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Niemann JH, Du C, Morlot S, Schmidt G, Auber B, Kaune B, Göhring G, Ripperger T, Schlegelberger B, Hofmann W, Smol T, Ait-Yahya E, Raimbault A, Lambilliotte A, Petit F, Steinemann D. De novo missense variants in the RAP1B gene identified in two patients with syndromic thrombocytopenia. Clin Genet 2020; 98:374-378. [PMID: 32627184 DOI: 10.1111/cge.13807] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 06/15/2020] [Accepted: 06/30/2020] [Indexed: 11/27/2022]
Abstract
We present two independent cases of syndromic thrombocytopenia with multiple malformations, microcephaly, learning difficulties, dysmorphism and other features. Exome sequencing identified two novel de novo heterozygous variants in these patients, c.35G>T p.(Gly12Val) and c.178G>C p.(Gly60Arg), in the RAP1B gene (NM_001010942.2). These variants have not been described previously as germline variants, however functional studies in literature strongly suggest a clinical implication of these two activating hot spot positions. We hypothesize that pathogenic missense variants in the RAP1B gene cause congenital syndromic thrombocytopenia with a spectrum of associated malformations and dysmorphism, possibly through a gain of function mechanism.
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Affiliation(s)
| | - Chen Du
- Department of Human Genetics, Hannover Medical School, Hanover, Germany
| | - Susanne Morlot
- Department of Human Genetics, Hannover Medical School, Hanover, Germany
| | - Gunnar Schmidt
- Department of Human Genetics, Hannover Medical School, Hanover, Germany
| | - Bernd Auber
- Department of Human Genetics, Hannover Medical School, Hanover, Germany
| | - Beate Kaune
- Department of Human Genetics, Hannover Medical School, Hanover, Germany
| | - Gudrun Göhring
- Department of Human Genetics, Hannover Medical School, Hanover, Germany
| | - Tim Ripperger
- Department of Human Genetics, Hannover Medical School, Hanover, Germany
| | | | - Winfried Hofmann
- Department of Human Genetics, Hannover Medical School, Hanover, Germany
| | - Thomas Smol
- CHU Lille, Laboratoire de Génétique Médicale, Lille, France
| | - Emilie Ait-Yahya
- CHU Lille, Bioinformatics Unit, Molecular Biology Facility, Lille, France
| | - Anna Raimbault
- Hôpital Saint Louis, Service d'Hématologie Biologique, Paris, France
| | | | | | - Doris Steinemann
- Department of Human Genetics, Hannover Medical School, Hanover, Germany
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2
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Titus HE, López-Juárez A, Silbak SH, Rizvi TA, Bogard M, Ratner N. Oligodendrocyte RasG12V expressed in its endogenous locus disrupts myelin structure through increased MAPK, nitric oxide, and notch signaling. Glia 2017; 65:1990-2002. [PMID: 28856719 DOI: 10.1002/glia.23209] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 07/18/2017] [Accepted: 08/04/2017] [Indexed: 01/28/2023]
Abstract
Costello syndrome (CS) is a gain of function Rasopathy caused by heterozygous activating mutations in the HRAS gene. Patients show brain dysfunction that can include abnormal brain white matter. Transgenic activation of HRas in the entire mouse oligodendrocyte lineage resulted in myelin defects and behavioral abnormalities, suggesting roles for disrupted myelin in CS brain dysfunction. Here, we studied a mouse model in which the endogenous HRas gene is conditionally replaced by mutant HRasG12V in mature oligodendrocytes, to separate effects in mature myelinating cells from developmental events. Increased myelin thickness due to decompaction was detectable within one month of HRasG12V expression in the corpus callosum of adult mice. Increases in active ERK and Nitric Oxide (NO) were present in HRas mutants and inhibition of NO synthase (NOS) or MEK each partially rescued myelin decompaction. In addition, genetic or pharmacologic inhibition of Notch signaling improved myelin compaction. Complete rescue of myelin structure required dual drug treatments combining MAPK, NO, or Notch inhibition; with MEK + NOS blockade producing the most robust effect. We suggest that individual or concomitant blockade of these pathways in CS patients may improve aspects of brain function.
