Kevin Haigis
- Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA
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26
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Abstract
The E2 factor (E2F) family of transcription factors are downstream targets of the retinoblastoma protein. E2F factors have been known for several years to be important regulators of S-phase entry. Recent studies have improved our understanding of the molecular mechanisms of action used by this transcriptional network. In addition, they have given us an appreciation of the fact that E2F has functions that reach beyond G1/S control and impact cell proliferation in several different ways. The discovery of new family members with unusual properties, the unexpected phenotypes of mutant animals, a diverse collection of biological activities, a large number of new putative target genes and the new modes of transcriptional regulation have all contributed to an increasingly complex view of E2F function. In this review, we will discuss these recent developments and describe how they are beginning to shape a new and revised picture of the E2F transcriptional program.
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Abstract
The retinoblastoma protein (pRB) and the pRB-related p107 and p130 comprise the 'pocket protein' family of cell cycle regulators. These proteins are best known for their roles in restraining the G1-S transition through the regulation of E2F-responsive genes. pRB and the p107/p130 pair are required for the repression of distinct sets of genes, potentially due to their selective interactions with E2Fs that are engaged at specific promoter elements. In addition to regulating E2F-responsive genes in a reversible manner, pocket proteins contribute to silencing of such genes in cells that are undergoing senescence or differentiation. Pocket proteins also affect the G1-S transition through E2F-independent mechanisms, such as by inhibiting Cdk2 or by stabilizing p27(Kip1), and they are implicated in the control of G0 exit, the spatial organization of replication, and genomic rereplication. New insights into pocket protein regulation have also been obtained. Kinases previously thought to be crucial to pocket protein phosphorylation have been shown to be redundant, and new modes of phosphorylation and dephosphorylation have been identified. Despite these advances, much remains to be learned about the pocket proteins, particularly with regard to their developmental and tumor suppressor functions. Thus continues the story of the pocket proteins and the cell cycle.
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Affiliation(s)
- David Cobrinik
- Dyson Vision Research Institute and Department of Ophthalmology, Weill Medical College of Cornell University, 1300 York Avenue, LC303, New York, NY 10021, USA.
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28
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Cinti C, Giordano A. The retinoblastoma gene family: its role in cancer onset and progression. ACTA ACUST UNITED AC 2005. [DOI: 10.1517/14728222.4.6.765] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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29
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Tominaga K, Magee DM, Matzuk MM, Pereira-Smith OM. PAM14, a novel MRG- and Rb-associated protein, is not required for development and T-cell function in mice. Mol Cell Biol 2004; 24:8366-73. [PMID: 15367658 PMCID: PMC516751 DOI: 10.1128/mcb.24.19.8366-8373.2004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2004] [Revised: 05/28/2004] [Accepted: 07/13/2004] [Indexed: 11/20/2022] Open
Abstract
PAM14 has been found to associate in complexes with the MORF4/MRG family of proteins as well as Rb, the tumor suppressor protein. This suggested that it might be involved in cell growth, immortalization, and/or senescence. To elucidate the in vivo function of PAM14, we characterized the expression pattern of mouse Pam14 and generated PAM14-deficient (Pam14(-/-)) mice. Pam14 was widely expressed in all mouse tissues and as early as 7 days during embryonic development. Despite this ubiquitous expression in wild-type mice, Pam14(-/-) mice were healthy and fertile. Response to mitogenic stimulation and production of interleukin-2 were the same in stimulated splenic T cells from Pam14(-/-) mice as in control littermates. Cell growth rates of mouse embryonic fibroblasts (MEFs) from all three genotypes were the same, and immortalized cells were obtained from all cell cultures during continuous culture. There was also no difference in expression of growth-related genes in response to serum stimulation in the null versus control MEFs. These data demonstrate that PAM14 is not essential for normal mouse development and cell cycle control. PAM14 likely acts as an adaptor protein in nucleoprotein complexes and is probably compensated for by another functionally redundant protein(s).
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Affiliation(s)
- Kaoru Tominaga
- Sam and Ann Barshop Center for Longevity and Aging Studies, Department of Cellular and Structural Biology, The University of Texas Health Science Center at San Antonio, San Antonio, TX 78245-3207, USA.
