151
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A systems' biology approach to study microRNA-mediated gene regulatory networks. BIOMED RESEARCH INTERNATIONAL 2013; 2013:703849. [PMID: 24350286 PMCID: PMC3848080 DOI: 10.1155/2013/703849] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2013] [Revised: 09/12/2013] [Accepted: 09/17/2013] [Indexed: 12/27/2022]
Abstract
MicroRNAs (miRNAs) are potent effectors in gene regulatory networks where aberrant miRNA expression can contribute to human diseases such as cancer. For a better understanding of the regulatory role of miRNAs in coordinating gene expression, we here present a systems biology approach combining data-driven modeling and model-driven experiments. Such an approach is characterized by an iterative process, including biological data acquisition and integration, network construction, mathematical modeling and experimental validation. To demonstrate the application of this approach, we adopt it to investigate mechanisms of collective repression on p21 by multiple miRNAs. We first construct a p21 regulatory network based on data from the literature and further expand it using algorithms that predict molecular interactions. Based on the network structure, a detailed mechanistic model is established and its parameter values are determined using data. Finally, the calibrated model is used to study the effect of different miRNA expression profiles and cooperative target regulation on p21 expression levels in different biological contexts.
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152
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Chou CF, Lin WJ, Lin CC, Luber CA, Godbout R, Mann M, Chen CY. DEAD box protein DDX1 regulates cytoplasmic localization of KSRP. PLoS One 2013; 8:e73752. [PMID: 24023901 PMCID: PMC3762726 DOI: 10.1371/journal.pone.0073752] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Accepted: 07/22/2013] [Indexed: 11/19/2022] Open
Abstract
mRNA decay mediated by the AU-rich elements (AREs) is one of the most studied post-transcriptional mechanisms and is modulated by ARE-binding proteins (ARE-BPs). To understand the regulation of K homology splicing regulatory protein (KSRP), a decay-promoting ARE-BP, we purified KSRP protein complexes and identified an RNA helicase, DDX1. We showed that down-regulation of DDX1 expression elevated cytoplasmic levels of KSRP and facilitated ARE-mediated mRNA decay. Association of KSRP with 14-3-3 proteins, that are predominately located in the cytoplasm, increased upon reduction of DDX1. We also demonstrated that KSRP associated with DDX1 or 14-3-3, but not both. These observations indicate that subcellular localization of KSRP is regulated by competing interactions with DDX1 or 14-3-3.
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Affiliation(s)
- Chu-Fang Chou
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Wei-Jye Lin
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Chen-Chung Lin
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Christian A. Luber
- Department of Proteomics and Signal Transduction, Max-Planck Institute of Biochemistry, Martinsried, Germany
| | - Roseline Godbout
- Department of Oncology, University of Alberta, Cross Cancer Institute, Edmonton, Alberta, Canada
| | - Matthias Mann
- Department of Proteomics and Signal Transduction, Max-Planck Institute of Biochemistry, Martinsried, Germany
| | - Ching-Yi Chen
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- * E-mail:
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153
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D’Agostino VG, Adami V, Provenzani A. A novel high throughput biochemical assay to evaluate the HuR protein-RNA complex formation. PLoS One 2013; 8:e72426. [PMID: 23951323 PMCID: PMC3741180 DOI: 10.1371/journal.pone.0072426] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Accepted: 07/10/2013] [Indexed: 12/14/2022] Open
Abstract
The RNA binding protein HuR/ELAVL1 binds to AU-rich elements (AREs) promoting the stabilization and translation of a number of mRNAs into the cytoplasm, dictating their fate. We applied the AlphaScreen technology using purified human HuR protein, expressed in a mammalian cell-based system, to characterize in vitro its binding performance towards a ssRNA probe whose sequence corresponds to the are present in TNFα 3’ untranslated region. We optimized the method to titrate ligands and analyzed the kinetic in saturation binding and time course experiments, including competition assays. The method revealed to be a successful tool for determination of HuR binding kinetic parameters in the nanomolar range, with calculated Kd of 2.5±0.60 nM, kon of 2.76±0.56*106 M-1 min-1, and koff of 0.007±0.005 min-1. We also tested the HuR-RNA complex formation by fluorescent probe-based RNA-EMSA. Moreover, in a 384-well plate format we obtained a Z-factor of 0.84 and an averaged coefficient of variation between controls of 8%, indicating that this biochemical assay fulfills criteria of robustness for a targeted screening approach. After a screening with 2000 small molecules and secondary verification with RNA-EMSA we identified mitoxantrone as an interfering compound with rHuR and TNFα probe complex formation. Notably, this tool has a large versatility and could be applied to other RNA Binding Proteins recognizing different RNA, DNA, or protein species. In addition, it opens new perspectives in the identification of small-molecule modulators of RNA binding proteins activity.
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Affiliation(s)
- Vito G. D’Agostino
- Laboratory of Genomic Screening, Centre for Integrative Biology, University of Trento, Mattarello, Trento, Italy
| | - Valentina Adami
- High Throughput Screening core facility, Centre for Integrative Biology, University of Trento, Mattarello, Trento, Italy
| | - Alessandro Provenzani
- Laboratory of Genomic Screening, Centre for Integrative Biology, University of Trento, Mattarello, Trento, Italy
- * E-mail:
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154
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Lindner C, Urbánek P, Pavelka B, Hartmann M, Herrlich P. A link between two tumorigenic proteins, CD44 and p21WAF1: CD44 increases phorbol ester-induced expression of p21WAF1 by stabilizing its mRNA and extending protein half-life. FEBS Lett 2013; 587:2698-704. [PMID: 23856463 DOI: 10.1016/j.febslet.2013.07.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 07/01/2013] [Indexed: 01/23/2023]
Abstract
The cell surface glycoprotein CD44 enhances phorbol-12-myristate 13-acetate (TPA)-induced expression of p21WAF1 by stabilizing its mRNA and enhancing the protein's half-life in several cell lines. Only the plasma membrane-anchored cytoplasmic tail of CD44 and its interacting ezrin, radixin, moesin (ERM) proteins are required for this effect. A mitogen activated kinase (MEK) inhibitor abolishes the action of CD44 on p21. Down-regulation of p21 dramatically decreased anchorage-independence of a cancer cell line, whereas CD44 expression in this background could partially rescue the phenotype.
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Affiliation(s)
- Christina Lindner
- Leibniz Institute for Age Research - Fritz Lipmann Institute, Beutenbergstr. 11, 07745 Jena, Germany
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155
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Abstract
Remodeling of RNA-protein complexes (mRNPs) plays a critical role in mRNA biogenesis and metabolism. However, relatively little is known about the underlying mechanism and regulation of the mRNP remodeling. In this issue of Genes & Development, Zhou and colleagues (pp. 1046-1058) report that a protein remodeling machine, the p97-UBXD8 complex, disassembles mRNPs containing the AU-rich elements (AREs) bound by HuR proteins in a nondegradative, ubiquitin signaling-dependent manner, revealing a novel mechanism to regulate mRNA turnover.
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Affiliation(s)
- Chyi-Ying A Chen
- Department of Biochemistry and Molecular Biology, The University of Texas Medical School at Houston, Houston, Texas 77030, USA
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156
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Al-Khalaf HH, Aboussekhra A. ATR controls the UV-related upregulation of the CDKN1A mRNA in a Cdk1/HuR-dependent manner. Mol Carcinog 2013; 53:979-87. [PMID: 23813879 DOI: 10.1002/mc.22066] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2013] [Revised: 05/13/2013] [Accepted: 05/31/2013] [Indexed: 11/10/2022]
Abstract
Ultraviolet (UV) light is a carcinogenic agent that upregulates the expression of several genes involved in various cellular processes, including cell cycle checkpoints and apoptosis. The universal cyclin-dependent kinase inhibitor p21(WAF1/Cip1) plays major roles in these processes, and the level of its corresponding message increases several times in response to UV-induced DNA damage. This upregulation is mainly posttranscriptional owing to HuR-dependent mRNA stabilization. Since the protein kinase Atr plays major roles during the cellular response to UV damage, we sought to investigate its possible implication in the stabilization of the p21(WAF1/Cip1) coding mRNA. We have shown that the UV-dependent accumulation of the CDKN1A mRNA is indeed under the control of the Atr protein kinase. Upon UV damage, Atr allows nuclear-cytoplasmic shuttling of the HuR protein, which binds the CDKN1A mRNA and reduces its turnover. This ATR-dependent effect is mediated through UV-related phosphorylation/inactivation of the Cdk1 protein kinase by Atr, which leads to the dissociation of HuR from Cdk1. Indeed, inhibition or shRNA specific knockdown of CDK1 in ATR-deficient cells enhanced the cytoplasmic level of HuR and restored the CDKN1A mRNA upregulation in response to UV damage. These results show that ATR stabilizes the CDKN1A message in response to UV damage through Cdk1-related cytoplasmic accumulation of HuR.
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Affiliation(s)
- Huda H Al-Khalaf
- Department of Molecular Oncology, King Faisal Specialist Hospital and Research Center, Riyadh, Kingdom of Saudi Arabia; The Joint Center for Genomics Research, King Abdulaziz City for Science and Technology, Riyadh, Kingdom of Saudi Arabia
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157
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Aparicio LA, Abella V, Valladares M, Figueroa A. Posttranscriptional regulation by RNA-binding proteins during epithelial-to-mesenchymal transition. Cell Mol Life Sci 2013; 70:4463-77. [PMID: 23715860 PMCID: PMC3827902 DOI: 10.1007/s00018-013-1379-0] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 05/10/2013] [Accepted: 05/16/2013] [Indexed: 12/22/2022]
Abstract
Epithelial-to-mesenchymal transition (EMT), one of the crucial steps for carcinoma cells to acquire invasive capacity, results from the disruption of cell–cell contacts and the acquisition of a motile mesenchymal phenotype. Although the transcriptional events controlling EMT have been extensively studied, in recent years, several posttranscriptional mechanisms have emerged as critical in the regulation of EMT during tumor progression. In this review, we highlight the regulation of posttranscriptional events in EMT by RNA-binding proteins (RBPs). RBPs are responsible for controlling pre-mRNA splicing, capping, and polyadenylation, as well as mRNA export, turnover, localization, and translation. We discuss the most relevant aspects of RBPs controlling the metabolism of EMT-related mRNAs, and describe the implication of novel posttranscriptional mechanisms regulating EMT in response to different signaling pathways. Novel insight into posttranscriptional regulation of EMT by RBPs is uncovering new therapeutic targets in cancer invasion and metastasis.
