101
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Chew GL, Pauli A, Schier AF. Conservation of uORF repressiveness and sequence features in mouse, human and zebrafish. Nat Commun 2016; 7:11663. [PMID: 27216465 PMCID: PMC4890304 DOI: 10.1038/ncomms11663] [Citation(s) in RCA: 129] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2016] [Accepted: 04/18/2016] [Indexed: 02/07/2023] Open
Abstract
Upstream open reading frames (uORFs) are ubiquitous repressive genetic elements in vertebrate mRNAs. While much is known about the regulation of individual genes by their uORFs, the range of uORF-mediated translational repression in vertebrate genomes is largely unexplored. Moreover, it is unclear whether the repressive effects of uORFs are conserved across species. To address these questions, we analyse transcript sequences and ribosome profiling data from human, mouse and zebrafish. We find that uORFs are depleted near coding sequences (CDSes) and have initiation contexts that diminish their translation. Linear modelling reveals that sequence features at both uORFs and CDSes modulate the translation of CDSes. Moreover, the ratio of translation over 5′ leaders and CDSes is conserved between human and mouse, and correlates with the number of uORFs. These observations suggest that the prevalence of vertebrate uORFs may be explained by their conserved role in repressing CDS translation. Upstream open reading frames (uORFs) can repress gene expression. Here, Guo-Liang Chew and colleagues use bioinformatics approaches to show that conservation of uORF-mediated translational repression is mediated by sequence features in human, mouse and zebrafish genomes.
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Affiliation(s)
- Guo-Liang Chew
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Andrea Pauli
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA
| | - Alexander F Schier
- Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts 02138, USA.,The Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, Massachusetts 02142, USA.,FAS Center for Systems Biology, Harvard University, Cambridge, Massachusetts 02138, USA.,Center for Brain Science, Harvard University, Cambridge, Massachusetts 02138, USA.,Harvard Stem Cell Institute, Harvard University, Cambridge, Massachusetts 02138, USA
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102
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SUMO5, a Novel Poly-SUMO Isoform, Regulates PML Nuclear Bodies. Sci Rep 2016; 6:26509. [PMID: 27211601 PMCID: PMC4876461 DOI: 10.1038/srep26509] [Citation(s) in RCA: 152] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 05/04/2016] [Indexed: 12/23/2022] Open
Abstract
Promyelocytic leukemia nuclear bodies (PML-NBs) are PML-based nuclear structures that regulate various cellular processes. SUMOylation, the process of covalently conjugating small ubiquitin-like modifiers (SUMOs), is required for both the formation and the disruption of PML-NBs. However, detailed mechanisms of how SUMOylation regulates these processes remain unknown. Here we report that SUMO5, a novel SUMO variant, mediates the growth and disruption of PML-NBs. PolySUMO5 conjugation of PML at lysine 160 facilitates recruitment of PML-NB components, which enlarges PML-NBs. SUMO5 also increases polySUMO2/3 conjugation of PML, resulting in RNF4-mediated disruption of PML-NBs. The acute promyelocytic leukemia oncoprotein PML-RARα blocks SUMO5 conjugation of PML, causing cytoplasmic displacement of PML and disruption of PML-NBs. Our work not only identifies a new member of the SUMO family but also reveals the mechanistic basis of the PML-NB life cycle in human cells.
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103
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Towards understanding pre-mRNA splicing mechanisms and the role of SR proteins. Gene 2016; 587:107-19. [PMID: 27154819 DOI: 10.1016/j.gene.2016.04.057] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 04/30/2016] [Indexed: 01/04/2023]
Abstract
Alternative pre-mRNA splicing provides a source of vast protein diversity by removing non-coding sequences (introns) and accurately linking different exonic regions in the correct reading frame. The regulation of alternative splicing is essential for various cellular functions in both pathological and physiological conditions. In eukaryotic cells, this process is commonly used to increase proteomic diversity and to control gene expression either co- or post-transcriptionally. Alternative splicing occurs within a megadalton-sized, multi-component machine consisting of RNA and proteins; during the splicing process, this complex undergoes dynamic changes via RNA-RNA, protein-protein and RNA-protein interactions. Co-transcriptional splicing functionally integrates the transcriptional machinery, thereby enabling the two processes to influence one another, whereas post-transcriptional splicing facilitates the coupling of RNA splicing with post-splicing events. This review addresses the structural aspects of spliceosomes and the mechanistic implications of their stepwise assembly on the regulation of pre-mRNA splicing. Moreover, the role of phosphorylation-based, signal-induced changes in the regulation of the splicing process is demonstrated.
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104
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Atanassov BS, Mohan RD, Lan X, Kuang X, Lu Y, Lin K, McIvor E, Li W, Zhang Y, Florens L, Byrum SD, Mackintosh SG, Calhoun-Davis T, Koutelou E, Wang L, Tang DG, Tackett AJ, Washburn MP, Workman JL, Dent SYR. ATXN7L3 and ENY2 Coordinate Activity of Multiple H2B Deubiquitinases Important for Cellular Proliferation and Tumor Growth. Mol Cell 2016; 62:558-71. [PMID: 27132940 DOI: 10.1016/j.molcel.2016.03.030] [Citation(s) in RCA: 104] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Revised: 02/04/2016] [Accepted: 03/25/2016] [Indexed: 10/21/2022]
Abstract
Histone H2B monoubiquitination (H2Bub1) is centrally involved in gene regulation. The deubiquitination module (DUBm) of the SAGA complex is a major regulator of global H2Bub1 levels, and components of this DUBm are linked to both neurodegenerative diseases and cancer. Unexpectedly, we find that ablation of USP22, the enzymatic center of the DUBm, leads to a reduction, rather than an increase, in global H2bub1 levels. In contrast, depletion of non-enzymatic components, ATXN7L3 or ENY2, results in increased H2Bub1. These observations led us to discover two H2Bub1 DUBs, USP27X and USP51, which function independently of SAGA and compete with USP22 for ATXN7L3 and ENY2 for activity. Like USP22, USP51 and USP27X are required for normal cell proliferation, and their depletion suppresses tumor growth. Our results reveal that ATXN7L3 and ENY2 orchestrate activities of multiple deubiquitinating enzymes and that imbalances in these activities likely potentiate human diseases including cancer.
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Affiliation(s)
- Boyko S Atanassov
- Department of Epigenetics & Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA; Center for Cancer Epigenetics, Houston, TX 77030, USA.
| | - Ryan D Mohan
- University of Missouri - Kansas City, Kansas City, MO 64110, USA
| | - Xianjiang Lan
- Department of Epigenetics & Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA; Center for Cancer Epigenetics, Houston, TX 77030, USA; Program in Epigenetics and Molecular Carcinogenesis, Graduate School of Biomedical Sciences, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA
| | - Xianghong Kuang
- Department of Epigenetics & Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA; Center for Cancer Epigenetics, Houston, TX 77030, USA
| | - Yue Lu
- Department of Epigenetics & Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA; Center for Cancer Epigenetics, Houston, TX 77030, USA
| | - Kevin Lin
- Department of Epigenetics & Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA; Center for Cancer Epigenetics, Houston, TX 77030, USA
| | - Elizabeth McIvor
- Department of Epigenetics & Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA; Center for Cancer Epigenetics, Houston, TX 77030, USA
| | - Wenqian Li
- Department of Epigenetics & Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA; Center for Cancer Epigenetics, Houston, TX 77030, USA; Program in Epigenetics and Molecular Carcinogenesis, Graduate School of Biomedical Sciences, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA
| | - Ying Zhang
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Laurence Florens
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Stephanie D Byrum
- University of Arkansas for Medical Sciences, Biochemistry and Molecular Biology, Little Rock, AR 72205, USA
| | - Samuel G Mackintosh
- University of Arkansas for Medical Sciences, Biochemistry and Molecular Biology, Little Rock, AR 72205, USA
| | - Tammy Calhoun-Davis
- Department of Epigenetics & Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA; Center for Cancer Epigenetics, Houston, TX 77030, USA
| | - Evangelia Koutelou
- Department of Epigenetics & Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA; Center for Cancer Epigenetics, Houston, TX 77030, USA
| | - Li Wang
- Department of Epigenetics & Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA; Center for Cancer Epigenetics, Houston, TX 77030, USA
| | - Dean G Tang
- Department of Epigenetics & Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA; Center for Cancer Epigenetics, Houston, TX 77030, USA
| | - Alan J Tackett
- University of Arkansas for Medical Sciences, Biochemistry and Molecular Biology, Little Rock, AR 72205, USA
| | - Michael P Washburn
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA; Department of Pathology and Laboratory Medicine, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Jerry L Workman
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
| | - Sharon Y R Dent
- Department of Epigenetics & Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA; Center for Cancer Epigenetics, Houston, TX 77030, USA; Program in Epigenetics and Molecular Carcinogenesis, Graduate School of Biomedical Sciences, University of Texas MD Anderson Cancer Center, Smithville, TX 78957, USA.
