201
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MicroRNAs in neural cell development and brain diseases. SCIENCE CHINA-LIFE SCIENCES 2012; 54:1103-12. [DOI: 10.1007/s11427-011-4249-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Accepted: 09/22/2011] [Indexed: 01/31/2023]
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202
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Abstract
MicroRNAs (miRNAs) are a class of small noncoding RNAs of ~22nt in length which are involved in the regulation of gene expression at the posttranscriptional level by degrading their target mRNAs and/or inhibiting their translation. Expressed ubiquitously or in a tissue-specific manner, miRNAs are involved in the regulation of many biological processes such as cell proliferation, differentiation, apoptosis, and the maintenance of normal cellular physiology. Many miRNAs are expressed in embryonic, postnatal, and adult hearts. Aberrant expression or genetic deletion of miRNAs is associated with abnormal cardiac cell differentiation, disruption of heart development, and cardiac dysfunction. This chapter will summarize the history, biogenesis, and processing of miRNAs as well as their function in heart development, remodeling, and disease.
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Affiliation(s)
- Ramón A Espinoza-Lewis
- Cardiovascular Research Division, Department of Cardiology, Children’s Hospital Boston, Harvard Medical School, Boston, Massachusetts, USA
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203
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Lei XX, Xu J, Ma W, Qiao C, Newman MA, Hammond SM, Huang Y. Determinants of mRNA recognition and translation regulation by Lin28. Nucleic Acids Res 2011; 40:3574-84. [PMID: 22210884 PMCID: PMC3333870 DOI: 10.1093/nar/gkr1279] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Lin28 is critical for stem cell maintenance and is also associated with advanced human malignancies. Our recent genome-wide studies mark Lin28 as a master post-transcriptional regulator of a subset of messenger RNAs important for cell growth and metabolism. However, the molecular basis underpinning the selective mRNA target regulation is unclear. Here, we provide evidence that Lin28 recognizes a unique motif in multiple target mRNAs, characterized by a small but critical ‘A’ bulge flanked by two G:C base pairs embedded in a complex secondary structure. This motif mediates Lin28-dependent stimulation of translation. As Lin28 is also known to inhibit the biogenesis of a cohort of miRNAs including let-7, we propose that Lin28 binding to different RNA types (precursor miRNAs versus mRNAs) may facilitate recruitment of different co-factors, leading to distinct regulatory outcomes. Our findings uncover a putative yet unexpected motif that may constitute a mechanistic base for the multitude of functions regulated by Lin28 in both stem cells and cancer cells.
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Affiliation(s)
- Xin-Xiang Lei
- Department of Obstetrics, Gynecology and Reproductive Sciences, Yale Stem Cell Center, Yale University School of Medicine, New Haven, CT 06510, USA
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204
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Kim YJ, Park SJ, Choi EY, Kim S, Kwak HJ, Yoo BC, Yoo H, Lee SH, Kim D, Park JB, Kim JH. PTEN modulates miR-21 processing via RNA-regulatory protein RNH1. PLoS One 2011; 6:e28308. [PMID: 22162762 PMCID: PMC3230587 DOI: 10.1371/journal.pone.0028308] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2011] [Accepted: 11/05/2011] [Indexed: 01/01/2023] Open
Abstract
Aberrant miR-21 expression is closely associated with cell proliferation, anti-apoptosis, migration, invasion, and metastasis in various cancers. However, the regulatory mechanism of miR-21 biogenesis is largely unknown. Here, we demonstrated that the tumor suppressor PTEN negatively regulates the expression of oncogenic miR-21 at the post-transcriptional level. Moreover, our results suggest that PTEN plays such a role through the indirect interaction with the Drosha complex. To elucidate how PTEN regulates pri- to pre-miR-21 processing, we attempted to find PTEN-interacting proteins and identified an RNA-regulatory protein, RNH1. Using the sensor to monitor pri-miR-21 processing, we demonstrated that RNH1 is necessary and sufficient for pri-miR-21 processing. Moreover, our results propose that the nuclear localization of RNH1 is important for this function. Further analysis showed that RNH1 directly interacts with the Drosha complex and that PTEN blocks this interaction. Taken together, these results suggest that the PTEN-mediated miR-21 regulation is achieved by inhibiting the interaction between the Drosha complex and RNH1, revealing previously unidentified role of PTEN in the oncogenic miR-21 biogenesis.