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Affiliation(s)
- Luis A Aparicio
- Servizo de Oncología Médica, Complejo Hospitalario Universitario A Coruña (CHUAC), SERGAS, A Coruña, Spain
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158
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Upregulation of the host SLC11A1 gene by Clostridium difficile toxin B facilitates glucosylation of Rho GTPases and enhances toxin lethality. Infect Immun 2013; 81:2724-32. [PMID: 23690404 DOI: 10.1128/iai.01177-12] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Pseudomembranous enterocolitis associated with Clostridium difficile infection is an important cause of morbidity and mortality in patients being treated with antibiotics. Two closely related large protein toxins produced by C. difficile, TcdA and TcdB, which act identically but at different efficiencies to glucosylate low-molecular-weight Rho GTPases, underlie the microbe's pathogenicity. Using antisense RNA encoded by a library of human expressed sequence tags (ESTs), we randomly inactivated host chromosomal genes in HeLa cells and isolated clones that survived exposure to ordinarily lethal doses of TcdB. This phenotypic screening and subsequent analysis identified solute carrier family 11 member 1 (SLC11A1; formerly NRAMP1), a divalent cation transporter crucial to host defense against certain microbes, as an enhancer of TcdB lethality. Whereas SLC11A1 normally is poorly expressed in human cells of nonmyeloid lineage, TcdB increased SLC11A1 mRNA abundance in such cells through the actions of the RNA-binding protein HuR. We show that short hairpin RNA (shRNA) directed against SLC11A1 reduced TcdB glucosylation of small Rho GTPases and, consequently, toxin lethality. Consistent with the previously known role of SLC11A1 in cation transport, these effects were enhanced by elevation of Mn(2+) in media; conversely, they were decreased by treatment with a chelator of divalent cations. Our findings reveal an unsuspected role for SLC11A1 in determining C. difficile pathogenicity, demonstrate the novel ability of a bacterial toxin to increase its cytotoxicity, establish a mechanistic basis for these effects, and suggest a therapeutic approach to mitigate cell killing by C. difficile toxins A and B.
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159
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Li Y, Yu J, DU D, Fu S, Chen Y, Yu F, Gao P. Involvement of post-transcriptional regulation of FOXO1 by HuR in 5-FU-induced apoptosis in breast cancer cells. Oncol Lett 2013; 6:156-160. [PMID: 23946796 PMCID: PMC3742653 DOI: 10.3892/ol.2013.1352] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2012] [Accepted: 09/04/2012] [Indexed: 12/28/2022] Open
Abstract
The post-transcriptional control of specific mRNAs is a widespread mechanism of gene regulation, which contributes to numerous biological processes in a number of cell types. The Forkhead box O (FoxO) transcription factor FOXO1 is an important tumor suppressor involved in apoptosis, the cell cycle, DNA damage repair and oxidative stress. Bioinformatic prediction identified that the 3' untranslated region (UTR) of FOXO1 is enriched with binding motifs for the human ELAV/Hu protein (HuR), indicating that FOXO1 is a potential target of HuR. Luciferase reporter assays demonstrate that HuR specifically regulates FOXO1 expression through AU-rich elements (AREs) within the FOXO1 3' UTR. Immunoprecipitation studies confirmed that HuR associates with FOXO1 mRNA in MDA-MB-231 breast cancer cells and that HuR upregulates FOXO1 mRNA levels through increased mRNA stability. Using a HuR loss- and gain-of-function approach, we revealed that FOXO1 expression was correspondingly decreased or increased in MDA-MB-231 cells. Functional assays demonstrated that HuR and FOXO1 expression levels were markedly enhanced upon 5-fluorouracil (5-FU) stimulation in MDA-MB-231 cells. Knockdown of HuR apparently abrogated 5-FU-induced apoptosis detected by caspase-3 activities. Furthermore, in HuR knockdown cells, additional overexpression of FOXO1 moderately recovered 5-FU-induced apoptosis, which verified that HuR-modulated apoptosis upon 5-FU treatment was partially mediated by its post-transcriptional regulation of FOXO1. Therefore, modulating FOXO1 expression has been suggested to lead to the development of new therapeutic treatments for certain types of cancer.
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Affiliation(s)
- Yunbo Li
- Norman Bethune College of Medicine, Jilin University, Changchun, Jilin 130041
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160
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Wang J, Guo Y, Chu H, Guan Y, Bi J, Wang B. Multiple functions of the RNA-binding protein HuR in cancer progression, treatment responses and prognosis. Int J Mol Sci 2013; 14:10015-41. [PMID: 23665903 PMCID: PMC3676826 DOI: 10.3390/ijms140510015] [Citation(s) in RCA: 202] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 04/22/2013] [Accepted: 04/25/2013] [Indexed: 12/16/2022] Open
Abstract
The human embryonic lethal abnormal vision-like protein, HuR, is a member of the Hu family of RNA-binding proteins. Over the past decade, this ubiquitously expressed protein has been extensively investigated in cancer research because it is involved in the regulation of mRNA stability and translation in many cell types. HuR activity and function is associated with its subcellular distribution, transcriptional regulation, translational and post-translational modifications. HuR regulation of target mRNAs is based on the interaction between the three specific domains of HuR protein and one or several U- or AU-rich elements (AREs) in the untranslated region of target mRNAs. A number of cancer-related transcripts containing AREs, including mRNAs for proto-oncogenes, cytokines, growth factors, and invasion factors, have been characterized as HuR targets. It has been proposed that HuR has a central tumorigenic activity by enabling multiple cancer phenotypes. In this review, we comprehensively survey the existing evidence with regard to the diverse functions of HuR in caner development and progression. The current data also suggest that HuR might be a novel and promising therapeutic target and a marker for treatment response and prognostic evaluation.
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Affiliation(s)
- Jun Wang
- Department of Oncology, General Hospital, Jinan Command of the People’s Liberation Army, Jinan 250031, China; E-Mails: (H.C.); (Y.G.); (J.B.); (B.W.)
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +86-531-5166-5336; Fax: +86-531-5166-6649
| | - Yan Guo
- Department of Outpatient, Military Command of Shandong Province, Jinan 250013, China; E-Mail:
| | - Huili Chu
- Department of Oncology, General Hospital, Jinan Command of the People’s Liberation Army, Jinan 250031, China; E-Mails: (H.C.); (Y.G.); (J.B.); (B.W.)
| | - Yaping Guan
- Department of Oncology, General Hospital, Jinan Command of the People’s Liberation Army, Jinan 250031, China; E-Mails: (H.C.); (Y.G.); (J.B.); (B.W.)
| | - Jingwang Bi
- Department of Oncology, General Hospital, Jinan Command of the People’s Liberation Army, Jinan 250031, China; E-Mails: (H.C.); (Y.G.); (J.B.); (B.W.)
| | - Baocheng Wang
- Department of Oncology, General Hospital, Jinan Command of the People’s Liberation Army, Jinan 250031, China; E-Mails: (H.C.); (Y.G.); (J.B.); (B.W.)
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161
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Kawagishi H, Hashimoto M, Nakamura H, Tsugawa T, Watanabe A, Kontoyiannis DL, Sugimoto M. HuR maintains a replicative life span by repressing the ARF tumor suppressor. Mol Cell Biol 2013; 33:1886-900. [PMID: 23508105 PMCID: PMC3647966 DOI: 10.1128/mcb.01277-12] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 03/07/2013] [Indexed: 01/08/2023] Open
Abstract
p19(ARF) plays an essential role in the senescence of mouse cells, and its expression is lost by methylation or deletion of the ARF locus; otherwise, p53 is inactivated to bypass senescence. ARF expression is tightly regulated, but little is known about its posttranscriptional regulation. Here, we show that an RNA-binding protein, HuR (human antigen R), represses ARF mRNA translation, thereby maintaining the replicative life span of mouse embryonic fibroblasts (MEFs). Loss of HuR results in premature senescence, with concomitant increases in p19(ARF) but not p16(Ink4a) levels, and this senescence is not observed in ARF-null MEFs that retain an intact Ink4a locus. HuR depletion does not alter ARF transcription or stability but enhances ribosome association with ARF mRNA. Under these conditions, ARF mRNA accumulates in nucleoli, where it associates with nucleolin. Furthermore, adipose-specific deletion of the HuR gene results in increased p19(ARF) expression in aged animals, which is accompanied by decreased insulin sensitivity. Together, our findings demonstrate that p19(ARF) is also regulated at the translational level, and this translational regulation restrains the cellular life span and tissue functions in vivo.
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Affiliation(s)
- Hiroyuki Kawagishi
- Research Institute, National Center for Geriatrics and Gerontology, Obu, Aichi, Japan
| | - Michihiro Hashimoto
- Research Institute, National Center for Geriatrics and Gerontology, Obu, Aichi, Japan
| | - Hideaki Nakamura
- Research Institute, National Center for Geriatrics and Gerontology, Obu, Aichi, Japan
| | - Takayuki Tsugawa
- Research Institute, National Center for Geriatrics and Gerontology, Obu, Aichi, Japan
| | - Atsushi Watanabe
- Research Institute, National Center for Geriatrics and Gerontology, Obu, Aichi, Japan
| | | | - Masataka Sugimoto
- Research Institute, National Center for Geriatrics and Gerontology, Obu, Aichi, Japan
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162
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Zhou HL, Geng C, Luo G, Lou H. The p97-UBXD8 complex destabilizes mRNA by promoting release of ubiquitinated HuR from mRNP. Genes Dev 2013; 27:1046-58. [PMID: 23618873 DOI: 10.1101/gad.215681.113] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The assembly and disassembly of ribonucleoproteins (RNPs) are dynamic processes that control every step of RNA metabolism, including mRNA stability. However, our knowledge of how RNP remodeling is achieved is largely limited to RNA helicase functions. Here, we report a previously unknown mechanism that implicates the ATPase p97, a protein-remodeling machine, in the dynamic regulation of mRNP disassembly. We found that p97 and its cofactor, UBXD8, destabilize p21, MKP-1, and SIRT1, three established mRNA targets of the RNA-binding protein HuR, by promoting release of HuR from mRNA. Importantly, ubiquitination of HuR with a short K29 chain serves as the signal for release. When cells are subjected to stress conditions, the steady-state levels of HuR ubiquitination change, suggesting a new mechanism through which HuR mediates the stress response. Our studies reveal a new paradigm in RNA biology: nondegradative ubiquitin signaling-dependent disassembly of mRNP promoted by the p97-UBXD8 complex to control mRNA stability.