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105
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Nakahigashi K, Takai Y, Kimura M, Abe N, Nakayashiki T, Shiwa Y, Yoshikawa H, Wanner BL, Ishihama Y, Mori H. Comprehensive identification of translation start sites by tetracycline-inhibited ribosome profiling. DNA Res 2016; 23:193-201. [PMID: 27013550 PMCID: PMC4909307 DOI: 10.1093/dnares/dsw008] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2015] [Accepted: 02/06/2016] [Indexed: 01/12/2023] Open
Abstract
Tetracycline-inhibited ribosome profiling (TetRP) provides a powerful new experimental tool for comprehensive genome-wide identification of translation initiation sites in bacteria. We validated TetRP by confirming the translation start sites of protein-coding genes in accordance with the 2006 version of Escherichia coli K-12 annotation record (GenBank U00096.2) and found ∼150 new start sites within 60 nucleotides of the annotated site. This analysis revealed 72 per cent of the genes whose initiation site annotations were changed from the 2006 GenBank record to the newer 2014 annotation record (GenBank U00096.3), indicating a high sensitivity. Also, results from reporter fusion and proteomics of N-terminally enriched peptides showed high specificity of the TetRP results. In addition, we discovered over 300 translation start sites within non-coding, intergenic regions of the genome, using a threshold that retains ∼2,000 known coding genes. While some appear to correspond to pseudogenes, others may encode small peptides or have previously unforeseen roles. In summary, we showed that ribosome profiling upon translation inhibition by tetracycline offers a simple, reliable and comprehensive experimental tool for precise annotation of translation start sites of expressed genes in bacteria.
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Affiliation(s)
- Kenji Nakahigashi
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0017, Japan
| | - Yuki Takai
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0017, Japan
| | - Michiko Kimura
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Nozomi Abe
- Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0017, Japan
| | - Toru Nakayashiki
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara 630-0101, Japan
| | - Yuh Shiwa
- Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Tokyo 156-8502, Japan
| | - Hirofumi Yoshikawa
- Genome Research Center, NODAI Research Institute, Tokyo University of Agriculture, Tokyo 156-8502, Japan Department of Bioscience, Tokyo University of Agriculture, Tokyo 156-8502, Japan
| | - Barry L Wanner
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115, USA
| | - Yasushi Ishihama
- Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
| | - Hirotada Mori
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Nara 630-0101, Japan
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106
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Lian X, Guo J, Gu W, Cui Y, Zhong J, Jin J, He QY, Wang T, Zhang G. Genome-Wide and Experimental Resolution of Relative Translation Elongation Speed at Individual Gene Level in Human Cells. PLoS Genet 2016; 12:e1005901. [PMID: 26926465 PMCID: PMC4771717 DOI: 10.1371/journal.pgen.1005901] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2015] [Accepted: 02/05/2016] [Indexed: 11/18/2022] Open
Abstract
In the process of translation, ribosomes first assemble on mRNAs (translation initiation) and then translate along the mRNA (elongation) to synthesize proteins. Elongation pausing is deemed highly relevant to co-translational folding of nascent peptides and the functionality of protein products, which positioned the evaluation of elongation speed as one of the central questions in the field of translational control. By integrating three types of RNA-seq methods, we experimentally and computationally resolved elongation speed, with our proposed elongation velocity index (EVI), a relative measure at individual gene level and under physiological condition in human cells. We successfully distinguished slow-translating genes from the background translatome. We demonstrated that low-EVI genes encoded more stable proteins. We further identified cell-specific slow-translating codons, which might serve as a causal factor of elongation deceleration. As an example for the biological relevance, we showed that the relatively slow-translating genes tended to be associated with the maintenance of malignant phenotypes per pathway analyses. In conclusion, EVI opens a new view to understand why human cells tend to avoid simultaneously speeding up translation initiation and decelerating elongation, and the possible cancer relevance of translating low-EVI genes to gain better protein quality. In protein synthesis, ribosome assembles to mRNA to initiate translation, followed by the process of elongation to read the codons along the mRNA molecule for polypeptide chain production. It is known that slowing down the elongation speed at certain regions of mRNA is critical for the correct folding of numerous proteins—the so-called “pause-to-fold”. However, it has been an open question to evaluate elongation speed under cellular physiological conditions in genome-wide scale. Here, we used three types of next-generation sequencing approaches to experimentally and computationally address this question. With a new relative measure of elongation velocity index (EVI), we successfully distinguished slow-translating genes. Their protein products are more stable than the background genes. We found that different cell types tended to have distinct slow-translating codons, which might be relevant to the cell/tissue specific tRNA composition. Such elongation deceleration is potentially disease-relevant: cancer cells tend to slow down numerous cancer-favorable genes, and vice versa. Furthermore, we justified that translation initiation and elongation are evolutionarily synergistic as no gene with both high initiation efficiency and low elongation speed was observed: that would cause a traffic jam of ribosomes that should be maximally avoided per evolution.
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Affiliation(s)
- Xinlei Lian
- Institute of Life and Health Engineering, Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Jinan University, Guangzhou, China
| | - Jiahui Guo
- Institute of Life and Health Engineering, Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Jinan University, Guangzhou, China
| | - Wei Gu
- Institute of Life and Health Engineering, Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Jinan University, Guangzhou, China
| | - Yizhi Cui
- Institute of Life and Health Engineering, Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Jinan University, Guangzhou, China
| | - Jiayong Zhong
- Institute of Life and Health Engineering, Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Jinan University, Guangzhou, China
| | - Jingjie Jin
- Institute of Life and Health Engineering, Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Jinan University, Guangzhou, China
| | - Qing-Yu He
- Institute of Life and Health Engineering, Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Jinan University, Guangzhou, China
- * E-mail: (GZ); (TW); (QYH)
| | - Tong Wang
- Institute of Life and Health Engineering, Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Jinan University, Guangzhou, China
- * E-mail: (GZ); (TW); (QYH)
| | - Gong Zhang
- Institute of Life and Health Engineering, Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Jinan University, Guangzhou, China
- * E-mail: (GZ); (TW); (QYH)
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107
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Abstract
The daily production of up to 1011 erythrocytes is tightly controlled to maintain the number of erythrocytes in peripheral blood between narrow boundaries. Availability of growth factors and nutrients, particularly iron, control the proliferation and survival of precursor cells partly through control of mRNA translation. General translation initiation mechanisms can selectively control translation of transcripts that carry specific structures in the UTRs. This selective mRNA translation is an important layer of gene expression regulation in erythropoiesis. Ribosome profiling is a recently developed high throughput sequencing technique for global mapping of translation initiation sites across the transcriptome. Here we describe what is known about control of mRNA translation in erythropoiesis and how ribosome profiling will help to further our knowledge. Ribosome footprinting will give insight in transcript-specific translation at codon resolution, which is of great value to understand many cellular processes during erythropoiesis. It will be of particular interest to understand responses to iron availability and reactive oxygen species (ROS), which affects translation initiation of transcripts harbouring upstream ORFs (uORF) and potential alternative downstream ORFs (aORF).
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108
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Hu Q, Merchante C, Stepanova AN, Alonso JM, Heber S. Genome-Wide Search for Translated Upstream Open Reading Frames in Arabidopsis Thaliana. IEEE Trans Nanobioscience 2016; 15:148-57. [PMID: 26886998 DOI: 10.1109/tnb.2016.2516950] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Upstream open reading frames (uORFs) are open reading frames that occur within the 5' UTR of an mRNA. uORFs have been found in many organisms. They play an important role in gene regulation, cell development, and in various metabolic processes. It is believed that translated uORFs reduce the translational efficiency of the main coding region. However, only few uORFs are experimentally characterized. In this paper, we use ribosome footprinting together with a semi-supervised approach based on stacking classification models to identify translated uORFs in Arabidopsis thaliana. Our approach identified 5360 potentially translated uORFs in 2051 genes. GO terms enriched in genes with translated uORFs include catalytic activity, binding, transferase activity, phosphotransferase activity, kinase activity, and transcription regulator activity. The reported uORFs occur with a higher frequency in multi-isoform genes, and some uORFs are affected by alternative transcript start sites or alternative splicing events. Association rule mining revealed sequence features associated with the translation status of the uORFs. We hypothesize that uORF translation is a complex process that might be regulated by multiple factors. The identified uORFs are available online at:https://www.dropbox.com/sh/zdutupedxafhly8/AABFsdNR5zDfiozB7B4igFcja?dl=0. This paper is the extended version of our research presented at ISBRA 2015.
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109
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Sheshukova EV, Shindyapina AV, Komarova TV, Dorokhov YL. “Matreshka” genes with alternative reading frames. RUSS J GENET+ 2016. [DOI: 10.1134/s1022795416020149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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110
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Popa A, Lebrigand K, Barbry P, Waldmann R. Pateamine A-sensitive ribosome profiling reveals the scope of translation in mouse embryonic stem cells. BMC Genomics 2016; 17:52. [PMID: 26764022 PMCID: PMC4712605 DOI: 10.1186/s12864-016-2384-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 01/06/2016] [Indexed: 01/02/2023] Open
Abstract
Background Open reading frames are common in long noncoding RNAs (lncRNAs) and 5’UTRs of protein coding transcripts (uORFs). The question of whether those ORFs are translated was recently addressed by several groups using ribosome profiling. Most of those studies concluded that certain lncRNAs and uORFs are translated, essentially based on computational analysis of ribosome footprints. However, major discrepancies remain on the scope of translation and the translational status of individual ORFs. In consequence, further criteria are required to reliably identify translated ORFs from ribosome profiling data. Results We examined the effect of the translation inhibitors pateamine A, harringtonine and puromycin on murine ES cell ribosome footprints. We found that pateamine A, a drug that targets eIF4A, allows a far more accurate identification of translated sequences than previously used drugs and computational scoring schemes. Our data show that at least one third but less than two thirds of ES cell lncRNAs are translated. We also identified translated uORFs in hundreds of annotated coding transcripts including key pluripotency transcripts, such as dicer, lin28, trim71, and ctcf. Conclusion Pateamine A inhibition data clearly increase the precision of the detection of translated ORFs in ribosome profiling experiments. Our data show that translation of lncRNAs and uORFs in murine ES cells is rather common although less pervasive than previously suggested. The observation of translated uORFs in several key pluripotency transcripts suggests that translational regulation by uORFs might be part of the network that defines mammalian stem cell identity. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-2384-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Alexandra Popa
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), University Nice Sophia Antipolis, CNRS, F06560, Sophia-Antipolis, France
| | - Kevin Lebrigand
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), University Nice Sophia Antipolis, CNRS, F06560, Sophia-Antipolis, France
| | - Pascal Barbry
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), University Nice Sophia Antipolis, CNRS, F06560, Sophia-Antipolis, France.