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Affiliation(s)
- Haley E Titus
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, 45229
| | - Alejandro López-Juárez
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, 45229
| | - Sadiq H Silbak
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, 45229
| | - Tilat A Rizvi
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, 45229
| | - Madeleine Bogard
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, 45229
| | - Nancy Ratner
- Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, 45229
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3
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Abstract
RAS mutations are among the most common genetic alterations found in cancerous tumors but rational criteria or strategies for targeting RAS-dependent tumors are only recently emerging. Clinical and laboratory data suggest that patient selection based on specific RAS mutations will be an essential component of these strategies. A thorough understanding of the biochemical and structural properties of mutant RAS proteins form the theoretical basis for these approaches. Direct inhibition of KRAS G12C by covalent inhibitors is a notable recent example of the RAS mutation-tailored approach that establishes a paradigm for other RAS mutation-centered strategies.
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Affiliation(s)
- Steven K Montalvo
- School of Medicine, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Lianbo Li
- Departments of Biochemistry & Radiation Oncology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Kenneth D Westover
- Departments of Biochemistry & Radiation Oncology, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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4
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Hartung AM, Swensen J, Uriz IE, Lapin M, Kristjansdottir K, Petersen USS, Bang JMV, Guerra B, Andersen HS, Dobrowolski SF, Carey JC, Yu P, Vaughn C, Calhoun A, Larsen MR, Dyrskjøt L, Stevenson DA, Andresen BS. The Splicing Efficiency of Activating HRAS Mutations Can Determine Costello Syndrome Phenotype and Frequency in Cancer. PLoS Genet 2016; 12:e1006039. [PMID: 27195699 PMCID: PMC4873146 DOI: 10.1371/journal.pgen.1006039] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 04/18/2016] [Indexed: 12/25/2022] Open
Abstract
Costello syndrome (CS) may be caused by activating mutations in codon 12/13 of the HRAS proto-oncogene. HRAS p.Gly12Val mutations have the highest transforming activity, are very frequent in cancers, but very rare in CS, where they are reported to cause a severe, early lethal, phenotype. We identified an unusual, new germline p.Gly12Val mutation, c.35_36GC>TG, in a 12-year-old boy with attenuated CS. Analysis of his HRAS cDNA showed high levels of exon 2 skipping. Using wild type and mutant HRAS minigenes, we confirmed that c.35_36GC>TG results in exon 2 skipping by simultaneously disrupting the function of a critical Exonic Splicing Enhancer (ESE) and creation of an Exonic Splicing Silencer (ESS). We show that this vulnerability of HRAS exon 2 is caused by a weak 3' splice site, which makes exon 2 inclusion dependent on binding of splicing stimulatory proteins, like SRSF2, to the critical ESE. Because the majority of cancer- and CS- causing mutations are located here, they affect splicing differently. Therefore, our results also demonstrate that the phenotype in CS and somatic cancers is not only determined by the different transforming potentials of mutant HRAS proteins, but also by the efficiency of exon 2 inclusion resulting from the different HRAS mutations. Finally, we show that a splice switching oligonucleotide (SSO) that blocks access to the critical ESE causes exon 2 skipping and halts proliferation of cancer cells. This unravels a potential for development of new anti-cancer therapies based on SSO-mediated HRAS exon 2 skipping.