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Affiliation(s)
- Hua-Lin Zhou
- Department of Genetics and Genome Sciences, Case Western Reserve University, Cleveland, Ohio 44106, USA.
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163
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Nakayama H, Fukuda S, Matsushita N, Nishida-Fukuda H, Inoue H, Shirakata Y, Hashimoto K, Higashiyama S. Human antigen R-mediated mRNA stabilization is required for ultraviolet B-induced autoinduction of amphiregulin in keratinocytes. J Biol Chem 2013; 288:10338-48. [PMID: 23430747 DOI: 10.1074/jbc.m112.417527] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
All members of the EGF family are produced as transmembrane precursors that are proteolytically processed into soluble forms by disintegrin and metalloproteinases (ADAMs) for autocrine/paracrine pathways. In turn, the ligand-activated EGF receptor (EGFR) induces the expression of EGF family members, so-called "autoinduction." However, it is not well understood how this autoinduction occurs. In this study, we investigated the molecular mechanism of the autoinduction of amphiregulin (AREG), a member of the EGF family. We found that ultraviolet B (UVB) exposure increased the AREG mRNA level by stabilization of its mRNA in a human immortalized keratinocyte cell line, HaCaT. The 3' UTR of AREG mRNA was responsible for binding to an mRNA-binding protein, human antigen R (HuR), and the interaction between AREG mRNA and HuR was enhanced by UVB. Inducible knockdown of HuR expression significantly decreased AREG mRNA stability. Interestingly, treatment of HaCaT cells with an EGFR inhibitor, an EGFR neutralizing antibody, or an ADAM inhibitor destabilized AREG mRNA. In the case of ADAM inhibition, administration of soluble AREG restored the mRNA level, indicating that the stabilization occurs in a shedding-dependent manner of EGFR ligands. The HuR dependence of AREG mRNA and protein expression was also confirmed in human primary keratinocytes. Taken together, we propose a novel mechanism by which HuR regulates the stability of AREG mRNA in keratinocytes after UVB exposure and suggest that targeting of HuR functions might be crucial for understanding skin cancers caused by aberrant EGF family member-EGFR signaling.
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Affiliation(s)
- Hironao Nakayama
- Department of Biochemistry and Molecular Genetics, Ehime University, Shitsukawa, Toon, Ehime 791-0295, Japan
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164
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Hoene M, Runge H, Häring HU, Schleicher ED, Weigert C. Interleukin-6 promotes myogenic differentiation of mouse skeletal muscle cells: role of the STAT3 pathway. Am J Physiol Cell Physiol 2013; 304:C128-36. [DOI: 10.1152/ajpcell.00025.2012] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Myogenic differentiation of skeletal muscle cells is characterized by a sequence of events that include activation of signal transducer and activator of transcription 3 (STAT3) and enhanced expression of its target gene Socs3. Autocrine effects of IL-6 may contribute to the activation of the STAT3-Socs3 cascade and thus to myogenic differentiation. The importance of IL-6 and STAT3 for the differentiation process was studied in C2C12 cells and in primary mouse wild-type and IL-6−/− skeletal muscle cells. In differentiating C2C12 myoblasts, the upregulation of IL-6 mRNA expression and protein secretion started after increased phosphorylation of STAT3 on tyrosine 705 and increased mRNA expression of Socs3 was observed. Knockdown of STAT3 and IL-6 mRNA in differentiating C2C12 myoblasts impaired the expression of the myogenic markers myogenin and MyHC IIb and subsequently myotube fusion. However, the knockdown of IL-6 did not prevent the induction of STAT3 tyrosine phosphorylation. The IL-6-independent activation of STAT3 was verified in differentiating primary IL-6−/− myoblasts. The phosphorylation of STAT3 and the expression levels of STAT3, Socs3, and myogenin during differentiation were comparable in the primary myoblasts independent of the genotype. However, IL-6−/− cells failed to induce MyHC IIb expression to the same level as in wild-type cells and showed reduced myotube formation. Supplementation of IL-6 could partially restore the fusion of IL-6−/− cells. These data demonstrate that IL-6 depletion during myogenic differentiation does not reduce the activation of the STAT3-Socs3 cascade, while IL-6 and STAT3 are both necessary to promote myotube fusion.
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Affiliation(s)
- Miriam Hoene
- Division of Pathobiochemistry and Clinical Chemistry, University Tuebingen, Tuebingen, Germany
- Paul Langerhans Institute Tuebingen, Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Centre Munich, University Tuebingen, Tuebingen, Germany
| | - Heike Runge
- Division of Pathobiochemistry and Clinical Chemistry, University Tuebingen, Tuebingen, Germany
| | - Hans Ulrich Häring
- Division of Endocrinology, Diabetology, Angiology, Nephrology, and Clinical Chemistry, Department of Internal Medicine, University Tuebingen, Tuebingen, Germany; and
- Paul Langerhans Institute Tuebingen, Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Centre Munich, University Tuebingen, Tuebingen, Germany
| | - Erwin D. Schleicher
- Division of Pathobiochemistry and Clinical Chemistry, University Tuebingen, Tuebingen, Germany
- Paul Langerhans Institute Tuebingen, Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Centre Munich, University Tuebingen, Tuebingen, Germany
| | - Cora Weigert
- Division of Pathobiochemistry and Clinical Chemistry, University Tuebingen, Tuebingen, Germany
- Paul Langerhans Institute Tuebingen, Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Centre Munich, University Tuebingen, Tuebingen, Germany
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165
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Abstract
Gene expression patterns change dramatically in aging and age-related events. The DNA microarray is now recognized as a useful device in molecular biology and widely used to identify the molecular mechanisms of aging and the biological effects of drugs for therapeutic purpose in age-related diseases. Recently, numerous technological advantages have led to the evolution of DNA microarrays and microarray-based techniques, revealing the genomic modification and all transcriptional activity. Here, we show the step-by-step methods currently used in our lab to handling the oligonucleotide microarray and miRNA microarray. Moreover, we introduce the protocols of ribonucleoprotein [RNP] immunoprecipitation followed by microarray analysis (RIP-chip) which reveal the target mRNA of age-related RNA-binding proteins.
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166
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Damgaard CK, Lykke-Andersen J. Regulation of ARE-mRNA Stability by Cellular Signaling: Implications for Human Cancer. Cancer Treat Res 2013; 158:153-80. [PMID: 24222358 DOI: 10.1007/978-3-642-31659-3_7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
During recent years, it has become clear that regulation of mRNA stability is an important event in the control of gene expression. The stability of a large class of mammalian mRNAs is regulated by AU-rich elements (AREs) located in the mRNA 3' UTRs. mRNAs with AREs are inherently labile but as a response to different cellular cues they can become either stabilized, allowing expression of a given gene, or further destabilized to silence their expression. These tightly regulated mRNAs include many that encode growth factors, proto-oncogenes, cytokines, and cell cycle regulators. Failure to properly regulate their stability can therefore lead to uncontrolled expression of factors associated with cell proliferation and has been implicated in several human cancers. A number of transfactors that recognize AREs and regulate the translation and degradation of ARE-mRNAs have been identified. These transfactors are regulated by signal transduction pathways, which are often misregulated in cancers. This chapter focuses on the function of ARE-binding proteins with an emphasis on their regulation by signaling pathways and the implications for human cancer.
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167
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Singh M, Martinez AR, Govindaraju S, Lee BS. HuR inhibits apoptosis by amplifying Akt signaling through a positive feedback loop. J Cell Physiol 2012; 228:182-9. [PMID: 22674407 DOI: 10.1002/jcp.24120] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Human antigen R (HuR) is a post-transcriptional regulator of gene expression that plays a key role in stabilizing mRNAs during cellular stress, leading to enhanced survival. HuR expression is tightly regulated through multiple transcription and post-transcriptional controls. Although HuR is known to stabilize a subset of mRNAs involved in cell survival, its role in the survival pathway of PI3-kinase/Akt signaling is unclear. Here, we show that in renal proximal tubule cells, HuR performs a central role in cell survival by amplifying Akt signaling in a positive feedback loop. Key to this feedback loop is HuR-mediated stabilization of mRNA encoding Grb10, an adaptor protein whose expression is critical for Akt activation. Stimulation of Akt by interaction with Grb10 then activates NF-κB, which further enhances HuR mRNA and protein expression. This feedback loop is active in unstressed cells, but its effects are increased during stress. Therefore, this study demonstrates a central role for HuR in Akt signaling and reveals a mechanism by which modest changes in HuR levels below or above normal may be amplified, potentially resulting in cell death or cellular transformation.
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Affiliation(s)
- Mamata Singh
- Department of Physiology and Cell Biology, The Ohio State University College of Medicine, Columbus, Ohio, USA
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168
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Freeman JA, Espinosa JM. The impact of post-transcriptional regulation in the p53 network. Brief Funct Genomics 2012; 12:46-57. [PMID: 23242178 PMCID: PMC3548162 DOI: 10.1093/bfgp/els058] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The p53 transcription factor regulates the synthesis of mRNAs encoding proteins involved in diverse cellular stress responses such as cell-cycle arrest, apoptosis, autophagy and senescence. In this review, we discuss how these mRNAs are concurrently regulated at the post-transcriptional level by microRNAs (miRNAs) and RNA-binding proteins (RBPs), which consequently modify the p53 transcriptional program in a cell type- and stimulus-specific manner. We also discuss the action of specific miRNAs and RBPs that are direct transcriptional targets of p53 and how they act coordinately with protein-coding p53 target genes to orchestrate p53-dependent cellular responses.
