101
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Broytman O, Westmark PR, Gurel Z, Malter JS. Rck/p54 interacts with APP mRNA as part of a multi-protein complex and enhances APP mRNA and protein expression in neuronal cell lines. Neurobiol Aging 2008; 30:1962-74. [PMID: 18378046 DOI: 10.1016/j.neurobiolaging.2008.02.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2007] [Revised: 01/28/2008] [Accepted: 02/19/2008] [Indexed: 01/25/2023]
Abstract
Overproduction of amyloid precursor protein (APP) and beta-amyloid likely contribute to neurodegeneration seen in Alzheimer's disease (AD). APP mRNA contains several, 3'-untranslated region (UTR), cis-acting regulatory elements. A 52 base element (52sce), immediately downstream from the stop codon, has been previously shown to complex with uncharacterized cytoplasmic proteins. In this study, we purify and identify six proteins that specifically bind to the 52sce, and show that these proteins interact with each other and with APP mRNA in intact human neuroblastoma cells. We also present evidence that at least one of these proteins, the DEAD-box helicase rck/p54, is involved in post-transcriptional regulation, as its overexpression in cultured cells results in elevated levels of APP mRNA and protein. These findings suggest a novel mechanism for post-transcriptional regulation of APP mRNA.
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Affiliation(s)
- Oleg Broytman
- Department of Pathology and Laboratory Medicine, Neuroscience Training Program, Waisman Center for Developmental Disabilities and Institute on Aging, University of Wisconsin, Madison, 1500 Highland Avenue, Madison, WI 53705, USA
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102
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Soundararajan S, Chen W, Spicer EK, Courtenay-Luck N, Fernandes DJ. The nucleolin targeting aptamer AS1411 destabilizes Bcl-2 messenger RNA in human breast cancer cells. Cancer Res 2008; 68:2358-65. [PMID: 18381443 DOI: 10.1158/0008-5472.can-07-5723] [Citation(s) in RCA: 376] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
We sought to determine whether nucleolin, a bcl-2 mRNA-binding protein, has a role in the regulation of bcl-2 mRNA stability in MCF-7 and MDA-MB-231 breast cancer cells. Furthermore, we examined the efficacy of the aptamer AS1411 in targeting nucleolin and inducing bcl-2 mRNA instability and cytotoxicity in these cells. AS1411 at 5 micromol/L inhibited the growth of MCF-7 and MDA-MB-231 cells, whereas 20 micromol/L AS1411 had no effect on the growth rate or viability of normal MCF-10A mammary epithelial cells. This selectivity of AS1411 was related to a greater uptake of AS1411 into the cytoplasm of MCF-7 cells compared with MCF-10A cells and to a 4-fold higher level of cytoplasmic nucleolin in MCF-7 cells. Stable siRNA knockdown of nucleolin in MCF-7 cells reduced nucleolin and bcl-2 protein levels and decreased the half-life of bcl-2 mRNA from 11 to 5 hours. Similarly, AS1411 (10 micromol/L) decreased the half-life of bcl-2 mRNA in MCF-7 and MDA-MB-231 cells to 1.0 and 1.2 hours, respectively. In contrast, AS1411 had no effect on the stability of bcl-2 mRNA in normal MCF-10A cells. AS1411 also inhibited the binding of nucleolin to the instability element AU-rich element 1 of bcl-2 mRNA in a cell-free system and in MCF-7 cells. Together, the results suggest that AS1411 acts as a molecular decoy by competing with bcl-2 mRNA for binding to cytoplasmic nucleolin in these breast cancer cell lines. This interferes with the stabilization of bcl-2 mRNA by nucleolin and may be one mechanism by which AS1411 induces tumor cell death.
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Affiliation(s)
- Sridharan Soundararajan
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
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103
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Abstract
OSM (oncostatin M) is a pleiotropic cytokine belonging to the IL (interleukin) 6 family that modulates the growth of some cancer cell lines. We have found that PMA treatment of human U937 lymphoma cells increased the steady-state levels of OSM mRNA. Furthermore, the half-life of OSM mRNA was increased from 2.3 to 6.2 h. Measurement of mRNA/hnRNA (heterogeneous nuclear RNA) ratios in PMA-treated cells suggests further that the increase in OSM mRNA is due to enhanced mRNA stability. Consistent with this, synthetic OSM mRNA transcripts decayed faster in extracts of untreated U937 cells than in extracts of PMA-treated cells. The 3'-untranslated region of OSM mRNA contains a putative ARE (AU-rich element) that may play a role in mRNA stabilization. Addition of the OSM ARE motif to the 3'-end of beta-globin mRNA increased its decay rate in vitro. Decay assays with beta-globin-ARE(OSM) and beta-globin transcripts indicate that PMA induces mRNA stabilization in an ARE-dependent manner. PMA also induces at least five OSM ARE-binding proteins. Supershift assays indicated that HuR is present in PMA-induced OSM mRNA-protein complexes. PMA treatment appears to induce translocation of HuR from the nucleus to the cytoplasm. RNA-decay assays indicated that HuR stabilizes OSM RNA in vitro. Additionally, immunodepletion of HuR from U937 cell extracts led to more rapid decay of OSM transcripts. Collectively, these findings suggest that the ARE plays a role in PMA-induced stabilization of OSM mRNA and that this process involves multiple ARE-binding proteins, including HuR.
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104
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Singh S, Khar A. Differential gene expression during apoptosis induced by a serum factor: role of mitochondrial F0-F1 ATP synthase complex. Apoptosis 2008; 10:1469-82. [PMID: 16215688 DOI: 10.1007/s10495-005-1394-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The number of genes that are up regulated or down regulated during apoptosis is large and still increasing. In an attempt to characterize differential gene expression during serum factor induced apoptosis in AK-5 cells (a rat histiocytoma), we found subunit 6 and subunit 8 of the transmembrane proton channel and subunit alpha of the catalytic core of the mitochondrial F(0)-F(1) ATP synthase complex to be up regulated during apoptosis. The increase in the expression levels of these subunits was concomitant with a transient increase in the intracellular ATP levels, suggesting that the increase in cellular ATP content is a result of the increase in the expression of ATP synthase subunits' gene and de novo protein synthesis. Depleting the cellular ATP levels with oligomycin inhibited apoptosis significantly, pointing to the requirement of ATP during apoptosis. Caspase 1 and caspase 3 activity and the loss of mitochondrial membrane potential were also inhibited by oligomycin during apoptosis in these cells, suggesting that the oligomycin induced inhibition of apoptosis could be due to inhibition of caspase activity and inhibition of mitochondrial depolarization. However, cytochrome C release during apoptosis was found to be completely independent of intracellular ATP content. Besides the ATP synthase complex genes, other mitochondrial genes like cytochrome C oxidase subunit II and III also showed elevated levels of expression during apoptosis. This kind of a mitochondrial gene expression profile suggests that in AK-5 cells, these genes are upregulated in a time-linked manner to ensure sufficient intracellular ATP levels and an efficient functioning of the mitochondrial respiratory chain for successful completion of the apoptotic pathway.
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Affiliation(s)
- S Singh
- Centre for Cellular & Molecular Biology, Uppal Road, Hyderabad, 500 007, India
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105
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Abdelmohsen K, Kuwano Y, Kim HH, Gorospe M. Posttranscriptional gene regulation by RNA-binding proteins during oxidative stress: implications for cellular senescence. Biol Chem 2008; 389:243-255. [PMID: 18177264 PMCID: PMC8481862 DOI: 10.1515/bc.2008.022] [Citation(s) in RCA: 215] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/25/2023]
Abstract
To respond adequately to oxidative stress, mammalian cells elicit rapid and tightly controlled changes in gene expression patterns. Besides alterations in the subsets of transcribed genes, two posttranscriptional processes prominently influence the oxidant-triggered gene expression programs: mRNA turnover and translation. Here, we review recent progress in our knowledge of the turnover and translation regulatory (TTR) mRNA-binding proteins (RBPs) that influence gene expression in response to oxidative damage. Specifically, we identify oxidant damage-regulated mRNAs that are targets of TTR-RBPs, we review the oxidant-triggered signaling pathways that govern TTR-RBP function, and we examine emerging evidence that TTR-RBP activity is altered with senescence and aging. Given the potent influence of TTR-RBPs upon oxidant-regulated gene expression profiles, we propose that the senescence-associated changes in TTR-RBPs directly contribute to the impaired responses to oxidant damage that characterize cellular senescence and advancing age.
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106
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Zhang J, Tsaprailis G, Bowden GT. Nucleolin stabilizes Bcl-X L messenger RNA in response to UVA irradiation. Cancer Res 2008; 68:1046-54. [PMID: 18281479 PMCID: PMC2373251 DOI: 10.1158/0008-5472.can-07-1927] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Our laboratory has previously reported that UVA irradiation can increase the expression of Bcl-X(L), an antiapoptotic molecule, by stabilizing its mRNA in cultured immortalized human keratinocytes. To understand the mechanism by which the Bcl-X(L) message is stabilized, we used a synthetic Bcl-X(L) 3'-untranslated region (UTR) to capture RNA-binding proteins. Nucleolin was identified as one of the binding proteins as determined by tandem mass spectrometry coupled to liquid chromatography analysis. Further study showed that nucleolin specifically recognized the AU-rich elements (AUUUA) in the 3'-UTR of the Bcl-X(L) mRNA and could stabilize the mRNA in vitro. Furthermore, overexpression of nucleolin stabilizes the Bcl-X(L) mRNA in HeLa cells, whereas reducing nucleolin by small interfering RNA shortens the Bcl-X(L) mRNA half-life. Interestingly, nucleolin physically interacted with polyadenylate [poly(A)]-binding protein through it RGG motifs. Its stabilizing effect on the Bcl-X(L) mRNA was dependent upon the presence of poly(A) tail. Based on these data, we propose a model in which nucleolin protects the Bcl-X(L) mRNA from nuclease degradation by enhancing the stability of the ribonucleoprotein loop structure.
