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Chen X, Yang HT, Zhang B, Phillips JW, Cheng D, Rigo F, Witte ON, Xing Y, Black DL. The RNA-binding proteins hnRNP H and F regulate splicing of a MYC-dependent HRAS exon in prostate cancer cells. Proc Natl Acad Sci U S A 2023; 120:e2220190120. [PMID: 37399401 PMCID: PMC10334793 DOI: 10.1073/pnas.2220190120] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 05/31/2023] [Indexed: 07/05/2023] Open
Abstract
The MYC proto-oncogene contributes to the pathogenesis of more than half of human cancers. Malignant transformation by MYC transcriptionally up-regulates the core pre-mRNA splicing machinery and causes misregulation of alternative splicing. However, our understanding of how splicing changes are directed by MYC is limited. We performed a signaling pathway-guided splicing analysis to identify MYC-dependent splicing events. These included an HRAS cassette exon repressed by MYC across multiple tumor types. To molecularly dissect the regulation of this HRAS exon, we used antisense oligonucleotide tiling to identify splicing enhancers and silencers in its flanking introns. RNA-binding motif prediction indicated multiple binding sites for hnRNP H and hnRNP F within these cis-regulatory elements. Using siRNA knockdown and cDNA expression, we found that both hnRNP H and F activate the HRAS cassette exon. Mutagenesis and targeted RNA immunoprecipitation implicate two downstream G-rich elements in this splicing activation. Analyses of ENCODE RNA-seq datasets confirmed hnRNP H regulation of HRAS splicing. Analyses of RNA-seq datasets across multiple cancers showed a negative correlation of HNRNPH gene expression with MYC hallmark enrichment, consistent with the effect of hnRNP H on HRAS splicing. Interestingly, HNRNPF expression showed a positive correlation with MYC hallmarks and thus was not consistent with the observed effects of hnRNP F. Loss of hnRNP H/F altered cell cycle progression and induced apoptosis in the PC3 prostate cancer cell line. Collectively, our results reveal mechanisms for MYC-dependent regulation of splicing and point to possible therapeutic targets in prostate cancers.
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Affiliation(s)
- Xinyuan Chen
- Molecular Biology Interdepartmental Doctoral Program, University of California, Los Angeles, CA90095
| | - Harry Taegyun Yang
- Bioinformatics Interdepartmental Graduate Program, University of California, Los Angeles, CA90095
| | - Beatrice Zhang
- Center for Computational and Genomic Medicine, The Children’s Hospital of Philadelphia, Philadelphia, PA19104
| | - John W. Phillips
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA90095
| | - Donghui Cheng
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA90095
| | - Frank Rigo
- Ionis Pharmaceuticals, Inc., 2855 Gazelle Ct., Carlsbad, CA92010
| | - Owen N. Witte
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA90095
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA90095
- Jonsson Comprehensive Cancer Center, University of California, Los Angeles, CA90095
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, CA90095
- Molecular Biology Institute, University of California, Los Angeles, CA90095
| | - Yi Xing
- Center for Computational and Genomic Medicine, The Children’s Hospital of Philadelphia, Philadelphia, PA19104
- Department of Pathology and Laboratory Medicine, University of Pennsylvania, Philadelphia, PA19104
| | - Douglas L. Black
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, CA90095
- Jonsson Comprehensive Cancer Center, University of California, Los Angeles, CA90095
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, CA90095
- Molecular Biology Institute, University of California, Los Angeles, CA90095
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2
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Abstract
One of the mechanisms potentially explaining the discrepancy between the number of human genes and the functional complexity of organisms is generating alternative splice variants, an attribute of the vast majority of multi-exon genes. Members of the RAS family, such as NRAS, KRAS and HRAS, all of which are of significant importance in cancer biology, are no exception. The structural and functional differences of these splice variants, particularly if they contain the canonical (and therefore routinely targeted for diagnostic purposes) hot spot mutations, pose a significant challenge for targeted therapies. We must therefore consider whether these alternative splice variants constitute a minor component as originally thought and how therapies targeting the canonical isoforms affect these alternative splice variants and their overall functions.
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Affiliation(s)
- Erzsébet Rásó
- 2nd Department of Pathology, Semmelweis University, Budapest, Hungary.
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3
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Ritchie C, Mack A, Harper L, Alfadhli A, Stork PJS, Nan X, Barklis E. Analysis of K-Ras Interactions by Biotin Ligase Tagging. Cancer Genomics Proteomics 2018. [PMID: 28647697 DOI: 10.21873/cgp.20034] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Mutations of the human K-Ras 4B (K-Ras) G protein are associated with a significant proportion of all human cancers. Despite this fact, a comprehensive analysis of K-Ras interactions is lacking. Our investigations focus on characterization of the K-Ras interaction network. MATERIALS AND METHODS We employed a biotin ligase-tagging approach, in which tagged K-Ras proteins biotinylate neighbor proteins in a proximity-dependent fashion, and proteins are identified via mass spectrometry (MS) sequencing. RESULTS In transfected cells, a total of 748 biotinylated proteins were identified from cells expressing biotin ligase-tagged K-Ras variants. Significant differences were observed between membrane-associated variants and a farnesylation-defective mutant. In pancreatic cancer cells, 56 K-Ras interaction partners were identified. Most of these were cytoskeletal or plasma membrane proteins, and many have been identified previously as potential cancer biomarkers. CONCLUSION Biotin ligase tagging offers a rapid and convenient approach to the characterization of K-Ras interaction networks.