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Affiliation(s)
- Justin A Freeman
- HHMI - University of Colorado at Boulder, 347 UCB, Boulder, CO 80309, USA
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169
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Chu PC, Chuang HC, Kulp SK, Chen CS. The mRNA-stabilizing factor HuR protein is targeted by β-TrCP protein for degradation in response to glycolysis inhibition. J Biol Chem 2012; 287:43639-50. [PMID: 23115237 DOI: 10.1074/jbc.m112.393678] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The mRNA-stabilizing protein HuR acts a stress response protein whose function and/or protein stability are modulated by diverse stress stimuli through posttranslational modifications. Here, we report a novel mechanism by which metabolic stress facilitates proteasomal degradation of HuR in cancer cells. In response to the glucose transporter inhibitor CG-5, HuR translocates to the cytoplasm, where it is targeted by the ubiquitin E3 ligase β-TrCP1 for degradation. The cytoplasmic localization of HuR is facilitated by PKCα-mediated phosphorylation at Ser-318 as the Ser-318 → alanine substitution abolishes the ability of the resulting HuR to bind PKCα and to undergo nuclear export. The mechanistic link between β-TrCP1 and HuR degradation was supported by the ability of ectopically expressed β-TrCP1 to mimic CG-5 to promote HuR degradation and by the protective effect of dominant negative inhibition of β-TrCP1 on HuR ubiquitination and degradation. Substrate targeting of HuR by β-TrCP1 was further verified by coimmunoprecipitation and in vitro GST pull-down assays and by the identification of a β-TrCP1 recognition site. Although HuR does not contain a DSG destruction motif, we obtained evidence that β-TrCP1 recognizes an unconventional motif, (296)EEAMAIAS(304), in the RNA recognition motif 3. Furthermore, mutational analysis indicates that IKKα-dependent phosphorylation at Ser-304 is crucial to the binding of HuR to β-TrCP1. Mechanistically, this HuR degradation pathway differs from that reported for heat shock and hypoxia, which underlies the complexity in the regulation of HuR turnover under different stress stimuli. The ability of glycolysis inhibitors to target the expression of oncogenic proteins through HuR degradation might foster novel strategies for cancer therapy.
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Affiliation(s)
- Po-Chen Chu
- Division of Medicinal Chemistry, College of Pharmacy and Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43221, USA
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170
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Identification of PADI2 as a potential breast cancer biomarker and therapeutic target. BMC Cancer 2012; 12:500. [PMID: 23110523 PMCID: PMC3571905 DOI: 10.1186/1471-2407-12-500] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Accepted: 10/27/2012] [Indexed: 12/25/2022] Open
Abstract
Background We have recently reported that the expression of peptidylarginine deiminase 2 (PADI2) is regulated by EGF in mammary cancer cells and appears to play a role in the proliferation of normal mammary epithelium; however, the role of PADI2 in the pathogenesis of human breast cancer has yet to be investigated. Thus, the goals of this study were to examine whether PADI2 plays a role in mammary tumor progression, and whether the inhibition of PADI activity has anti-tumor effects. Methods RNA-seq data from a collection of 57 breast cancer cell lines was queried for PADI2 levels, and correlations with known subtype and HER2/ERBB2 status were evaluated. To examine PADI2 expression levels during breast cancer progression, the cell lines from the MCF10AT model were used. The efficacy of the PADI inhibitor, Cl-amidine, was tested in vitro using MCF10DCIS cells grown in 2D-monolayers and 3D-spheroids, and in vivo using MCF10DCIS tumor xenografts. Treated MCF10DCIS cells were examined by flow-cytometry to determine the extent of apoptosis and by RT2 Profiler PCR Cell Cycle Array to detect alterations in cell cycle associated genes. Results We show by RNA-seq that PADI2 mRNA expression is highly correlated with HER2/ERBB2 (p = 2.2 × 106) in luminal breast cancer cell lines. Using the MCF10AT model of breast cancer progression, we then demonstrate that PADI2 expression increases during the transition of normal mammary epithelium to fully malignant breast carcinomas, with a strong peak of PADI2 expression and activity being observed in the MCF10DCIS cell line, which models human comedo-DCIS lesions. Next, we show that a PADI inhibitor, Cl-amidine, strongly suppresses the growth of MCF10DCIS monolayers and tumor spheroids in culture. We then carried out preclinical studies in nude (nu/nu) mice and found that Cl-amidine also suppressed the growth of xenografted MCF10DCIS tumors by more than 3-fold. Lastly, we performed cell cycle array analysis of Cl-amidine treated and control MCF10DCIS cells, and found that the PADI inhibitor strongly affects the expression of several cell cycle genes implicated in tumor progression, including p21, GADD45α, and Ki67. Conclusion Together, these results suggest that PADI2 may function as an important new biomarker for HER2/ERBB2+ tumors and that Cl-amidine represents a new candidate for breast cancer therapy.
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171
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St Laurent G, Shtokalo D, Heydarian M, Palyanov A, Babiy D, Zhou J, Kumar A, Urcuqui-Inchima S. Insights from the HuR-interacting transcriptome: ncRNAs, ubiquitin pathways, and patterns of secondary structure dependent RNA interactions. Mol Genet Genomics 2012; 287:867-79. [PMID: 23052832 DOI: 10.1007/s00438-012-0722-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 09/17/2012] [Indexed: 12/22/2022]
Abstract
The HuR protein regulates the expression of thousands of cellular transcripts by modulating mRNA splicing, trafficking, translation, and stability. Although it serves as a model of RNA-protein interactions, many features of HuR's interactions with RNAs remain unknown. In this report, we deployed the cryogenic RNA immunoprecipitation technique to analyze HuR-interacting RNAs with the Affymetrix all-exon microarray platform. We revealed several thousand novel HuR-interacting RNAs, including hundreds of non-coding RNAs such as natural antisense transcripts from stress responsive loci. To gain insight into the mechanisms of specificity and sensitivity of HuR's interaction with its target RNAs, we searched HuR-interacting RNAs for composite patterns of primary sequence and secondary structure. We provide evidence that secondary structures of 66-75 nucleotides enhance HuR's recognition of its specific RNA targets composed of short primary sequence patterns. We validated thousands of these RNAs by analysis of overlap with recently published findings, including HuR's interaction with RNAs in the pathways of RNA splicing and stability. Finally, we observed a striking enrichment for members of ubiquitin ligase pathways among the HuR-interacting mRNAs, suggesting a new role for HuR in the regulation of protein degradation to mirror its known function in protein translation.
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Affiliation(s)
- Georges St Laurent
- Grupo de Inmunovirologia, Universidad de Antioquia, Calle 67 Número 53-108, Medellin, Antioquia, Colombia.
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172
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Gummadi L, Taylor L, Curthoys NP. Concurrent binding and modifications of AUF1 and HuR mediate the pH-responsive stabilization of phosphoenolpyruvate carboxykinase mRNA in kidney cells. Am J Physiol Renal Physiol 2012; 303:F1545-54. [PMID: 23019227 DOI: 10.1152/ajprenal.00400.2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Onset of metabolic acidosis leads to a pronounced increase in renal expression of phosphoenolpyruvate carboxykinase (PEPCK). This response, which is mediated in part by stabilization of PEPCK mRNA, is effectively modeled by treating LLC-PK(1)-F(+)-9C cells with an acidic medium. siRNA knockdown of HuR prevented the pH-responsive increase in PEPCK mRNA half-life suggesting that HuR is necessary for this response. A recruitment assay, using a reporter mRNA in which the pH response elements of the PEPCK 3'-UTR were replaced with six MS2 stem-loop sequences, was developed to test this hypothesis. The individual recruitment of a chimeric protein containing the MS2 coat protein and either HuR or p40AUF1 failed to produce a pH-responsive stabilization. However, the concurrent expression of both chimeric proteins was sufficient to produce a pH-responsive increase in the half-life of the reporter mRNA. siRNA knockdown of AUF1 produced slight increases in basal levels of PEPCK mRNA and protein, but partially inhibited the pH-responsive increases. Complete inhibition of the latter response was achieved by knockdown of both RNA-binding proteins. The results suggest that binding of HuR and AUF1 has opposite effects on basal expression, but may interact to mediate the pH-responsive increase in PEPCK mRNA. Two-dimensional gel electrophoresis indicated that treatment with acidic medium caused a decrease in phosphorylation of HuR, but may increase phosphorylation of the multiple AUF1 isoforms. Thus, the pH-responsive stabilization of PEPCK mRNA requires the concurrent binding of HuR and AUF1 and may be mediated by changes in their extent of covalent modification.
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Affiliation(s)
- Lakshmi Gummadi
- Dept. of Biochemistry and Molecular Biology, Colorado State Univ., Ft. Collins, CO 80523-1870, USA
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173
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Plateroti M, de Araujo PR, da Silva AE, Penalva LOF. The RNA-Binding Protein Musashi1: A Major Player in Intestinal Epithelium Renewal and Colon Cancer Development. CURRENT COLORECTAL CANCER REPORTS 2012; 8:290-297. [PMID: 23914149 DOI: 10.1007/s11888-012-0141-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Aberrant gene expression is the cause and the consequence of tumorigenesis. A major component of gene expression is translation regulation; a process whose main players are RNA-binding-proteins (RBPs). More than 800 RBPs have been identified in the human genome and several of them have been shown to control gene networks associated with relevant cancer processes. A more systematic characterization of RBPs starts to reveal that similar to transcription factors, they can function as tumor suppressors or oncogenes. A relevant example is Musashi1 (Msi1), which is emerging as a critical regulator of tumorigenesis in multiple cancer types, including colon cancer. Msi1 is a stem marker in several tissues and is critical in maintaining the balance between self-renewal and differentiation. However, a boost in Msi1 expression can most likely lead cells towards an oncogenic pathway. In this article, we discuss the parallels between Msi1 function in normal renewal of intestinal epithelium and in colon cancer.
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Affiliation(s)
- Michelina Plateroti
- Centre de Génétique et de Physiologie Moléculaire et Cellulaire, Université Claude Bernard Lyon 1, France. 16 Rue Raphael Dubois, 69622 Villeurbanne, Cedex France
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174
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Wang W. Regulatory RNA-binding proteins in senescence. Ageing Res Rev 2012; 11:485-90. [PMID: 22414963 DOI: 10.1016/j.arr.2012.02.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 02/08/2012] [Accepted: 02/08/2012] [Indexed: 11/18/2022]
Abstract
The expression of senescence-associated genes, which governs the progression and the maintenance of senescence, is regulated at multiple levels. Apart from the transcriptional mechanisms that control cellular senescence, studies over the past decade have revealed that post-transcriptional gene regulation, especially through changes in mRNA turnover and translation, critically influences protein expression patterns in the senescent cell. Among the post-transcriptional regulatory factors, RNA-binding proteins (RBPs) are particularly influential in the establishment of senescence-associated protein profiles. In this review, I discuss the current knowledge of the role of RBPs in cellular senescence and the molecular mechanisms that regulate their function.