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Affiliation(s)
- Jack Zhang
- Arizona Cancer Center, University of Arizona, Tuczon, Arizona
| | | | - G. Tim Bowden
- Arizona Cancer Center, University of Arizona, Tuczon, Arizona
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107
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Chen X, Kube DM, Cooper MJ, Davis PB. Cell surface nucleolin serves as receptor for DNA nanoparticles composed of pegylated polylysine and DNA. Mol Ther 2008; 16:333-42. [PMID: 18059369 DOI: 10.1038/sj.mt.6300365] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Compacted DNA nanoparticles deliver transgenes efficiently to the lung following intrapulmonary dosing. Here we show that nucleolin, a protein known to shuttle between the nucleus, cytoplasm, and cell surface, is a receptor for DNA nanoparticles at the cell surface. By using surface plasmon resonance (SPR), we demonstrate that nucleolin binds to DNA nanoparticles directly. The presence of nucleolin on the surface of HeLa and 16HBEo- cells was confirmed by surface biotinylation assay and immunofluorescence. Rhodamine-labeled DNA nanoparticles colocalize with nucleolin on the cell surface, as well as in the cytoplasm and nucleus, but not with transferrin or markers of early endosome or lysosome following cellular uptake. Reducing nucleolin on the cell surface by serum-free medium or siRNA against nucleolin treatment leads to significant reduction in luciferase reporter gene activity, while overexpressing nucleolin has the opposite effect. Competition for binding to DNA nanoparticles with exogenous purified nucleolin decreases the transfection efficiency by 60-90% in a dose-dependent manner. Therefore, the data strongly suggest that cell surface nucleolin serves as a receptor for DNA nanoparticles, and that nucleolin is essential for internalization and/or transport of the nanoparticles from cell surface to the nucleus.
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Affiliation(s)
- Xuguang Chen
- Department of Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA
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108
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Nucleolin – Characteristics of Protein and its Role in Biology of Cancers and Viral Infections. ACTA ACUST UNITED AC 2008. [DOI: 10.2478/v10052-008-0003-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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109
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Tien CL, Wen FC, Hsieh M. The polyglutamine-expanded protein ataxin-3 decreases bcl-2 mRNA stability. Biochem Biophys Res Commun 2008; 365:232-8. [DOI: 10.1016/j.bbrc.2007.10.162] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2007] [Accepted: 10/23/2007] [Indexed: 11/27/2022]
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110
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Grinstein E, Wernet P. Cellular signaling in normal and cancerous stem cells. Cell Signal 2007; 19:2428-33. [PMID: 17651940 DOI: 10.1016/j.cellsig.2007.06.021] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2007] [Accepted: 06/21/2007] [Indexed: 12/30/2022]
Abstract
Self-renewing divisions of normal and cancerous stem cells are responsible for the initiation and maintenance of normal and certain cancerous tissues, respectively. Recent findings suggest that tumor surveillance mechanisms can reduce regenerative capacity and frequency of normal stem cells, thereby contributing to tissue aging. Signaling pathways promoting self-renewal of stem cells can also drive proliferation in cancer. The BMI-1 proto-oncogene is required for the maintenance of tissue-specific stem cells and is involved in carcinogenesis within the same tissues. BMI-1 promotes self-renewal of stem cells largely by interfering with two central cellular tumor suppressor pathways, p16(Ink4a)/retinoblastoma protein (Rb) and ARF/p53, whose disruption is a hallmark of cancer. Nucleolin, an Rb-associated protein, is abundant in proliferating cancerous cells and likely contributes to the maintenance of human CD34-positive stem/progenitor cells of hematopoiesis. Elucidation of the involvement of proto-oncogenes and tumor suppressors in the maintenance of stem cells might have therapeutic implications.
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Affiliation(s)
- Edgar Grinstein
- Institute of Transplantation Diagnostics and Cellular Therapeutics, Heinrich Heine University Medical Center, 40225 Düsseldorf, Germany.
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111
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Lee PT, Liao PC, Chang WC, Tseng JT. Epidermal growth factor increases the interaction between nucleolin and heterogeneous nuclear ribonucleoprotein K/poly(C) binding protein 1 complex to regulate the gastrin mRNA turnover. Mol Biol Cell 2007; 18:5004-13. [PMID: 17928403 PMCID: PMC2096583 DOI: 10.1091/mbc.e07-04-0384] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2007] [Revised: 09/21/2007] [Accepted: 10/03/2007] [Indexed: 11/11/2022] Open
Abstract
Gastrin, a gastrointestinal hormone responsible for gastric acid secretion, has been confirmed as a growth factor for gastrointestinal tract malignancies. High expression of gastrin mRNA was observed in pancreatic and colorectal cancer; however, the mechanism is unclear. Epidermal growth factor (EGF) was found to increase gastrin mRNA stability, indicating mRNA turnover regulation mechanism is involved in the control of gastrin mRNA expression. Using biotin-labeled RNA probe pull-down assay combined with mass spectrometry analysis, we identified the heterogeneous nuclear ribonucleoprotein K (hnRNP K) and poly(C) binding protein 1 (PCBP1) bound with the C-rich region in gastrin mRNA 3' untranslated region. Nucleolin bound with the AGCCCU motif and interacted with hnRNP K were also demonstrated. Under EGF treatment, we observed the amount of nucleolin interacting with hnRNP K and gastrin mRNA increased. Using small interfering RNA technology to define their functional roles, we found hnRNP K, PCBP1, and nucleolin were all responsible for stabilizing gastrin mRNA. Moreover, nucleolin plays a crucial role in mediating the increased gastrin mRNA stability induced by EGF signaling. Besides, we also observed hnRNP K/PCBP1 complex bound with the C-rich region in the gastrin mRNA increased nucleolin binding with gastrin mRNA. Finally, a novel binding model was proposed.
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Affiliation(s)
- Pin-Tse Lee
- *Department of Pharmacology and
- Institute of Basic Medical Sciences, College of Medicine, and Center for Gene Regulation and Signal Transduction Research, National Cheng Kung University, Tainan, Taiwan 701; and
| | - Pao-Chi Liao
- Department of Occupational Health, College of Medicine, National Cheng Kung University, Tainan, Taiwan 701
| | - Wen-Chang Chang
- *Department of Pharmacology and
- Institute of Basic Medical Sciences, College of Medicine, and Center for Gene Regulation and Signal Transduction Research, National Cheng Kung University, Tainan, Taiwan 701; and
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112
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Xie C, Nguyen N, Zhu Y, Li YQ. Detection of the Recombinant Proteins in Single Transgenic Microbial Cell Using Laser Tweezers and Raman Spectroscopy. Anal Chem 2007; 79:9269-75. [DOI: 10.1021/ac0710329] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Changan Xie
- Department of Physics and Department of Biology, East Carolina University, Greenville, North Carolina 27858
| | - Nhu Nguyen
- Department of Physics and Department of Biology, East Carolina University, Greenville, North Carolina 27858
| | - Yong Zhu
- Department of Physics and Department of Biology, East Carolina University, Greenville, North Carolina 27858
| | - Yong-qing Li
- Department of Physics and Department of Biology, East Carolina University, Greenville, North Carolina 27858
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113
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Abstract
Many oncogenes, growth factor, cytokine and cell-cycle genes are regulated post-transcriptionally. The major mechanism is by controlling the rate of mRNA turnover for transcripts bearing destabilizing cis-elements. To date, only a handful of regulatory factors have been identified that appear to control a large pool of target mRNAs, suggesting that a slight perturbation in the control mechanism may generate wide-ranging effects that could contribute to the development of a complex disorder such as cancer. In support of this view, mRNA turnover responds to signalling pathways that are often overactive in cancer, suggesting a post-transcriptional component in addition to the well-recognised transcriptional aspect of oncogenesis. Here the authors review examples of deregulated post-transcriptional control in oncogenesis, discuss post-transcriptionally regulated transcripts of oncologic significance, and consider the key role of signalling pathways in linking both processes and as an enticing therapeutic prospect.
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Affiliation(s)
- Don Benjamin
- Institute for Medical Microbiology, Petersplatz 10, 4001 Basel, Switzerland.
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114
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Kalousek I, Brodska B, Otevrelova P, Röselova P. Actinomycin D upregulates proapoptotic protein Puma and downregulates Bcl-2 mRNA in normal peripheral blood lymphocytes. Anticancer Drugs 2007; 18:763-72. [PMID: 17581298 DOI: 10.1097/cad.0b013e3280adc905] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
We have examined the ability of actinomycin D to induce apoptosis in human peripheral blood lymphocytes. Run-On assays were performed to specify the primary molecular damage, reverse transcription-PCR, Western blots and flow cytometry studies were performed to ascertain which proteins of the apoptosis machinery were affected to cause actinomycin D-induced cell death. Expression of 23 apoptosis-related genes was investigated. The down-regulation of ribosomal RNA synthesis caused by actinomycin D induced a mitochondria-dependent apoptosis. Although the expression of the majority of examined genes remained indifferent against actinomycin D activity, the cellular level of p53 protein increased, subsequently upregulating both Puma mRNA and protein. Puma-mediated mitochondrial apoptosis was accompanied by nucleolin cleavage and Bcl-2 mRNA destabilization. The stability of the cellular level of Bcl-2 protein independent of a mRNA decrease suggests that protection of Bcl-2 protein against proteasomal degradation can moderate the apoptotic process. In peripheral blood lymphocytes cultured in vitro, the apoptosis induced by a low concentration of actinomycin D (10 nmol/l) is dependent on p53 and Puma activation. This apoptotic pathway is demonstrated in peripheral blood lymphocytes for the first time. A different apoptotic pathway induced in peripheral blood lymphocytes using this drug has, however, been previously revealed by other authors. The combination of cell specificity and dose-dependent effects can likely play a decisive role in apoptosis observed in peripheral blood lymphocytes after genotoxic drug application.