| | - Rainer Waldmann
- Institut de Pharmacologie Moléculaire et Cellulaire (IPMC), University Nice Sophia Antipolis, CNRS, F06560, Sophia-Antipolis, France
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111
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Liu B, Qian SB. Characterizing inactive ribosomes in translational profiling. ACTA ACUST UNITED AC 2016; 4:e1138018. [PMID: 27335722 DOI: 10.1080/21690731.2015.1138018] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 12/20/2015] [Accepted: 12/28/2015] [Indexed: 01/10/2023]
Abstract
The broad impact of translational regulation has emerged explosively in the last few years in part due to the technological advance in genome-wide interrogation of gene expression. During mRNA translation, the majority of actively translating ribosomes exist as polysomes in cells with multiple ribosomes loaded on a single transcript. The importance of the monosome, however, has been less appreciated in translational profiling analysis. Here we report that the monosome fraction isolated by sucrose sedimentation contains a large quantity of inactive ribosomes that do not engage on mRNAs to direct translation. We found that the elongation factor eEF2, but not eEF1A, stably resides in these non-translating ribosomes. This unique feature permits direct evaluation of ribosome status under various stress conditions and in the presence of translation inhibitors. Ribosome profiling reveals that the monosome has a similar but not identical pattern of ribosome footprints compared to the polysome. We show that the association of free ribosomal subunits minimally contributes to ribosome occupancy outside of the coding region. Our results not only offer a quantitative method to monitor ribosome availability, but also uncover additional layers of ribosome status needed to be considered in translational profiling analysis.
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Affiliation(s)
- Botao Liu
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, USA; Graduate Field of Genetics, Genomics, and Development, Cornell University, Ithaca, NY, USA; Present address: Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, MA, USA
| | - Shu-Bing Qian
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, USA; Graduate Field of Genetics, Genomics, and Development, Cornell University, Ithaca, NY, USA
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112
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Mouilleron H, Delcourt V, Roucou X. Death of a dogma: eukaryotic mRNAs can code for more than one protein. Nucleic Acids Res 2016; 44:14-23. [PMID: 26578573 PMCID: PMC4705651 DOI: 10.1093/nar/gkv1218] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2015] [Revised: 10/26/2015] [Accepted: 10/28/2015] [Indexed: 12/13/2022] Open
Abstract
mRNAs carry the genetic information that is translated by ribosomes. The traditional view of a mature eukaryotic mRNA is a molecule with three main regions, the 5' UTR, the protein coding open reading frame (ORF) or coding sequence (CDS), and the 3' UTR. This concept assumes that ribosomes translate one ORF only, generally the longest one, and produce one protein. As a result, in the early days of genomics and bioinformatics, one CDS was associated with each protein-coding gene. This fundamental concept of a single CDS is being challenged by increasing experimental evidence indicating that annotated proteins are not the only proteins translated from mRNAs. In particular, mass spectrometry (MS)-based proteomics and ribosome profiling have detected productive translation of alternative open reading frames. In several cases, the alternative and annotated proteins interact. Thus, the expression of two or more proteins translated from the same mRNA may offer a mechanism to ensure the co-expression of proteins which have functional interactions. Translational mechanisms already described in eukaryotic cells indicate that the cellular machinery is able to translate different CDSs from a single viral or cellular mRNA. In addition to summarizing data showing that the protein coding potential of eukaryotic mRNAs has been underestimated, this review aims to challenge the single translated CDS dogma.
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Affiliation(s)
- Hélène Mouilleron
- Department of biochemistry, Université de Sherbrooke, Sherbrooke, Quebec J1E 4K8, Canada PROTEO, Quebec Network for Research on Protein Function, Structure, and Engineering, Quebec, Canada
| | - Vivian Delcourt
- Department of biochemistry, Université de Sherbrooke, Sherbrooke, Quebec J1E 4K8, Canada PROTEO, Quebec Network for Research on Protein Function, Structure, and Engineering, Quebec, Canada Inserm U-1192, Laboratoire de Protéomique, Réponse Inflammatoire, Spectrométrie de Masse (PRISM), Université de Lille 1, Cité Scientifique, 59655 Villeneuve D'Ascq, France
| | - Xavier Roucou
- Department of biochemistry, Université de Sherbrooke, Sherbrooke, Quebec J1E 4K8, Canada PROTEO, Quebec Network for Research on Protein Function, Structure, and Engineering, Quebec, Canada
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113
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Abstract
Regulation of translation initiation is a central control point in protein synthesis. Variations of start codon selection contribute to protein diversity and complexity. Systemic mapping of start codon positions and precise measurement of the corresponding initiation rate would transform our understanding of translational control. Here we describe a ribosome profiling approach that enables identification of translation initiation sites on a genome-wide scale. By capturing initiating ribosomes using lactimidomycin, this approach permits qualitative and quantitative analysis of alternative translation initiation.
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Affiliation(s)
- Xiangwei Gao
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, 14853, USA
| | - Ji Wan
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, 14853, USA
| | - Shu-Bing Qian
- Division of Nutritional Sciences, Cornell University, Ithaca, NY, 14853, USA.
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114
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Olexiouk V, Menschaert G. Identification of Small Novel Coding Sequences, a Proteogenomics Endeavor. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 926:49-64. [PMID: 27686805 DOI: 10.1007/978-3-319-42316-6_4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The identification of small proteins and peptides has consistently proven to be challenging. However, technological advances as well as multi-omics endeavors facilitate the identification of novel small coding sequences, leading to new insights. Specifically, the application of next generation sequencing technologies (NGS), providing accurate and sample specific transcriptome / translatome information, into the proteomics field led to more comprehensive results and new discoveries. This book chapter focuses on the inclusion of RNA-Seq and RIBO-Seq also known as ribosome profiling, an RNA-Seq based technique sequencing the +/- 30 bp long fragments captured by translating ribosomes. We emphasize the identification of micropeptides and neo-antigens, two distinct classes of small translation products, triggering our current understanding of biology. RNA-Seq is capable of capturing sample specific genomic variations, enabling focused neo-antigen identification. RIBO-Seq can identify translation events in small open reading frames which are considered to be non-coding, leading to the discovery of micropeptides. The identification of small translation products requires the integration of multi-omics data, stressing the importance of proteogenomics in this novel research area.
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Affiliation(s)
- Volodimir Olexiouk
- Lab of Bioinformatics and Computational Genomics (BioBix), Faculty of Bioscience Engineering, Department of Mathematical Modelling, Statistics and Bioinformatics, Ghent University, Coupure Links 653, Building A, Ghent, 9000, Belgium.
| | - Gerben Menschaert
- Lab of Bioinformatics and Computational Genomics (BioBix), Faculty of Bioscience Engineering, Department of Mathematical Modelling, Statistics and Bioinformatics, Ghent University, Coupure Links 653, Building A, Ghent, 9000, Belgium
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Bartholomäus A, Del Campo C, Ignatova Z. Mapping the non-standardized biases of ribosome profiling. Biol Chem 2016; 397:23-35. [DOI: 10.1515/hsz-2015-0197] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2015] [Accepted: 08/25/2015] [Indexed: 01/30/2023]
Abstract
Abstract
Ribosome profiling is a new emerging technology that uses massively parallel amplification of ribosome-protected fragments and next-generation sequencing to monitor translation in vivo with codon resolution. Studies using this approach provide insightful views on the regulation of translation on a global cell-wide level. In this review, we compare different experimental set-ups and current protocols for sequencing data analysis. Specifically, we review the pitfalls at some experimental steps and highlight the importance of standardized protocol for sample preparation and data processing pipeline, at least for mapping and normalization.
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116
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Detecting actively translated open reading frames in ribosome profiling data. Nat Methods 2015; 13:165-70. [PMID: 26657557 DOI: 10.1038/nmeth.3688] [Citation(s) in RCA: 301] [Impact Index Per Article: 30.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 10/28/2015] [Indexed: 12/23/2022]
Abstract
RNA-sequencing protocols can quantify gene expression regulation from transcription to protein synthesis. Ribosome profiling (Ribo-seq) maps the positions of translating ribosomes over the entire transcriptome. We have developed RiboTaper (available at https://ohlerlab.mdc-berlin.de/software/), a rigorous statistical approach that identifies translated regions on the basis of the characteristic three-nucleotide periodicity of Ribo-seq data. We used RiboTaper with deep Ribo-seq data from HEK293 cells to derive an extensive map of translation that covered open reading frame (ORF) annotations for more than 11,000 protein-coding genes. We also found distinct ribosomal signatures for several hundred upstream ORFs and ORFs in annotated noncoding genes (ncORFs). Mass spectrometry data confirmed that RiboTaper achieved excellent coverage of the cellular proteome. Although dozens of novel peptide products were validated in this manner, few of the currently annotated long noncoding RNAs appeared to encode stable polypeptides. RiboTaper is a powerful method for comprehensive de novo identification of actively used ORFs from Ribo-seq data.