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Affiliation(s)
- Youn-Jae Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Korea
- Specific Organs Cancer Branch, Research Institute, National Cancer Center, Ilsan, Korea
| | - Se-Jeong Park
- Carcinogenesis Branch, Research Institute, National Cancer Center, Ilsan, Korea
| | - Eun Young Choi
- Specific Organs Cancer Branch, Research Institute, National Cancer Center, Ilsan, Korea
| | - Sol Kim
- Carcinogenesis Branch, Research Institute, National Cancer Center, Ilsan, Korea
| | - Hee Jin Kwak
- Specific Organs Cancer Branch, Research Institute, National Cancer Center, Ilsan, Korea
| | - Byong Chul Yoo
- Colorectal Cancer Branch, Research Institute, National Cancer Center, Ilsan, Korea
| | - Heon Yoo
- Specific Organs Cancer Branch, Research Institute, National Cancer Center, Ilsan, Korea
| | - Seung-Hoon Lee
- Specific Organs Cancer Branch, Research Institute, National Cancer Center, Ilsan, Korea
| | - Daesoo Kim
- Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejeon, Korea
| | - Jong Bae Park
- Specific Organs Cancer Branch, Research Institute, National Cancer Center, Ilsan, Korea
- * E-mail: (JHK); (JBP)
| | - Jong Heon Kim
- Carcinogenesis Branch, Research Institute, National Cancer Center, Ilsan, Korea
- * E-mail: (JHK); (JBP)
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205
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Pilotte J, Dupont-Versteegden EE, Vanderklish PW. Widespread regulation of miRNA biogenesis at the Dicer step by the cold-inducible RNA-binding protein, RBM3. PLoS One 2011; 6:e28446. [PMID: 22145045 PMCID: PMC3228759 DOI: 10.1371/journal.pone.0028446] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Accepted: 11/08/2011] [Indexed: 12/31/2022] Open
Abstract
MicroRNAs (miRNAs) play critical roles in diverse cellular events through their effects on translation. Emerging data suggest that modulation of miRNA biogenesis at post-transcriptional steps by RNA-binding proteins is a key point of regulatory control over the expression of some miRNAs and the cellular processes they influence. However, the extent and conditions under which the miRNA pathway is amenable to regulation at posttranscriptional steps are poorly understood. Here we show that RBM3, a cold-inducible, developmentally regulated RNA-binding protein and putative protooncogene, is an essential regulator of miRNA biogenesis. Utilizing miRNA array, Northern blot, and PCR methods, we observed that over 60% of miRNAs detectable in a neuronal cell line were significantly downregulated by knockdown of RBM3. Conversely, for select miRNAs assayed by Northern blot, induction of RBM3 by overexpression or mild hypothermia increased their levels. Changes in miRNA expression were accompanied by changes in the levels of their ~70 nt precursors, whereas primary transcript levels were unaffected. Mechanistic studies revealed that knockdown of RBM3 does not reduce Dicer activity or impede transport of pre-miRNAs into the cytoplasm. Rather, we find that RBM3 binds directly to ~70 nt pre-miRNA intermediates and promotes / de-represses their ability as larger ribonucleoproteins (pre-miRNPs) to associate with active Dicer complexes. Our findings suggest that the processing of a majority of pre-miRNPs by Dicer is subject to an intrinsic inhibitory influence that is overcome by RBM3 expression. RBM3 may thus orchestrate changes in miRNA expression during hypothermia and other cellular stresses, and in the euthermic contexts of early development, differentiation, and oncogenesis where RBM3 expression is highly elevated. Additionally, our data suggest that temperature-dependent changes in miRNA expression mediated by RBM3 may contribute to the therapeutic effects of hypothermia, and are an important variable to consider in in vitro studies of translation-dependent cellular events.