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Affiliation(s)
- Ivan Kalousek
- Department of Cellular Biochemistry, Institute of Hematology and Blood Transfusion, U Nemocnice 1, 128-20 Prague, Czech Republic.
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115
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Abstract
Aptamers, also termed as decoys or "chemical antibodies," represent an emerging class of therapeutics. They are short DNA or RNA oligonucleotides or peptides that assume a specific and stable three-dimensional shape in vivo, thereby providing specific tight binding to protein targets. In some cases and as opposed to antisense oligonucleotides, effects can be mediated against extracellular targets, thereby preventing a need for intracellular transportation. The first aptamer approved for use in man is a RNA-based molecule (Macugen, pegaptanib) that is administered locally (intravitreally) to treat age-related macular degeneration by targeting vascular endothelial growth factor. The most advanced aptamer in the cancer setting is AS1411, formerly known as AGRO100, which is being administered systemically in clinical trials. AS1411 is a 26-mer unmodified guanosine-rich oligonucleotide, which induces growth inhibition in vitro, and has shown activity against human tumor xenografts in vivo. The mechanism underlying its antiproliferative effects in cancer cells seems to involve initial binding to cell surface nucleolin and internalization, leading to an inhibition of DNA replication. In contrast to other unmodified oligonucleotides, AS1411 is relatively stable in serum-containing medium, probably as a result of the formation of dimers and a quartet structure. In a dose escalation phase I study in patients with advanced solid tumors, doses up to 10 mg/kg/d (using a four or seven continuous infusion regime) have been studied. Promising signs of activity have been reported (multiple cases of stable disease and one near complete response in a patient with renal cancer) in the absence of any significant adverse effects. Further trials are ongoing in renal and non-small cell lung cancers. In preclinical studies, additional aptamers have been described against several cancer targets, such as tenascin-C, the transcription factor signal transducer and activator of transcription 3, and antiapoptotic and Ku proteins.
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116
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Grinstein E, Du Y, Santourlidis S, Christ J, Uhrberg M, Wernet P. Nucleolin regulates gene expression in CD34-positive hematopoietic cells. J Biol Chem 2007; 282:12439-49. [PMID: 17255095 DOI: 10.1074/jbc.m608068200] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CD34 glycoprotein in human hematopoiesis is expressed on a subset of progenitor cells capable of self-renewal, multilineage differentiation, and hematopoietic reconstitution. Nucleolin is an abundant multifunctional phosphoprotein of growing eukaryotic cells, involved in regulation of gene transcription, chromatin remodeling, and RNA metabolism, whose transcripts are enriched in murine hematopoietic stem cells, as opposed to differentiated tissue. Here we show that, in human CD34-positive hematopoietic cells, nucleolin activates endogenous CD34 and Bcl-2 gene expression, and cell surface CD34 protein expression is thereby enhanced by nucleolin. Nucleolin-mediated activation of CD34 gene transcription results from direct sequence-specific interactions with the CD34 promoter region. Nucleolin expression prevails in CD34-positive cells mobilized into peripheral blood (PB), as opposed to CD34-negative peripheral blood mononuclear cells (PBMCs). Therefore, in intact CD34-positive mobilized PB cells, a recruitment of nucleolin to the CD34 promoter region takes place, accompanied by nucleosomal determinants of gene activity, which are absent from the CD34 promoter region in CD34-negative PBMCs. Our data show that nucleolin acts as a component of the gene regulation program of CD34-positive hematopoietic cells and provide further insights into processes by which human CD34-positive hematopoietic stem/progenitor cells are maintained.
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Affiliation(s)
- Edgar Grinstein
- Institute of Transplantation Diagnostics and Cellular Therapeutics, Heinrich Heine University Medical Center, 40225 Düsseldorf, Germany.
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117
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Otake Y, Soundararajan S, Sengupta TK, Kio EA, Smith JC, Pineda-Roman M, Stuart RK, Spicer EK, Fernandes DJ. Overexpression of nucleolin in chronic lymphocytic leukemia cells induces stabilization of bcl2 mRNA. Blood 2007; 109:3069-75. [PMID: 17179226 PMCID: PMC1852223 DOI: 10.1182/blood-2006-08-043257] [Citation(s) in RCA: 172] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Accepted: 11/08/2006] [Indexed: 01/29/2023] Open
Abstract
B-cell chronic lymphocytic leukemia (CLL) is characterized by the accumulation of clonal B cells that are resistant to apoptosis as a result of bcl2 oncogene overexpression. Studies were done to determine the mechanism for the up-regulation of bcl-2 protein observed in CD19+ CLL cells compared with CD19+ B cells from healthy volunteers. The 11-fold higher level of bcl-2 protein in CLL cells was positively correlated with a 26-fold elevation in the cytosolic level of nucleolin, a bcl2 mRNA-stabilizing protein. Measurements of the bcl2 heterogeneous nuclear/bcl2 mRNA (hnRNA)/mRNA ratios and the rates of bcl2 mRNA decay in cell extracts indicated that the 3-fold higher steady-state level of bcl2 mRNA in CLL cells was the result of increased bcl2 mRNA stability. Nucleolin was present throughout the nucleus and cytoplasm of CLL cells, whereas in normal B cells nucleolin was only detected in the nucleus. The addition of recombinant human nucleolin to extracts of normal B cells markedly slowed the rate of bcl2 mRNA decay. SiRNA knockdown of nucleolin in MCF-7 cells resulted in decreased levels of bcl2mRNA and protein but no change in beta-actin. These results indicate that bcl-2 overexpression in CLL cells is related to stabilization of bcl2 mRNA by nucleolin.
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MESH Headings
- B-Lymphocytes/drug effects
- B-Lymphocytes/metabolism
- Cell Line, Tumor
- Cell Nucleus/metabolism
- Cytoplasm/metabolism
- Female
- Gene Expression
- Genes, bcl-2
- Humans
- In Vitro Techniques
- Leukemia, Lymphocytic, Chronic, B-Cell/genetics
- Leukemia, Lymphocytic, Chronic, B-Cell/metabolism
- Male
- Phosphoproteins/antagonists & inhibitors
- Phosphoproteins/genetics
- Phosphoproteins/metabolism
- Phosphoproteins/pharmacology
- RNA Stability
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Small Interfering/genetics
- RNA-Binding Proteins/antagonists & inhibitors
- RNA-Binding Proteins/genetics
- RNA-Binding Proteins/metabolism
- RNA-Binding Proteins/pharmacology
- Recombinant Proteins/genetics
- Recombinant Proteins/pharmacology
- Nucleolin
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Affiliation(s)
- Yoko Otake
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, SC 29425, USA
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118
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Abstract
This review addresses the scope of influence of mRNA decay on cellular functions and its potential role in normal and malignant hematopoiesis. Evidence is emerging that leukemic oncogenes and hematopoietic cytokines interact with mRNA decay pathways. These pathways can co-regulate functionally related genes through specific motifs in the 3'-untranslated region of targeted transcripts. The steps that link external stimuli to transcript turnover are not fully understood, but include subcellular relocalization or post-transcriptional modification of specific transcript-stabilizing or -destabilizing proteins. Improper functioning of these regulators of mRNA turnover can impede normal cellular differentiation or promote cancers. By delineating how subsets of transcripts decay in synchrony during normal hematopoiesis, it may be possible to determine whether this post-transcriptional regulatory pathway is hijacked in leukemogenesis.
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Affiliation(s)
- R A Steinman
- University of Pittsburgh Cancer Institute, Department of Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.
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119
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Chowdhury B, Krishnan S, Tsokos CG, Robertson JW, Fisher CU, Nambiar MP, Tsokos GC. Stability and translation of TCR zeta mRNA are regulated by the adenosine-uridine-rich elements in splice-deleted 3' untranslated region of zeta-chain. THE JOURNAL OF IMMUNOLOGY 2007; 177:8248-57. [PMID: 17114503 DOI: 10.4049/jimmunol.177.11.8248] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Systemic lupus erythematosus (SLE) T cells display reduced expression of TCR zeta protein. Recently, we reported that in SLE T cells, the residual TCR zeta protein is predominantly derived from an alternatively spliced form that undergoes splice deletion of 562 nt (from 672 to 1233 bases) within the 3' untranslated region (UTR) of TCR zeta mRNA. The stability and translation of the alternatively spliced form of TCR zeta mRNA are low compared with that of the wild-type TCR zeta mRNA. We report that two adenosine-uridine-rich sequence elements (AREs), defined by the splice-deleted 3' UTR region, but not an ARE located upstream are responsible for securing TCR zeta mRNA stability and translation. The stabilizing effect of the splice-deleted region-defined AREs extended to the luciferase mRNA and was not cell type-specific. The findings demonstrate distinct sequences within the splice-deleted region 672 to 1233 of the 3' UTR, which regulate the transcription, mRNA stability, and translation of TCR zeta mRNA. The absence of these sequences represents a molecular mechanism that contributes to altered TCR zeta-chain expression in lupus.