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Affiliation(s)
- Christopher Ritchie
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, OR, U.S.A
| | - Andrew Mack
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, OR, U.S.A
| | - Logan Harper
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, OR, U.S.A
| | - Ayna Alfadhli
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, OR, U.S.A
| | - Philip J S Stork
- Department of Vollum Institute, Oregon Health & Science University, Portland, OR, U.S.A
| | - Xiaolin Nan
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, U.S.A
| | - Eric Barklis
- Department of Molecular Microbiology and Immunology, Oregon Health & Science University, Portland, OR, U.S.A.
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4
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Abstract
Since its discovery in 1979, p53 has been on the forefront of cancer research. It is considered a master gene of cancer suppression and is found mutated in around 50% of all human tumors. In addition, the progressive identification of p53-related transcription factors p63 and p73 as well as their multiple isoforms have added further layers of complexity to an already dense network. Among the numerous models used to unravel the p53 family mysteries, S. cerevisiae has been particularly useful. This seemingly naive model allows the expression of a functional human p53 and thus the assessment of p53 intrinsic transcriptional activity. The aim of this article is to review the various contributions that the budding yeast has made to the understanding of p53, p63 and p73 biology and to envision new possible directions for yeast-based assays in the field of cancer as well as other p53-family-related diseases.
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5
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Fåhraeus R, Olivares-Illana V. MDM2's social network. Oncogene 2013; 33:4365-76. [PMID: 24096477 DOI: 10.1038/onc.2013.410] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Revised: 08/17/2013] [Accepted: 08/17/2013] [Indexed: 12/22/2022]
Abstract
MDM2 is considered a hub protein due to its capacity to interact with a large number of different partners of which p53 is most well described. MDM2 is an E3 ubiquitin ligase, and many, but not all, of its interactions relate directly to this activity, such as substrates, adaptors or bridges, promoters, inhibitors or complementary factors. Some interactions serve regulatory functions that in response to cellular stresses control the localisation and functions of MDM2 including protein kinases, ribosomal proteins and proteases. Moreover, interactions with nucleotides serve other functions such as mRNA to regulate protein synthesis and DNA to control transcription. To perform such a pleiotropic panorama of different functions, MDM2 is subjected to a multitude of post-translational modifications and is expressed in different isoforms. The large and diverse interactome is made possible due to the plasticity of MDM2 and in this review we have listed the MDM2 interactions until now and we will discuss how this multifaceted protein can interact with such a variety of substrates to provide a key intermediary role in different signalling pathways.
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Affiliation(s)
- R Fåhraeus
- Cibles Therapeutiques, Equipe Labellisée Ligue Contre le Cancer, INSERM Unité 940, Institut de Génétique Moléculaire, Université Paris 7, Hôpital St Louis, 27 rue Juliette Dodu, Paris, France
| | - V Olivares-Illana
- Instituto de Física, Universidad Autónoma de San Luis Potosí, Av. Manuel Nava, Zona Universitaria, San Luis Potosí, México
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6
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Kelemen O, Convertini P, Zhang Z, Wen Y, Shen M, Falaleeva M, Stamm S. Function of alternative splicing. Gene 2013; 514:1-30. [PMID: 22909801 PMCID: PMC5632952 DOI: 10.1016/j.gene.2012.07.083] [Citation(s) in RCA: 512] [Impact Index Per Article: 46.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2012] [Revised: 07/21/2012] [Accepted: 07/30/2012] [Indexed: 12/15/2022]
Abstract
Almost all polymerase II transcripts undergo alternative pre-mRNA splicing. Here, we review the functions of alternative splicing events that have been experimentally determined. The overall function of alternative splicing is to increase the diversity of mRNAs expressed from the genome. Alternative splicing changes proteins encoded by mRNAs, which has profound functional effects. Experimental analysis of these protein isoforms showed that alternative splicing regulates binding between proteins, between proteins and nucleic acids as well as between proteins and membranes. Alternative splicing regulates the localization of proteins, their enzymatic properties and their interaction with ligands. In most cases, changes caused by individual splicing isoforms are small. However, cells typically coordinate numerous changes in 'splicing programs', which can have strong effects on cell proliferation, cell survival and properties of the nervous system. Due to its widespread usage and molecular versatility, alternative splicing emerges as a central element in gene regulation that interferes with almost every biological function analyzed.
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Affiliation(s)
- Olga Kelemen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Paolo Convertini
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Zhaiyi Zhang
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Yuan Wen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Manli Shen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Marina Falaleeva
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
| | - Stefan Stamm
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky, United States of America
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7
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Abstract
Mdm2 is an essential regulator of the p53 tumor suppressor. Mdm2 is modified at transcriptional, post-transcriptional, and post-translational levels to control p53 activity in normal versus stressed cells. Importantly, errors in these regulatory mechanisms can result in aberrant Mdm2 expression and failure to initiate programmed cell death in response to DNA damage. Such errors can have severe consequences as evidenced by tumor phenotypes resulting from amplification at the Mdm2 locus and changes in post-transcriptional and post-translational regulation of Mdm2. Although Mdm2 mediated inhibition of p53 is well characterized, Mdm2 interacts with many additional proteins and also targets many of these for proteosomal degradation. Mdm2 also has E3-ligase independent functions and p53-independent functions that have important implications for genome stability and cancer.