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Affiliation(s)
- Anne-Mette Hartung
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Jeff Swensen
- Caris Life Sciences, Phoenix, Arizona, United States of America
- Department of Pathology, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- ARUP Laboratories, Salt Lake City, Utah, United States of America
| | - Inaki E. Uriz
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Morten Lapin
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Karen Kristjansdottir
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Ulrika S. S. Petersen
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Jeanne Mari V. Bang
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Barbara Guerra
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Henriette Skovgaard Andersen
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Steven F. Dobrowolski
- Department of Pathology, Children's Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
| | - John C. Carey
- Department of Pediatrics, University of Utah, Salt Lake City, Utah, United States of America
| | - Ping Yu
- ARUP Laboratories, Salt Lake City, Utah, United States of America
| | - Cecily Vaughn
- ARUP Laboratories, Salt Lake City, Utah, United States of America
| | - Amy Calhoun
- Department of Pediatrics, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Martin R. Larsen
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
| | - Lars Dyrskjøt
- Department of Molecular Medicine, Aarhus University Hospital, Aarhus, Denmark
| | - David A. Stevenson
- Division of Medical Genetics, Stanford University, Stanford, California, United States of America
| | - Brage S. Andresen
- Department of Biochemistry and Molecular Biology and The Villum Center for Bioanalytical Sciences, University of Southern Denmark, Odense M, Denmark
- * E-mail:
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5
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Saraç ÖS, Atalay V, Cetin-Atalay R. GOPred: GO molecular function prediction by combined classifiers. PLoS One 2010; 5:e12382. [PMID: 20824206 PMCID: PMC2930845 DOI: 10.1371/journal.pone.0012382] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Accepted: 06/22/2010] [Indexed: 11/18/2022] Open
Abstract
Functional protein annotation is an important matter for in vivo and in silico biology. Several computational methods have been proposed that make use of a wide range of features such as motifs, domains, homology, structure and physicochemical properties. There is no single method that performs best in all functional classification problems because information obtained using any of these features depends on the function to be assigned to the protein. In this study, we portray a novel approach that combines different methods to better represent protein function. First, we formulated the function annotation problem as a classification problem defined on 300 different Gene Ontology (GO) terms from molecular function aspect. We presented a method to form positive and negative training examples while taking into account the directed acyclic graph (DAG) structure and evidence codes of GO. We applied three different methods and their combinations. Results show that combining different methods improves prediction accuracy in most cases. The proposed method, GOPred, is available as an online computational annotation tool (http://kinaz.fen.bilkent.edu.tr/gopred).
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Affiliation(s)
- Ömer Sinan Saraç
- Department of Computer Engineering, Middle East Technical University, Ankara, Turkey
| | - Volkan Atalay
- Department of Computer Engineering, Middle East Technical University, Ankara, Turkey
| | - Rengul Cetin-Atalay
- Department of Molecular Biology and Genetics, Faculty of Science, Bilkent University, Ankara, Turkey
- * E-mail:
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6
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Abstract
Ras genes are the most common targets for somatic gain-of-function mutations in human cancer. Recently, germline mutations that affect components of the Ras-Raf-mitogen-activated and extracellular-signal regulated kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) pathway were shown to cause several developmental disorders, including Noonan, Costello and cardio-facio-cutaneous syndromes. Many of these mutant alleles encode proteins with aberrant biochemical and functional properties. Here we will discuss the implications of germline mutations in the Ras-Raf-MEK-ERK pathway for understanding normal developmental processes and cancer pathogenesis.
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Affiliation(s)
- Suzanne Schubbert
- Department of Pediatrics, University of California, 513 Parnassus Avenue, Room HSE-302, San Francisco, California 94143, USA
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7
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Zampino G, Pantaleoni F, Carta C, Cobellis G, Vasta I, Neri C, Pogna EA, De Feo E, Delogu A, Sarkozy A, Atzeri F, Selicorni A, Rauen KA, Cytrynbaum CS, Weksberg R, Dallapiccola B, Ballabio A, Gelb BD, Neri G, Tartaglia M. Diversity, parental germline origin, and phenotypic spectrum of de novo HRAS missense changes in Costello syndrome. Hum Mutat 2007; 28:265-72. [PMID: 17054105 DOI: 10.1002/humu.20431] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Activating mutations in v-Ha-ras Harvey rat sarcoma viral oncogene homolog (HRAS) have recently been identified as the molecular cause underlying Costello syndrome (CS). To further investigate the phenotypic spectrum associated with germline HRAS mutations and characterize their molecular diversity, subjects with a diagnosis of CS (N = 9), Noonan syndrome (NS; N = 36), cardiofaciocutaneous syndrome (CFCS; N = 4), or with a phenotype suggestive of these conditions but without a definitive diagnosis (N = 12) were screened for the entire coding sequence of the gene. A de novo heterozygous HRAS change was detected in all the subjects diagnosed with CS, while no lesion was observed with any of the other phenotypes. While eight cases shared the recurrent c.34G>A change, a novel c.436G>A transition was observed in one individual. The latter affected residue, p.Ala146, which contributes to guanosine triphosphate (GTP)/guanosine diphosphate (GDP) binding, defining a novel class of activating HRAS lesions that perturb development. Clinical characterization indicated that p.Gly12Ser was associated with a homogeneous phenotype. By analyzing the genomic region flanking the HRAS mutations, we traced the parental origin of lesions in nine informative families and demonstrated that de novo mutations were inherited from the father in all cases. We noted an advanced age at conception in unaffected fathers transmitting the mutation.