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Affiliation(s)
- Bhabadeb Chowdhury
- Department of Cellular Injury, Walter Reed Army Institute of Research, 503 Robert Grant Avenue, Silver Spring, MD 20910, USA
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120
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Akuzawa N, Nobata S, Shinozawa T. Truncated midkine correlates with sensitivity to anticancer drugs and malignancy in human tumor cell line. Cell Biochem Funct 2007; 25:687-91. [PMID: 17066487 DOI: 10.1002/cbf.1376] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Midkine (MK) is a heparin binding growth factor having functions of neurite-outgrowth, mitogenesis and tissue repair. This molecule is involved in tumor growth and metastasis. The MK molecule consists of five exons, but there is a truncated isoform, lacking exon 3. We established SW13 cells transfected with the human truncated MK cDNA. These cells were induced to undergo apoptosis by anticancer agents, cisplatin, etoposide (ETP), mitomycin C (MMC) and paclitaxel (PAX). Truncated midkine (tMK) suppressed cell death and helped the cells to be viable. When the cells were cultured on dishes coated with extracellular matrix molecules, spontaneous detachment occurred in the tMK expressing cells. Also tMK enhanced cell invasion. These results suggest that expression of tMK has cell-protective functions and plays important roles in carcinogenesis and malignancy. Furthermore, it is suggested that tMK has a greater ability of malignant transformation than full-length MK. Whether tMK is expressed or not will be useful information for improving cancer chemotherapy.
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Affiliation(s)
- Natsuyo Akuzawa
- Department of Biological and Chemical Engineering, Faculty of Engineering, Gunma University, Kiryu, Gunma, Japan
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121
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Guo X, Ma J, Sun J, Gao G. The zinc-finger antiviral protein recruits the RNA processing exosome to degrade the target mRNA. Proc Natl Acad Sci U S A 2006; 104:151-6. [PMID: 17185417 PMCID: PMC1765426 DOI: 10.1073/pnas.0607063104] [Citation(s) in RCA: 216] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Zinc-finger antiviral protein (ZAP) is a host antiviral factor that specifically inhibits the replication of Moloney murine leukemia virus (MLV) and Sindbis virus (SIN) by preventing accumulation of the viral mRNA in the cytoplasm. In previous studies, we demonstrated that ZAP directly binds to its specific target mRNAs. In this article, we provide evidence indicating that ZAP recruits the RNA processing exosome to degrade the target RNA. ZAP comigrated with the exosome in sucrose or glycerol velocity gradient centrifugation. Immunoprecipitation of ZAP coprecipitated the exosome components. In vitro pull-down assays indicated that ZAP directly interacted with the exosome component hRrp46p and that the binding region of ZAP was mapped to amino acids 224-254. Depletion of the exosome component hRrp41p or hRrp46p with small interfering RNA significantly reduced ZAP's destabilizing activity. These findings suggest that ZAP is a trans-acting factor that modulates mRNA stability.
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Affiliation(s)
- Xuemin Guo
- Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Jing Ma
- Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Jing Sun
- Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
| | - Guangxia Gao
- Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China
- *To whom correspondence should be addressed. E-mail:
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122
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Saxena A, Rorie CJ, Dimitrova D, Daniely Y, Borowiec JA. Nucleolin inhibits Hdm2 by multiple pathways leading to p53 stabilization. Oncogene 2006; 25:7274-88. [PMID: 16751805 DOI: 10.1038/sj.onc.1209714] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2006] [Revised: 04/17/2006] [Accepted: 04/17/2006] [Indexed: 12/27/2022]
Abstract
Nucleolin is a c-Myc-induced gene product with defined roles in ribosomal RNA processing and the inhibition of chromosomal DNA replication following stress. Here we find that changes in nucleolin protein levels in unstressed cells cause parallel changes in the amount of p53 protein. Alterations in p53 levels arise from nucleolin binding to the p53 antagonist Hdm2, resulting in the inhibition of both p53 ubiquitination and Hdm2 auto-ubiquitination. Nucleolin does not alter p53 ubiquitination by human papillomavirus E6, indicating that the effect is specific for Hdm2. Although the inhibition of ligase activity would be expected to stabilize Hdm2, we instead find that nucleolin also reduces Hdm2 protein levels, demonstrating that nucleolin inhibits Hdm2 using multiple mechanisms. Increases in nucleolin levels in unstressed cells led to higher expression of p21(cip1/waf1), a reduced rate of cellular proliferation, and an increase in apoptosis. Thus, nucleolin has a number of properties in common with the tumor suppressor ARF (alternate reading frame). We propose that nucleolin, like ARF, responds to hyperproliferative signals by upregulation of p53 through Hdm2 inhibition.
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Affiliation(s)
- A Saxena
- Department of Biochemistry and New York University Cancer Institute, New York University School of Medicine, New York, NY 10016, USA
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123
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Fähling M, Mrowka R, Steege A, Nebrich G, Perlewitz A, Persson PB, Thiele BJ. Translational control of collagen prolyl 4-hydroxylase-alpha(I) gene expression under hypoxia. J Biol Chem 2006; 281:26089-101. [PMID: 16837461 DOI: 10.1074/jbc.m604939200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Hypoxia is a pro-fibrotic stimulus, which is associated with enhanced collagen synthesis, as well as with augmented collagen prolyl 4-hydroxylase (C-P4H) activity. C-P4H activity is controlled mainly by regulated expression of the alpha C-P4H subunit. In this study we demonstrate that the increased synthesis of C-P4H-alpha(I) protein in human HT1080 fibroblasts under long term hypoxia (36 h, 1% oxygen) is controlled at the translational level. This is mediated by an interaction of RNA-binding protein nucleolin (approximately 64 kDa form) at the 5'- and 3'-untranslated regions (UTR) of the mRNA. The 5'/3'-UTR-dependent mechanism elevates the C-P4H-alpha(I) expression rate 2.3-fold, and participates in a 5.3-fold increased protein level under long term hypoxia. The interaction of nucleolin at the 5'-UTR occurs directly and depends on the existence of an AU-rich element. Statistical evaluation of the approximately 64-kDa nucleolin/RNA interaction studies revealed a core binding sequence, corresponding to UAAAUC or AAAUCU. At the 3'-UTR, nucleolin assembles indirectly via protein/protein interaction, with the help of another 3'-UTR-binding protein, presumably annexin A2. The increased protein level of the approximately 64-kDa nucleolin under hypoxia can be attributed to an autocatalytic cleavage of a high molecular weight nucleolin form, without alterations in nucleolin mRNA concentration. Thus, the alteration of translational efficiency by nucleolin, which occurs through a hypoxia inducible factor independent pathway, is an important step in C-P4H-alpha(I) regulation under hypoxia.
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Affiliation(s)
- Michael Fähling
- Charité, Universitätsmedizin Berlin, Institut für Vegetative Physiologie, D-10117 Berlin, Germany.
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124
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Grinstein E, Shan Y, Karawajew L, Snijders PJF, Meijer CJLM, Royer HD, Wernet P. Cell cycle-controlled interaction of nucleolin with the retinoblastoma protein and cancerous cell transformation. J Biol Chem 2006; 281:22223-22235. [PMID: 16698799 DOI: 10.1074/jbc.m513335200] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Retinoblastoma protein (Rb) is a multifunctional tumor suppressor, frequently inactivated in certain types of human cancer. Nucleolin is an abundant multifunctional phosphoprotein of proliferating and cancerous cells, recently identified as cell cycle-regulated transcription activator, controlling expression of human papillomavirus type 18 (HPV18) oncogenes in cervical cancer. Here we find that nucleolin is associated with Rb in intact cells in the G1 phase of the cell cycle, and the complex formation is mediated by the growth-inhibitory domain of Rb. Association with Rb inhibits the DNA binding function of nucleolin and in consequence the interaction of nucleolin with the HPV18 enhancer, resulting in Rb-mediated repression of the HPV18 oncogenes. The intracellular distribution of nucleolin in epithelial cells is Rb-dependent, and an altered nucleolin localization in human cancerous tissues results from a loss of Rb. Our findings suggest that deregulated nucleolin activity due to a loss of Rb contributes to tumor development in malignant diseases, thus providing further insights into the molecular network for the Rb-mediated tumor suppression.
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Affiliation(s)
- Edgar Grinstein
- Institute of Transplantation Diagnostics and Cellular Therapeutics, Heinrich Heine University Medical Center, 40225 Düsseldorf, Germany.
| | - Ying Shan
- Max-Delbrück Center for Molecular Medicine, 13125 Berlin, Germany; Institute of Molecular Pharmacology, 13125 Berlin, Germany
| | - Leonid Karawajew
- Robert-Rossle-Clinic at the HELIOS Klinikum Berlin-Buch, Charite Medical School, 13125 Berlin, Germany
| | - Peter J F Snijders
- Department of Pathology, Vrije Universiteit Medical Center, 1007 MB Amsterdam, The Netherlands
| | - Chris J L M Meijer
- Department of Pathology, Vrije Universiteit Medical Center, 1007 MB Amsterdam, The Netherlands
| | - Hans-Dieter Royer
- Max-Delbrück Center for Molecular Medicine, 13125 Berlin, Germany; Center for Advanced European Studies, 53175 Bonn, Germany
| | - Peter Wernet
- Institute of Transplantation Diagnostics and Cellular Therapeutics, Heinrich Heine University Medical Center, 40225 Düsseldorf, Germany
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125
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Abstract
Kidneys are essential for acid-base homeostasis, especially when organisms cope with changes in acid or base dietary intake. Because collecting ducts constitute the final site for regulating urine acid-base balance, we undertook to identify the gene network involved in acid-base transport and regulation in the mouse outer medullary collecting duct (OMCD). For this purpose, we combined kidney functional studies and quantitative analysis of gene expression in OMCDs, by transcriptome and candidate gene approaches, during metabolic acidosis. Furthermore, to better delineate the set of genes concerned with acid-base disturbance, the OMCD transcriptome of acidotic mice was compared with that of both normal mice and mice undergoing an adaptative response through potassium depletion. Metabolic acidosis, achieved through an NH4Cl-supplemented diet for 3 days, not only induced acid secretion but also stimulated the aldosterone and vasopressin systems and triggered cell proliferation. Accordingly, metabolic acidosis increased the expression of genes involved in acid-base transport, sodium transport, water transport, and cell proliferation. In particular, >25 transcripts encoding proteins involved in urine acidification (subunits of H-ATPase, kidney anion exchanger, chloride channel Clcka, carbonic anhydrase-2, aldolase) were co-regulated during acidosis. These transcripts, which cooperate to achieve a similar function and are co-regulated during acidosis, constitute a functional unit that we propose to call a "regulon".