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117
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Saghatelian A, Couso JP. Discovery and characterization of smORF-encoded bioactive polypeptides. Nat Chem Biol 2015; 11:909-16. [PMID: 26575237 PMCID: PMC4956473 DOI: 10.1038/nchembio.1964] [Citation(s) in RCA: 197] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 10/19/2015] [Indexed: 12/13/2022]
Abstract
Analysis of genomes, transcriptomes and proteomes reveals the existence of hundreds to thousands of translated, yet non-annotated, short open reading frames (small ORFs or smORFs). The discovery of smORFs and their protein products, smORF-encoded polypeptides (SEPs), points to a fundamental gap in our knowledge of protein-coding genes. Various studies have identified central roles for smORFs in metabolism, apoptosis and development. The discovery of these bioactive SEPs emphasizes the functional potential of this unexplored class of biomolecules. Here, we provide an overview of this emerging field and highlight the opportunities for chemical biology to answer fundamental questions about these novel genes. Such studies will provide new insights into the protein-coding potential of genomes and identify functional genes with roles in biology and disease.
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Affiliation(s)
- Alan Saghatelian
- Clayton Foundation Laboratories for Peptide Biology, Helmsley Center for Genomic Medicine, Salk Institute for Biological Studies, San Diego, CA 92037
| | - Juan Pablo Couso
- School of Life Sciences, University of Sussex, Falmer, Brighton, BN1 6PU, UK
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118
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Tian Y, Yang JE. Emerging landscape of short open reading frame-encoded peptides. Shijie Huaren Xiaohua Zazhi 2015; 23:4954-4960. [DOI: 10.11569/wcjd.v23.i31.4954] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Short open reading frames (sORFs) are a common feature of genomes of human and other species, but their coding potential remains unknown. Innovations in proteomics and high-throughput analyses of translation start sites have resulted in the identification of hundreds of putative coding sORFs, and some of them have been verified to be able to translated into short peptides (<100 amino acids). Moreover, recent findings reveal their diverse functions in various biological processes including development and differentiation. This review discusses the translation, identification and biological function of short peptides.
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119
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Housman G, Ulitsky I. Methods for distinguishing between protein-coding and long noncoding RNAs and the elusive biological purpose of translation of long noncoding RNAs. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2015; 1859:31-40. [PMID: 26265145 DOI: 10.1016/j.bbagrm.2015.07.017] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2015] [Revised: 06/18/2015] [Accepted: 07/19/2015] [Indexed: 12/12/2022]
Abstract
Long noncoding RNAs (lncRNAs) are a diverse class of RNAs with increasingly appreciated functions in vertebrates, yet much of their biology remains poorly understood. In particular, it is unclear to what extent the current catalog of over 10,000 annotated lncRNAs is indeed devoid of genes coding for proteins. Here we review the available computational and experimental schemes for distinguishing between coding and noncoding transcripts and assess the conclusions from their recent genome-wide applications. We conclude that the model most consistent with the available data is that a large number of mammalian lncRNAs undergo translation, but only a very small minority of such translation events results in stable and functional peptides. The outcomes of the majority of the translation events and their potential biological purposes remain an intriguing topic for future investigation. This article is part of a Special Issue entitled: Clues to long noncoding RNA taxonomy1, edited by Dr. Tetsuro Hirose and Dr. Shinichi Nakagawa.
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Affiliation(s)
- Gali Housman
- Department of Biological Regulation, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Igor Ulitsky
- Department of Biological Regulation, Weizmann Institute of Science, Rehovot 76100, Israel.
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Abstract
Viral genomes harbor a variety of unusual translational phenomena that allow them to pack coding information more densely and evade host restriction mechanisms imposed by the cellular translational apparatus. Annotating translated sequences within these genomes thus poses particular challenges, but identifying the full complement of proteins encoded by a virus is critical for understanding its life cycle and defining the epitopes it presents for immune surveillance. Ribosome profiling is an emerging technique for global analysis of translation that offers direct and experimental annotation of viral genomes. Ribosome profiling has been applied to two herpesvirus genomes, those of human cytomegalovirus and Kaposi's sarcoma-associated herpesvirus, revealing translated sequences within presumptive long noncoding RNAs and identifying other micropeptides. Synthesis of these proteins has been confirmed by mass spectrometry and by identifying T cell responses following infection. Ribosome profiling in other viruses will likely expand further our understanding of viral gene regulation and the proteome.
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Affiliation(s)
- Noam Stern-Ginossar
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 76100, Israel;
| | - Nicholas T Ingolia
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720;
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121
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Aeschimann F, Xiong J, Arnold A, Dieterich C, Großhans H. Transcriptome-wide measurement of ribosomal occupancy by ribosome profiling. Methods 2015; 85:75-89. [PMID: 26102273 DOI: 10.1016/j.ymeth.2015.06.013] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2015] [Revised: 06/10/2015] [Accepted: 06/15/2015] [Indexed: 01/08/2023] Open
Abstract
Gene expression profiling provides a tool to analyze the internal states of cells or organisms, and their responses to perturbations. While global measurements of mRNA levels have thus been widely used for many years, it is only through the recent development of the ribosome profiling technique that an analogous examination of global mRNA translation programs has become possible. Ribosome profiling reveals which RNAs are being translated to what extent and where the translated open reading frames are located. In addition, different modes of translation regulation can be distinguished and characterized. Here, we present an optimized, step-by-step protocol for ribosome profiling. Although established in Caenorhabditis elegans, our protocol and optimization approaches should be equally usable for other model organisms or cell culture with little adaptation. Next to providing a protocol, we compare two different methods for isolation of single ribosomes and two different library preparations, and describe strategies to optimize the RNase digest and to reduce ribosomal RNA contamination in the libraries. Moreover, we discuss bioinformatic strategies to evaluate the quality of the data and explain how the data can be analyzed for different applications. In sum, this article seeks to facilitate the understanding, execution, and optimization of ribosome profiling experiments.
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Affiliation(s)
- Florian Aeschimann
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Jieyi Xiong
- Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Straße 9b, 50931 Cologne, Germany
| | - Andreas Arnold
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland
| | - Christoph Dieterich
- Max Planck Institute for Biology of Ageing, Joseph-Stelzmann-Straße 9b, 50931 Cologne, Germany.
| | - Helge Großhans
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, 4058 Basel, Switzerland.
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122
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Bahrami-Samani E, Vo DT, de Araujo PR, Vogel C, Smith AD, Penalva LOF, Uren PJ. Computational challenges, tools, and resources for analyzing co- and post-transcriptional events in high throughput. WILEY INTERDISCIPLINARY REVIEWS. RNA 2015; 6:291-310. [PMID: 25515586 PMCID: PMC4397117 DOI: 10.1002/wrna.1274] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 10/24/2014] [Accepted: 10/29/2014] [Indexed: 11/10/2022]
Abstract
Co- and post-transcriptional regulation of gene expression is complex and multifaceted, spanning the complete RNA lifecycle from genesis to decay. High-throughput profiling of the constituent events and processes is achieved through a range of technologies that continue to expand and evolve. Fully leveraging the resulting data is nontrivial, and requires the use of computational methods and tools carefully crafted for specific data sources and often intended to probe particular biological processes. Drawing upon databases of information pre-compiled by other researchers can further elevate analyses. Within this review, we describe the major co- and post-transcriptional events in the RNA lifecycle that are amenable to high-throughput profiling. We place specific emphasis on the analysis of the resulting data, in particular the computational tools and resources available, as well as looking toward future challenges that remain to be addressed.
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Affiliation(s)
- Emad Bahrami-Samani
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA
| | - Dat T. Vo
- Children’s Cancer Research Institute and Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, TX
| | - Patricia Rosa de Araujo
- Children’s Cancer Research Institute and Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, TX
| | - Christine Vogel
- Center for Genomics and Systems Biology, Department of Biology, New York University, New York, NY
| | - Andrew D. Smith
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA
| | - Luiz O. F. Penalva
- Children’s Cancer Research Institute and Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio, TX
| | - Philip J. Uren
- Molecular and Computational Biology, Department of Biological Sciences, University of Southern California, Los Angeles, CA
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123
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Michel AM, Ahern AM, Donohue CA, Baranov PV. GWIPS-viz as a tool for exploring ribosome profiling evidence supporting the synthesis of alternative proteoforms. Proteomics 2015; 15:2410-6. [PMID: 25736862 PMCID: PMC4832365 DOI: 10.1002/pmic.201400603] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Revised: 02/03/2015] [Accepted: 02/26/2015] [Indexed: 01/08/2023]
Abstract
The boundaries of protein coding sequences are more difficult to define at the 5′ end than at the 3′ end due to potential multiple translation initiation sites (TISs). Even in the presence of phylogenetic data, the use of sequence information only may not be sufficient for the accurate identification of TISs. Traditional proteomics approaches may also fail because the N‐termini of newly synthesized proteins are often processed. Thus ribosome profiling (ribo‐seq), producing a snapshot of the ribosome distribution across the entire transcriptome, is an attractive experimental technique for the purpose of TIS location exploration. The GWIPS‐viz (Genome Wide Information on Protein Synthesis visualized) browser (http://gwips.ucc.ie) provides free access to the genomic alignments of ribo‐seq data and corresponding mRNA‐seq data along with relevant annotation tracks. In this brief, we illustrate how GWIPS‐viz can be used to explore the ribosome occupancy at the 5′ ends of protein coding genes to assess the activity of AUG and non‐AUG TISs responsible for the synthesis of proteoforms with alternative or heterogeneous N‐termini. The presence of ribo‐seq tracks for various organisms allows for cross‐species comparison of orthologous genes and the availability of datasets from multiple laboratories permits the assessment of the technical reproducibility of the ribosome densities.