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30
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de las Cuevas N, Urcelay E, Hermida OG, Saíz-Diaz RA, Bermejo F, Ayuso MS, Martín-Requero A. Ca2+/calmodulin-dependent modulation of cell cycle elements pRb and p27kip1 involved in the enhanced proliferation of lymphoblasts from patients with Alzheimer dementia. Neurobiol Dis 2003; 13:254-63. [PMID: 12901840 DOI: 10.1016/s0969-9961(03)00040-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Failure of cell cycle regulation in neurons might be critically involved in the process of neurodegeneration in Alzheimer's disease (AD). We present here evidence to support the hypothesis that cell cycle alterations occur in cells other than neurons in AD sufferers. Lymphocytes from AD patients immortalized with Epstein-Barr virus showed an enhanced rate of proliferation and increased phosphorylation of the retinoblastoma protein (pRb) and other members of the family of pocket proteins compared with cell lines derived from normal age-matched controls. The calmodulin antagonist calmidazolium, as well as W-7 and W-13, abrogated the enhanced activity of AD cells without altering the normal basal rate of proliferation. The effect of calmidazolium was accompanied by partially dephosphorylation of pRb. No changes were found in the expression levels of the G1 cyclin/Cdks complexes. However, lymphoblasts derived from AD patients showed reduced levels of the Cdk inhibitor p27(kip1), which were restored after anti-calmodulin treatment of the cultures. These observations suggest that in AD cells the enhanced rates of cell proliferation and phosphorylation of pRb and the intracellular content of p27(kip1) may be interrelated events controlled by a mechanism dependent on the Ca(2+)/calmodulin signaling pathway. The distinct functional features of lymphoblastoid cells from AD patients offer an invaluable, noninvasive tool to investigate the etiopathogenesis, and eventually, for the early diagnosis and prognosis of this devastating disease.
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Affiliation(s)
- Natividad de las Cuevas
- Department of Pathophysiology and Human Molecular Genetics, Centro de Investigaciones Biológicas (CSIC), Velázquez 144, 28006, Madrid, Spain
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31
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Landsberg RL, Sero JE, Danielian PS, Yuan TL, Lee EY, Lees JA. The role of E2F4 in adipogenesis is independent of its cell cycle regulatory activity. Proc Natl Acad Sci U S A 2003; 100:2456-61. [PMID: 12604789 PMCID: PMC151362 DOI: 10.1073/pnas.0138064100] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2002] [Accepted: 12/31/2002] [Indexed: 01/04/2023] Open
Abstract
The E2F and pocket protein families are known to play an important role in the regulation of both cellular proliferation and terminal differentiation. In this study, we have used compound E2F and pocket protein mutant mouse embryonic fibroblasts to dissect the role of these proteins in adipogenesis. This analysis shows that loss of E2F4 allows cells to undergo spontaneous differentiation. The ability of E2F4 to prevent adipogenesis seems to be quite distinct from the known properties of E2F. First, it can be separated from any change in either E2F-responsive gene expression or cell cycle regulation. Second, it is a specific property of E2F4, and not other E2Fs, and it occurs independently of E2F4's ability to interact with pocket proteins. In addition, E2F4 loss does not override the differentiation defect resulting from pRB loss even though it completely suppresses the proliferation defect of Rb(-/-) mouse embryonic fibroblasts. This finding definitively separates the known, positive role of pRB in adipogenesis from its cell cycle function and shows that this pocket protein is required to act downstream of E2F4 in the differentiation process.
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Affiliation(s)
- Rebecca L Landsberg
- Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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32
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Abstract
Since its discovery, the retinoblastoma (RB) tumour-suppressor protein has been a focal point of cancer research. Accumulating evidence indicates a complex role for RB in cell proliferation, differentiation and survival. To further complicate matters, proteins that are related to RB have redundant as well as antagonistic functions. Recent studies of knockout mice and cells that lack one or more of these proteins have begun to clarify their various context-specific functions and the unique activity of this tumour suppressor.
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Affiliation(s)
- Marie Classon
- MGH Cancer Center, Building 149, 13th Street, Room 7330, Charlestown, Massachusetts 02129, USA.