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Affiliation(s)
- Lydie Cheval
- Laboratoire de Physiologie et Génomique Rénales, Unité mixte de recherche 7134, Centre National de la Recherche Scientifique/Université Pierre et Marie Curie, Institut Fédératif de Recherche 58, Paris cedex 6, France
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126
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Segal SP, Dunckley T, Parker R. Sbp1p affects translational repression and decapping in Saccharomyces cerevisiae. Mol Cell Biol 2006; 26:5120-30. [PMID: 16782896 PMCID: PMC1489156 DOI: 10.1128/mcb.01913-05] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2005] [Revised: 10/31/2005] [Accepted: 03/31/2006] [Indexed: 11/20/2022] Open
Abstract
The relationship between translation and mRNA turnover is critical to the regulation of gene expression. One major pathway for mRNA turnover occurs by deadenylation, which leads to decapping and subsequent 5'-to-3' degradation of the body of the mRNA. Prior to mRNA decapping, a transcript exits translation and enters P bodies to become a potential decapping substrate. To understand the transition from translation to decapping, it is important to identify the factors involved in this process. In this work, we identify Sbp1p (formerly known as Ssb1p), an abundant RNA binding protein, as a high-copy-number suppressor of a conditional allele in the decapping enzyme. Sbp1p overexpression restores normal decay rates in decapping-defective strains and increases P-body size and number. In addition, Sbp1p promotes translational repression of mRNA during glucose deprivation. Moreover, P-body formation is reduced in strains lacking Sbp1p. Sbp1p acts in conjunction with Dhh1p, as it is required for translational repression and P-body formation in pat1Delta strains under these conditions. These results identify Sbp1p as a new protein that functions in the transition of mRNAs from translation to an mRNP complex destined for decapping.
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Affiliation(s)
- Scott P Segal
- Department of Molecular Cellular Biology and Howard Hughes Medical Institute, University of Arizona, 1007 E. Lowell St., Tucson, AZ 85721, USA
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127
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Girvan AC, Teng Y, Casson LK, Thomas SD, Jüliger S, Ball MW, Klein JB, Pierce WM, Barve SS, Bates PJ. AGRO100 inhibits activation of nuclear factor-kappaB (NF-kappaB) by forming a complex with NF-kappaB essential modulator (NEMO) and nucleolin. Mol Cancer Ther 2006; 5:1790-9. [PMID: 16891465 DOI: 10.1158/1535-7163.mct-05-0361] [Citation(s) in RCA: 183] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
AGRO100, also known as AS1411, is an experimental anticancer drug that recently entered human clinical trials. It is a member of a novel class of antiproliferative agents known as G-rich oligonucleotides (GRO), which are non-antisense, guanosine-rich phosphodiester oligodeoxynucleotides that form stable G-quadruplex structures. The biological activity of GROs results from their binding to specific cellular proteins as aptamers. One important target protein of GROs has been previously identified as nucleolin, a multifunctional protein expressed at high levels by cancer cells. Here, we report that AGRO100 also associates with nuclear factor-kappaB (NF-kappaB) essential modulator (NEMO), which is a regulatory subunit of the inhibitor of kappaB (IkappaB) kinase (IKK) complex, and also called IKKgamma. In the classic NF-kappaB pathway, the IKK complex is required for phosphorylation of IkappaBalpha and subsequent activation of the transcription factor NF-kappaB. We found that treatment of cancer cells with AGRO100 inhibits IKK activity and reduces phosphorylation of IkappaBalpha in response to tumor necrosis factor-alpha stimulation. Using a reporter gene assay, we showed that AGRO100 blocks both tumor necrosis factor-alpha-induced and constitutive NF-kappaB activity in human cancer cell lines derived from cervical, prostate, breast, and lung carcinomas. In addition, we showed that, in AGRO100-treated cancer cells, NEMO is coprecipitated by nucleolin, indicating that both proteins are present in the same complex. Our studies suggest that abrogation of NF-kappaB activity may contribute to the anticancer effects of AGRO100 and that nucleolin may play a previously unknown role in regulating the NF-kappaB pathway.
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Affiliation(s)
- Allicia C Girvan
- University of Louisville, 580 South Preston Street, Delia Baxter Building 321, Louisville, KY 40202-1756, USA
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128
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Wu YL, Dudognon C, Nguyen E, Hillion J, Pendino F, Tarkanyi I, Aradi J, Lanotte M, Tong JH, Chen GQ, Ségal-Bendirdjian E. Immunodetection of human telomerase reverse-transcriptase (hTERT) re-appraised: nucleolin and telomerase cross paths. J Cell Sci 2006; 119:2797-806. [PMID: 16772337 DOI: 10.1242/jcs.03001] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
The involvement of telomerase in cellular immortalization and senescence has often been assessed by means of telomerase expression at the RNA level and quantification of telomerase activity by the telomeric repeat amplification protocol assay. However, these methods either neglected the existence of various telomerase splice variants, or ignored the nonconventional functions of telomerase independent of its ability to elongate and maintain telomere length. Immunodetection of telomerase is now being recognized as a necessary approach to precisely elucidate its roles in oncogenesis and senescence. A few antibodies directed against the catalytic subunit of the human telomerase (hTERT) are currently used but their specificity is not always demonstrated. A survey of the literature showed inconsistencies and led us to comparatively re-evaluate the most frequently used antibodies. Surprisingly, mass spectrometry, two-dimensional gel analysis and immunofluorescent experiments revealed that the most frequently used hTERT immunoprobe, a mouse monoclonal antibody that was claimed to be directed against an hTERT protein epitope, in fact recognizes nucleolin rather than telomerase. Our findings have interesting implications regarding the biology of nucleolin and telomerase in the context of pathophysiological investigations recently carried out.
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Affiliation(s)
- Ying-Li Wu
- INSERM U685, Hôpital Saint-Louis, Institut d'Hématologie, 1 avenue Claude Vellefaux, 75010 Paris, France
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129
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Bose S, Sengupta T, Bandyopadhyay S, Spicer E. Identification of Ebp1 as a component of cytoplasmic bcl-2 mRNP (messenger ribonucleoprotein particle) complexes. Biochem J 2006; 396:99-107. [PMID: 16396631 PMCID: PMC1449993 DOI: 10.1042/bj20051548] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Revised: 12/24/2005] [Accepted: 01/06/2006] [Indexed: 11/17/2022]
Abstract
The 3'-UTR (untranslated region) of bcl-2 mRNA contains an ARE (AU-rich element) that potentially regulates the stability of bcl-2 mRNA in a cell specific fashion. Previous studies have demonstrated that multiple proteins interact with bcl-2 mRNA in HL-60 (human leukaemia-60) cells, potentially contributing to the overexpression of Bcl-2 protein. Treatment of HL-60 cells with taxol or okadaic acid has been shown to induce destabilization of bcl-2 mRNA, which was associated with decreased binding of trans-acting factors to bcl-2 mRNA. Nucleolin has been identified as one of the bcl-2 mRNA-binding proteins [Sengupta, Bandyopadhyay, Fernandes and Spicer (2004) J. Biol. Chem. 279, 10855-10863]. In an effort to identify additional bcl-2 mRNA-binding proteins, two polypeptides of approx. 45 kDa and 60 kDa were isolated from HL-60 cells by ARE(bcl-2) (transcripts that contain bcl-2 AREs) RNA affinity chromatography. These proteins were identified as the human proliferation associated protein, Ebp1, and human DRBP76 (double stranded RNA-binding protein 76) respectively, by MALDI (matrix-assisted laser-desorption ionization)-MS. RNA electrophoretic mobility shift assays indicated that recombinant Ebp1 binds to ARE(bcl-2) RNA but not to the group 1 ARE present in GM-CSF (granulocyte macrophage-colony stimulating factor) mRNA in vitro. Antibody supershift assays demonstrated that Ebp1 is present in protein-ARE(bcl-2) RNA complexes formed with cytosolic HL-60 extracts. The interaction of Ebp1 with bcl-2 mRNA in HL-60 cells was also demonstrated by RNA co-immunoprecipitation assays. This interaction was not detected in extracts of taxol-treated HL-60 cells. Immunoprecipitation assays further revealed that Ebp1 co-precipitates with nucleolin from HL-60 cytoplasmic extracts. The observation that co-precipitation was decreased when extracts were treated with RNase suggests that Ebp1 and nucleolin are present in the same bcl-2 mRNP (messenger ribonucleoprotein particle) complexes. RNA-decay assays further demonstrated that Ebp1 decreased the rate of decay of beta-globin-ARE(bcl-2) transcripts in HL-60 cell extracts. Collectively, these results indicate a novel function for Ebp1 in contributing to the regulation of bcl-2 expression in HL-60 cells.