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Affiliation(s)
- Audrey M Michel
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Anna M Ahern
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Claire A Donohue
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
| | - Pavel V Baranov
- School of Biochemistry and Cell Biology, University College Cork, Cork, Ireland
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124
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de Klerk E, Fokkema IFAC, Thiadens KAMH, Goeman JJ, Palmblad M, den Dunnen JT, von Lindern M, 't Hoen PAC. Assessing the translational landscape of myogenic differentiation by ribosome profiling. Nucleic Acids Res 2015; 43:4408-28. [PMID: 25873627 PMCID: PMC4482065 DOI: 10.1093/nar/gkv281] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Accepted: 03/21/2015] [Indexed: 01/08/2023] Open
Abstract
The formation of skeletal muscles is associated with drastic changes in protein requirements known to be safeguarded by tight control of gene transcription and mRNA processing. The contribution of regulation of mRNA translation during myogenesis has not been studied so far. We monitored translation during myogenic differentiation of C2C12 myoblasts, using a simplified protocol for ribosome footprint profiling. Comparison of ribosome footprints to total RNA showed that gene expression is mostly regulated at the transcriptional level. However, a subset of transcripts, enriched for mRNAs encoding for ribosomal proteins, was regulated at the level of translation. Enrichment was also found for specific pathways known to regulate muscle biology. We developed a dedicated pipeline to identify translation initiation sites (TISs) and discovered 5333 unannotated TISs, providing a catalog of upstream and alternative open reading frames used during myogenesis. We identified 298 transcripts with a significant switch in TIS usage during myogenesis, which was not explained by alternative promoter usage, as profiled by DeepCAGE. Also these transcripts were enriched for ribosomal protein genes. This study demonstrates that differential mRNA translation controls protein expression of specific subsets of genes during myogenesis. Experimental protocols, analytical workflows, tools and data are available through public repositories (http://lumc.github.io/ribosome-profiling-analysis-framework/).
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Affiliation(s)
- Eleonora de Klerk
- Department of Human Genetics, Leiden University Medical Center, Postzone S4-P, PO Box 9600, 2300 RC Leiden, The Netherlands
| | - Ivo F A C Fokkema
- Department of Human Genetics, Leiden University Medical Center, Postzone S4-P, PO Box 9600, 2300 RC Leiden, The Netherlands
| | - Klaske A M H Thiadens
- Department of Hematopoiesis, Sanquin Research and Landsteiner Laboratory, AMC/UvA, 1066CX 125 Amsterdam, The Netherlands
| | - Jelle J Goeman
- Biostatistics, Department for Health Evidence, Radboud University Medical Center, Postzone 133, P.O. Box 9101, 6500 HB Nijmegen, The Netherlands
| | - Magnus Palmblad
- Center for Proteomics and Metabolomics, Leiden University Medical Center, 2300 RC Leiden, The Netherlands
| | - Johan T den Dunnen
- Department of Human Genetics, Leiden University Medical Center, Postzone S4-P, PO Box 9600, 2300 RC Leiden, The Netherlands
| | - Marieke von Lindern
- Department of Hematopoiesis, Sanquin Research and Landsteiner Laboratory, AMC/UvA, 1066CX 125 Amsterdam, The Netherlands
| | - Peter A C 't Hoen
- Department of Human Genetics, Leiden University Medical Center, Postzone S4-P, PO Box 9600, 2300 RC Leiden, The Netherlands
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125
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Tang S, Lomsadze A, Borodovsky M. Identification of protein coding regions in RNA transcripts. Nucleic Acids Res 2015; 43:e78. [PMID: 25870408 PMCID: PMC4499116 DOI: 10.1093/nar/gkv227] [Citation(s) in RCA: 290] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Accepted: 03/05/2015] [Indexed: 01/08/2023] Open
Abstract
Massive parallel sequencing of RNA transcripts by next-generation technology (RNA-Seq) generates critically important data for eukaryotic gene discovery. Gene finding in transcripts can be done by statistical (alignment-free) as well as by alignment-based methods. We describe a new tool, GeneMarkS-T, for ab initio identification of protein-coding regions in RNA transcripts. The algorithm parameters are estimated by unsupervised training which makes unnecessary manually curated preparation of training sets. We demonstrate that (i) the unsupervised training is robust with respect to the presence of transcripts assembly errors and (ii) the accuracy of GeneMarkS-T in identifying protein-coding regions and, particularly, in predicting translation initiation sites in modelled as well as in assembled transcripts compares favourably to other existing methods.
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Affiliation(s)
- Shiyuyun Tang
- School of Biology, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Alexandre Lomsadze
- Joint Georgia Tech and Emory Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA
| | - Mark Borodovsky
- Joint Georgia Tech and Emory Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA School of Computational Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA Center for Bioinformatics and Computational Genomics, Georgia Institute of Technology, Atlanta, GA 30332, USA Department of Biological and Medical Physics, Moscow Institute of Physics and Technology, Moscow, Russia
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126
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Smith JE, Baker KE. Nonsense-mediated RNA decay--a switch and dial for regulating gene expression. Bioessays 2015; 37:612-23. [PMID: 25820233 DOI: 10.1002/bies.201500007] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Nonsense-mediated RNA decay (NMD) represents an established quality control checkpoint for gene expression that protects cells from consequences of gene mutations and errors during RNA biogenesis that lead to premature termination during translation. Characterization of NMD-sensitive transcriptomes has revealed, however, that NMD targets not only aberrant transcripts but also a broad array of mRNA isoforms expressed from many endogenous genes. NMD is thus emerging as a master regulator that drives both fine and coarse adjustments in steady-state RNA levels in the cell. Importantly, while NMD activity is subject to autoregulation as a means to maintain homeostasis, modulation of the pathway by external cues provides a means to reprogram gene expression and drive important biological processes. Finally, the unanticipated observation that transcripts predicted to lack protein-coding capacity are also sensitive to this translation-dependent surveillance mechanism implicates NMD in regulating RNA function in new and diverse ways.
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Affiliation(s)
- Jenna E Smith
- Center for RNA Molecular Biology, Case Western Reserve University, Cleveland, OH, USA
| | - Kristian E Baker
- Center for RNA Molecular Biology, Case Western Reserve University, Cleveland, OH, USA
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127
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de Klerk E, 't Hoen PAC. Alternative mRNA transcription, processing, and translation: insights from RNA sequencing. Trends Genet 2015; 31:128-39. [PMID: 25648499 DOI: 10.1016/j.tig.2015.01.001] [Citation(s) in RCA: 226] [Impact Index Per Article: 22.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2014] [Revised: 12/22/2014] [Accepted: 01/05/2015] [Indexed: 12/13/2022]
Abstract
The human transcriptome comprises >80,000 protein-coding transcripts and the estimated number of proteins synthesized from these transcripts is in the range of 250,000 to 1 million. These transcripts and proteins are encoded by less than 20,000 genes, suggesting extensive regulation at the transcriptional, post-transcriptional, and translational level. Here we review how RNA sequencing (RNA-seq) technologies have increased our understanding of the mechanisms that give rise to alternative transcripts and their alternative translation. We highlight four different regulatory processes: alternative transcription initiation, alternative splicing, alternative polyadenylation, and alternative translation initiation. We discuss their transcriptome-wide distribution, their impact on protein expression, their biological relevance, and the possible molecular mechanisms leading to their alternative regulation. We conclude with a discussion of the coordination and the interdependence of these four regulatory layers.
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Affiliation(s)
- Eleonora de Klerk
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Peter A C 't Hoen
- Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.
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128
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Abstract
Over the past decade, high-throughput studies have identified many novel transcripts. While their existence is undisputed, their coding potential and functionality have remained controversial. Recent computational approaches guided by ribosome profiling have indicated that translation is far more pervasive than anticipated and takes place on many transcripts previously assumed to be non-coding. Some of these newly discovered translated transcripts encode short, functional proteins that had been missed in prior screens. Other transcripts are translated, but it might be the process of translation rather than the resulting peptides that serves a function. Here, we review annotation studies in zebrafish to discuss the challenges of placing RNAs onto the continuum that ranges from functional protein-encoding mRNAs to potentially non-functional peptide-producing RNAs to non-coding RNAs. As highlighted by the discovery of the novel signaling peptide Apela/ELABELA/Toddler, accurate annotations can give rise to exciting opportunities to identify the functions of previously uncharacterized transcripts.
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Affiliation(s)
- Andrea Pauli
- Department of Molecular and Cellular Biology, Harvard University, MA, USA
| | - Eivind Valen
- Department of Molecular and Cellular Biology, Harvard University, MA, USA
| | - Alexander F. Schier
- Department of Molecular and Cellular Biology, Harvard University, MA, USA
- The Broad Institute of Massachusetts Institute of Technology and Harvard, Cambridge, MA, USA
- FAS Center for Systems Biology, Harvard University, Cambridge, MA, USA
- Center for Brain Science, Harvard University, Cambridge, MA, USA
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129
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Hu Q, Merchante C, Stepanova AN, Alonso JM, Heber S. A Stacking-Based Approach to Identify Translated Upstream Open Reading Frames in Arabidopsis Thaliana. BIOINFORMATICS RESEARCH AND APPLICATIONS 2015. [DOI: 10.1007/978-3-319-19048-8_12] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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130
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Quantitative profiling of initiating ribosomes in vivo. Nat Methods 2014; 12:147-53. [PMID: 25486063 PMCID: PMC4344187 DOI: 10.1038/nmeth.3208] [Citation(s) in RCA: 192] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2014] [Accepted: 10/30/2014] [Indexed: 12/29/2022]
Abstract
Cells have evolved exquisite mechanisms to fine-tune the rate of protein synthesis in response to stress. Systemic mapping of start codon positions and precise measurement of the corresponding initiation rate would transform our understanding of translational control. Here we present quantitative translation initiation sequencing (QTI-seq), where the initiating ribosomes can be profiled in real time at single nucleotide resolution. The resultant initiation map not only delineates variations of start codon selection, but also highlights a dynamic range of initiation rates in response to nutrient starvation. The integrated data set provides unique insights into principles of alternative translation and mechanisms controlling different aspects of translation initiation. Using RiboTag mice, QTI-seq permits tissue-specific profiling of initiating ribosomes in vivo. Liver cell-specific ribosome profiling uncovers a robust translational reprogramming of the proteasome system in fasted mice. Our findings illuminate the prevalence and dynamic nature of translational regulation pivotal to physiological adaptation in vivo.