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33
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Zhao XC, Qu X, Mathews DE, Schaller GE. Effect of ethylene pathway mutations upon expression of the ethylene receptor ETR1 from Arabidopsis. PLANT PHYSIOLOGY 2002; 130:1983-91. [PMID: 12481081 PMCID: PMC166709 DOI: 10.1104/pp.011635] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2002] [Revised: 08/18/2002] [Accepted: 08/30/2002] [Indexed: 05/20/2023]
Abstract
The ethylene receptor family of Arabidopsis consists of five members, one of these being ETR1. The effect of ethylene pathway mutations upon expression of ETR1 was examined. For this purpose, ETR1 levels were quantified in mutant backgrounds containing receptor loss-of-function mutations, ethylene-insensitive mutations, and constitutive ethylene response mutations. Ethylene-insensitive mutations of ETR1 resulted in a posttranscriptional increase in levels of the mutant receptor. Treatment of seedlings with silver, which leads to ethylene insensitivity, also resulted in an increase in levels of ETR1. Loss-of-function mutations of ETR1 resulted in both transcriptional and posttranscriptional changes in levels of the receptor. Most other ethylene pathway mutations, including a newly isolated T-DNA insertion mutation in the gene encoding the ethylene receptor ERS1, had relatively minor effects upon the expression of ETR1. Our results indicate that mutations in ETR1 can affect expression at the posttranscriptional level, and suggest that these posttranscriptional changes may contribute to the phenotypes observed in the mutants. Our results also refine the model on how mutations in ethylene receptors are able to confer dominant ethylene insensitivity upon plants.
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Affiliation(s)
- Xue-Chu Zhao
- Department of Biochemistry, University of New Hampshire, Durham 03824, USA
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34
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Tonini T, Hillson C, Claudio PP. Interview with the retinoblastoma family members: do they help each other? J Cell Physiol 2002; 192:138-50. [PMID: 12115720 DOI: 10.1002/jcp.10117] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The ultimate destiny of a cell to undergo division, differentiation, survival, and death results from an intricate balance between multiple regulators including oncogenes, tumor suppressor genes, and cell cycle associated proteins. Deregulation of the cell cycle machinery switches the phenotype from a normal cell to a cancerous cell. Fundamental alterations of tumor suppressor genes may result in an unregulated cell cycle with the accumulation of mutations and eventual neoplastic transformation. As such, one may define cancer as a genetic disease of the cell cycle. In this review, we will emphasize our current understanding of how the cell cycle machinery maintains cellular homeostasis by studying the consequences of its deregulation.
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Affiliation(s)
- Tiziana Tonini
- Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, Temple University, Philadelphia, Pennsylvania, USA
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35
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Zhu JW, Field SJ, Gore L, Thompson M, Yang H, Fujiwara Y, Cardiff RD, Greenberg M, Orkin SH, DeGregori J. E2F1 and E2F2 determine thresholds for antigen-induced T-cell proliferation and suppress tumorigenesis. Mol Cell Biol 2001; 21:8547-64. [PMID: 11713289 PMCID: PMC100017 DOI: 10.1128/mcb.21.24.8547-8564.2001] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
E2F activity is critical for the control of the G(1) to S phase transition. We show that the combined loss of E2F1 and E2F2 results in profound effects on hematopoietic cell proliferation and differentiation, as well as increased tumorigenesis and decreased lymphocyte tolerance. The loss of E2F1 and E2F2 impedes B-cell differentiation, and hematopoietic progenitor cells in the bone marrow of mice lacking E2F1 and E2F2 exhibit increased cell cycling. Importantly, we show that E2F1 and E2F2 double-knockout T cells exhibit more rapid entry into S phase following antigenic stimulation. Furthermore, T cells lacking E2F1 and E2F2 proliferate much more extensively in response to subthreshold antigenic stimulation. Consistent with these observations, E2F1/E2F2 mutant mice are highly predisposed to the development of tumors, and some mice exhibit signs of autoimmunity.
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Affiliation(s)
- J W Zhu
- Department of Biochemistry and Molecular Genetics, University of Colorado Health Sciences Center, 4200 E. Ninth Ave., Denver, CO 80262, USA
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36
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Ciarmatori S, Scott PH, Sutcliffe JE, McLees A, Alzuherri HM, Dannenberg JH, te Riele H, Grummt I, Voit R, White RJ. Overlapping functions of the pRb family in the regulation of rRNA synthesis. Mol Cell Biol 2001; 21:5806-14. [PMID: 11486020 PMCID: PMC87300 DOI: 10.1128/mcb.21.17.5806-5814.2001] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2001] [Accepted: 05/07/2001] [Indexed: 12/25/2022] Open
Abstract
The "pocket" proteins pRb, p107, and p130 are a family of negative growth regulators. Previous studies have demonstrated that overexpression of pRb can repress transcription by RNA polymerase (Pol) I. To assess whether pRb performs this role under physiological conditions, we have examined pre-rRNA levels in cells from mice lacking either pRb alone or combinations of the three pocket proteins. Pol I transcription was unaffected in pRb-knockout fibroblasts, but specific disruption of the entire pRb family deregulated rRNA synthesis. Further analysis showed that p130 shares with pRb the ability to repress Pol I transcription, whereas p107 is ineffective in this system. Production of rRNA is abnormally elevated in Rb(-/-) p130(-/-) fibroblasts. Furthermore, overexpression of p130 can inhibit an rRNA promoter both in vitro and in vivo. This reflects an ability of p130 to bind and inactivate the upstream binding factor, UBF. The data imply that rRNA synthesis in living cells is subject to redundant control by endogenous pRb and p130.