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Affiliation(s)
- Wengong Wang
- Department of Biochemistry and Molecular Biology, Peking University Health Science Center, 38 Xueyuan Road, Beijing 100191, PR China.
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175
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Zhang J, Chen QM. Far upstream element binding protein 1: a commander of transcription, translation and beyond. Oncogene 2012; 32:2907-16. [PMID: 22926519 DOI: 10.1038/onc.2012.350] [Citation(s) in RCA: 90] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The far upstream binding protein 1 (FBP1) was first identified as a DNA-binding protein that regulates c-Myc gene transcription through binding to the far upstream element (FUSE) in the promoter region 1.5 kb upstream of the transcription start site. FBP1 collaborates with TFIIH and additional transcription factors for optimal transcription of the c-Myc gene. In recent years, mounting evidence suggests that FBP1 acts as an RNA-binding protein and regulates mRNA translation or stability of genes, such as GAP43, p27(Kip) and nucleophosmin. During retroviral infection, FBP1 binds to and mediates replication of RNA from Hepatitis C and Enterovirus 71. As a nuclear protein, FBP1 may translocate to the cytoplasm in apoptotic cells. The interaction of FBP1 with p38/JTV-1 results in FBP1 ubiquitination and degradation by the proteasomes. Transcriptional and post-transcriptional regulations by FBP1 contribute to cell proliferation, migration or cell death. FBP1 association with carcinogenesis has been reported in c-Myc dependent or independent manner. This review summarizes biochemical features of FBP1, its mechanism of action, FBP family members and the involvement of FBP1 in carcinogenesis.
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Affiliation(s)
- J Zhang
- Department of Pharmacology, University of Arizona, Tucson, AZ 85724, USA
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176
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Boucas J, Riabinska A, Jokic M, Herter-Sprie GS, Chen S, Höpker K, Reinhardt HC. Posttranscriptional regulation of gene expression-adding another layer of complexity to the DNA damage response. Front Genet 2012; 3:159. [PMID: 22936947 PMCID: PMC3427493 DOI: 10.3389/fgene.2012.00159] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2012] [Accepted: 08/06/2012] [Indexed: 12/13/2022] Open
Abstract
In response to DNA damage, cells activate a complex, kinase-based signaling network to arrest the cell cycle and allow time for DNA repair, or, if the extend of damage is beyond repair capacity, induce apoptosis. This signaling network, which is collectively referred to as the DNA damage response (DDR), is primarily thought to consist of two components—a rapid phosphorylation-driven signaling cascade that results in immediate inhibition of Cdk/cyclin complexes and a delayed transcriptional response that promotes a prolonged cell cycle arrest through the induction of Cdk inhibitors, such as p21. In recent years a third layer of complexity has emerged that involves potent posttranscriptional regulatory mechanisms that control the cellular response to DNA damage. Although much has been written on the relevance of the DDR in cancer and on the post-transcriptional role of microRNAs (miRs) in cancer, the post-transcriptional regulation of the DDR by non-coding RNAs and RNA-binding proteins (RBPs) still remains elusive in large parts. Here, we review the recent developments in this exciting new area of research in the cellular response to genotoxic stress. We put specific emphasis on the role of RBPs and the control of their function through DNA damage-activated protein kinases.
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Affiliation(s)
- Jorge Boucas
- Division of Hematology and Oncology, Center for Internal Medicine, University Hospital of Cologne Cologne, Germany
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177
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Zhu Q, Lin L, Cheng Q, Xu Q, Zhang J, Tomlinson S, Jin J, Chen X, He S. The role of acid sphingomyelinase and caspase 5 in hypoxia-induced HuR cleavage and subsequent apoptosis in hepatocytes. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:1453-61. [PMID: 22906436 DOI: 10.1016/j.bbalip.2012.08.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Revised: 07/14/2012] [Accepted: 08/02/2012] [Indexed: 11/24/2022]
Abstract
A previous data showed that the hypoxia mimetic compound CoCl(2) induced cleavage of HuR and subsequent apoptosis in human oral cancer cells. We also previously demonstrated that exposure of NT-2 human neuronal precursor cells to hypoxia resulted in changes in sphingolipid levels and apoptosis. Since it is known that CoCl(2) induces cleavage of HuR, we investigated whether there is a link between HuR cleavage and the observed sphingolipid changes in cells exposed to hypoxia, and whether this link is associated with the induction of apoptosis. Exposure of hepatocytes to direct hypoxia by means of a hypoxic chamber resulted in acid sphingomyelinase activation and ceramide elevation. The elevation in ceramide levels was associated with activation of caspase 5 and the subsequent cleavage of HuR and apoptotic cell death. These data raise the possibility that acid sphingomyelinase and caspase 5 are each potential targets for treating hypoxia (ischemia)-induced liver injury.
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Affiliation(s)
- Qun Zhu
- Department of Hepatobiliary Surgery, Affiliated Hospital of Guilin Medical University, Guilin, 541001, Guangxi, People's Republic of China
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178
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Pineda DM, Rittenhouse DW, Valley CC, Cozzitorto JA, Burkhart RA, Leiby B, Winter JM, Weber MC, Londin ER, Rigoutsos I, Yeo CJ, Gorospe M, Witkiewicz AK, Sachs JN, Brody JR. HuR's post-transcriptional regulation of Death Receptor 5 in pancreatic cancer cells. Cancer Biol Ther 2012; 13:946-55. [PMID: 22785201 DOI: 10.4161/cbt.20952] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Apoptosis is one of the core signaling pathways disrupted in pancreatic ductal adenocarcinoma (PDA). Death receptor 5 (DR5) is a member of the tumor necrosis factor (TNF)-receptor superfamily that is expressed in cancer cells. Binding of TNF-related apoptosis-inducing ligand (TRAIL) to DR5 is a potent trigger of the extrinsic apoptotic pathway, and numerous clinical trials are based on DR5-targeted therapies for cancer, including PDA. Human antigen R (HuR), an RNA-binding protein, regulates a select number of transcripts under stress conditions. Here we report that HuR translocates from the nucleus to the cytoplasm of PDA cells upon treatment with a DR5 agonist. High doses of DR5 agonist induce cleavage of both HuR and caspase 8. HuR binds to DR5 mRNA at the 5'-untranslated region (UTR) in PDA cells in response to different cancer-associated stressors and subsequently represses DR5 protein expression; silencing HuR augments DR5 protein production by enabling its translation and thus enhances apoptosis. In PDA specimens (n = 53), negative HuR cytoplasmic expression correlated with elevated DR5 expression (odds ratio 16.1, p < 0.0001). Together, these data demonstrate a feedback mechanism elicited by HuR-mediated repression of the key apoptotic membrane protein DR5.
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Affiliation(s)
- Danielle M Pineda
- Department of Surgery, Division of Surgical Research, Jefferson Medical College, Thomas Jefferson University, Philadelphia, PA, USA
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179
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Posttranscriptional regulation of connexin-43 expression. Arch Biochem Biophys 2012; 524:23-9. [DOI: 10.1016/j.abb.2012.03.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 03/10/2012] [Accepted: 03/12/2012] [Indexed: 12/26/2022]
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180
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Lai X, Schmitz U, Gupta SK, Bhattacharya A, Kunz M, Wolkenhauer O, Vera J. Computational analysis of target hub gene repression regulated by multiple and cooperative miRNAs. Nucleic Acids Res 2012; 40:8818-34. [PMID: 22798498 PMCID: PMC3467055 DOI: 10.1093/nar/gks657] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
MicroRNA (miRNA) target hubs are genes that can be simultaneously targeted by a comparatively large number of miRNAs, a class of non-coding RNAs that mediate post-transcriptional gene repression. Although the details of target hub regulation remain poorly understood, recent experiments suggest that pairs of miRNAs can cooperate if their binding sites reside in close proximity. To test this and other hypotheses, we established a novel approach to investigate mechanisms of collective miRNA repression. The approach presented here combines miRNA target prediction and transcription factor prediction with data from the literature and databases to generate a regulatory map for a chosen target hub. We then show how a kinetic model can be derived from the regulatory map. To validate our approach, we present a case study for p21, one of the first experimentally proved miRNA target hubs. Our analysis indicates that distinctive expression patterns for miRNAs, some of which interact cooperatively, fine-tune the features of transient and long-term regulation of target genes. With respect to p21, our model successfully predicts its protein levels for nine different cellular functions. In addition, we find that high abundance of miRNAs, in combination with cooperativity, can enhance noise buffering for the transcription of target hubs.
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Affiliation(s)
- Xin Lai
- Department of Systems Biology and Bioinformatics, University of Rostock, 18051 Rostock, Germany
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181
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Al-Haj L, Blackshear PJ, Khabar KSA. Regulation of p21/CIP1/WAF-1 mediated cell-cycle arrest by RNase L and tristetraprolin, and involvement of AU-rich elements. Nucleic Acids Res 2012; 40:7739-52. [PMID: 22718976 PMCID: PMC3439922 DOI: 10.1093/nar/gks545] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The p21Cip1/WAF1 plays an important role in cell-cycle arrest. Here, we find that RNase L regulates p21-mediated G1 growth arrest in AU-rich elements-dependent manner. We found a significant loss of p21 mRNA expression in RNASEL−/− MEFs and that the overexpression of RNase L in HeLa cells induces p21 mRNA expression. The p21 mRNA half-life significantly changes as a result of RNase L modulation, indicating a post-transcriptional effect. Indeed, we found that RNase L promotes tristetraprolin (TTP/ZFP36) mRNA decay. This activity was not seen with dimerization- and nuclease-deficient RNase L mutants. Deficiency in TTP led to increases in p21 mRNA and protein. With induced ablation of RNase L, TTP mRNA and protein expressions were higher, while p21 expression became reduced. We further establish that TTP, but not C124R TTP mutant, binds to, and accelerates the decay of p21 mRNA. The p21 mRNA half-life was prolonged in TTP−/− MEFs. The TTP regulation of p21 mRNA decay required functional AU-rich elements. Thus, we demonstrate a novel mechanism of regulating G1 growth arrest by an RNase L-TTP-p21 axis.