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Affiliation(s)
- Maurisa F Riley
- Department of Genetics, University of Texas M.D. Anderson Cancer Center, Houston, TX, USA
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8
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Contente S, Yeh TJA, Friedman RM. H-ras localizes to cell nuclei and varies with the cell cycle. Genes Cancer 2011; 2:166-72. [PMID: 21779490 PMCID: PMC3111243 DOI: 10.1177/1947601911405042] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 02/18/2011] [Accepted: 03/04/2011] [Indexed: 01/10/2023] Open
Abstract
H-Ras functions as a signal switch molecule in numerous signaling pathways in the cytoplasm, requiring H-Ras localization to the inner surface of the cytoplasmic membrane, and H-Ras is considered to be a cytoplasmic protein. Immunoblot studies of cells transformed by overexpression of c-H-ras indicated that H-Ras protein was present in both cytoplasmic and nuclear extracts, suggesting a possible correlation of nuclear H-Ras and cellular transformation. Unexpectedly, additional studies revealed that H-Ras protein was also present in the nuclei of nontransformed and primary mouse cells, which do not overexpress H-Ras. Mouse fibroblast NIH 3T3 cells, L cells, and a primary fibroblast line all had H-Ras present in both cytoplasmic and nuclear extracts. Nuclear extracts of cells synchronized by growth without serum displayed an increasing amount of H-Ras and cyclin D1 as cells grew after serum addition. Treatment with farnesyltransferase inhibitor caused loss of H-Ras from the nucleus. Immunofluorescence in situ studies of nuclei from synchronized cultures showed that H-Ras protein appeared in and disappeared from the nuclei as the cells moved through the growth cycle. This cycling occurred in both nontransformed and ras-transformed cells. Flow cytometry measurements on parallel cultures revealed that the time point at which the greatest percentage of cells were in S phase, for each line, corresponded to appearance of a noticeably stronger in situ signal for H-Ras. H-Ras may participate in nuclear signaling pathways associated with replication in addition to its cytoplasmic signaling functions.
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Affiliation(s)
- Sara Contente
- Department of Pathology, F. Edward Hébert School of Medicine, and United States Military Cancer Institute, Uniformed Services University of the Health Sciences, Bethesda, MD, USA
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9
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An JH, Kim JW, Jang SM, Kim CH, Kang EJ, Choi KH. Gelsolin negatively regulates the activity of tumor suppressor p53 through their physical interaction in hepatocarcinoma HepG2 cells. Biochem Biophys Res Commun 2011; 412:44-9. [PMID: 21801713 DOI: 10.1016/j.bbrc.2011.07.034] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Accepted: 07/08/2011] [Indexed: 10/18/2022]
Abstract
As a transcription factor, p53 modulates several cellular responses including cell-cycle control, apoptosis, and differentiation. In this study, we have shown that an actin regulatory protein, gelsolin (GSN), can physically interact with p53. The nuclear localization of p53 is inhibited by GSN overexpression in hepatocarcinoma HepG2 cells. Additionally, we demonstrate that GSN negatively regulates p53-dependent transcriptional activity of a reporter construct, driven by the p21-promoter. Furthermore, p53-mediated apoptosis was repressed in GSN-transfected HepG2 cells. Taken together, these results suggest that GSN binds to p53 and this interaction leads to the inhibition of p53-induced apoptosis by anchoring of p53 in the cytoplasm in HepG2 cells.
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Affiliation(s)
- Joo-Hee An
- Department of Life Science (BK21 Program), College of Natural Sciences, Chung-Ang University, Seoul 156-756, Republic of Korea
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10
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David CJ, Manley JL. Alternative pre-mRNA splicing regulation in cancer: pathways and programs unhinged. Genes Dev 2011; 24:2343-64. [PMID: 21041405 DOI: 10.1101/gad.1973010] [Citation(s) in RCA: 621] [Impact Index Per Article: 47.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Alternative splicing of mRNA precursors is a nearly ubiquitous and extremely flexible point of gene control in humans. It provides cells with the opportunity to create protein isoforms of differing, even opposing, functions from a single gene. Cancer cells often take advantage of this flexibility to produce proteins that promote growth and survival. Many of the isoforms produced in this manner are developmentally regulated and are preferentially re-expressed in tumors. Emerging insights into this process indicate that pathways that are frequently deregulated in cancer often play important roles in promoting aberrant splicing, which in turn contributes to all aspects of tumor biology.
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Affiliation(s)
- Charles J David
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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11
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Ozaki T, Kubo N, Nakagawara A. p73-Binding Partners and Their Functional Significance. INTERNATIONAL JOURNAL OF PROTEOMICS 2011; 2010:283863. [PMID: 22084676 PMCID: PMC3195385 DOI: 10.1155/2010/283863] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Accepted: 10/26/2010] [Indexed: 12/21/2022]
Abstract
p73 is one of the tumor-suppressor p53 family of nuclear transcription factor. As expected from the structural similarity between p53 and p73, p73 has a tumor-suppressive function. However, p73 was rarely mutated in human primary tumors. Under normal physiological conditions, p73 is kept at an extremely low level to allow cells normal growth. In response to a certain subset of DNA damages, p73 is induced dramatically and transactivates an overlapping set of p53-target genes implicated in the promotion of cell cycle arrest and/or apoptotic cell death. Cells undergo cell cycle arrest and/or apoptotic cell death depending on the type and strength of DNA damages. p73 is regulated largely through the posttranslational modifications such as phosphorylation and acetylation. These chemical modifications are tightly linked to direct protein-protein interactions. In the present paper, the authors describe the functional significance of the protein-protein interactions in the regulation of proapoptotic p73.