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Affiliation(s)
- S Ciarmatori
- Division of Molecular Biology of the Cell II, German Cancer Research Centre, Im Neuenheimer Feld 280, D-69120 Heidelberg, Germany
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37
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Abstract
p107 and p130 were originally identified as targets of the transforming domains of viral oncoproteins encoded by small DNA tumor viruses. Together with pRB, the protein product of the retinoblastoma gene (Rb), p107 and p130 represent a family of closely related proteins that play critical roles in the regulation of cell proliferation. p107, p130, and pRB are transcriptional regulators whose activities are coupled to the cell cycle. Each of these proteins associates with E2F and is directly regulated by phosphorylation by cyclin-dependent kinases. In vivo studies of p107 and p130 function have revealed that their roles overlap extensively with one another and with pRB. In addition, the analysis of mice (and cell lines derived from these animals) deficient in these proteins shows that the individual members of this family harbor distinct functions that, at present, are poorly understood. The characterization of tumor cells continues to emphasize the important and somewhat unique role of pRB in tumor suppression, and the evidence linking the specific inactivation of p107 or p130 to tumor development remains quite limited. In this review we summarize the biochemical and functional properties of p107 and p130, and we compare and contrast these properties to those of pRB.
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Affiliation(s)
- M Classon
- MGH Cancer Center, Building 149, 13th Street, Charlestown, Massachusetts 02129, USA
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38
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Abstract
Two fundamental molecular pathways, the pRB and p53 pathways, regulate cell growth and cell death. The importance of these pathways in cellular growth control is underscored by the observation that members of these pathways are found mutated in all human cancers. These two pathways have typically been studied and described independently. However, as we discuss here, recent data have revealed an intimate molecular and genetic interaction between the p53 and pRB pathways.
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Affiliation(s)
- C L Stewart
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada
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39
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Sage J, Mulligan GJ, Attardi LD, Miller A, Chen S, Williams B, Theodorou E, Jacks T. Targeted disruption of the three Rb-related genes leads to loss of G(1) control and immortalization. Genes Dev 2000; 14:3037-50. [PMID: 11114892 PMCID: PMC317090 DOI: 10.1101/gad.843200] [Citation(s) in RCA: 471] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2000] [Accepted: 10/24/2000] [Indexed: 11/24/2022]
Abstract
The retinoblastoma protein, pRB, and the closely related proteins p107 and p130 are important regulators of the mammalian cell cycle. Biochemical and genetic studies have demonstrated overlapping as well as distinct functions for the three proteins in cell cycle control and mouse development. However, the role of the pRB family as a whole in the regulation of cell proliferation, cell death, or cell differentiation is not known. We generated embryonic stem (ES) cells and other cell types mutant for all three genes. Triple knock-out mouse embryonic fibroblasts (TKO MEFs) had a shorter cell cycle than wild-type, single, or double knock-out control cells. TKO cells were resistant to G(1) arrest following DNA damage, despite retaining functional p53 activity. They were also insensitive to G(1) arrest signals following contact inhibition or serum starvation. Finally, TKO MEFs did not undergo senescence in culture and do possess some characteristics of transformed cells. Our results confirm the essential role of the Rb family in the control of the G(1)/S transition, place the three Rb family members downstream of multiple cell cycle control pathways, and further the link between loss of cell cycle control and tumorigenesis.
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Affiliation(s)
- J Sage
- Department of Biology and Center for Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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40
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Dannenberg JH, van Rossum A, Schuijff L, te Riele H. Ablation of the retinoblastoma gene family deregulates G(1) control causing immortalization and increased cell turnover under growth-restricting conditions. Genes Dev 2000; 14:3051-64. [PMID: 11114893 PMCID: PMC317114 DOI: 10.1101/gad.847700] [Citation(s) in RCA: 327] [Impact Index Per Article: 13.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2000] [Accepted: 10/25/2000] [Indexed: 02/02/2023]
Abstract
The retinoblastoma suppressor pRB belongs to the family of so-called pocket proteins, which also includes p107 and p130. These proteins may functionally overlap in cell cycle control and tumor suppression. We have generated an isogenic set of embryonic stem (ES) cell lines carrying single or compound loss-of-function mutations in the Rb gene family, including a cell line completely devoid of all three pocket proteins. None of the knockout combinations affected the growth characteristics of ES cells; however, concomitant ablation of all three pocket proteins strongly impaired their differentiation capacity. For the generated genotypes, primary mouse embryonic fibroblasts (MEFs) also were obtained. While inactivation of Rb alone did not alleviate the senescence response of MEFs, pRB/p107-deficient MEFs, after having adapted to in vitro culturing, continued to proliferate at modest rate. Additional ablation of p130 rendered MEFs completely insensitive to senescence-inducing signals and strongly increased their proliferation rate. Although triple-knockout MEFs retained anchorage dependence, they lacked proper G(1) control and showed increased cell turnover under growth-inhibiting conditions.