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Key Words
- bcl-2 expression
- double stranded rna-binding protein 76 (drbp76)
- ebp1
- human leukaemia-60 cells (hl-60)
- mrna binding
- nucleolin
- aebsf, 4-(2-aminoethyl) benzenesulphonyl fluoride hydrochloride
- are, au-rich element
- drbp76, double stranded rna-binding protein 76
- dtt, dithiothreitol
- gapdh, glyceraldehyde-3-phosphate dehydrogenase
- gst, glutathione s-transferase
- hl-60, human leukaemia-60
- iptg, isopropylthio-galactoside
- mrnp, messenger ribonucleoprotein particle
- maldi, matrix-assisted laser desorption ionization
- np-40, nonidet p40
- rt, reverse transcriptase
- rrna, ribosomal rna
- utr, untranslated region
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Affiliation(s)
- Sudeep K. Bose
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, 173 Ashley Avenue, P.O. Box 250509, Charleston, SC 29425, U.S.A
| | - Tapas K. Sengupta
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, 173 Ashley Avenue, P.O. Box 250509, Charleston, SC 29425, U.S.A
| | - Sumita Bandyopadhyay
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, 173 Ashley Avenue, P.O. Box 250509, Charleston, SC 29425, U.S.A
| | - Eleanor K. Spicer
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, 173 Ashley Avenue, P.O. Box 250509, Charleston, SC 29425, U.S.A
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130
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Martelli AM, Faenza I, Billi AM, Manzoli L, Evangelisti C, Falà F, Cocco L. Intranuclear 3'-phosphoinositide metabolism and Akt signaling: new mechanisms for tumorigenesis and protection against apoptosis? Cell Signal 2006; 18:1101-7. [PMID: 16516442 DOI: 10.1016/j.cellsig.2006.01.011] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2006] [Revised: 01/17/2006] [Accepted: 01/17/2006] [Indexed: 11/17/2022]
Abstract
Lipid second messengers, particularly those derived from the polyphosphoinositide metabolism, play a pivotal role in multiple cell signaling networks. Phosphoinositide 3-kinase (PI3K) generate 3'-phosphorylated inositol lipids that are key players in a multitude of cell functions. One of the best characterized targets of PI3K lipid products is the serine/threonine protein kinase Akt (protein kinase B, PKB). Recent findings have implicated the PI3K/Akt pathway in tumorigenesis because it stimulates cell proliferation and suppresses apoptosis. However, it was thought that this signal transduction network would exert its carcinogenetic effects mainly by operating in the cytoplasm. Evidence accumulated over the past 15 years has highlighted the presence of an autonomous nuclear inositol lipid cycle, and strongly suggests that lipid molecules are important components of signaling pathways operating at the nuclear level. PI3K, its lipid product phosphatidylinositol (3,4,5) trisphosphate (PtdIns(3,4,5)P3), and Akt have been identified within the nucleus and recent data suggest that they counteract apoptosis also by operating in this cell compartment through a block of caspase-activated DNase and inhibition of chromatin condensation. In this review, we shall summarize the most updated and intriguing findings about nuclear PI3K/PtdIns(3,4,5)P3/Akt in relationship with tumorigenesis and suppression of apoptotic stimuli.
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Affiliation(s)
- Alberto M Martelli
- Dipartimento di Scienze Anatomiche Umane e Fisiopatologia dell'Apparato Locomotore, Sezione di Anatomia Umana, Cell Signalling Laboratory, Università di Bologna, via Irnerio 48, 40126 Bologna, Italy.
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131
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Jiang Y, Xu XS, Russell JE. A nucleolin-binding 3' untranslated region element stabilizes beta-globin mRNA in vivo. Mol Cell Biol 2006; 26:2419-29. [PMID: 16508016 PMCID: PMC1430272 DOI: 10.1128/mcb.26.6.2419-2429.2006] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2005] [Revised: 08/19/2005] [Accepted: 12/14/2005] [Indexed: 11/20/2022] Open
Abstract
The normal expression of human beta globin is critically dependent upon the constitutively high stability of its encoding mRNA. Unlike with alpha-globin mRNA, the specific cis-acting determinants and trans-acting factors that participate in stabilizing beta-globin mRNA are poorly described. The current work uses a linker-scanning strategy to identify a previously unknown determinant of mRNA stability within the beta-globin 3' untranslated region (3'UTR). The new determinant is positioned on an mRNA half-stem opposite a pyrimidine-rich sequence targeted by alphaCP/hnRNP-E, a factor that plays a critical role in stabilizing human alpha-globin mRNA. Mutations within the new determinant destabilize beta-globin mRNA in intact cells while also ablating its 3'UTR-specific interaction with the polyfunctional RNA-binding factor nucleolin. We speculate that 3'UTR-bound nucleolin enhances mRNA stability by optimizing alphaCP access to its functional binding site. This model is favored by in vitro evidence that alphaCP binding is enhanced both by cis-acting stem-destabilizing mutations and by the trans-acting effects of supplemental nucleolin. These studies suggest a mechanism for beta-globin mRNA stability that is related to, but distinct from, the mechanism that stabilizes human alpha-globin mRNA.
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Affiliation(s)
- Yong Jiang
- Department of Medicine (Hematology/Oncology), Abramson University of Pennsylvania School of Medicine and The Children's Hospital of Philadelphia, Philadelphia, PA 19104, USA
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132
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Zhang Y, Bhatia D, Xia H, Castranova V, Shi X, Chen F. Nucleolin links to arsenic-induced stabilization of GADD45alpha mRNA. Nucleic Acids Res 2006; 34:485-95. [PMID: 16421274 PMCID: PMC1342039 DOI: 10.1093/nar/gkj459] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2005] [Revised: 01/05/2006] [Accepted: 01/05/2006] [Indexed: 01/31/2023] Open
Abstract
The present study shows that arsenic induces GADD45alpha (growth arrest and DNA damage inducible gene 45alpha) mainly through post-transcriptional mechanism. Treatment of the human bronchial epithelial cell line, BEAS-2B, with arsenic(III) chloride (As3+) resulted in a significant increase in GADD45alpha protein and mRNA. However, As3+ only exhibited a marginal effect on the transcription of the GADD45alpha gene. The accumulation of GADD45alpha mRNA is largely achieved by the stabilization of GADD45alpha mRNA in the cellular response to As3+. As3+ is able to induce binding of mRNA stabilizing proteins, nucleolin and less potently, HuR, to the GADD45alpha mRNA. Although As3+ was unable to affect the expression of nucleolin, treatment of the cells with As3+ resulted in re-distribution of nucleolin from nucleoli to nucleoplasm. Silencing of the nucleolin mRNA by RNA interference reversed As3+-induced stabilization of the GADD45alpha mRNA and accumulation of the GADD45alpha protein. Stabilization of GADD45alpha mRNA, thus, represents a novel mechanism contributing to the production of GADD45alpha and cell cycle arrest in response to As3+.
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Affiliation(s)
- Yadong Zhang
- Institute for Nutritional Sciences, Chinese Academy of SciencesShanghai 200031, China
- School of Medicine, West Virginia UniversityMorgantown, WV 26506, USA
| | - Deepak Bhatia
- The Health Effects Laboratory Division, National Institute for Occupational Safety and HealthMorgantown, WV 26505, USA
| | - Hongfeng Xia
- Institute for Nutritional Sciences, Chinese Academy of SciencesShanghai 200031, China
| | - Vince Castranova
- The Health Effects Laboratory Division, National Institute for Occupational Safety and HealthMorgantown, WV 26505, USA
| | - Xianglin Shi
- Institute for Nutritional Sciences, Chinese Academy of SciencesShanghai 200031, China
- The Health Effects Laboratory Division, National Institute for Occupational Safety and HealthMorgantown, WV 26505, USA
| | - Fei Chen
- School of Medicine, West Virginia UniversityMorgantown, WV 26506, USA
- The Health Effects Laboratory Division, National Institute for Occupational Safety and HealthMorgantown, WV 26505, USA
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133
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Barreau C, Paillard L, Osborne HB. AU-rich elements and associated factors: are there unifying principles? Nucleic Acids Res 2006; 33:7138-50. [PMID: 16391004 PMCID: PMC1325018 DOI: 10.1093/nar/gki1012] [Citation(s) in RCA: 758] [Impact Index Per Article: 42.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The control of mRNA stability is an important process that allows cells to not only limit, but also rapidly adjust, the expression of regulatory factors whose over expression may be detrimental to the host organism. Sequence elements rich in A and U nucleotides or AU-rich elements (AREs) have been known for many years to target mRNAs for rapid degradation. In this survey, after briefly summarizing the data on the sequence characteristics of AREs, we present an analysis of the known ARE-binding proteins (ARE-BP) with respect to their mRNA targets and the consequences of their binding to the mRNA. In this analysis, both the changes in mRNA stability and the lesser studied effects on translation are considered. This analysis highlights the multitude of mRNAs bound by one ARE-BP and conversely the large number of ARE-BP that associate with any particular ARE-containing mRNA. This situation is discussed with respect to functional redundancies or antagonisms. The potential relationship between mRNA stability and translation is also discussed. Finally, we present several hypotheses that could unify the published data and suggest avenues for future research.