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Affiliation(s)
- Julie Pilotte
- Department of Neurobiology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Esther E. Dupont-Versteegden
- Department of Rehabilitation Sciences, College of Health Sciences, University of Kentucky, Lexington, Kentucky, United States of America
| | - Peter W. Vanderklish
- Department of Neurobiology, The Scripps Research Institute, La Jolla, California, United States of America
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206
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Nam Y, Chen C, Gregory RI, Chou JJ, Sliz P. Molecular basis for interaction of let-7 microRNAs with Lin28. Cell 2011; 147:1080-91. [PMID: 22078496 DOI: 10.1016/j.cell.2011.10.020] [Citation(s) in RCA: 290] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Revised: 08/05/2011] [Accepted: 10/06/2011] [Indexed: 01/22/2023]
Abstract
MicroRNAs (miRNAs) are small noncoding RNA molecules that regulate gene expression. Among these, members of the let-7 miRNA family control many cell-fate determination genes to influence pluripotency, differentiation, and transformation. Lin28 is a specific, posttranscriptional inhibitor of let-7 biogenesis. We report crystal structures of mouse Lin28 in complex with sequences from let-7d, let-7-f1, and let-7 g precursors. The two folded domains of Lin28 recognize two distinct regions of the RNA and are sufficient for inhibition of let-7 in vivo. We also show by NMR spectroscopy that the linker connecting the two folded domains is flexible, accommodating Lin28 binding to diverse let-7 family members. Protein-RNA complex formation imposes specific conformations on both components that could affect downstream recognition by other processing factors. Our data provide a molecular explanation for Lin28 specificity and a model for how it regulates let-7.
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Affiliation(s)
- Yunsun Nam
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
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207
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Janas MM, Khaled M, Schubert S, Bernstein JG, Golan D, Veguilla RA, Fisher DE, Shomron N, Levy C, Novina CD. Feed-forward microprocessing and splicing activities at a microRNA-containing intron. PLoS Genet 2011; 7:e1002330. [PMID: 22028668 PMCID: PMC3197686 DOI: 10.1371/journal.pgen.1002330] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2011] [Accepted: 08/16/2011] [Indexed: 01/03/2023] Open
Abstract
The majority of mammalian microRNA (miRNA) genes reside within introns of protein-encoding and non-coding genes, yet the mechanisms coordinating primary transcript processing into both mature miRNA and spliced mRNA are poorly understood. Analysis of melanoma invasion suppressor miR-211 expressed from intron 6 of melastatin revealed that microprocessing of miR-211 promotes splicing of the exon 6–exon 7 junction of melastatin by a mechanism requiring the RNase III activity of Drosha. Additionally, mutations in the 5′ splice site (5′SS), but not in the 3′SS, branch point, or polypyrimidine tract of intron 6 reduced miR-211 biogenesis and Drosha recruitment to intron 6, indicating that 5′SS recognition by the spliceosome promotes microprocessing of miR-211. Globally, knockdown of U1 splicing factors reduced intronic miRNA expression. Our data demonstrate novel mutually-cooperative microprocessing and splicing activities at an intronic miRNA locus and suggest that the initiation of spliceosome assembly may promote microprocessing of intronic miRNAs. MicroRNA (miRNA) genes are transcribed as long primary RNAs containing local hairpins that are excised by the Microprocessor complex minimally composed of Drosha and DGCR8. Most mammalian miRNAs reside in introns of protein-encoding and non-coding genes, but it is unclear how microprocessing of an intronic miRNA and splicing at the host gene intron affect each other. We recently reported that in melanoma, a miRNA expressed from intron 6 of melastatin (miR-211) assumes the tumor suppressive function of its host gene. In our current work, we detected elevated melastatin exon 6–exon 7 junctions relative to other exon-exon junctions that lack intronic miRNAs, suggesting that microprocessing promotes splicing. We show that microprocessing of miR-211 precedes completion of splicing of the exon 6–exon 7 junctions and that Drosha's endonuclease activity is required to facilitate exon 6–exon 7 junction formation. Additionally, we found that the first step of spliceosome assembly, recognition of the 5′ splice site by the U1 snRNP complex, promotes microprocessing of miR-211 and other intronic but not intergenic miRNAs. Our findings reveal a mutually cooperative, physical, and functional coupling of intronic miRNA biogenesis and splicing at the host intron, and they suggest a global positive effect of spliceosome assembly on intronic miRNA microprocessing.