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Affiliation(s)
- Latifa Al-Haj
- Program in BioMolecular Research, King Faisal Specialist Hospital and Research Centre, Riyadh 11211, Saudi Arabia
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182
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The H19 lincRNA is a developmental reservoir of miR-675 that suppresses growth and Igf1r. Nat Cell Biol 2012; 14:659-65. [PMID: 22684254 PMCID: PMC3389517 DOI: 10.1038/ncb2521] [Citation(s) in RCA: 640] [Impact Index Per Article: 53.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2011] [Accepted: 05/10/2012] [Indexed: 12/15/2022]
Abstract
The H19 large intergenic noncoding RNA (lincRNA) is one of the most highly abundant and conserved transcripts in mammalian development, being expressed in both embryonic and extraembryonic cell lineages, yet its physiological function is unknown. Here we show that miR-675, a microRNA (miRNA) embedded within H19’s first exon, is expressed exclusively in the placenta from the gestational time point when placental growth normally ceases, and placentas that lack H19 continue to grow. Overexpression of miR-675 in a range of embryonic and extraembryonic cell lines results in their reduced proliferation; targets of the miRNA are upregulated in the H19 null placenta, including the growth promoting Insulin-like growth factor 1 receptor (Igf1r). Moreover, the excision of miR-675 from H19 is dynamically regulated by the stress response RNA binding protein HuR. These results suggest that H19’s main physiological role is in limiting growth of the placenta prior to birth, by regulated processing of miR-675. The controlled release of miR-675 from H19 may also allow rapid inhibition of cell proliferation in response to cellular stress or oncogenic signals.
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183
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Ibrahem MD, Khairy HM, Ibrahim MA. Laboratory exposure of Oreochromis niloticus to crude microcystins (containing microcystin-LR) extracted from Egyptian locally isolated strain (Microcystis aeruginosa Kützing): biological and biochemical studies. FISH PHYSIOLOGY AND BIOCHEMISTRY 2012; 38:899-908. [PMID: 22095249 DOI: 10.1007/s10695-011-9577-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 11/08/2011] [Indexed: 05/31/2023]
Abstract
Cyanobacterial blooms exert negative impacts on fisheries and water management authorities. Recently, it has gained global attention, as elevated earth warming and environmental pollution are accelerating algal growth. Oreochromis niloticus (O. niloticus) is a worldwide and the most commonly cultured fish in Egypt. The biological interaction of the living organisms to the surrounding environment must continuously be assessed to predict future effects of the ongoing hazards on fish. The study was designed to examine the possible biological and biochemical response of O. niloticus exposed to different concentrations of microcystins crude extract (containing microcystin-LR). Three equal groups of O. niloticus were assigned for intraperitoneal injection of three different doses: 100, 200, and 400 μg m(-1) dried aqueous microcystins extract, for 10 days. Clinical, condition factor (K) and hepatosomatic index (HIS) were estimated. Biochemical alterations were evaluated via lipid peroxidation, DNA fragmentation assay and electrophoretic analysis of fragmented DNA using agarose gel electrophoresis. The results showed that there were discernible behavioral and clinical alterations. Significant differences in K and HIS were observed between treatments. Also, significant elevations were observed in lipid peroxidation level and in the DNA fragmentation percentage in the exposed fish to the doses of 200 and 400 μg m(-1) of microcystins crude extract. The current study addresses the possible toxic effects of microcystins crude extract to O. niloticus. The results cleared that microcystins crude extract (containing MC-LR) is toxic to O. niloticus in time- and dose-dependent manners.
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Affiliation(s)
- Mai D Ibrahem
- Department of Fish Diseases and Management, Faculty of Veterinary Medicine, Cairo University, Giza, Egypt.
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184
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Matoulkova E, Michalova E, Vojtesek B, Hrstka R. The role of the 3' untranslated region in post-transcriptional regulation of protein expression in mammalian cells. RNA Biol 2012; 9:563-76. [PMID: 22614827 DOI: 10.4161/rna.20231] [Citation(s) in RCA: 253] [Impact Index Per Article: 21.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The untranslated regions (UTRs) at the 3'end of mRNA transcripts contain important sequences that influence the fate of mRNA and thus proteosynthesis. In this review, we summarize the information known to date about 3'end processing, sequence characteristics including related binding proteins and the role of 3'UTRs in several selected signaling pathways to delineate their importance in the regulatory processes in mammalian cells. In addition to reviewing recent advances in the more well known aspects, such as cleavage and polyadenylation processes that influence mRNA stability and location, we concentrate on some newly emerging concepts of the role of the 3'UTR, including alternative polyadenylation sites in relation to proliferation and differentiation and the recognition of the multi-functional properties of non-coding RNAs, including miRNAs that commonly target the 3'UTR. The emerging picture is of a highly complex set of regulatory systems that include autoregulation, cooperativity and competition to fine tune proteosynthesis in context-dependent manners.
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185
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Yi X, Hong M, Gui B, Chen Z, Li L, Xie G, Liang J, Wang X, Shang Y. RNA processing and modification protein, carbon catabolite repression 4 (Ccr4), arrests the cell cycle through p21-dependent and p53-independent pathway. J Biol Chem 2012; 287:21045-57. [PMID: 22547059 DOI: 10.1074/jbc.m112.355321] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Ccr4d is a new member of the Ccr4 (carbon catabolite repression 4) family of proteins that are implicated in the regulation of mRNA stability and translation through mRNA deadenylation. However, Ccr4d is not believed to be involved in mRNA deadenylation. Thus, its biological function and mechanistic activity remain to be determined. Here, we report that Ccr4d is broadly expressed in various normal tissues, and the expression of Ccr4d is markedly down-regulated during cell cycle progression. We showed that Ccr4d inhibits cell proliferation and induces cell cycle arrest at G(1) phase. Our experiments further revealed that Ccr4d regulates the expression of p21 in a p53-independent manner. Mechanistic studies indicated that Ccr4d strongly bound to the 3'-UTR of p21 mRNA, leading to the stabilization of p21 mRNA. Interestingly, we found that the expression of Ccr4d is down-regulated in various tumor tissues. Collectively, our data indicate that Ccr4d functions as an anti-proliferating protein through the induction of cell cycle arrest via a p21-dependent and p53-independent pathway and suggest that Ccr4d might have an important role in carcinogenesis.
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Affiliation(s)
- Xia Yi
- Key Laboratory of Carcinogenesis and Translational Research, Ministry of Education, Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Beijing 100191, China
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186
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Downregulation of HuR as a new mechanism of doxorubicin resistance in breast cancer cells. Mol Cancer 2012; 11:13. [PMID: 22436134 PMCID: PMC3325864 DOI: 10.1186/1476-4598-11-13] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 03/21/2012] [Indexed: 11/10/2022] Open
Abstract
Background HuR, an RNA binding protein involved in the post-transcriptional regulation of a wide spectrum of mRNAs, has been demonstrated to be a determinant of carcinogenesis and tumor aggressiveness in several cancer types. In this study, we investigated the role of HuR in the apoptosis and in the chemoresistance induced by the widely used anticancer drug doxorubicin in human breast cancer cells (MCF-7). Results We showed that HuR acts in the early phase of cell response to doxorubicin, being induced to translocate into the cytoplasm upon phosphorylation. Reducing HuR levels diminished the apoptotic response to doxorubicin. Doxorubicin-induced apoptosis was also correlated with the presence of HuR in the cytoplasm. Rottlerin, which was able to block HuR nuclear export, had correspondingly antagonistic effects with doxorubicin on cell toxicity. The proapoptotic activity of HuR was not due to cleavage to an active form, as was previously reported. In in vitro selected doxorubicin resistant MCF-7 cells (MCF-7/doxoR) overexpressing the multidrug resistance (MDR) related ABCG2 transporter, we observed a significant HuR downregulation that was paralleled by a corresponding downregulation of HuR targets and by loss of rottlerin toxicity. Restoration of HuR expression in these cells resensitized MCF-7/doxoR cells to doxorubicin, reactivating the apoptotic response. Conclusions The present study shows that HuR is necessary to elicit the apoptotic cell response to doxorubicin and that restoration of HuR expression in resistant cells resensitizes them to the action of this drug, thereby identifying HuR as a key protein in doxorubicin pharmacology.
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187
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Cho SJ, Jung YS, Zhang J, Chen X. The RNA-binding protein RNPC1 stabilizes the mRNA encoding the RNA-binding protein HuR and cooperates with HuR to suppress cell proliferation. J Biol Chem 2012; 287:14535-44. [PMID: 22371495 DOI: 10.1074/jbc.m111.326827] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The RNA-binding protein HuR, a member of the embryonic lethal abnormal vision/Hu protein family, plays a critical role in many cellular processes, including cell proliferation, angiogenesis, and inflammatory response. Despite significant progresses in understanding how HuR functions, the mechanism by which HuR expression is controlled is still poorly understood. Here, we showed that RNA-binding protein RNPC1 post-transcriptionally regulates HuR expression via mRNA stability. Specifically, we showed that overexpression of RNPC1 increases, whereas knockdown or knock-out of RNPC1 decreases, the level of HuR transcript and protein. Moreover, we showed that RNPC1, but not mutant RNPC1 deficient in RNA binding, stabilizes HuR transcript via binding to its 3'-untranslated region. Furthermore, to determine the biological significance of RNPC1-enhanced HuR expression, we showed that HuR, by repressing c-Myc expression, facilitates RNPC1-mediated growth suppression. Together, we have uncovered a novel mechanism by which HuR is regulated by RNPC1 via mRNA stability and HuR is a mediator of RNPC1-induced growth suppression.