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Affiliation(s)
- Toshinori Ozaki
- Laboratory of Anti-tumor Research, Chiba Cancer Center Research Institute, Chiba 260-8717, Japan
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12
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Muttray AF, O'Toole TF, Morrill W, Van Beneden RJ, Baldwin SA. An invertebrate mdm homolog interacts with p53 and is differentially expressed together with p53 and ras in neoplastic Mytilus trossulus haemocytes. Comp Biochem Physiol B Biochem Mol Biol 2010; 156:298-308. [PMID: 20417299 DOI: 10.1016/j.cbpb.2010.04.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2010] [Revised: 04/17/2010] [Accepted: 04/17/2010] [Indexed: 02/07/2023]
Abstract
The mussel Mytilus trossulus can develop a neoplasia of the haemolymph, which occurs with high frequency (up to 40%) in nature. Associated with this disease are pro-apoptotic tumor-suppressor protein p53 isoforms, which are highly conserved between molluscs and vertebrates. The vertebrate wildtype p53 protein is maintained at low levels by the MDM2 protein in non-stressed cells to prevent undesired apoptosis. Identification of a putative invertebrate MDM-like homolog suggests early evolution of this mechanism of p53 regulation. The M. trossulus MDM homolog consists of a conserved NH(2)-terminal p53 binding domain, an acidic domain with highly conserved phosphorylation sites, and a highly conserved C-terminal RING-finger Zn-binding domain. Although BLAST queries predict this homologue to be more similar to vertebrate MDM2 than to MDM4, phylogenetic analysis suggests that it may be an ancestral form to both vertebrate MDM genes. Using yeast-two-hybrid assays and pull-down assays, we show that this molluscan MDM is able to bind to its p53 counterpart. We also show that MDM expression levels are directly correlated with p53 expression levels in healthy and in neoplastic haemocytes, but not with other p53 isoforms or with the proto-oncogene RAS. The combination of expression levels of five gene transcripts (p53, mdm, ras, Np63/73, and TAp63/73) is significantly correlated with late-stage haemic neoplasia in M. trossulus.
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Affiliation(s)
- Annette F Muttray
- University of British Columbia, Department of Chemical and Biological Engineering, Vancouver, B.C., Canada.
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13
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P19 H-ras induces G1/S phase delay maintaining cells in a reversible quiescence state. PLoS One 2009; 4:e8513. [PMID: 20046837 PMCID: PMC2798614 DOI: 10.1371/journal.pone.0008513] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2009] [Accepted: 11/20/2009] [Indexed: 12/31/2022] Open
Abstract
Background Three functional c-ras genes, known as c-H-ras, c-K-ras, and c-N-ras, have been largely studied in mammalian cells with important insights into normal and tumorigenic cellular signal transduction events. Two K-Ras mRNAs are obtained from the same pre-mRNA by alternative splicing. H-Ras pre-mRNA can also be alternatively spliced in the IDX and 4A terminal exons, yielding the p19 and p21 proteins, respectively. However, despite the Ras gene family's established role in tumorigenic cellular signal transduction events, little is known about p19 function. Previous results showed that p19 did not interact with two known p21 effectors, Raf1 and Rin1, but was shown to interact with RACK1, a scaffolding protein that promotes multi-protein complexes in different signaling pathways (Cancer Res 2003, 63 p5178). This observation suggests that p19 and p21 play differential and complementary roles in the cell. Principal Findings We found that p19 regulates telomerase activity through its interaction with p73α/β proteins. We also found that p19 overexpression induces G1/S phase delay; an observation that correlates with hypophosphorylation of both Akt and p70SK6. Similarly, we also observed that FOXO1 is upregulated when p19 is overexpressed. The three observations of (1) hypophosphorylation of Akt, (2) G1/S phase delay and (3) upregulation of FOXO1 lead us to conclude that p19 induces G1/S phase delay, thereby maintaining cells in a reversible quiescence state and preventing entry into apoptosis. We then assessed the effect of p19 RNAi on HeLa cell growth and found that p19 RNAi increases cell growth, thereby having the opposite effect of arrest of the G1/S phase or producing a cellular quiescence state. Significance Interestingly, p19 induces FOXO1 that in combination with the G1/S phase delay and hypophosphorylation of both Akt and p70SK6 leads to maintenance of a reversible cellular quiescence state, thereby preventing entry into apoptosis.