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Affiliation(s)
- Giuseppe Zampino
- Istituto di Clinica Pediatrica, Università Cattolica del Sacro Cuore, Rome, Italy
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8
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Gelb BD, Tartaglia M. Noonan syndrome and related disorders: dysregulated RAS-mitogen activated protein kinase signal transduction. Hum Mol Genet 2006; 15 Spec No 2:R220-6. [PMID: 16987887 DOI: 10.1093/hmg/ddl197] [Citation(s) in RCA: 149] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Noonan syndrome is a relatively common, genetically heterogeneous Mendelian trait with a pleiomorphic phenotype. Prior to the period covered in this review, missense mutations in PTPN11 had been found to account for nearly 50% of Noonan syndrome cases. That gene encodes SHP-2, a protein tyrosine kinase that plays diverse roles in signal transduction including signaling via the RAS-mitogen activated protein kinase (MAPK) pathway. Noonan syndrome-associated PTPN11 mutations are gain-of-function, with most disrupting SHP-2's activation-inactivation mechanism. Here, we review recent information that has elucidated further the types and effects of PTPN11 defects in Noonan syndrome and compare them to the related, but specific, missense PTPN11 mutations causing other diseases including LEOPARD syndrome and leukemias. These new data derive from biochemical and cell biological studies as well as animal modeling with fruit flies and chick embryos. The discovery of KRAS missense mutation as a minor cause of Noonan syndrome and the pathogenetic mechanisms of those mutants is discussed. Finally, the elucidation of gene defects underlying two phenotypically related disorders, Costello and cardio-facio-cutaneous syndromes is also reviewed. As these genes also encode proteins relevant for RAS-MAPK signal transduction, all of the syndromes discussed in this article now can be understood to constitute a class of disorders caused by dysregulated RAS-MAPK signaling.
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Affiliation(s)
- Bruce D Gelb
- Department of Pediatrics and Human Genetics, Mount Sinai School of Medicine, One Gustave Levy Place, Box 1040, New York, NY 10029, USA.
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9
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Aoki Y, Niihori T, Kawame H, Kurosawa K, Ohashi H, Tanaka Y, Filocamo M, Kato K, Suzuki Y, Kure S, Matsubara Y. Germline mutations in HRAS proto-oncogene cause Costello syndrome. Nat Genet 2005; 37:1038-40. [PMID: 16170316 DOI: 10.1038/ng1641] [Citation(s) in RCA: 507] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Accepted: 07/27/2005] [Indexed: 11/09/2022]
Abstract
Costello syndrome is a multiple congenital anomaly and mental retardation syndrome characterized by coarse face, loose skin, cardiomyopathy and predisposition to tumors. We identified four heterozygous de novo mutations of HRAS in 12 of 13 affected individuals, all of which were previously reported as somatic and oncogenic mutations in various tumors. Our observations suggest that germline mutations in HRAS perturb human development and increase susceptibility to tumors.
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Affiliation(s)
- Yoko Aoki
- Department of Medical Genetics, Tohoku University School of Medicine, 1-1 Seiryo-machi, Sendai 980-8574, Japan.