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Affiliation(s)
- Maja M. Janas
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, United States of America
- Broad Institute of Harvard and MIT, Cambridge, Massachusetts, United States of America
| | - Mehdi Khaled
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, United States of America
- Broad Institute of Harvard and MIT, Cambridge, Massachusetts, United States of America
- Cutaneous Biology Research Center, Harvard Medical School, Charlestown, Massachusetts, United States of America
| | - Steffen Schubert
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, United States of America
- Broad Institute of Harvard and MIT, Cambridge, Massachusetts, United States of America
| | - Jacob G. Bernstein
- MIT Media Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States of America
| | - David Golan
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Rosa A. Veguilla
- Cutaneous Biology Research Center, Harvard Medical School, Charlestown, Massachusetts, United States of America
| | - David E. Fisher
- Cutaneous Biology Research Center, Harvard Medical School, Charlestown, Massachusetts, United States of America
| | - Noam Shomron
- Department of Cell and Developmental Biology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Carmit Levy
- Department of Human Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- * E-mail: (CL); (CDN)
| | - Carl D. Novina
- Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, United States of America
- Broad Institute of Harvard and MIT, Cambridge, Massachusetts, United States of America
- * E-mail: (CL); (CDN)
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208
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Desjardins A, Yang A, Bouvette J, Omichinski JG, Legault P. Importance of the NCp7-like domain in the recognition of pre-let-7g by the pluripotency factor Lin28. Nucleic Acids Res 2011; 40:1767-77. [PMID: 22013165 PMCID: PMC3287177 DOI: 10.1093/nar/gkr808] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The pluripotency factor Lin28 is a highly conserved protein comprising a unique combination of RNA-binding motifs, an N-terminal cold-shock domain and a C-terminal region containing two retroviral-type CCHC zinc-binding domains. An important function of Lin28 is to inhibit the biogenesis of the let-7 family of microRNAs through a direct interaction with let-7 precursors. Here, we systematically characterize the determinants of the interaction between Lin28 and pre-let-7g by investigating the effect of protein and RNA mutations on in vitro binding. We determine that Lin28 binds with high affinity to the extended loop of pre-let-7g and that its C-terminal domain contributes predominantly to the affinity of this interaction. We uncover remarkable similarities between this C-terminal domain and the NCp7 protein of HIV-1, not only in terms of primary structure but also in their modes of RNA binding. This NCp7-like domain of Lin28 recognizes a G-rich bulge within pre-let-7g, which is adjacent to one of the Dicer cleavage sites. We hypothesize that the NCp7-like domain initiates RNA binding and partially unfolds the RNA. This partial unfolding would then enable multiple copies of Lin28 to bind the extended loop of pre-let-7g and protect the RNA from cleavage by the pre-microRNA processing enzyme Dicer.
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Affiliation(s)
- Alexandre Desjardins
- Département de Biochimie, Université de Montréal, CP 6128, Succursale Centre-Ville, Montréal, QC, Canada H3C 3J7
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209
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Briata P, Lin WJ, Giovarelli M, Pasero M, Chou CF, Trabucchi M, Rosenfeld MG, Chen CY, Gherzi R. PI3K/AKT signaling determines a dynamic switch between distinct KSRP functions favoring skeletal myogenesis. Cell Death Differ 2011; 19:478-87. [PMID: 21886180 DOI: 10.1038/cdd.2011.117] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Skeletal myogenesis is orchestrated by distinct regulatory signaling pathways, including PI3K/AKT, that ultimately control muscle gene expression. Recently discovered myogenic micro-RNAs (miRNAs) are deeply implicated in muscle biology. Processing of miRNAs from their primary transcripts is emerging as a major step in the control of miRNA levels and might be well suited to be regulated by extracellular signals. Here we report that the RNA binding protein KSRP is required for the correct processing of primary myogenic miRNAs upon PI3K/AKT activation in myoblasts C2C12 and in the course of injury-induced muscle regeneration, as revealed by Ksrp knock-out mice analysis. PI3K/AKT activation regulates in opposite ways two distinct KSRP functions inhibiting its ability to promote decay of myogenin mRNA and activating its ability to favor maturation of myogenic miRNAs. This dynamic regulatory switch eventually contributes to the activation of the myogenic program.