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Affiliation(s)
- J H Dannenberg
- The Netherlands Cancer Institute, Division of Molecular Biology, 1066 CX Amsterdam, The Netherlands
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41
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Cheng L, Rossi F, Fang W, Mori T, Cobrinik D. Cdk2-dependent phosphorylation and functional inactivation of the pRB-related p130 protein in pRB(-), p16INK4A(+) tumor cells. J Biol Chem 2000; 275:30317-25. [PMID: 10906146 DOI: 10.1074/jbc.m005707200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The retinoblastoma family proteins pRB, p107, and p130 are phosphorylated and released from E2Fs in the late G(1) phase of the cell cycle. This phosphorylation is thought to contribute to the derepression of E2F-responsive genes and to be mediated, in part, by Cdk4 and Cdk6. Evidence that Cdk4/6 activity is inhibited by p16(INK4A) in most pRB(-) cells suggests that p107 and p130 may be underphosphorylated and remain associated with E2Fs during G(1)-S progression in cells that lack pRB. To examine this, we evaluated the cell cycle-dependent phosphorylation and E2F binding abilities of p107 and p130 in pRB(-), p16(+) Saos-2 osteosarcoma cells. p130, but not p107, was phosphorylated and released from E2F-4 in late G(1) and S phase cells, although p130 phosphorylation differed qualitatively in these and other pRB(-), p16(+) cells as compared with pRB(+), p16(-) cell types. p130 phosphorylation occurred in the absence of cyclin D-Cdk4/6 complexes, coincided with cyclin E- and Cdk2-associated kinase activity, and was prevented by expression of dominant negative Cdk2. Moreover, dominant negative Cdk2 prevented the dissociation of endogenous p130-E2F-4 complexes and inhibited E2F-4-dependent transcription. These findings show that p130 can be phosphorylated and functionally inactivated in a Cdk2-dependent process, and they highlight the involvement of distinct Cdks in the regulation of different pRB family proteins.
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Affiliation(s)
- L Cheng
- Departments of Medicine and Pathology, and the Institute of Cancer Genetics, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA
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42
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Classon M, Salama S, Gorka C, Mulloy R, Braun P, Harlow E. Combinatorial roles for pRB, p107, and p130 in E2F-mediated cell cycle control. Proc Natl Acad Sci U S A 2000; 97:10820-5. [PMID: 10995475 PMCID: PMC27107 DOI: 10.1073/pnas.190343497] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Numerous studies have implicated the pRB family of nuclear proteins in the control of cell cycle progression. Although over-expression experiments have revealed that each of these proteins, pRB, p107, and p130, can induce a G(1) cell cycle arrest, mouse knockouts demonstrated distinct developmental requirements for these proteins, as well as partial functional redundancy between family members. To study the mechanism by which the closely related pRB family proteins contribute to cell cycle progression, we generated 3T3 fibroblasts derived from embryos that lack one or more of these proteins (pRB(-/-), p107(-/-), p130(-/-), pRB(-/-)/p107(-/-), pRB(-/-)/p130(-/-), and p107(-/-)/p130(-/-)). By comparing the growth and cell cycle characteristics of these cells, we have observed clear differences in the manner in which they transit through the G(1) and S phases as well as exit from the cell cycle. Deletion of Rb, or more than one of the family members, results in a shortening of G(1) and a lengthening of S phase, as well as a reduction in growth factor requirements. In addition, the individual cell lines showed differential regulation of a subset of E2F-dependent gene promoters, as well as differences in cell cycle-dependent kinase activity. Taken together, these observations suggest that the closely related pRB family proteins affect cell cycle progression through distinct biochemical mechanisms and that their coordinated action may contribute to their diverse functions in various physiological settings.
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Affiliation(s)
- M Classon
- Massachusetts General Hospital Cancer Center, Building 149, 13th Street, Charlestown, MA 02129, USA.