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14
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Jang SM, Kim JW, Kim CH, Kim D, Rhee S, Choi KH. p19(ras) Represses proliferation of non-small cell lung cancer possibly through interaction with Neuron-Specific Enolase (NSE). Cancer Lett 2009; 289:91-8. [PMID: 19713034 DOI: 10.1016/j.canlet.2009.08.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2009] [Revised: 07/28/2009] [Accepted: 08/02/2009] [Indexed: 10/20/2022]
Abstract
p19(ras) is an alternative splicing product of the proto-oncogene c-H-ras pre-mRNA. In this study, we identified a novel p19(ras)-binding protein, Neuron-Specific Enolase (NSE), using the yeast two-hybrid method. NSE is one of the enolase families that convert 2-phospho-d-glycerate (PGA) to phosphoenolpyruvate (PEP) in the glycolysis pathway. In both endogenous and over-expressed systems, we confirmed interactions between p19(ras) and NSE via co-immunoprecipitation assay. We also identified the interaction region of p19(ras), which is required for binding with NSE. When full-length p19(ras) and C-terminal region are bound to NSE, it inhibits the enzymatic activity of NSE. Furthermore, p19(ras) interacted with Enolase alpha (Enoalpha) and repressed its enzymatic activity in vitro. p19(ras) repressed lung cancer cell proliferation mostly increased by NSE in H1299 cells. Taken together, these results suggest that p19(ras) is a novel regulator to suppress cell proliferation in lung cancer through the interaction with NSE.
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Affiliation(s)
- Sang-Min Jang
- Department of Life Science (BK21 program), College of Natural Sciences, Chung-Ang University, Seoul 156-756, Republic of Korea
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15
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Bouska A, Eischen CM. Murine double minute 2: p53-independent roads lead to genome instability or death. Trends Biochem Sci 2009; 34:279-86. [PMID: 19447627 DOI: 10.1016/j.tibs.2009.02.006] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2009] [Revised: 02/17/2009] [Accepted: 02/20/2009] [Indexed: 11/29/2022]
Abstract
The oncoprotein murine double minute 2 (Mdm2) is frequently overexpressed in many types of human malignancies. Although Mdm2 has an essential role in negatively regulating the p53 tumor suppressor, it also has less well characterized p53-independent functions that influence pathways that are crucial for controlling tumorigenesis. In addition to the impact Mdm2 has on p53-independent apoptosis, mounting evidence is linking increased Mdm2 levels to altered cell-cycle regulation, DNA replication and DNA repair leading to loss of genome stability. Mdm2 involvement in pathways that influence chromosome stability and cell death, distinct from its role in the p53 pathway, strengthens the position of Mdm2 as a desirable therapeutic target for the treatment of human cancers.
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Affiliation(s)
- Alyssa Bouska
- Department of Internal Medicine, University of Nebraska Medical Center, Omaha, NE 68198, USA
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16
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Abstract
Differential subcellular compartmentalization of the three main Ras isoforms (H-Ras, N-Ras and K-Ras) is believed to underlie their biological differences. Modulatable interactions between cellular membranes and Ras C-terminal hypervariable region motifs determine differences in trafficking and the relative proportions of each isoform in cell-surface signalling nanoclusters and intracellular endoplasmic reticulum/Golgi, endosomal and mitochondrial compartments. Ras regulators, effectors and scaffolds are also differentially distributed, potentially enabling preferential coupling to specific signalling pathways in each subcellular location. Here we summarize the mechanisms underlying compartment-specific Ras signalling and the outputs generated.
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17
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Jang S, Kim J, Choi K. p19rasAccelerates p73β‐mediated apoptosis through a caspase‐3 dependent pathway. Anim Cells Syst (Seoul) 2009. [DOI: 10.1080/19768354.2009.9647235] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
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18
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Camats M, Guil S, Kokolo M, Bach-Elias M. P68 RNA helicase (DDX5) alters activity of cis- and trans-acting factors of the alternative splicing of H-Ras. PLoS One 2008; 3:e2926. [PMID: 18698352 PMCID: PMC2491553 DOI: 10.1371/journal.pone.0002926] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2008] [Accepted: 07/18/2008] [Indexed: 02/07/2023] Open
Abstract
Background H-Ras pre-mRNA undergoes an alternative splicing process to render two proteins, namely p21 H-Ras and p19 H-Ras, due to either the exclusion or inclusion of the alternative intron D exon (IDX), respectively. p68 RNA helicase (p68) is known to reduce IDX inclusion. Principal Findings Here we show that p68 unwinds the stem-loop IDX-rasISS1 structure and prevents binding of hnRNP H to IDX-rasISS1. We also found that p68 alters the dynamic localization of SC35, a splicing factor that promotes IDX inclusion. The knockdown of hnRNP A1, FUS/TLS and hnRNP H resulted in upregulation of the expression of the gene encoding the SC35-binding protein, SFRS2IP. Finally, FUS/TLS was observed to upregulate p19 expression and to stimulate IDX inclusion, and in vivo RNAi-mediated depletion of hnRNP H decreased p19 H-Ras abundance. Significance Taken together, p68 is shown to be an essential player in the regulation of H-Ras expression as well as in a vital transduction signal pathway tied to cell proliferation and many cancer processes.