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Affiliation(s)
- P Briata
- Gene Expression Regulation Laboratory, Istituto Nazionale per la Ricerca sul Cancro, Largo R .Benzi 10, Genoa, Italy.
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210
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De Vito C, Riggi N, Suvà ML, Janiszewska M, Horlbeck J, Baumer K, Provero P, Stamenkovic I. Let-7a is a direct EWS-FLI-1 target implicated in Ewing's sarcoma development. PLoS One 2011; 6:e23592. [PMID: 21853155 PMCID: PMC3154507 DOI: 10.1371/journal.pone.0023592] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Accepted: 07/20/2011] [Indexed: 12/21/2022] Open
Abstract
Ewing's sarcoma family tumors (ESFT) are the second most common bone malignancy in children and young adults, characterized by unique chromosomal translocations that in 85% of cases lead to expression of the EWS-FLI-1 fusion protein. EWS-FLI-1 functions as an aberrant transcription factor that can both induce and suppress members of its target gene repertoire. We have recently demonstrated that EWS-FLI-1 can alter microRNA (miRNA) expression and that miRNA145 is a direct EWS-FLI-1 target whose suppression is implicated in ESFT development. Here, we use miRNA arrays to compare the global miRNA expression profile of human mesenchymal stem cells (MSC) and ESFT cell lines, and show that ESFT display a distinct miRNA signature that includes induction of the oncogenic miRNA 17–92 cluster and repression of the tumor suppressor let-7 family. We demonstrate that direct repression of let-7a by EWS-FLI-1 participates in the tumorigenic potential of ESFT cells in vivo. The mechanism whereby let-7a expression regulates ESFT growth is shown to be mediated by its target gene HMGA2, as let-7a overexpression and HMGA2 repression both block ESFT cell tumorigenicity. Consistent with these observations, systemic delivery of synthetic let-7a into ESFT-bearing mice restored its expression in tumor cells, decreased HMGA2 expression levels and resulted in ESFT growth inhibition in vivo. Our observations provide evidence that deregulation of let-7a target gene expression participates in ESFT development and identify let-7a as promising new therapeutic target for one of the most aggressive pediatric malignancies.
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Affiliation(s)
- Claudio De Vito
- Faculty of Biology and Medicine, Institute of Pathology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland
| | - Nicolo Riggi
- Faculty of Biology and Medicine, Institute of Pathology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland
| | - Mario-Luca Suvà
- Faculty of Biology and Medicine, Institute of Pathology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland
| | - Michalina Janiszewska
- Faculty of Biology and Medicine, Institute of Pathology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland
| | - Janine Horlbeck
- Faculty of Biology and Medicine, Institute of Pathology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland
| | - Karine Baumer
- Faculty of Biology and Medicine, Institute of Pathology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland
| | - Paolo Provero
- Department of Biochemistry, Molecular Biology and Biotechnology, University of Torino, Torino, Italy
| | - Ivan Stamenkovic
- Faculty of Biology and Medicine, Institute of Pathology, Centre Hospitalier Universitaire Vaudois, University of Lausanne, Lausanne, Switzerland
- * E-mail:
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211
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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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212
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Abstract
Enterovirus 71 (EV71) infections continue to remain an important public health problem around the world, especially in the Asia-Pacific region. There is a significant mortality rate following such infections, and there is neither any proven therapy nor a vaccine for EV71. This has spurred much fundamental research into the replication of the virus. In this review, we discuss recent work identifying host cell factors which regulate the synthesis of EV71 RNA and proteins. Three of these proteins, heterogeneous nuclear ribonucleoprotein A1 (hnRNP A1), far-upstream element-binding protein 2 (FBP2), and FBP1 are nuclear proteins which in EV71-infected cells are relocalized to the cytoplasm, and they influence EV71 internal ribosome entry site (IRES) activity. hnRNP A1 stimulates IRES activity but can be replaced by hnRNP A2. FBP2 is a negative regulatory factor with respect to EV71 IRES activity, whereas FBP1 has the opposite effect. Two other proteins, hnRNP K and reticulon 3, are required for the efficient synthesis of viral RNA. The cleavage stimulation factor 64K subunit (CstF-64) is a host protein that is involved in the 3' polyadenylation of cellular pre-mRNAs, and recent work suggests that in EV71-infected cells, it may be cleaved by the EV71 3C protease. Such a cleavage would impair the processing of pre-mRNA to mature mRNAs. Host cell proteins play an important role in the replication of EV71, but much work remains to be done in order to understand how they act.