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Affiliation(s)
- Seong-Jun Cho
- Center for Comparative Oncology, University of California, Davis, California 95616, USA
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188
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Paukku K, Backlund M, De Boer RA, Kalkkinen N, Kontula KK, Lehtonen JYA. Regulation of AT1R expression through HuR by insulin. Nucleic Acids Res 2012; 40:5250-61. [PMID: 22362742 PMCID: PMC3384301 DOI: 10.1093/nar/gks170] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Angiotensin II type 1 receptor (AT1R) has a pathophysiological role in hypertension, atherosclerosis and heart failure. Type 2 diabetes is hyperinsulinemic state and a major risk factor for atherosclerosis and hypertension. It is known that hyperinsulinemia upregulates AT1R expression post-transcriptionally by increasing the half-life of AT1R mRNA, but little is known about the mechanism of this effect. In the present study, we first identified AT1R 3′-UTR as a mediator of insulin effect. Using 3′-UTR as a bait, we identified through analysis of insulin-stimulated cell lysates by affinity purification and mass spectrometry HuR as an insulin-regulated AT1R mRNA binding protein. By ribonucleoprotein immunoprecipitation, we found HuR binding to AT1R to be increased by insulin. Overexpression of HuR leads to increased AT1R expression in a 3′-UTR-dependent manner. Both insulin and HuR overexpression stabilize AT1R 3′-UTR and their responsive element within 3′-UTR are located within the same region. Cell fractionation demonstrated that insulin induced HuR translocation from nucleus to cytoplasm increased HuR binding to cytoplasmic AT1R 3′-UTR. Consistent with HuR translocation playing a mechanistic role in HuR effect, a reduction in the cytoplasmic levels of HuR either by silencing of HuR expression or by inhibition of HuR translocation into cytoplasm attenuated insulin response. These results show that HuR translocation to cytoplasm is enhanced by insulin leading to AT1R upregulation through HuR-mediated stabilization of AT1R mRNA.
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Affiliation(s)
- Kirsi Paukku
- Research Program for Molecular Medicine, Biomedicum Helsinki, FIN-00014 University of Helsinki, Finland
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189
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Sullivan KD, Gallant-Behm CL, Henry RE, Fraikin JL, Espinosa JM. The p53 circuit board. Biochim Biophys Acta Rev Cancer 2012; 1825:229-44. [PMID: 22333261 DOI: 10.1016/j.bbcan.2012.01.004] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Revised: 01/27/2012] [Accepted: 01/28/2012] [Indexed: 12/17/2022]
Abstract
The p53 tumor suppressor is embedded in a large gene network controlling diverse cellular and organismal phenotypes. Multiple signaling pathways converge onto p53 activation, mostly by relieving the inhibitory effects of its repressors, MDM2 and MDM4. In turn, signals originating from increased p53 activity diverge into distinct effector pathways to deliver a specific cellular response to the activating stimuli. Much attention has been devoted to dissecting how the various input pathways trigger p53 activation and how the activity of the p53 protein itself can be modulated by a plethora of co-factors and post-translational modifications. In this review we will focus instead on the multiple configurations of the effector pathways. We will discuss how p53-generated signals are transmitted, amplified, resisted and eventually integrated by downstream gene circuits operating at the transcriptional, post-transcriptional and post-translational levels. We will also discuss how context-dependent variations in these gene circuits define the cellular response to p53 activation and how they may impact the clinical efficacy of p53-based targeted therapies.
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Affiliation(s)
- Kelly D Sullivan
- Howard Hughes Medical Institute & Department of Molecular, Cellular and Developmental Biology, The University of Colorado at Boulder, Boulder, CO 80309-0347, USA
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190
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He Y, Zhang X, Zeng X, Huang Y, Wei JA, Han L, Li CX, Zhang GW. HuR-mediated posttranscriptional regulation of p21 is involved in the effect of Glycyrrhiza uralensis licorice aqueous extract on polyamine-depleted intestinal crypt cells proliferation. J Nutr Biochem 2012; 23:1285-93. [PMID: 22217517 DOI: 10.1016/j.jnutbio.2011.07.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Revised: 05/17/2011] [Accepted: 07/26/2011] [Indexed: 01/06/2023]
Abstract
Glycyrrhiza uralensis licorice has long been used worldwide as a food additive and herbal medicine. It possesses a remarkable healing action on gastrointestinal ulcers. The present study was carried out to assess the effect of licorice on intestinal crypt cell proliferation and to investigate the corresponding molecular mechanism. Considering the role of crypt stem cells in intestinal mucosa repair, a well-established cytostatic cellular model, polyamine-depleted IEC-6 cells, was utilized to evaluate the effect of aqueous licorice on the proliferation of intestinal crypt cells. The growth inhibition of IEC-6 cells caused by alpha-difluoromethylornithine could be significantly reversed by concomitant treatment with 40 μg/ml and 80 μg/ml licorice aqueous extract. In particular, the restoration of cell cycle progression was accompanied by a decrease in p21 mRNA level and cytoplasmic accumulation of the RNA-binding protein HuR, which was shown to be involved in the destabilization of p21 mRNA. Using a biotin pull-down assay and a luciferase assay, it was found that licorice-modulated p21 mRNA expression was achieved by HuR-targeted AU-rich and U-rich elements that resided in the 3' untranslated region of p21 mRNA. These results demonstrate that licorice can exert its action on stimulating the growth of intestinal crypt cells by regulating p21 mRNA level at the posttranscriptional level by HuR.
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Affiliation(s)
- Yi He
- Central Laboratory of the Second Affiliated Hospital, Guangzhou University of Chinese Medicine, Guangzhou 510120, P.R. China
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191
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Morandell S, Yaffe MB. Exploiting synthetic lethal interactions between DNA damage signaling, checkpoint control, and p53 for targeted cancer therapy. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2012; 110:289-314. [PMID: 22749150 DOI: 10.1016/b978-0-12-387665-2.00011-0] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
DNA damage signaling and checkpoint control pathways are among the most commonly mutated networks in human tumors. Emerging data suggest that synthetic lethal interactions between mutated oncogenes or tumor suppressor genes with molecules involved in the DNA damage response and DNA repair pathways can be therapeutically exploited to preferentially kill cancer cells. In this review, we discuss the concept of synthetic lethality with a focus on p53, a commonly lost tumor suppressor gene, in the context of DNA damage signaling. We describe several recent examples in which this concept was successfully applied to target tumor cells in culture or in mouse models, as well as in human cancer patients.
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Affiliation(s)
- Sandra Morandell
- Department of Biology, David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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192
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Gomez-Santos L, Vazquez-Chantada M, Mato JM, Martinez-Chantar ML. SAMe and HuR in liver physiology: usefulness of stem cells in hepatic differentiation research. Methods Mol Biol 2012; 826:133-49. [PMID: 22167646 DOI: 10.1007/978-1-61779-468-1_12] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
S-Adenosylmethionine, abbreviated as SAM, SAMe or AdoMet, is the principal methyl group donor in the mammalian cell and the first step metabolite of the methionine cycle, being synthesized by MAT (methionine adenosyltransferase) from methionine and ATP. About 60 years after its identification, SAMe is admitted as a key hepatic regulator whose level needs to be maintained within a specific range in order to avoid liver damage. Recently, in vitro and in vivo studies have demonstrated the regulatory role of SAMe in HGF (hepatocyte growth factor)-mediated hepatocyte proliferation through a mechanism that implicates the activation of the non-canonical LKB1/AMPK/eNOS cascade and HuR function. Regarding hepatic differentiation, cellular SAMe content varies depending on the status of the cell, being lower in immature than in adult hepatocytes. This finding suggests a SAMe regulatory effect also in this cellular process, which very recently was reported and related to HuR activity. Although in the last years this and other discoveries contributed to throw light into the tangle of regulatory mechanisms that govern this complex process, an overall understanding is still a challenge. For this purpose, the in vitro hepatic differentiation culture systems by using stem cells or fetal hepatoblasts are considered as valuable tools which, in combination with the methods used in current days to elucidate cell signaling pathways, surely will help to clear up this question.
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Affiliation(s)
- Laura Gomez-Santos
- Metabolomics Unit, CIC bioGUNE, Technology Park of Bizkaia, Bizkaia, Basque Country, Spain.
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193
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MicroRNAs as a novel cellular senescence regulator. Ageing Res Rev 2012; 11:41-50. [PMID: 21689787 DOI: 10.1016/j.arr.2011.06.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 05/09/2011] [Accepted: 06/02/2011] [Indexed: 12/26/2022]
Abstract
Cellular senescence is a program activated in normal cells in response to various types of stresses and is manifested by permanent arrest of cell cycle. Cellular senescence is closely related to tumor suppression, and may contribute to the ageing of organisms. The complex senescence cell phenotype has many different mechanisms. Recent studies have provided important insights regarding the role played by miRNAs during cellular senescence as a novel molecular mechanism. In this article, we will review the latest advances in the identification and validation of senescence-regulatory miRNAs and the possible mechanisms.
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194
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Abstract
The cytoplasmic events that control mammalian gene expression, primarily mRNA stability and translation, potently influence the cellular response to internal and external signals. The ubiquitous RNA-binding protein (RBP) HuR is one of the best-studied regulators of cytoplasmic mRNA fate. Through its post-transcriptional influence on specific target mRNAs, HuR can alter the cellular response to proliferative, stress, apoptotic, differentiation, senescence, inflammatory and immune stimuli. In light of its central role in important cellular functions, HuR's role in diseases in which these responses are aberrant is increasingly appreciated. Here, we review the mechanisms that control HuR function, its influence on target mRNAs, and how impairment in HuR-governed gene expression programs impact upon different disease processes. We focus on HuR's well-recognized implication in cancer and chronic inflammation, and discuss emerging studies linking HuR to cardiovascular, neurological, and muscular pathologies. We also discuss the progress, potential, and challenges of targeting HuR therapeutically.