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131
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Michel AM, Andreev DE, Baranov PV. Computational approach for calculating the probability of eukaryotic translation initiation from ribo-seq data that takes into account leaky scanning. BMC Bioinformatics 2014; 15:380. [PMID: 25413677 PMCID: PMC4245810 DOI: 10.1186/s12859-014-0380-4] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 11/05/2014] [Indexed: 11/29/2022] Open
Abstract
Background Ribosome profiling (ribo-seq) provides experimental data on the density of elongating or initiating ribosomes at the whole transcriptome level that can be potentially used for estimating absolute levels of translation initiation at individual Translation Initiation Sites (TISs). These absolute levels depend on the mutual organisation of TISs within individual mRNAs. For example, according to the leaky scanning model of translation initiation in eukaryotes, a strong TIS downstream of another strong TIS is unlikely to be productive, since only a few scanning ribosomes would be able to reach the downstream TIS. In order to understand the dependence of translation initiation efficiency on the surrounding nucleotide context, it is important to estimate the strength of TISs independently of their mutual organisation, i.e. to estimate with what probability a ribosome would initiate at a particular TIS. Results We designed a simple computational approach for estimating the probabilities of ribosomes initiating at individual start codons using ribosome profiling data. The method is based on the widely accepted leaky scanning model of translation initiation in eukaryotes which postulates that scanning ribosomes may skip a start codon if the initiation context is unfavourable and continue on scanning. We tested our approach on three independent ribo-seq datasets obtained in mammalian cultured cells. Conclusions Our results suggested that the method successfully discriminates between weak and strong TISs and that the majority of numerous non-AUG TISs reported recently are very weak. Therefore the high frequency of non-AUG TISs observed in ribosome profiling experiments is due to their proximity to mRNA 5′-ends rather than their strength. Detectable translation initiation at non-AUG codons downstream of AUG codons is comparatively infrequent. The leaky scanning method will be useful for the characterization of differences in start codon selection between tissues, developmental stages and in response to stress conditions. Electronic supplementary material The online version of this article (doi:10.1186/s12859-014-0380-4) contains supplementary material, which is available to authorized users.
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King HA, Gerber AP. Translatome profiling: methods for genome-scale analysis of mRNA translation. Brief Funct Genomics 2014; 15:22-31. [PMID: 25380596 DOI: 10.1093/bfgp/elu045] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
During the past decade, there has been a rapidly increased appreciation of the role of translation as a key regulatory node in gene expression. Thereby, the development of methods to infer the translatome, which refers to the entirety of mRNAs associated with ribosomes for protein synthesis, has facilitated the discovery of new principles and mechanisms of translation and expanded our view of the underlying logic of protein synthesis. Here, we review the three main methodologies for translatome analysis, and we highlight some of the recent discoveries made using each technique. We first discuss polysomal profiling, a classical technique that involves the separation of mRNAs depending on the number of bound ribosomes using a sucrose gradient, and which has been combined with global analysis tools such as DNA microarrays or high-throughput RNA sequencing to identify the RNAs in polysomal fractions. We then introduce ribosomal profiling, a recently established technique that enables the mapping of ribosomes along mRNAs at near-nucleotide resolution on a global scale. We finally refer to ribosome affinity purification techniques that are based on the cell-type-specific expression of tagged ribosomal proteins, allowing the capture of translatomes from specialized cells in organisms. We discuss the advantages and disadvantages of these three main techniques in the pursuit of defining the translatome, and we speculate about future developments.
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133
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Gawron D, Gevaert K, Van Damme P. The proteome under translational control. Proteomics 2014; 14:2647-62. [PMID: 25263132 DOI: 10.1002/pmic.201400165] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Revised: 08/21/2014] [Accepted: 09/23/2014] [Indexed: 02/02/2023]
Abstract
A single eukaryotic gene can give rise to a variety of protein forms (proteoforms) as a result of genetic variation and multilevel regulation of gene expression. In addition to alternative splicing, an increasing line of evidence shows that alternative translation contributes to the overall complexity of proteomes. Identifying the repertoire of proteins and micropeptides expressed by alternative selection of (near-)cognate translation initiation sites and different reading frames however remains challenging with contemporary proteomics. MS-enabled identification of proteoforms is expected to benefit from transcriptome and translatome data by the creation of customized and sample-specific protein sequence databases. Here, we focus on contemporary integrative omics approaches that complement proteomics with DNA- and/or RNA-oriented technologies to elucidate the mechanisms of translational control. Together, these technologies enable to map the translation (initiation) landscape and more comprehensively define the inventory of proteoforms raised upon alternative translation, thus assisting in the (re-)annotation of genomes.
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Affiliation(s)
- Daria Gawron
- Department of Medical Protein Research, VIB, Ghent, Belgium; Department of Biochemistry, Ghent University, Ghent, Belgium
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134
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Tsotakos N, Silveyra P, Lin Z, Thomas N, Vaid M, Floros J. Regulation of translation by upstream translation initiation codons of surfactant protein A1 splice variants. Am J Physiol Lung Cell Mol Physiol 2014; 308:L58-75. [PMID: 25326576 DOI: 10.1152/ajplung.00058.2014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Surfactant protein A (SP-A), a molecule with roles in lung innate immunity and surfactant-related functions, is encoded by two genes in humans: SFTPA1 (SP-A1) and SFTPA2 (SP-A2). The mRNAs from these genes differ in their 5'-untranslated regions (5'-UTR) due to differential splicing. The 5'-UTR variant ACD' is exclusively found in transcripts of SP-A1, but not in those of SP-A2. Its unique exon C contains two upstream AUG codons (uAUGs) that may affect SP-A1 translation efficiency. The first uAUG (u1) is in frame with the primary start codon (p), but the second one (u2) is not. The purpose of this study was to assess the impact of uAUGs on SP-A1 expression. We employed RT-qPCR to determine the presence of exon C-containing SP-A1 transcripts in human RNA samples. We also used in vitro techniques including mutagenesis, reporter assays, and toeprinting analysis, as well as in silico analyses to determine the role of uAUGs. Exon C-containing mRNA is present in most human lung tissue samples and its expression can, under certain conditions, be regulated by factors such as dexamethasone or endotoxin. Mutating uAUGs resulted in increased luciferase activity. The mature protein size was not affected by the uAUGs, as shown by a combination of toeprint and in silico analysis for Kozak sequence, secondary structure, and signal peptide and in vitro translation in the presence of microsomes. In conclusion, alternative splicing may introduce uAUGs in SP-A1 transcripts, which in turn negatively affect SP-A1 translation, possibly affecting SP-A1/SP-A2 ratio, with potential for clinical implication.
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Affiliation(s)
- Nikolaos Tsotakos
- Center for Host Defense, Inflammation and Lung Disease (CHILD) Research, Department of Pediatrics, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Patricia Silveyra
- Center for Host Defense, Inflammation and Lung Disease (CHILD) Research, Department of Pediatrics, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Zhenwu Lin
- Department of Cellular and Molecular Physiology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Neal Thomas
- Center for Host Defense, Inflammation and Lung Disease (CHILD) Research, Department of Pediatrics, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania; Department of Public Health Sciences, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania; and
| | - Mudit Vaid
- Center for Host Defense, Inflammation and Lung Disease (CHILD) Research, Department of Pediatrics, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania
| | - Joanna Floros
- Center for Host Defense, Inflammation and Lung Disease (CHILD) Research, Department of Pediatrics, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania; Department of Obstetrics and Gynecology, The Pennsylvania State University College of Medicine, Hershey, Pennsylvania
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135
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Kearse MG, Todd PK. Repeat-associated non-AUG translation and its impact in neurodegenerative disease. Neurotherapeutics 2014; 11:721-31. [PMID: 25005000 PMCID: PMC4391382 DOI: 10.1007/s13311-014-0292-z] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Nucleotide repeat expansions underlie numerous human neurological disorders. Repeats can trigger toxicity through multiple pathogenic mechanisms, including RNA gain-of-function, protein gain-of-function, and protein loss-of-function pathways. Traditionally, inference of the underlying pathogenic mechanism derives from the repeat location, with dominantly inherited repeats within transcribed noncoding sequences eliciting toxicity predominantly as RNA via sequestration of specific RNA binding proteins. However, recent findings question this assumption and suggest that repeats outside of annotated open reading frames may also trigger toxicity through a novel form of protein translational initiation known as repeat-associated non-AUG (RAN) translation. To date, RAN translation has been implicated in 4 nucleotide repeat expansion disorders: spinocerebellar ataxia type 8; myotonic dystrophy type 1 with CTG•CAG repeats; C9orf72 amyotrophic lateral sclerosis/frontotemporal dementia with GGGGCC•GGCCCC repeats; and fragile X-associated tremor/ataxia syndrome with CGG repeats. RAN translation contributes to hallmark pathological characteristics in these disorders by producing homopolymeric or dipeptide repeat proteins. Here, we review what is known about RAN translation, with an emphasis on how differences in both repeat sequence and context may confer different requirements for unconventional initiation. We then discuss how this new mechanism of translational initiation might function in normal physiology and lay out a roadmap for addressing the numerous questions that remain.