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Affiliation(s)
| | | | - H. Beverley Osborne
- To whom correspondence should be addressed. Tel: +33 223 23 4523; Fax: +33 223 23 4478;
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134
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Fähling M, Steege A, Perlewitz A, Nafz B, Mrowka R, Persson PB, Thiele BJ. Role of nucleolin in posttranscriptional control of MMP-9 expression. BIOCHIMICA ET BIOPHYSICA ACTA 2005; 1731:32-40. [PMID: 16153722 DOI: 10.1016/j.bbaexp.2005.08.005] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2005] [Revised: 07/28/2005] [Accepted: 08/05/2005] [Indexed: 10/25/2022]
Abstract
Matrix-metalloproteinases (MMPs), which are able to degrade extra cellular matrix (ECM) components, are crucial in ECM-remodeling, under physiological (e.g., embryogenesis, wound healing, angiogenesis) or pathophysiological conditions (e.g., arthritis, cancer progression and metastasis, fibrosis). Treating HT1080 cells, a human fibrosarcoma cell line, with the iron chelator 2,2-Dipyridyl, which mimics certain aspects of hypoxia, leads to a 3-fold elevated Matrix-metalloproteinase-9 (MMP-9) protein level. This elevation occurs within 3 h, without any change of mRNA-concentration. The rapid increase in MMP-9 expression is caused by an enhancement of translational efficiency characterized by a recruitment of translationally inactive MMP-9 mRNP-complexes into the rough endoplasmatic reticulum (rER). Reporter gene assays, which depend on the untranslated regions (UTR) of MMP-9 mRNA, reveal that the posttranscriptional regulation is mainly attributed to the 3'UTR. RNA/protein interaction studies indicate that the elevated binding of nucleolin ( approximately 64 kDa form) to the 3'UTR may be of major importance for the increased efficiency of MMP-9 translation. The results show that MMP-9 expression can be regulated posttranscriptionally, affecting the efficiency of translation and localization of the mRNA.
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Affiliation(s)
- Michael Fähling
- Charité, Universitätsmedizin Berlin, Institut für Vegetative Physiologie, 10117 Berlin, Germany.
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135
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Gringhuis SI, García-Vallejo JJ, van Het Hof B, van Dijk W. Convergent actions of I kappa B kinase beta and protein kinase C delta modulate mRNA stability through phosphorylation of 14-3-3 beta complexed with tristetraprolin. Mol Cell Biol 2005; 25:6454-63. [PMID: 16024783 PMCID: PMC1190353 DOI: 10.1128/mcb.25.15.6454-6463.2005] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Regulation of gene expression at the level of mRNA stability is a major topic of research; however, knowledge about the regulatory mechanisms affecting the binding and function of AU-rich element (ARE)-binding proteins (AUBPs) in response to extracellular signals is minimal. The beta1,4-galactosyltransferase 1 (beta4GalT1) gene enabled us to study the mechanisms involved in binding of tristetraprolin (TTP) as the stability of its mRNA is regulated solely through one ARE bound by TTP in resting human umbilical vein endothelial cells. Here, we provide evidence that the complex formation of TTP with 14-3-3beta is required to bind beta4GalT1 mRNA and promote its decay. Furthermore, upon tumor necrosis factor alpha stimulation, the activation of both Ikappabeta kinase and protein kinase Cdelta is involved in the phosphorylation of 14-3-3beta on two serine residues, paralleled by release of binding of TTP and 14-3-3beta from beta4GalT1 mRNA, nuclear sequestration of TTP, and beta4GalT1 mRNA stabilization. Thus, a key mechanism regulating mRNA binding and function of the destabilizing AUBP TTP involves the phosphorylation status of 14-3-3beta.
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Affiliation(s)
- Sonja I Gringhuis
- Department of Molecular Cell Biology and Immunology, VU Medical Center, P.O. Box 7057, 1007 MC Amsterdam, The Netherlands.
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136
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Fu Z, Fenselau C. Proteomic evidence for roles for nucleolin and poly[ADP-ribosyl] transferase in drug resistance. J Proteome Res 2005; 4:1583-91. [PMID: 16212410 DOI: 10.1021/pr0501158] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
One-hundred twenty-four proteins have been identified in the soluble nuclear protein mixture from MCF-7 human breast cancer cells, of which more than 90% are classically categorized as nuclear proteins. Proteins were also studied from three drug resistant MDF-7 lines, selected previously from the same parent line by exposure to etoposide, to mitoxantrone, or to adriamycin in the presence of verapamil. Both quantitative gel comparisons and stable isotope labeling were used to identify a total of fourteen proteins whose abundances are altered by more than 2-fold in the three resistant lines. Several cytoskeleton proteins, cytokeratin 8, cytokeratin 19, septin 2, and alpha tropomyosin, are decreased in common across the three resistant cell lines. PARP-l (poly[ADP-ribosyl]transefrase or connexion) is found to be less abundant in all three resistant lines. Nucleolin is more abundant in lines resistant to etoposide and mitoxantrone, while the mitotic checkpoint protein BUB 3 is more abundant in the line resistant to adriamycin/verapamil.
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Affiliation(s)
- Zongming Fu
- Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA
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137
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Xia Q, Wang HX, Wang J, Zhang JY, Liu BY, Li AL, Lv M, Hu MR, Yu M, Feng JN, Yang SC, Zhang XM, Shen BF. Proteomic analysis of interleukin 6-induced differentiation in mouse myeloid leukemia cells. Int J Biochem Cell Biol 2005; 37:1197-207. [PMID: 15778084 DOI: 10.1016/j.biocel.2004.11.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2004] [Revised: 11/01/2004] [Accepted: 11/16/2004] [Indexed: 11/24/2022]
Abstract
Cytokine-induced differentiation of myeloid leukemia cells has important therapeutic implications, but the mechanism remains to be clarified. M1 cell, a mouse acute myeloid leukemia cell line, which underwent growth inhibition, terminal differentiation and apoptosis in response to IL-6, was selected as an experimental model to study on the molecular mechanisms of myeloid cell differentiation on a proteome-wide scale. Cell differentiation was evaluated by cell morphology and CD11b expression. With two-dimensional (2D) gel analyses, 17 protein spots showed obvious changes in quantity during the process of differentiation were found. With matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF-MS) or/and nano-electrospray ionization MS/MS (ESI-MS/MS) analysis, 15 protein spots were identified. The mRNA levels of these 15 proteins during differentiation were also examined using a semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis. Except two proteins, the mRNA levels demonstrated similar expression patterns to what the proteomic analysis revealed. The identified proteins were known to be involved in different cellular functions, including protein synthesis, transcription, signal transduction, cell cycle control, cell rescue and defense, cellular organization, and metabolism. Notably, seven proteins were not described before to be involved in differentiation. Our data provide novel information for a better understanding of the mechanisms by which terminal differentiation of acute myeloid leukemia cells induced by IL-6.
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MESH Headings
- Animals
- Apoptosis/drug effects
- CD11b Antigen/biosynthesis
- Cell Differentiation/drug effects
- Cell Line, Tumor
- Cystatin B
- Cystatins/biosynthesis
- Electrophoresis, Gel, Two-Dimensional
- Fructose-Bisphosphate Aldolase/biosynthesis
- Interleukin-6/pharmacology
- Leukemia, Myeloid, Acute/metabolism
- Leukemia, Myeloid, Acute/pathology
- Membrane Proteins/biosynthesis
- Mice
- Peroxidases/biosynthesis
- Peroxiredoxins
- Proteomics
- Recombinant Proteins/pharmacology
- Reverse Transcriptase Polymerase Chain Reaction
- Spectrometry, Mass, Electrospray Ionization
- Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
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Affiliation(s)
- Qing Xia
- Department of Molecular Immunology, Beijing Institute of Basic Medical Science, TaiPing Road 27, Beijing 100850, PR China
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138
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Zheng X, Zhang Y, Chen YQ, Castranova V, Shi X, Chen F. Inhibition of NF-kappaB stabilizes gadd45alpha mRNA. Biochem Biophys Res Commun 2005; 329:95-9. [PMID: 15721278 DOI: 10.1016/j.bbrc.2005.01.105] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2005] [Indexed: 11/29/2022]
Abstract
Growth arrest- and DNA damage-inducible protein alpha (gadd45alpha) is an important regulator for cell cycle, genomic stability, and cell apoptosis. In the present report, we demonstrated that NF-kappaB inhibition due to Ikkbeta deficiency enhanced the stability of gadd45alpha mNRA. Using embryo fibroblast cells derived from wild type (wt) or Ikkbeta gene knockout (Ikkbeta(-/-)) mice, reverse transcription-polymerase chain reaction revealed a three- to fourfold increase of gadd45alpha mRNA in Ikkbeta(-/-) cells compared with wt cells. The deficiency in Ikkbeta substantially decreased basal NF-kappaB activity and increased accumulation of reactive oxygen species (ROS). However, such deficiency had no effect on the basal expression or activity of Akt, FoxO3a, p53, and c-myc that regulate the transcription of gadd45alpha gene positively or negatively. Analysis of gadd45alpha mRNA stability showed a ROS-dependent increase in the half-life of gadd45alpha mRNA in Ikkbeta(-/-) cells. Immunoprecipitation experiments indicated an increased binding of a RNA stabilizing protein, nucleolin, to gadd45alpha mRNA in Ikkbeta(-/-) cells. The binding of nucleolin to gadd45alpha mRNA could be prevented by the antioxidant, N-acetyl-cysteine. Thus, these data are the first to suggest that inhibition of Ikkbeta-NF-kappaB signaling up-regulates the expression of gadd45alpha mNRA through a post-transcriptional, rather than a transcriptional, mechanism.