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10
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Clark-Maguire S, Mains PE. mei-1, a gene required for meiotic spindle formation in Caenorhabditis elegans, is a member of a family of ATPases. Genetics 1994; 136:533-46. [PMID: 8150281 PMCID: PMC1205806 DOI: 10.1093/genetics/136.2.533] [Citation(s) in RCA: 80] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Meiotic spindle formation in the female germline of Caenorhabditis elegans requires expression of the gene mei-1. We have cloned mei-1 by transformation rescue and found that it resides near a hot spot for recombination, in an area of high gene density. The highest levels of mei-1 mRNA accumulate in the female germline of adult hermaphrodites as well as in fertilized embryos. The message persists for several hours after the protein functions in embryos, implying the need for post-transcriptional regulation. Two alternatively spliced messages are made that would result in proteins that differ internally by three amino acids; the larger of the two mRNAs is preferentially enriched in the female germline. The sequence of mei-1 shows that it is a member of a newly described family of ATPases that share a highly conserved nucleotide-binding site; four dominant-negative mutations of mei-1 are found at or near this region. Divergent roles ascribed to this family include membrane function, proteolysis, transcription and cell cycle regulation.
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Affiliation(s)
- S Clark-Maguire
- Department of Medical Biochemistry, University of Calgary, Alberta, Canada
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11
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Kinetics of interaction between normal and proline 12 Ras and the GTPase-activating proteins, p120-GAP and neurofibromin. The significance of the intrinsic GTPase rate in determining the transforming ability of ras. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(19)74211-2] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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12
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Affiliation(s)
- J R Broach
- Department of Biology, Princeton University, New Jersey 08544
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13
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Fults D, Maness PF, Nakamura Y, White R. The N-ras oncogene is activated in a human medulloblastoma cell line. Brain Res 1989; 503:281-7. [PMID: 2691018 DOI: 10.1016/0006-8993(89)91675-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Medulloblastoma is a malignant brain tumor of early childhood whose cells resemble the primitive neuroepithelial cells found normally in the developing nervous system. Medulloblastoma may be caused by mutational events affecting primitive neuroepithelial cells and preventing their differentiation into postmitotic neurons. The human ras genes, H-ras, K-ras and N-ras, are members of a family of proto-oncogenes that are targets for mutational changes that convert these normal genes into active, transforming oncogenes. Here we report that the N-ras oncogene is activated in the human medulloblastoma cell line TE 671 by a mutation at the third position of codon 61. A point mutation at this location corresponds to a substitution of histidine for glutamine in the N-ras gene product, p21. The oncogenic activation was shown by focus-formation in NIH 3T3 cell transfection assays. The location of the mutation was established using oligonucleotide hybridization assays enhanced through in vitro amplification of N-ras coding sequences using the Taq polymerase chain reaction. N-ras activation may be one of the mutational events that subvert normal neuroectodermal differentiation and lead to medulloblastoma in children.
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Affiliation(s)
- D Fults
- Division of Neurosurgery, University of Utah, Salt Lake City 84132
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14
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Coburn J, Wyatt RT, Iglewski BH, Gill DM. Several GTP-binding Proteins, Including p21c-H-ras, Are Preferred Substrates of Pseudomonas aeruginosa Exoenzyme S. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(18)81894-4] [Citation(s) in RCA: 98] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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15
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John J, Frech M, Wittinghofer A. Biochemical properties of Ha-ras encoded p21 mutants and mechanism of the autophosphorylation reaction. J Biol Chem 1988. [DOI: 10.1016/s0021-9258(18)37854-2] [Citation(s) in RCA: 84] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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16
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Satoh T, Nakamura S, Nakafuku M, Kaziro Y. Studies on ras proteins. Catalytic properties of normal and activated ras proteins purified in the absence of protein denaturants. BIOCHIMICA ET BIOPHYSICA ACTA 1988; 949:97-109. [PMID: 3275466 DOI: 10.1016/0167-4781(88)90059-0] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Normal (Gly12) and activated (Val12) Ha-ras proteins were produced in Escherichia coli, and purified to an apparent homogeneity without using any protein denaturants. The purified proteins contained an equimolar amount of GDP. They were stable in the presence of 5 mM Mg2+ and 25% (v/v) glycerol when incubated at 60 degrees C for 5 min. The binding of GDP to the protein was greatly stabilized by Mg2+. In the presence of 10 mM Mg2+, the bound GDP hardly exchanged with external guanine nucleotides, even at 30 degrees C. The exchange reaction was markedly enhanced in the presence of 10 mM EDTA or 120 mM ammonium sulfate. The rate-limiting step of the exchange reaction was the dissociation of the bound GDP from the ras protein, and this step was facilitated 40- to 100-fold by the addition of EDTA or ammonium sulfate. The dissociation rate of the normal (Gly12) ras protein was 2- to 3-fold faster than that of the activated (Val12) protein. The dissociation constants (Kd) for GDP of the normal and activated ras proteins were 1.2 X 10(-8) and 3.1 X 10(-9) M, respectively. The overall turnover rate of GTPase activity of the normal ras protein (10.8 mmol.mol-1.min-1) was about 10-fold higher than that of the activated protein (1.1 mmol.mol-1.min-1) in the absence of Mg2+ (less than 10(-8) M).