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213
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Golan-Gerstl R, Cohen M, Shilo A, Suh SS, Bakàcs A, Coppola L, Karni R. Splicing factor hnRNP A2/B1 regulates tumor suppressor gene splicing and is an oncogenic driver in glioblastoma. Cancer Res 2011; 71:4464-72. [PMID: 21586613 DOI: 10.1158/0008-5472.can-10-4410] [Citation(s) in RCA: 183] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The process of alternative splicing is widely misregulated in cancer, but the contribution of splicing regulators to cancer development is largely unknown. In this study, we found that the splicing factor hnRNP A2/B1 is overexpressed in glioblastomas and is correlated with poor prognosis. Conversely, patients who harbor deletions of the HNRNPA2B1 gene show better prognosis than average. Knockdown of hnRNP A2/B1 in glioblastoma cells inhibited tumor formation in mice. In contrast, overexpression of hnRNP A2/B1 in immortal cells led to malignant transformation, suggesting that HNRNPA2B1 is a putative proto-oncogene. We then identified several tumor suppressors and oncogenes that are regulated by HNRNPA2B1, among them are c-FLIP, BIN1, and WWOX, and the proto-oncogene RON. Knockdown of RON inhibited hnRNP A2/B1 mediated transformation, which implied that RON is one of the mediators of HNRNPA2B1 oncogenic activity. Together, our results indicate that HNRNPA2B1 is a novel oncogene in glioblastoma and a potential new target for glioblastoma therapy.
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Affiliation(s)
- Regina Golan-Gerstl
- Department of Biochemistry and Molecular Biology, the Institute for Medical Research Israel-Canada, Hebrew University-Hadassah Medical School, Jerusalem, Israel
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214
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Grabowski P. Alternative splicing takes shape during neuronal development. Curr Opin Genet Dev 2011; 21:388-94. [PMID: 21511457 DOI: 10.1016/j.gde.2011.03.005] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Accepted: 03/23/2011] [Indexed: 11/28/2022]
Abstract
The spatial and temporal control of alternative splicing is a major mechanism used to generate proteomic diversity in the brain. Microarray and Next Generation Sequencing approaches reveal mechanistic insights about networks of tissue-specific RNA binding proteins and micro RNAs that coordinate suites of alternative splicing patterns during neuronal differentiation. In the context of large-scale changes, one alternative splicing switch during embryonic brain development is crucial for neuronal migration and the laminar organization of the cerebral cortex. A major challenge to understand alternative splicing at the systems level is now being approached by the design of integrative modeling approaches that predict the combinatorial control of brain-specific exons.