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43
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Abstract
Analysis of tumor-derived mutations has led to the suggestion that p16INK4a, cyclin D1, cdk4, and the retinoblastoma protein (pRB) are components of a regulatory pathway that is inactivated in most tumor cells. Cell cycle arrest induced by p16INK4a, an inhibitor of cyclin D-dependent kinases, requires pRB, and it has been proposed that this G1 arrest is mediated by pRB-E2F repressor complexes. By comparing the properties of primary mouse embryonic fibroblasts specifically lacking pRB-family members, we find that pRB is insufficient for a p16INK4a-induced arrest. In addition to pRB, a second function provided by either p107 or p130, two pRB-related proteins, is required for p16INK4a to block DNA synthesis. We infer that p16INK4a-induced arrest is not mediated exclusively by pRB, but depends on the nonredundant functions of at least two pRB-family members.
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Affiliation(s)
- J L Bruce
- Laboratory of Molecular Oncology, Massachusetts General Hospital Cancer Center, Charlestown 02129, USA
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44
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Humbert PO, Rogers C, Ganiatsas S, Landsberg RL, Trimarchi JM, Dandapani S, Brugnara C, Erdman S, Schrenzel M, Bronson RT, Lees JA. E2F4 is essential for normal erythrocyte maturation and neonatal viability. Mol Cell 2000; 6:281-91. [PMID: 10983976 DOI: 10.1016/s1097-2765(00)00029-0] [Citation(s) in RCA: 145] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The retinoblastoma protein (pRB) plays a key role in the control of normal development and proliferation through the regulation of the E2F transcription factors. We generated a mutant mouse model to assess the in vivo role of the predominant E2F family member, E2F4. Remarkably, loss of E2F4 had no detectable effect on either cell cycle arrest or proliferation. However, E2F4 was essential for normal development. E2f4-/- mice died of an increased susceptibility to opportunistic infections that appeared to result from craniofacial defects. They also displayed a variety of erythroid abnormalities that arose from a cell autonomous defect in late stage maturation. This suggests that E2F4 makes a major contribution to the control of erythrocyte development by the pRB tumor suppressor.
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Affiliation(s)
- P O Humbert
- Department of Biology, Massachusetts Institute of Technology, Cambridge 02139, USA
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45
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Tieman DM, Taylor MG, Ciardi JA, Klee HJ. The tomato ethylene receptors NR and LeETR4 are negative regulators of ethylene response and exhibit functional compensation within a multigene family. Proc Natl Acad Sci U S A 2000; 97:5663-8. [PMID: 10792050 PMCID: PMC25885 DOI: 10.1073/pnas.090550597] [Citation(s) in RCA: 192] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The plant hormone ethylene is involved in many developmental processes, including fruit ripening, abscission, senescence, and leaf epinasty. Tomato contains a family of ethylene receptors, designated LeETR1, LeETR2, NR, LeETR4, and LeETR5, with homology to the Arabidopsis ETR1 ethylene receptor. Transgenic plants with reduced LeETR4 gene expression display multiple symptoms of extreme ethylene sensitivity, including severe epinasty, enhanced flower senescence, and accelerated fruit ripening. Therefore, LeETR4 is a negative regulator of ethylene responses. Reduced expression of this single gene affects multiple developmental processes in tomato, whereas in Arabidopsis multiple ethylene receptors must be inactivated to increase ethylene response. Transgenic lines with reduced NR mRNA levels exhibit normal ethylene sensitivity but elevated levels of LeETR4 mRNA, indicating a functional compensation of LeETR4 for reduced NR expression. Overexpression of NR in lines with lowered LeETR4 gene expression eliminates the ethylene-sensitive phenotype, indicating that despite marked differences in structure these ethylene receptors are functionally redundant.
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Affiliation(s)
- D M Tieman
- Horticultural Sciences, University of Florida, P.O. Box 110690, Gainesville, FL 32611-0690, USA
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46
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Abstract
In the cellular program leading to DNA synthesis, signals that drive cells into S-phase converge at the level of CDK activity. The products of at least three different gene families, Ink4, Cip/Kip and the pRb pocket-protein family, suppress S-phase entry. Ink4 proteins act by antagonizing the formation and activation of cyclin D-CDK4 complexes, of which the ultimate downstream target as related to S-phase entry appears to be pRb. Cip/Kip inhibitors impinge upon that pathway by inhibiting CDK2 kinases that participate in the inactivation of pRb and, like cyclin E, may also have roles independent of pRb. How the activities of these three classes of proteins are coordinated remains obscure. In recent years, development of mouse models has accelerated the elucidation of this complex network, showing roles that are sometimes cooperative and sometimes overlapping. We will discuss the interrelationships between Cip/Kip inhibitors and the components of the pRb pathway, and how their activities ultimately regulate cell proliferation.