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Affiliation(s)
- T Satoh
- Institute of Medical Science, University of Tokyo, Japan
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17
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Hiwasa T, Sakiyama S, Noguchi S, Ha JM, Miyazawa T, Yokoyama S. Degradation of a cAMP-binding protein is inhibited by human c-Ha-ras gene products. Biochem Biophys Res Commun 1987; 146:731-8. [PMID: 3304283 DOI: 10.1016/0006-291x(87)90590-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Incubation of the particulate fraction of cell extract prepared from NIH3T3 mouse fibroblasts resulted in preferential proteolytic degradation of a cAMP-binding protein. The proteolysis was inhibited by human c-Ha-ras gene products produced by Escherichia coli. The proteolysis was observed at pH 6 to 7, and inhibited by antipain and leupeptin. These results suggest that cAMP-binding proteins might be cleaved by thiol proteinases. In fact, c-Ha-ras gene products were proved to inhibit the cathepsin B-like activity present in the particulate fraction.
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18
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Feuerstein J, Kalbitzer HR, John J, Goody RS, Wittinghofer A. Characterisation of the metal-ion-GDP complex at the active sites of transforming and nontransforming p21 proteins by observation of the 17O-Mn superhyperfine coupling and by kinetic methods. EUROPEAN JOURNAL OF BIOCHEMISTRY 1987; 162:49-55. [PMID: 3028791 DOI: 10.1111/j.1432-1033.1987.tb10540.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Kinetic studies on the interaction of three Ha-ras-encoded p21 proteins with GDP and MgGDP have yielded values for the association (10(6)-10(7) M-1 s-1) and dissociation (10(-3)-10(-5) s-1) rate constants at 0 degrees C. Dramatic differences in the rate constants were not observed for the three proteins. Under non-physiological conditions (absence of Mg2+), the rate constant for GDP release was an order of magnitude faster for the viral protein p21v than for the cellular form p21c or the T24 mutant p21t, but this was reduced to a factor of about 3 in the presence of Mg2+. In all cases, there was an increase of about one order of magnitude in the rate of GDP release on removing magnesium. The binding affinities ranged from 5.7 X 10(10) M-1 for p21c to 1.3 X 10(11) M-1 for p21v. Electron paramagnetic resonance (EPR) measurements on Mn2+ bound together with stereospecifically 17O-labelled GDP showed direct coordination of a beta-phosphate oxygen to the metal ion with a superhyperfine coupling constant of 0.16-0.22 mT, but no interaction with the alpha-phosphate oxygens at the active site of all three proteins. The association constant of Mn(II) to p21 proteins in the absence of nucleotides was estimated to be greater than 10(5) M-1. In agreement with the EPR results, experiments on the metal ion dependence of the binding of thiophosphate analogs of GDP provided further evidence for the absence of direct coordination of the metal ion to the alpha-phosphate group. These results have been used to construct a model for the interactions of Mg X GDP with the active site of p21 proteins.
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19
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