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Affiliation(s)
- Paula Grabowski
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA, USA
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215
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Kawahara H, Okada Y, Imai T, Iwanami A, Mischel PS, Okano H. Musashi1 cooperates in abnormal cell lineage protein 28 (Lin28)-mediated let-7 family microRNA biogenesis in early neural differentiation. J Biol Chem 2011; 286:16121-30. [PMID: 21378162 DOI: 10.1074/jbc.m110.199166] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Musashi1 (Msi1) is an RNA-binding protein that is highly expressed in neural stem/progenitor cells (NS/PCs) as well as in other tissue stem cells. Msi1 binds to the 3'-UTR of its target mRNAs in NS/PCs, prevents their translation, and interferes with NS/PC differentiation. We previously showed that Msi1 competes with eIF4G to bind poly(A)-binding protein and inhibits assembly of the 80 S ribosome. Here we show that Msi1 works in concert with Lin28 to regulate post-transcriptional microRNA (miRNA) biogenesis in the cropping step, which occurs in the nucleus. Lin28 and its binding partner terminal uridylyltransferase 4 (TUT4) are known to maintain embryonic stem cell pluripotency by blocking let-7 miRNA biogenesis at the dicing step. Interestingly, we found that during early neural differentiation of embryonic stem cells, Msi1 enhanced the localization of Lin28 to the nucleus and also inhibited the nuclear cropping step of another let-7 family miRNA, miR98. These results suggest that Msi1 can influence stem cell maintenance and differentiation by controlling the subcellular localization of proteins involved in miRNA biogenesis, as well as by regulating the translation of its target mRNA.
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Affiliation(s)
- Hironori Kawahara
- Department of Physiology, Keio University School of Medicine, Shinjuku, Tokyo, Japan
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216
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Van Wynsberghe PM, Kai ZS, Massirer KB, Burton VH, Yeo GW, Pasquinelli AE. LIN-28 co-transcriptionally binds primary let-7 to regulate miRNA maturation in Caenorhabditis elegans. Nat Struct Mol Biol 2011; 18:302-8. [PMID: 21297634 PMCID: PMC3077891 DOI: 10.1038/nsmb.1986] [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] [Received: 05/15/2010] [Accepted: 11/23/2010] [Indexed: 01/08/2023]
Abstract
The highly conserved let-7 microRNA (miRNA) regulates developmental pathways across animal phyla. Mis-expression of let-7 causes lethality in Caenorhabditis elegans and has been associated with several human diseases. We show that timing of let-7 expression in developing worms is under complex transcriptional and post-transcriptional control. Expression of let-7 primary transcripts oscillates during each larval stage but precursor and mature let-7 miRNAs do not accumulate until later in development after lin-28 activity has diminished. We demonstrate that LIN-28 binds endogenous primary let-7 transcripts co-transcriptionally. We further show that LIN-28 binds endogenous primary let-7 transcripts in the nuclear compartment of human ES cells, suggesting that this LIN-28 activity is conserved across species. We conclude that co-transcriptional interaction of LIN-28 with let-7 primary transcripts blocks Drosha processing and, thus, precocious expression of mature let-7 during early development.
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When Cellular Networks Run Out of Control. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2011; 102:165-242. [DOI: 10.1016/b978-0-12-415795-8.00006-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Regulation of lin-4 miRNA expression, organismal growth and development by a conserved RNA binding protein in C. elegans. Dev Biol 2010; 348:210-21. [PMID: 20937268 DOI: 10.1016/j.ydbio.2010.10.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Revised: 09/23/2010] [Accepted: 10/02/2010] [Indexed: 12/19/2022]
Abstract
Transcription and multiple processing steps are required to produce specific 22 nucleotide microRNAs (miRNAs) that can regulate the expression of target genes. In C. elegans, mature lin-4 miRNA accumulates at the end of the first larval stage to repress its direct targets lin-14 and lin-28, allowing the progression of several somatic cell types to later larval fates. In this study, we characterized the expression of endogenous lin-4 and found that temporally regulated independent transcripts, but not constitutive lin-4 containing RNAs derived from an overlapping gene, are processed to mature lin-4 miRNA. Through an RNAi screen, we identified a conserved RNA binding protein gene rbm-28 (R05H10.2), homologous to the human RBM28 and yeast Nop4p proteins, that is important for lin-4 expression in C. elegans. We also demonstrate that rbm-28 genetically interacts with the lin-4 developmental timing pathway and uncover a previously unrecognized role for lin-14 and lin-28 in coordinating organismal growth.
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