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Affiliation(s)
- Xue Zheng
- Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Science, Shanghai 200031, PR China
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139
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Kim K, Dimitrova DD, Carta KM, Saxena A, Daras M, Borowiec JA. Novel checkpoint response to genotoxic stress mediated by nucleolin-replication protein a complex formation. Mol Cell Biol 2005; 25:2463-74. [PMID: 15743838 PMCID: PMC1061594 DOI: 10.1128/mcb.25.6.2463-2474.2005] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2004] [Revised: 06/14/2004] [Accepted: 12/13/2004] [Indexed: 11/20/2022] Open
Abstract
Human replication protein A (RPA), the primary single-stranded DNA-binding protein, was previously found to be inhibited after heat shock by complex formation with nucleolin. Here we show that nucleolin-RPA complex formation is stimulated after genotoxic stresses such as treatment with camptothecin or exposure to ionizing radiation. Complex formation in vitro and in vivo requires a 63-residue glycine-arginine-rich (GAR) domain located at the extreme C terminus of nucleolin, with this domain sufficient to inhibit DNA replication in vitro. Fluorescence resonance energy transfer studies demonstrate that the nucleolin-RPA interaction after stress occurs both in the nucleoplasm and in the nucleolus. Expression of the GAR domain or a nucleolin mutant (TM) with a constitutive interaction with RPA is sufficient to inhibit entry into S phase. Increasing cellular RPA levels by overexpression of the RPA2 subunit minimizes the inhibitory effects of nucleolin GAR or TM expression on chromosomal DNA replication. The arrest is independent of p53 activation by ATM or ATR and does not involve heightened expression of p21. Our data reveal a novel cellular mechanism that represses genomic replication in response to genotoxic stress by inhibition of an essential DNA replication factor.
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Affiliation(s)
- Kyung Kim
- Department of Biochemistry, New York University School of Medicine, 550 First Ave., MSB-383, New York, NY 10016, USA
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140
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Ning B, Shih C. Nucleolar localization of human hepatitis B virus capsid protein. J Virol 2004; 78:13653-68. [PMID: 15564475 PMCID: PMC533942 DOI: 10.1128/jvi.78.24.13653-13668.2004] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2004] [Accepted: 08/12/2004] [Indexed: 01/02/2023] Open
Abstract
Wild-type human hepatitis B virus (HBV) exhibits selective export of virions containing mature genomes. In contrast, changing an isoleucine to a leucine at amino acid 97 (I97L) of the HBV core antigen (HBcAg) causes it to release immature genomes. To elucidate the structure-function relationship of HBcAg at amino acid 97, we systematically replaced the isoleucine residue at this position with 18 other amino acids via mutagenesis. Twelve of the 18 mutants exhibited no significant phenotype, while five new mutants displayed strong phenotypes. The I97D mutant had a near lethal phenotype, the I97P mutant exhibited a significantly reduced level of virion secretion, and the I97G mutant lacked the full-length relaxed circular form of viral DNA. The tip of the spike of the capsid particle is known to contain a predominant B-cell epitope. However, the recognition of this exposed epitope by an anti-HBc antibody appeared to be affected by the I97E mutation or by histidine tagging at the C terminus of mutant HBcAg, which is presumably in the capsid interior. Surprisingly, the nuclear HBcAg of mutants I97E and I97W, produced from either a replicon or an expression vector, was found to be colocalized with nucleolin and B23 at a frequency of nearly 100% by confocal immunofluorescence microscopy. In contrast, this colocalization occurred with wild-type HBcAg only to a limited extent. We also noted that nucleolin-colocalizing cells were often binucleated or apoptotic, suggesting that the presence of HBcAg in the nucleolus may perturb cytokinesis. The mechanism of this phenomenon and its potential involvement in liver pathogenesis are discussed. To our knowledge, this is the first report of nucleolar HBcAg in culture.
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Affiliation(s)
- Bo Ning
- Department of Pathology, WHO Collaborating Center for Tropical Diseases and Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch, Galveston, TX 77555-0609, USA
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141
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Otake Y, Sengupta TK, Bandyopadhyay S, Spicer EK, Fernandes DJ. Retinoid-induced apoptosis in HL-60 cells is associated with nucleolin down-regulation and destabilization of Bcl-2 mRNA. Mol Pharmacol 2004; 67:319-26. [PMID: 15492114 DOI: 10.1124/mol.104.006080] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
All-trans retinoic acid (ATRA) induces differentiation of promyelocytic leukemia cells, but the mechanisms by which cellular differentiation leads to apoptosis are not well understood. Studies were done to address the question whether ATRA-induced apoptosis is a consequence of destabilization of bcl-2 mRNA and decreased cellular levels of the anti-apoptotic protein, bcl-2. ATRA induced differentiation of HL-60 cells along the granulocytic pathway within 48 h. The half-lives of bcl-2 mRNA in HL-60 cells incubated with ATRA for 48 or 72 h were reduced to 39 and 7% of the corresponding untreated control values, respectively. Cellular differentiation was accompanied by down-regulation of the cytoplasmic levels of nucleolin, a bcl-2 mRNA-stabilizing protein. Binding of a bcl-2 mRNA instability element (AU-rich element-1) to nucleolin in S100 extracts from ATRA-treated cells was decreased to 15% of control within 72 h. The decay of 5' capped, polyadenylated bcl-2 mRNA transcripts containing ARE-1 was more rapid in S100 extracts from ATRA-treated cells compared with untreated cells. However, when recombinant nucleolin was added to extracts of ATRA-treated cells, the rate of bcl-2 mRNA decay was similar to the rate in extracts of untreated cells. These results provide evidence that ATRA-induced apoptosis is a consequence of cellular differentiation, which leads to nucleolin down-regulation and bcl-2 mRNA instability.
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Affiliation(s)
- Yoko Otake
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, 173 Ashley Avenue, P.O. Box 250509, Charleston, SC 29425, USA
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142
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Lee JH, Jeon MH, Seo YJ, Lee YJ, Ko JH, Tsujimoto Y, Lee JH. CA repeats in the 3'-untranslated region of bcl-2 mRNA mediate constitutive decay of bcl-2 mRNA. J Biol Chem 2004; 279:42758-64. [PMID: 15294893 DOI: 10.1074/jbc.m407357200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
An AU-rich element (ARE) in the 3'-untranslated region (UTR) of bcl-2 mRNA has previously been shown to be responsible for destabilizing bcl-2 mRNA during apoptosis through increasing AUF1 binding. In the present study, we investigated the effect of the region upstream of the ARE on bcl-2 mRNA stability using serial deletion constructs of the 3'-UTR of bcl-2. Deletion of 30 nucleotides mostly consisting of the CA repeats, located upstream of the ARE, resulted in the stabilization of bcl-2 mRNA abundance, in the absence or presence of the ARE. The specificity of the CA repeats in terms of destabilizing bcl-2 mRNA was proven by the substituting the CA repeats with other alternative repeats of purine/pyrimidine, but this had no effect on the stability of bcl-2 mRNA. CA repeats alone, however, failed to confer instability to bcl-2 or gfp reporter mRNAs, indicating a requirement for additional sequences in the upstream region of the 3'-UTR. Serial deletion and replacement of a part of the region upstream of the CA repeats revealed that the entire 131-nucleotide upstream region is an essential prerequisite for the CA repeat-dependent destabilization of bcl-2 mRNA. Unlike the ARE, CA repeat-mediated degradation of bcl-2 mRNA was not accelerated upon apoptotic stimulus. Moreover, the upstream sequences and CA repeats are conserved among mammals. Collectively, CA repeats contribute to the constitutive decay of bcl-2 mRNA in the steady states, thereby maintaining appropriate bcl-2 levels in mammalian cells.
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Affiliation(s)
- Jung-Hee Lee
- Department of Biochemistry, The Catholic University of Korea, Seoul 137-701, Korea
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143
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Singh K, Laughlin J, Kosinski PA, Covey LR. Nucleolin is a second component of the CD154 mRNA stability complex that regulates mRNA turnover in activated T cells. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2004; 173:976-85. [PMID: 15240685 DOI: 10.4049/jimmunol.173.2.976] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CD154 (CD40L) mRNA turnover is regulated in part at the posttranscriptional level by a protein complex (termed Complex I) that binds to a highly CU-rich region of the 3'UTR. Polypyrimidine tract-binding protein (PTB) has previously been identified as a major RNA-binding protein in Complex I. Nondenaturing gel filtration of total extract from Jurkat T cells demonstrated that the CD154 mRNA-binding activity migrates as a approximately 200-kDa complex, indicating the presence of multiple complex-associated proteins. We have currently undertaken a biochemical approach to further characterize Complex I and observed that it segregates over DEAE-Sepharose into two subcomplexes (termed I-L and I-U). Furthermore, nucleolin was identified as a component of both subcomplexes and was shown that it is the major RNA-binding protein in I-U. To directly demonstrate the biological significance of Complex I binding to the CD154 transcript, cytoplasm from human Jurkat cells was fractionated over a sucrose gradient and the different cellular fractions subjected to immunoprecipitation with anti-PTB and anti-nucleolin Abs. RT-PCR of the immunoprecipitated products using CD154-specific primers clearly demonstrated that nucleolin and PTB are associated with CD154 mRNA in both the ribonucleoprotein and polysome fractions. These data strongly support a model whereby nucleolin and PTB are integral to the stability of CD154 mRNA and are components of the CD154 ribonucleoprotein particle associated with actively translating ribosomes.
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Affiliation(s)
- Karnail Singh
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854, USA
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