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Affiliation(s)
- A Vidal
- Laboratory of Cell Cycle Regulation, Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021, USA.
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Genetic alterations of the retinoblastoma-related gene RB2/p130 identify different pathogenetic mechanisms in and among Burkitt's lymphoma subtypes. THE AMERICAN JOURNAL OF PATHOLOGY 2000; 156:751-60. [PMID: 10702389 PMCID: PMC1876836 DOI: 10.1016/s0002-9440(10)64941-3] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Alterations of cell cycle-associated genes probably contribute to the pathogenesis of Burkitt's Lymphoma (BL), in addition to c-myc translocation. Mutations disrupting the nuclear localization signal of the retinoblastoma-related gene RB2/p130 have been documented recently in BL cell lines and primary tumors. Given the importance of the RB2/p130 gene in controlling cell growth, mutations of this gene may result in uncontrolled cell proliferation. We tested the expression and genomic organization of the RB2/p130 gene in relation to the proliferative features of a series of BL samples collected from the endemic and sporadic regions, regardless of whether the samples were acquired immune deficiency syndrome (AIDS)-related. The expression of the Rb2/p130, p107, and cell proliferation-related proteins (cyclin A and B) was determined by immunohistochemistry. The structures of exons 19 through 22 of the RB2/p130 gene, encoding for the B domain and C terminus, were analyzed by polymerase chain reaction (PCR) analysis and single-strand conformation polymorphism (SSCP) technique. The direct PCR products were sequenced to identify the actual mutations. Our results suggest that BL is composed of a mixture of molecular types with distinct genetic and phenotypic patterns, probably resulting from different pathogenetic mechanisms. In endemic BL, the RB2/p130 gene is mutated in most of the cases, and the protein is restricted to the cytoplasm. In AIDS-related BL, high levels of nuclear expression of the wild-type pRb2/p130, p107, and cell proliferation-related proteins were detected. This finding is in line with the molecular mechanisms observed in virus-linked oncogenesis. Sporadic BLs were mainly characterized by the low nuclear values of the wild-type pRb2/p130 and, conversely, the high values of p107. The increased cell proliferation due to different alterations of cell growth control by Rb-related proteins may be the first step in lymphomagenesis, during which additional genetic changes, including missense mutations of c-myc, may subsequently occur.
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Lam EW, Glassford J, van der Sman J, Banerji L, Pizzey AR, Shaun N, Thomas B, Klaus GG. Modulation of E2F activity in primary mouse B cells following stimulation via surface IgM and CD40 receptors. Eur J Immunol 1999; 29:3380-9. [PMID: 10540350 DOI: 10.1002/(sici)1521-4141(199910)29:10<3380::aid-immu3380>3.0.co;2-c] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Since signals via CD40 and the B cell receptor are known to synergize to induce B cell activation, we have analyzed the pocket protein/E2F complexes in mouse B lymphocytes following stimulation by anti-IgM, anti-CD40, alone or together. We find that E2F4 and DP1 form the predominant E2F heterodimers in the G0 and G1 phases of the cell cycle, complexed with hypophosphorylated p130. During late G1 and S phase this complex is replaced by at least three different E2F complexes, one of which is an E2F complex containing p107 or pRB as well as two "free" E2F complexes consisting of E2F4/DP1 and E2F1-3/DP1. These effects were mirrored by the levels and phosphorylation status of the three pocket proteins. We also observed an increase in electrophoretic mobility of DP1 and E2F4 as B cells progressed from G0 into early G1, resulting from their dephosphorylation. This is known to correlate with a decrease in DNA binding capacity of these proteins and could also be important for derepression of genes negatively regulated through E2F sites in their promoters. These results therefore indicate that the pRB/E2F pathway integrates proliferative signals emanating from the sIgM and CD40 receptors.
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Affiliation(s)
- E W Lam
- Ludwig Institute for Cancer Research and Section of Virology and Cell Biology Imperial College School of Medicine at St Mary's, London, GB.