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Affiliation(s)
- Maria Camats
- Unidad de Splicing, Instituto de Investigaciones Biomédicas de Barcelona-Consejo Superior de Investigaciones Científicas, Barcelona, Spain
| | - Sonia Guil
- Unidad de Splicing, Instituto de Investigaciones Biomédicas de Barcelona-Consejo Superior de Investigaciones Científicas, Barcelona, Spain
| | - Mariette Kokolo
- Unidad de Splicing, Instituto de Investigaciones Biomédicas de Barcelona-Consejo Superior de Investigaciones Científicas, Barcelona, Spain
| | - Montse Bach-Elias
- Unidad de Splicing, Instituto de Investigaciones Biomédicas de Barcelona-Consejo Superior de Investigaciones Científicas, Barcelona, Spain
- * E-mail:
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Tozluoğlu M, Karaca E, Haliloglu T, Nussinov R. Cataloging and organizing p73 interactions in cell cycle arrest and apoptosis. Nucleic Acids Res 2008; 36:5033-49. [PMID: 18660513 PMCID: PMC2528188 DOI: 10.1093/nar/gkn481] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
We have compiled the p73-mediated cell cycle arrest and apoptosis pathways. p73 is a member of the p53 family, consisting of p53, p63 and p73. p73 exists in several isoforms, presenting different domain structures. p73 functions not only as a tumor suppressor in apoptosis but also as differentiator in embryo development. p53 mutations are responsible for half of the human cancers; p73 can partially substitute mutant p53 as tumor suppressor. The pathways we assembled create a p73-centered network consisting of 53 proteins and 176 interactions. We clustered our network into five functional categories: Upregulation, Activation, Suppression, Transcriptional Activity and Degradation. Our literature searches led to discovering proteins (c-Jun and pRb) with apparent opposing functional effects; these indicate either currently missing proteins and interactions or experimental misidentification or functional annotation. For convenience, here we present the p73 network using the molecular interaction map (MIM) notation. The p73 MIM is unique amongst MIMs, since it further implements detailed domain features. We highlight shared pathways between p53 and p73. We expect that the compiled and organized network would be useful to p53 family-based studies.
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Affiliation(s)
- Melda Tozluoğlu
- Polymer Research Center and Chemical Engineering Department, Bogazici University, Bebek-Istanbul 80815, Turkey
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20
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Lee SY, Kim JW, Jeong MH, An JH, Jang SM, Song KH, Choi KH. Microtubule-associated Protein 1B Light Chain (MAP1B-LC1) negatively regulates the activity of tumor suppressor p53 in neuroblastoma cells. FEBS Lett 2008; 582:2826-32. [DOI: 10.1016/j.febslet.2008.07.021] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2008] [Revised: 07/12/2008] [Accepted: 07/14/2008] [Indexed: 10/21/2022]
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21
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Oh YK, Lee HJ, Jeong MH, Rhee M, Mo JW, Song EH, Lim JY, Choi KH, Jo I, Park SI, Gao B, Kwon Y, Kim WH. Role of activating transcription factor 3 on TAp73 stability and apoptosis in paclitaxel-treated cervical cancer cells. Mol Cancer Res 2008; 6:1232-49. [PMID: 18644986 PMCID: PMC3783268 DOI: 10.1158/1541-7786.mcr-07-0297] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Taxol (paclitaxel) is a potent anticancer drug that has been found to be effective against several tumor types, including cervical cancer. However, the exact mechanism underlying the antitumor effects of paclitaxel is poorly understood. Here, paclitaxel induced the apoptosis of cervical cancer HeLa cells and correlated with the enhanced activation of caspase-3 and TAp73, which was strongly inhibited by TAp73beta small interfering RNA (siRNA). In wild-type activating transcription factor 3 (ATF3)-overexpressed cells, paclitaxel enhanced apoptosis through increased alpha and beta isoform expression of TAp73; however, these events were attenuated in cells containing inactive COOH-terminal-deleted ATF3 [ATF3(DeltaC)] or ATF3 siRNA. In contrast, paclitaxel-induced ATF3 expression did not change in TAp73beta-overexpressed or TAp73beta siRNA-cotransfected cells. Furthermore, paclitaxel-induced ATF3 translocated into the nucleus where TAp73beta is expressed, but not in ATF3(DeltaC) or TAp73beta siRNA-transfected cells. As confirmed by the GST pull-down assay, ATF3 bound to the DNA-binding domain of p73, resulting in the activation of p21 or Bax transcription, a downstream target of p73. Overexpression of ATF3 prolonged the half-life of TAp73beta by inhibiting its ubiquitination and thereby enhancing its transactivation and proapoptotic activities. Additionally, ATF3 induced by paclitaxel potentiated the stability of TAp73beta, not its transcriptional level. Chromatin immunoprecipitation analyses show that TAp73beta and ATF3 are recruited directly to the p21 and Bax promoter. Collectively, these results reveal that overexpression of ATF3 potentiates paclitaxel-induced apoptosis of HeLa cells, at least in part, by enhancing TAp73beta's stability and its transcriptional activity. The investigation shows that ATF3 may function as a tumor-inhibiting factor through direct regulatory effects on TAp73beta, suggesting a functional link between ATF3 and TAp73beta.