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Affiliation(s)
- Michael G. Kearse
- />Department of Neurology, University of Michigan Medical School, 4005 BSRB, 109 Zina Pitcher Place, Ann Arbor, MI 48109-2200 USA
| | - Peter K. Todd
- />Department of Neurology, University of Michigan Medical School, 4005 BSRB, 109 Zina Pitcher Place, Ann Arbor, MI 48109-2200 USA
- />Veterans Affairs Medical Center, Ann Arbor, MI 48105 USA
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Zupanic A, Meplan C, Grellscheid SN, Mathers JC, Kirkwood TBL, Hesketh JE, Shanley DP. Detecting translational regulation by change point analysis of ribosome profiling data sets. RNA (NEW YORK, N.Y.) 2014; 20:1507-1518. [PMID: 25147239 PMCID: PMC4174433 DOI: 10.1261/rna.045286.114] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2014] [Accepted: 06/25/2014] [Indexed: 06/03/2023]
Abstract
Ribo-Seq maps the location of translating ribosomes on mature mRNA transcripts. While during normal translation, ribosome density is constant along the length of the mRNA coding region, this can be altered in response to translational regulatory events. In the present study, we developed a method to detect translational regulation of individual mRNAs from their ribosome profiles, utilizing changes in ribosome density. We used mathematical modeling to show that changes in ribosome density should occur along the mRNA at the point of regulation. We analyzed a Ribo-Seq data set obtained for mouse embryonic stem cells and showed that normalization by corresponding RNA-Seq can be used to improve the Ribo-Seq quality by removing bias introduced by deep-sequencing and alignment artifacts. After normalization, we applied a change point algorithm to detect changes in ribosome density present in individual mRNA ribosome profiles. Additional sequence and gene isoform information obtained from the UCSC Genome Browser allowed us to further categorize the detected changes into different mechanisms of regulation. In particular, we detected several mRNAs with known post-transcriptional regulation, e.g., premature termination for selenoprotein mRNAs and translational control of Atf4, but also several more mRNAs with hitherto unknown translational regulation. Additionally, our approach proved useful for identification of new transcript isoforms.
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Affiliation(s)
- Anze Zupanic
- Centre for Integrated Systems Biology of Ageing and Nutrition, Institute for Ageing and Health, Newcastle University, Newcastle-upon-Tyne, NE4 5PL, United Kingdom Department of Environmental Toxicology, Eawag: Swiss Federal Institute of Aquatic Science and Technology, 8600 Dübendorf, Switzerland
| | - Catherine Meplan
- Institute for Cell and Molecular Biosciences and Human Nutrition Research Centre, Newcastle University, Newcastle-upon-Tyne, NE2 4HH, United Kingdom
| | - Sushma N Grellscheid
- School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, United Kingdom
| | - John C Mathers
- Centre for Integrated Systems Biology of Ageing and Nutrition, Institute for Ageing and Health, Newcastle University, Newcastle-upon-Tyne, NE4 5PL, United Kingdom
| | - Tom B L Kirkwood
- Centre for Integrated Systems Biology of Ageing and Nutrition, Institute for Ageing and Health, Newcastle University, Newcastle-upon-Tyne, NE4 5PL, United Kingdom
| | - John E Hesketh
- Institute for Cell and Molecular Biosciences and Human Nutrition Research Centre, Newcastle University, Newcastle-upon-Tyne, NE2 4HH, United Kingdom
| | - Daryl P Shanley
- Centre for Integrated Systems Biology of Ageing and Nutrition, Institute for Ageing and Health, Newcastle University, Newcastle-upon-Tyne, NE4 5PL, United Kingdom
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137
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Aspden JL, Eyre-Walker YC, Phillips RJ, Amin U, Mumtaz MAS, Brocard M, Couso JP. Extensive translation of small Open Reading Frames revealed by Poly-Ribo-Seq. eLife 2014; 3:e03528. [PMID: 25144939 PMCID: PMC4359375 DOI: 10.7554/elife.03528] [Citation(s) in RCA: 258] [Impact Index Per Article: 23.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2014] [Accepted: 08/19/2014] [Indexed: 12/11/2022] Open
Abstract
Thousands of small Open Reading Frames (smORFs) with the potential to encode small peptides of fewer than 100 amino acids exist in our genomes. However, the number of smORFs actually translated, and their molecular and functional roles are still unclear. In this study, we present a genome-wide assessment of smORF translation by ribosomal profiling of polysomal fractions in Drosophila. We detect two types of smORFs bound by multiple ribosomes and thus undergoing productive translation. The ‘longer’ smORFs of around 80 amino acids resemble canonical proteins in translational metrics and conservation, and display a propensity to contain transmembrane motifs. The ‘dwarf’ smORFs are in general shorter (around 20 amino-acid long), are mostly found in 5′-UTRs and non-coding RNAs, are less well conserved, and have no bioinformatic indicators of peptide function. Our findings indicate that thousands of smORFs are translated in metazoan genomes, reinforcing the idea that smORFs are an abundant and fundamental genome component. DOI:http://dx.doi.org/10.7554/eLife.03528.001 To produce a protein, a stretch of DNA must first be transcribed to produce a molecule of messenger RNA (mRNA). The genetic information copied from the DNA is then read three letters at a time, in groups called codons. Each codon either encodes a particular amino acid to be added into a protein or provides further instructions: ‘start codons’ mark the beginning of a protein; ‘stop codons’ mark its end. The DNA between these two points is called an open reading frame (or ORF)—however, not all ORFs produce proteins. Most proteins are made of several hundred amino acids, but the genomes of animals contain thousands of ORFs that would generate much smaller proteins made of fewer than 100 amino acids, if they were translated. It is, however, unclear how many of these small ORFs are converted into mRNA molecules and functional proteins. Ribosomes are large molecular machines that translate the code in mRNA molecules and join together the appropriate amino acids in the right order to make a protein. Ribosome profiling is a technique that identifies which mRNA molecules are translated into proteins by determining the sequences of all the mRNA molecules bound to ribosomes at a particular moment. The mRNA sequences can then be compared with the sequence of the whole genome to work out which ORFs they correspond to. Ribosome profiling has been used to detect translated small ORFs, but the method yields a relatively high false positive rate as some mRNAs can bind to ribosomes without being translated. To better detect small protein-producing ORFs, Aspden et al. developed a technique based on ribosome profiling called Poly-Ribo-Seq. The method takes advantage of the fact that during active translation, clusters of multiple ribosomes, called polysomes, bind mRNAs. Poly-Ribo-Seq isolates these polysomes and determines the sequence bound by each of the ribosomes, thereby reducing the number of false positives. Applying Poly-Ribo-Seq to cells from the fruit fly Drosophila allowed Aspden et al. to identify two types of short ORF. The first type codes for proteins that are around 80 amino acids long and are translated with the same efficiency as larger ORFs. The sequences of these ORFs are found in other species, match at least in part sequences of known functional ORFs, and the proteins produced are found in specific locations inside cells. These small proteins may contribute to membrane integrity or function. Together, these properties suggest that these mRNAs create functional small proteins. The second pool consists of very small ORFs (‘dwarf smORFs’) that code for around 20 amino acids, which are not translated so often and do not show many similarities with other species. As the findings of Aspden et al. suggest that a large fraction of Drosophila small ORFs are translated into proteins, the next challenge will be to determine the roles of these small proteins in cells. DOI:http://dx.doi.org/10.7554/eLife.03528.002
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Affiliation(s)
- Julie L Aspden
- School of Life Sciences, University of Sussex, Brighton, United Kingdom
| | | | - Rose J Phillips
- School of Life Sciences, University of Sussex, Brighton, United Kingdom
| | - Unum Amin
- School of Life Sciences, University of Sussex, Brighton, United Kingdom
| | | | - Michele Brocard
- School of Life Sciences, University of Sussex, Brighton, United Kingdom
| | - Juan-Pablo Couso
- School of Life Sciences, University of Sussex, Brighton, United Kingdom
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138
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Zhang J, Lou X, Shen H, Zellmer L, Sun Y, Liu S, Xu N, Liao DJ. Isoforms of wild type proteins often appear as low molecular weight bands on SDS-PAGE. Biotechnol J 2014; 9:1044-54. [PMID: 24906056 DOI: 10.1002/biot.201400072] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Revised: 04/03/2014] [Accepted: 06/04/2014] [Indexed: 11/08/2022]
Abstract
Immunoblotting, after polyacrylamide gel electrophoresis with sodium dodecyl sulfate (SDS-PAGE), is a technique commonly used to detect specific proteins. SDS-PAGE often results in the visualization of protein band(s) in addition to the one expected based on the theoretical molecular mass (TMM) of the protein of interest. To determine the likelihood of additional band(s) being nonspecific, we used liquid chromatography - mass spectrometry to identify proteins that were extracted from bands with the apparent molecular mass (MM) of 40 and 26 kD, originating from protein extracts derived from non-malignant HEK293 and cancerous MDA-MB231 (MB231) cells separated using SDS-PAGE. In total, approximately 57% and 21% of the MS/MS spectra were annotated as peptides in the two cell samples, respectively. Moreover, approximately 24% and 36.2% of the identified proteins from HEK293 and MB231 cells matched their TMMs. Of the identified proteins, 8% from HEK293 and 26% from MB231 had apparent MMs that were larger than predicted, and 67% from HEK293 and 37% from MB231 exhibited smaller MM values than predicted. These revelations suggest that interpretation of the positive bands of immunoblots should be conducted with caution. This study also shows that protein identification performed by mass spectrometry on bands excised from SDS-PAGE gels could make valuable contributions to the identification of cancer biomarkers, and to cancer-therapy studies.