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Affiliation(s)
- Subramanya Srikantan
- Laboratory of Molecular Biology and Immunology, NIA-IRP, NIH, Baltimore, MD 21224, USA
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195
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Nitric oxide-sensitive guanylyl cyclase is differentially regulated by nuclear and non-nuclear estrogen pathways in anterior pituitary gland. PLoS One 2011; 6:e29402. [PMID: 22216273 PMCID: PMC3247256 DOI: 10.1371/journal.pone.0029402] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Accepted: 11/28/2011] [Indexed: 11/19/2022] Open
Abstract
17β-estradiol (E2) regulates hormonal release as well as proliferation and cell death in the pituitary. The main nitric oxide receptor, nitric oxide sensitive- or soluble guanylyl cyclase (sGC), is a heterodimer composed of two subunits, α and β, that catalyses cGMP formation. α1β1 is the most abundant and widely expressed heterodimer, showing the greater activity. Previously we have shown that E2 decreased sGC activity but exerts opposite effects on sGC subunits increasing α1 and decreasing β1 mRNA and protein levels. In the present work we investigate the mechanisms by which E2 differentially regulates sGC subunits' expression on rat anterior pituitary gland. Experiments were performed on primary cultures of anterior pituitary cells from adult female Wistar rats at random stages of estrous cycle. After 6 h of E2 treatment, α1 mRNA and protein expression is increased while β1 levels are down-regulated. E2 effects on sGC expression are partially dependent on de novo transcription while de novo translation is fully required. E2 treatment decreased HuR mRNA stabilization factor and increased AUF1 p37 mRNA destabilization factor. E2-elicited β1 mRNA decrease correlates with a mRNA destabilization environment in the anterior pituitary gland. On the other hand, after 6 h of treatment, E2-BSA (1 nM) and E2-dendrimer conjugate (EDC, 1 nM) were unable to modify α1 or β1 mRNA levels, showing that nuclear receptor is involved in E2 actions. However, at earlier times (3 h), 1 nM EDC causes a transient decrease of α1 in a PI3k-dependent fashion. Our results show for the first time that E2 is able to exert opposite actions in the anterior pituitary gland, depending on the activation of classical or non-classical pathways. Thus, E2 can also modify sGC expression through membrane-initiated signals bringing to light a new point of regulation in NO/sGC pathway.
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196
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Melanson BD, Bose R, Hamill JD, Marcellus KA, Pan EF, McKay BC. The role of mRNA decay in p53-induced gene expression. RNA (NEW YORK, N.Y.) 2011; 17:2222-2234. [PMID: 22020975 PMCID: PMC3222134 DOI: 10.1261/rna.030122.111] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2011] [Accepted: 09/13/2011] [Indexed: 05/31/2023]
Abstract
The p53 tumor suppressor is a DNA-damage-responsive sequence-specific transcriptional activator. The sustained activation of the p53 response is incompatible with cell growth and viability. To circumvent this issue, a variety of negative feedback loops exist to limit the duration of p53 activation. Despite our understanding of p53 regulation, very little is known about the effect of transient p53 activation on the long-term expression of p53 target genes. Here we used a temperature-sensitive variant of p53 and oligonucleotide microarrays to monitor gene expression during and following reversible p53 activation. The expression of most p53-induced transcripts was rapidly reversible, consistent with active mRNA decay. Representative 3' UTRs derived from short-lived transcripts (i.e., DDB2 and GDF15) conferred instability on a heterologous mRNA, while 3' UTRs derived from more stable transcripts (i.e., CRYAB and TP53I3) did not. The 3' UTRs derived from unstable p53-induced mRNAs were significantly longer than those derived from stable mRNAs. These 3' UTRs had high uridine and low cytosine content, leading to a higher density of U-, AU-, and GU-rich sequences. Remarkably, short-lived p53 targets were induced faster, reaching maximum transcript levels earlier than the stable p53 targets. Taken together, the evidence indicates that the p53 transcriptional response has evolved with primarily short-lived target mRNAs and that post-transcription processes play a prominent role in the p53 response.
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Affiliation(s)
- Brian D. Melanson
- Cancer Therapeutics Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada K1H 8L6
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5
| | - Reetesh Bose
- Cancer Therapeutics Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada K1H 8L6
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5
| | - Jeff D. Hamill
- Cancer Therapeutics Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada K1H 8L6
| | - Kristen A. Marcellus
- Cancer Therapeutics Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada K1H 8L6
| | - Elysia F. Pan
- Cancer Therapeutics Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada K1H 8L6
| | - Bruce C. McKay
- Cancer Therapeutics Program, Ottawa Hospital Research Institute, Ottawa, Ontario, Canada K1H 8L6
- Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5
- Department of Medicine, Ottawa Hospital, Ottawa, Ontario, Canada K1H 8L6
- Department of Radiology, Ottawa Hospital, Ottawa, Ontario, Canada K1H 8L6
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197
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Al-Alwan M, Olabi S, Ghebeh H, Barhoush E, Tulbah A, Al-Tweigeri T, Ajarim D, Adra C. Fascin is a key regulator of breast cancer invasion that acts via the modification of metastasis-associated molecules. PLoS One 2011; 6:e27339. [PMID: 22076152 PMCID: PMC3208623 DOI: 10.1371/journal.pone.0027339] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Accepted: 10/13/2011] [Indexed: 12/21/2022] Open
Abstract
The actin-bundling protein, fascin, is a member of the cytoskeletal protein family that has restricted expression in specialized normal cells. However, many studies have reported the induction of this protein in various transformed cells including breast cancer cells. While the role of fascin in the regulation of breast cancer cell migration has been previously shown, the underlying molecular mechanism remained poorly defined. We have used variety of immunological and functional assays to study whether fascin regulates breast cancer metastasis-associated molecules. In this report we found a direct relationship between fascin expression in breast cancer patients and; metastasis and shorter disease-free survival. Most importantly, in vitro interference with fascin expression by loss or gain of function demonstrates a central role for this protein in regulating the cell morphology, migration and invasion potential. Our results show that fascin regulation of invasion is mediated via modulating several metastasis-associated genes. We show for the first time that fascin down-regulates the expression and nuclear translocation of a key metastasis suppressor protein known as breast cancer metastasis suppressor-1 (BRMS1). In addition, fascin up-regulates NF-kappa B activity, which is essential for metastasis. Importantly, fascin up-regulates other proteins that are known to be critical for the execution of metastasis such as urokinase-type plasminogen activator (uPA) and the matrix metalloproteases (MMP)-2 and MMP-9. This study demonstrates that fascin expression in breast cancer cells establishes a gene expression profile consistent with metastatic tumors and offers a potential therapeutic intervention in metastatic breast cancer treatment through fascin targeting.
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Affiliation(s)
- Monther Al-Alwan
- Stem Cell Therapy Program, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.
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198
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Al-Khalaf HH, Hendrayani SF, Aboussekhra A. ATR controls the p21(WAF1/Cip1) protein up-regulation and apoptosis in response to low UV fluences. Mol Carcinog 2011; 51:930-8. [PMID: 21976111 DOI: 10.1002/mc.20864] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2011] [Revised: 09/06/2011] [Accepted: 09/09/2011] [Indexed: 11/09/2022]
Abstract
The universal cyclin-dependent kinase inhibitor p21(WAF1/Cip1) promotes cell cycle arrest and inhibits apoptosis in response to UV-induced DNA damage. Since the protein kinase ATR plays a major role in the cellular response to these carcinogenic lesions, we investigated the possible role of ATR in the modulation of p21(WAF1/Cip1) expression in response to UVC radiation. We have shown that p21(WAF1/Cip1) is up-regulated in human fibroblast and epithelial cells, but only in response to low UV fluences and low passage cells. Importantly, this up-regulation is ATR-dependent. In fact, in ATR-deficient or caffeine-treated cells UV light rather down-regulated the p21(WAF1/Cip1) protein through SKP2-dependent ubiquitination and degradation via the proteasomal pathway. Furthermore, we present evidence that ATR inhibits apoptosis in response to low fluences of UV light, through inhibiting the cleavage of caspase 3 and PARP as well as the repression of the proapoptotic proteins BAX and BAK. Interestingly, ATR is also required for the stability of the p21(WAF1/Cip1) protein in absence of genotoxic stress. Together, these results indicate that during the cellular response to low UVC fluences the ATR protein kinase up-regulates p21(WAF1/Cip1) and inhibits apoptosis. © 2011 Wiley Periodicals, Inc.
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Affiliation(s)
- Huda H Al-Khalaf
- King Faisal Specialist Hospital and Research Center, Department of Biological and Medical Research, Riyadh, KSA
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199
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Dai W, Zhang G, Makeyev EV. RNA-binding protein HuR autoregulates its expression by promoting alternative polyadenylation site usage. Nucleic Acids Res 2011; 40:787-800. [PMID: 21948791 PMCID: PMC3258158 DOI: 10.1093/nar/gkr783] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
RNA-binding protein HuR modulates the stability and translational efficiency of messenger RNAs (mRNAs) encoding essential components of the cellular proliferation, growth and survival pathways. Consistent with these functions, HuR levels are often elevated in cancer cells and reduced in senescent and quiescent cells. However, the molecular mechanisms that control HuR expression are poorly understood. Here we show that HuR protein autoregulates its abundance through a negative feedback loop that involves interaction of the nuclear HuR protein with a GU-rich element (GRE) overlapping with the HuR major polyadenylation signal (PAS2). An increase in the cellular HuR protein levels stimulates the expression of long HuR mRNA species containing an AU-rich element (ARE) that destabilizes the mRNAs and thus reduces the protein production output. The PAS2 read-through occurs due to a reduced recruitment of the CstF-64 subunit of the pre-mRNA cleavage stimulation factor in the presence of the GRE-bound HuR. We propose that this mechanism maintains HuR homeostasis in proliferating cells. Since only the nuclear HuR is expected to contribute to the auto-regulation, our model may explain the longstanding observation that the increase in the total HuR expression in cancer cells often correlates with the accumulation of its substantial fraction in the cytoplasm.
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Affiliation(s)
- Weijun Dai
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, SBS-02n-45, Singapore, 637551, Singapore
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van Kouwenhove M, Kedde M, Agami R. MicroRNA regulation by RNA-binding proteins and its implications for cancer. Nat Rev Cancer 2011; 11:644-56. [PMID: 21822212 DOI: 10.1038/nrc3107] [Citation(s) in RCA: 474] [Impact Index Per Article: 36.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Non-protein-coding transcripts have been conserved throughout evolution, indicating that crucial functions exist for these RNAs. For example, microRNAs (miRNAs) have been found to modulate most cellular processes. The protein classes of RNA-binding proteins include essential regulators of miRNA biogenesis, turnover and activity. RNA-RNA and protein-RNA interactions are essential for post-transcriptional regulation in normal development and may be deregulated in disease. In reviewing emerging concepts of the interplay between miRNAs and RNA-binding proteins, we highlight the implications of these complex layers of regulation in cancer initiation and progression.
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Affiliation(s)
- Marieke van Kouwenhove
- Division of Gene Regulation, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX, Amsterdam, The Netherlands
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