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Affiliation(s)
- Yeo Kyoung Oh
- Division of Intractable Diseases, Center for Biomedical Sciences, NIH
| | - Hyun Jung Lee
- Division of Intractable Diseases, Center for Biomedical Sciences, NIH
| | - Mi-Hee Jeong
- Laboratory of Molecular Biology, Department of Biology, College of Natural Science, Chung-Ang University
| | - Marie Rhee
- Division of Intractable Diseases, Center for Biomedical Sciences, NIH
| | - Ji-Won Mo
- Division of Intractable Diseases, Center for Biomedical Sciences, NIH
| | - Eun Hyeon Song
- Division of Intractable Diseases, Center for Biomedical Sciences, NIH
| | - Joong-Yeon Lim
- Division of Intractable Diseases, Center for Biomedical Sciences, NIH
| | - Kyung-Hee Choi
- Laboratory of Molecular Biology, Department of Biology, College of Natural Science, Chung-Ang University
| | - Inho Jo
- Department of Molecular Medicine, School of Medicine, Ewha Womans University, Seoul, Korea
| | - Sang Ick Park
- Division of Intractable Diseases, Center for Biomedical Sciences, NIH
| | - Bin Gao
- Section on Liver Biology, Laboratory of Physiologic Studies, National Institute on Alcohol Abuse and Alcoholism, NIH, Bethesda, Maryland
| | - Yongil Kwon
- Gynecologic Oncology, Kangdong Sacred Heart Hospital, Hallym University, Seoul, Korea
| | - Won-Ho Kim
- Division of Intractable Diseases, Center for Biomedical Sciences, NIH
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Kim JW, Song PI, Jeong MH, An JH, Lee SY, Jang SM, Song KH, Armstrong CA, Choi KH. TIP60 Represses Transcriptional Activity of p73β via an MDM2-bridged Ternary Complex. J Biol Chem 2008; 283:20077-86. [DOI: 10.1074/jbc.m800161200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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23
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Kim JW, Kim WH, Jeong MH, Jang SM, Song KH, Park SI, Song PI, Kang KH, Choi KH. p19(ras) amplifies p73beta-induced apoptosis through mitochondrial pathway. Biochem Biophys Res Commun 2008; 373:146-50. [PMID: 18555006 DOI: 10.1016/j.bbrc.2008.06.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2008] [Accepted: 06/03/2008] [Indexed: 11/18/2022]
Abstract
p73 and p53 have been known to play an important role in cellular damage responses such as apoptosis. Although p73 is a structural and functional homolog of p53 tumor suppressor gene, much less is known about the mechanism of p73-induced apoptotic cell death. In this study, we demonstrate that p19(ras) interaction with p73beta amplifies p73beta-induced apoptotic signaling responses including Bax mitochondrial translocation, cytochrome c release, increased production of reactive oxygen species (ROS) and loss of mitochondrial transmembrane potential (DeltaPsi(m)). Furthermore, endogenous expression of p19(ras) and p73beta is significantly increased by Taxol treatment, and Taxol-enhanced endogenous p73beta transcriptional activities are further amplified by p19(ras), which markedly increased cellular apoptosis in p53-null SAOS2 cancer cell line. These results have important implications for understanding the molecular events of p19(ras) to p73 functions in cancer cells.
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Affiliation(s)
- Jung-Woong Kim
- Department of Life Science, College of Natural Sciences, Chung-Ang University, 221 Heuksuk Dong, Dongjak Ku, Seoul 156-756, Republic of Korea
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24
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Patra SK. Ras regulation of DNA-methylation and cancer. Exp Cell Res 2008; 314:1193-201. [PMID: 18282569 DOI: 10.1016/j.yexcr.2008.01.012] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2007] [Revised: 01/13/2008] [Accepted: 01/16/2008] [Indexed: 01/14/2023]
Abstract
Genome wide hypomethylation and regional hypermethylation of cancer cells and tissues remain a paradox, though it has received a convincing confirmation that epigenetic switching systems, including DNA-methylation represent a fundamental regulatory mechanism that has an impact on genome maintenance and gene transcription. Methylated cytosine residues of vertebrate DNA are transmitted by clonal inheritance through the strong preference of DNA methyltransferase, DNMT1, for hemimethylated-DNA. Maintenance of methylation patterns is necessary for normal development of mice, and aberrant methylation patterns are associated with many human tumours. DNMT1 interacts with many proteins during cell cycle progression, including PCNA, p53, EZH2 and HP1. Ras family of GTPases promotes cell proliferation by its oncogenic nature, which transmits signals by multiple pathways in both lipid raft dependent and independent fashion. DNA-methylation-mediated repression of DNA-repair protein O6-methylguanine DNA methyltransferase (MGMT) gene and increased rate of K-Ras mutation at codon for amino acids 12 and 13 have been correlated with a secondary role for Ras-effector homologues (RASSFs) in tumourigenesis. Lines of evidence suggest that DNA-methylation associated repression of tumour suppressors and apoptotic genes and ceaseless proliferation of tumour cells are regulated in part by Ras-signaling. Control of Ras GTPase signaling might reduce the aberrant methylation and accordingly may reduce the risk of cancer development.
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Affiliation(s)
- Samir Kumar Patra
- Cancer Epigenetics Research, Kalyani (B-7/183), Nadia, West Bengal, India.
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Kim J, Lee S, Jeong M, Jang S, Song K, Kim C, Kim Y, Choi K. Interaction of microtubule‐associated protein 1B light chain (MAP1B‐LC1) and p53 represses transcriptional activity of p53. Anim Cells Syst (Seoul) 2008. [DOI: 10.1080/19768354.2008.9647157] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
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26
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Omerovic J, Laude AJ, Prior IA. Ras proteins: paradigms for compartmentalised and isoform-specific signalling. Cell Mol Life Sci 2007; 64:2575-89. [PMID: 17628742 PMCID: PMC2561238 DOI: 10.1007/s00018-007-7133-8] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Ras GTPases mediate a wide variety of cellular processes by converting a multitude of extracellular stimuli into specific biological responses including proliferation, differentiation and survival. In mammalian cells, three ras genes encode four Ras isoforms (H-Ras, K-Ras4A, K-Ras4B and N-Ras) that are highly homologous but functionally distinct. Differences between the isoforms, including their post-translational modifications and intracellular sorting, mean that Ras has emerged as an important model system of compartmentalised signalling and membrane biology. Ras isoforms in different subcellular locations are proposed to recruit distinct upstream and downstream accessory proteins and activate multiple signalling pathways. Here, we summarise data relating to isoform-specific signalling, its role in disease and the mechanisms promoting compartmentalised signalling. Further understanding of this field will reveal the role of Ras signalling in development, cellular homeostasis and cancer and may suggest new therapeutic approaches.