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Sangfelt O, Erickson S, Castro J, Heiden T, Gustafsson A, Einhorn S, Grandér D. Molecular mechanisms underlying interferon-alpha-induced G0/G1 arrest: CKI-mediated regulation of G1 Cdk-complexes and activation of pocket proteins. Oncogene 1999; 18:2798-810. [PMID: 10362250 DOI: 10.1038/sj.onc.1202609] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
One prominent effect of IFNs is their cell growth-inhibitory activity. The mechanism behind this inhibition of proliferation is still not fully understood. In this study, the effect of IFN-alpha treatment on cell cycle progression has been analysed in three lymphoid cell lines, Daudi, U-266 and H9. Examination of the growth-arrested cell populations shows that Daudi cells accumulate in a G0-like state, whereas U-266 cells arrest later in G1. H9 cells are completely resistant to IFN-alpha's cell growth-inhibitory effects. The G0/G1-phase arrest is preceded by a rapid induction of the cyclin-dependent kinase inhibitors (CKIs), p21 and p15. In parallel, the activities of the G1 Cdks are significantly reduced. In addition to p21/p15 induction, IFN-alpha regulates the expression of another CKI, p27, presumably by a post-transcriptional mechanism. In the G1 Cdk-complexes, there is first an increased binding of p21 and p15 to their respective kinases. At longer exposure times, when Cdk-bound p15 and p21 decline, p27 starts to accumulate. Furthermore, we found that IFN-alpha not only suppresses the phosphorylation of pRb, but also alters the phosphorylation and expression of the other pocket proteins p130 and p107. These data suggest that induction of p21/p15 is involved in the primary IFN-alpha response inhibiting G1 Cdk activity, whereas increased p27 expression is part of a second set of events which keep these Cdks in their inactive form. Moreover, elevated levels of p27 correlated with a dissociation of cyclin E/Cdk2-p130 or p107 complexes to yield cyclin E/Cdk2-p27 complexes. In resistant H9 cells, which possess a homozygous deletion of the p15/p16 genes and lack p21 protein expression, IFN-alpha causes no detectable changes in p27 expression and, furthermore, no effects are observed on either pocket proteins in this cell line. Taken together, these data suggest that the early decline in G1 Cdk activity, subsequent changes in phosphorylation of pocket proteins, and G1/G0 arrest following IFN-alpha treatment, is not primarily due to loss of the G1 kinase components, but result from the inhibitory action of CKIs on these complexes.
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Affiliation(s)
- O Sangfelt
- Department of Oncology/Pathology, Karolinska Hospital and Institute, Stockholm, Sweden
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Lind EF, Wayne J, Wang QZ, Staeva T, Stolzer A, Petrie HT. Bcl-2-Induced Changes in E2F Regulatory Complexes Reveal the Potential for Integrated Cell Cycle and Cell Death Functions. THE JOURNAL OF IMMUNOLOGY 1999. [DOI: 10.4049/jimmunol.162.9.5374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
Proliferation and cell death are tightly linked fates during cell and tissue differentiation. In the past few years, it has been shown that Bcl-2 exhibits a potent cell cycle inhibitory effect, in addition to its better known role in the antagonism of cell death. In the present study, we show that the cell cycle effects of Bcl-2 apparently occur at the level of E2F control of gene transcription. Under conditions of normal cell growth, or under conditions that lead to cell death in the absence of Bcl-2, bcl-2 expression results in a reduction of free (active) E2F isoforms and in an increase in the formation of higher-order (inactive) complexes. Bcl-2-induced changes in E2F complex formation are paralleled by an apparent increase in pRb regulatory activity, by the up-regulation of p130 protein expression, and by the formation of E2F/p130 complexes at the expense of those consisting of E2F/p107. Cells lacking bcl-2 expression respond to growth factor withdrawal in the opposite manner, by the liberation of E2F from inactivating complexes and by continued cell cycle leading to cell death. These analyses reveal a mechanism for cell cycle regulation by Bcl-2 that occurs at the level of E2F transcriptional activity. Further, since specific E2F activities are clearly linked to the induction of cell death, these findings may help to consolidate the cell survival and cell cycle effects of Bcl-2 through a common transcriptional mechanism.
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Affiliation(s)
- Evan F. Lind
- *Immunology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021; and
| | - Jay Wayne
- *Immunology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021; and
| | - Qi-Zhi Wang
- *Immunology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021; and
| | - Teodora Staeva
- *Immunology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021; and
- †Cornell University Graduate School of Medical Sciences, New York, NY 10021
| | - Amy Stolzer
- *Immunology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021; and
- †Cornell University Graduate School of Medical Sciences, New York, NY 10021
| | - Howard T. Petrie
- *Immunology Program, Memorial Sloan-Kettering Cancer Center, New York, NY 10021; and
- †Cornell University Graduate School of Medical Sciences, New York, NY 10021
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