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Affiliation(s)
- J. Omerovic
- Physiological Laboratory, University of Liverpool, Crown St., Liverpool, L69 3BX UK
| | - A. J. Laude
- Physiological Laboratory, University of Liverpool, Crown St., Liverpool, L69 3BX UK
| | - I. A. Prior
- Physiological Laboratory, University of Liverpool, Crown St., Liverpool, L69 3BX UK
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Barbier J, Dutertre M, Bittencourt D, Sanchez G, Gratadou L, de la Grange P, Auboeuf D. Regulation of H-ras splice variant expression by cross talk between the p53 and nonsense-mediated mRNA decay pathways. Mol Cell Biol 2007; 27:7315-33. [PMID: 17709397 PMCID: PMC2168895 DOI: 10.1128/mcb.00272-07] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
When cells are exposed to a genotoxic stress, a DNA surveillance pathway that involves p53 is activated, allowing DNA repair. Eukaryotic cells have also evolved a mechanism called mRNA surveillance that controls the quality of mRNAs. Indeed, mutant mRNAs carrying premature translation termination codons (PTCs) are selectively degraded by the nonsense-mediated mRNA decay (NMD) pathway. However, in the case of particular genes, such as proto-oncogenes, mutations that do not create PTCs and therefore that do not induce mRNA degradation, can be harmful to cells. In this study, we showed that the H-ras gene in the absence of mutations produces an NMD-target splice variant that is degraded in the cytosol. We observed that a treatment with the genotoxic stress inducer camptothecin for 6 h favored the production of the H-ras NMD-target transcript degraded in the cytosol by the NMD process. Our data indicated that the NMD process allowed the elimination of transcripts produced in response to a short-term treatment with camptothecin from the major proto-oncogene H-ras, independently of PTCs induced by mutations. The camptothecin effects on H-ras gene expression were p53 dependent and involved in part modulation of the SC35 splicing factor. Interestingly, a long-term treatment with camptothecin as well as p53 overexpression for 24 h resulted in the accumulation of the H-ras NMD target in the cytosol, although the NMD process was not completely inhibited as other NMD targets are not stabilized. Finally, Upf1, a major NMD effector, was necessary for optimal p53 activation by camptothecin, which is consistent with recent data showing that NMD effectors are required for genome stability. In conclusion, we identified cross talk between the p53 and NMD pathways that regulates the expression levels of H-ras splice variants.
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Affiliation(s)
- Jérôme Barbier
- INSERM U685, Equipe AVENIR, Hopital Saint-Louis, 1 Avenue Claude Vellefaux, Paris 75010, France
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28
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Abstract
The p53-related genes p63 and p73 exhibit significant structural homology to p53; however, they do not function as classical tumor suppressors and are rarely mutated in human cancers. Both p63 and p73 exhibit tissue-specific roles in normal development and a complex contribution to tumorigenesis that is due to their expression as multiple protein isoforms. The predominant p63/p73 isoforms expressed both in normal development and in many tumors lack the conserved transactivation (TA) domain; these isoforms instead exhibit a truncated N-terminus (DeltaN) and function at least in part as transcriptional repressors. p63 and p73 isoforms are regulated through both transcriptional and post-translational mechanisms, and they in turn regulate diverse cellular functions including proliferation, survival and differentiation. The net effect of p63/p73 expression in a given context depends on the ratio of TA/DeltaN isoforms expressed, on physical interaction between p63 and p73 isoforms, and on functional interactions with p53 at the promoters of specific downstream target genes. These multifaceted interactions occur in diverse ways in tumor-specific contexts, demonstrating a functional 'p53 family network' in human tumorigenesis. Understanding the regulation and mechanistic contributions of p63 and p73 in human cancers may ultimately provide new therapeutic opportunities for a variety of these diseases.
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Affiliation(s)
- M P Deyoung
- Massachusetts General Hospital Cancer Center, Boston, MA 02114, USA
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29
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Abstract
p53 is the most commonly mutated gene in human cancer. It is now known that the p53 family proteins p63 and p73 play important roles in tumor suppression as well as in development. Because p63 and p73 are rarely mutated in human cancer, understanding the signaling pathways that activate p63 and p73 will not only shed light on the developmental processes regulated by p63 and p73 but may also yield insight into ways to harness p63 and p73 activity for cancer therapy. Recent research has shown that an alternative splice form of c-H-ras, called p19ras, is a positive regulator of p73beta through a mechanism that involves the E3 ubiquitin ligase Mdm2. Implications for this previously unidentified means of regulation are discussed in light of tumor suppression and are extended to p53 and p63.
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Affiliation(s)
- Kelly Lynn Harms
- Department of Cell Biology, University of Alabama, Birmingham, AL 35294, USA
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