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Affiliation(s)
- Ju Zhang
- CAS Key Laboratory of Genome Sciences and Information, Beijing Institute of Genomics, Chinese Academy of Sciences, Beijing, P. R. China
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139
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Baboo S, Cook PR. "Dark matter" worlds of unstable RNA and protein. Nucleus 2014; 5:281-6. [PMID: 25482115 PMCID: PMC4152340 DOI: 10.4161/nucl.29577] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2014] [Revised: 06/10/2014] [Accepted: 06/13/2014] [Indexed: 12/11/2022] Open
Abstract
Astrophysicists use the term "dark matter" to describe the majority of the matter and/or energy in the universe that is hidden from view, and biologists now apply it to the new families of RNA they are uncovering. We review evidence for an analogous hidden world containing peptides. The critical experiments involved pulse-labeling human cells with tagged amino acids for periods as short as five seconds. Results are extraordinary in two respects: both nucleus and cytoplasm become labeled, and most signals disappear with a half-life of less than one minute. Just as the synthesis of each mature mRNA is regulated by the abortive production of hundreds of shorter transcripts that are quickly degraded, it seems that the synthesis of each full-length protein in the stable proteome is regulated by an apparently wasteful production and degradation of shorter peptides. Some of the nuclear synthesis is probably a byproduct of nuclear ribosomes proofreading newly-made RNA for inappropriately-placed termination codons (a process that triggers "nonsense-mediated decay"). We speculate that some "dark-matter" peptides will play other important roles in the cell.
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Affiliation(s)
- Sabyasachi Baboo
- Sir William Dunn School of Pathology; University of Oxford; Oxford, UK
| | - Peter R Cook
- Sir William Dunn School of Pathology; University of Oxford; Oxford, UK
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140
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Baboo S, Bhushan B, Jiang H, Grovenor CRM, Pierre P, Davis BG, Cook PR. Most human proteins made in both nucleus and cytoplasm turn over within minutes. PLoS One 2014; 9:e99346. [PMID: 24911415 PMCID: PMC4050049 DOI: 10.1371/journal.pone.0099346] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 05/13/2014] [Indexed: 12/25/2022] Open
Abstract
In bacteria, protein synthesis can be coupled to transcription, but in eukaryotes it is believed to occur solely in the cytoplasm. Using pulses as short as 5 s, we find that three analogues – L-azidohomoalanine, puromycin (detected after attaching fluors using ‘click’ chemistry or immuno-labeling), and amino acids tagged with ‘heavy’ 15N and 13C (detected using secondary ion mass spectrometry) – are incorporated into the nucleus and cytoplasm in a process sensitive to translational inhibitors. The nuclear incorporation represents a significant fraction of the total, and labels in both compartments have half-lives of less than a minute; results are consistent with most newly-made peptides being destroyed soon after they are made. As nascent RNA bearing a premature termination codon (detected by fluorescence in situ hybridization) is also eliminated by a mechanism sensitive to a translational inhibitor, the nuclear turnover of peptides is probably a by-product of proof-reading the RNA for stop codons (a process known as nonsense-mediated decay). We speculate that the apparently-wasteful turnover of this previously-hidden (‘dark-matter’) world of peptide is involved in regulating protein production.
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Affiliation(s)
- Sabyasachi Baboo
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Bhaskar Bhushan
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Haibo Jiang
- Department of Materials, University of Oxford, Oxford, United Kingdom
| | | | - Philippe Pierre
- Centre d′Immunologie de Marseille-Luminy, Aix-Marseille Université, Marseille, France
- Institut National de la Santé et de la Recherche Médicale, U1104, Marseille, France
- Centre National de la Recherche Scientifique, Unités Mixtes de Recherche 7280, Marseille, France
| | - Benjamin G. Davis
- Chemistry Research Laboratory, Department of Chemistry, University of Oxford, Oxford, United Kingdom
| | - Peter R. Cook
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
- * E-mail:
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141
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Crappé J, Van Criekinge W, Menschaert G. Little things make big things happen: A summary of micropeptide encoding genes. EUPA OPEN PROTEOMICS 2014. [DOI: 10.1016/j.euprot.2014.02.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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142
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Van Damme P, Gawron D, Van Criekinge W, Menschaert G. N-terminal proteomics and ribosome profiling provide a comprehensive view of the alternative translation initiation landscape in mice and men. Mol Cell Proteomics 2014; 13:1245-61. [PMID: 24623590 DOI: 10.1074/mcp.m113.036442] [Citation(s) in RCA: 102] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Usage of presumed 5'UTR or downstream in-frame AUG codons, next to non-AUG codons as translation start codons contributes to the diversity of a proteome as protein isoforms harboring different N-terminal extensions or truncations can serve different functions. Recent ribosome profiling data revealed a highly underestimated occurrence of database nonannotated, and thus alternative translation initiation sites (aTIS), at the mRNA level. N-terminomics data in addition showed that in higher eukaryotes around 20% of all identified protein N termini point to such aTIS, to incorrect assignments of the translation start codon, translation initiation at near-cognate start codons, or to alternative splicing. We here report on more than 1700 unique alternative protein N termini identified at the proteome level in human and murine cellular proteomes. Customized databases, created using the translation initiation mapping obtained from ribosome profiling data, additionally demonstrate the use of initiator methionine decoded near-cognate start codons besides the existence of N-terminal extended protein variants at the level of the proteome. Various newly identified aTIS were confirmed by mutagenesis, and meta-analyses demonstrated that aTIS reside in strong Kozak-like motifs and are conserved among eukaryotes, hinting to a possible biological impact. Finally, TargetP analysis predicted that the usage of aTIS often results in altered subcellular localization patterns, providing a mechanism for functional diversification.
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Affiliation(s)
- Petra Van Damme
- Department of Medical Protein Research, VIB, B-9000 Ghent, Belgium
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143
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Emerging evidence for functional peptides encoded by short open reading frames. Nat Rev Genet 2014; 15:193-204. [PMID: 24514441 DOI: 10.1038/nrg3520] [Citation(s) in RCA: 402] [Impact Index Per Article: 36.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Short open reading frames (sORFs) are a common feature of all genomes, but their coding potential has mostly been disregarded, partly because of the difficulty in determining whether these sequences are translated. Recent innovations in computing, proteomics and high-throughput analyses of translation start sites have begun to address this challenge and have identified hundreds of putative coding sORFs. The translation of some of these has been confirmed, although the contribution of their peptide products to cellular functions remains largely unknown. This Review examines this hitherto overlooked component of the proteome and considers potential roles for sORF-encoded peptides.
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144
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Skarshewski A, Stanton-Cook M, Huber T, Al Mansoori S, Smith R, Beatson SA, Rothnagel JA. uPEPperoni: an online tool for upstream open reading frame location and analysis of transcript conservation. BMC Bioinformatics 2014; 15:36. [PMID: 24484385 PMCID: PMC3914846 DOI: 10.1186/1471-2105-15-36] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Accepted: 01/11/2014] [Indexed: 01/17/2023] Open
Abstract
BACKGROUND Several small open reading frames located within the 5' untranslated regions of mRNAs have recently been shown to be translated. In humans, about 50% of mRNAs contain at least one upstream open reading frame representing a large resource of coding potential. We propose that some upstream open reading frames encode peptides that are functional and contribute to proteome complexity in humans and other organisms. We use the term uPEPs to describe peptides encoded by upstream open reading frames. RESULTS We have developed an online tool, termed uPEPperoni, to facilitate the identification of putative bioactive peptides. uPEPperoni detects conserved upstream open reading frames in eukaryotic transcripts by comparing query nucleotide sequences against mRNA sequences within the NCBI RefSeq database. The algorithm first locates the main coding sequence and then searches for open reading frames 5' to the main start codon which are subsequently analysed for conservation. uPEPperoni also determines the substitution frequency for both the upstream open reading frames and the main coding sequence. In addition, the uPEPperoni tool produces sequence identity heatmaps which allow rapid visual inspection of conserved regions in paired mRNAs. CONCLUSIONS uPEPperoni features user-nominated settings including, nucleotide match/mismatch, gap penalties, Ka/Ks ratios and output mode. The heatmap output shows levels of identity between any two sequences and provides easy recognition of conserved regions. Furthermore, this web tool allows comparison of evolutionary pressures acting on the upstream open reading frame against other regions of the mRNA. Additionally, the heatmap web applet can also be used to visualise the degree of conservation in any pair of sequences. uPEPperoni is freely available on an interactive web server at http://upep-scmb.biosci.uq.edu.au.
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Affiliation(s)
| | | | | | | | | | | | - Joseph A Rothnagel
- School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, QLD 4072, Australia.
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145
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Dassi E, Re A, Leo S, Tebaldi T, Pasini L, Peroni D, Quattrone A. AURA 2: Empowering discovery of post-transcriptional networks. ACTA ACUST UNITED AC 2014; 2:e27738. [PMID: 26779400 PMCID: PMC4705823 DOI: 10.4161/trla.27738] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Revised: 12/11/2013] [Accepted: 01/05/2014] [Indexed: 12/19/2022]
Abstract
Post-transcriptional regulation (PTR) of gene expression is now recognized as a major determinant of cell phenotypes. The recent availability of methods to map protein-RNA interactions in entire transcriptomes such as RIP, CLIP and their variants, together with global polysomal and ribosome profiling techniques, are driving the exponential accumulation of vast amounts of data on mRNA contacts in cells, and of corresponding predictions of PTR events. However, this exceptional quantity of information cannot be exploited at its best to reconstruct potential PTR networks, as it still lies scattered throughout several databases and in isolated reports of single interactions. To address this issue, we developed the second and vastly enhanced version of the Atlas of UTR Regulatory Activity (AURA 2), a meta-database centered on mapping interaction of trans-factors with human and mouse UTRs. AURA 2 includes experimentally demonstrated binding sites for RBPs, ncRNAs, thousands of cis-elements, variations, RNA epigenetics data and more. Its user-friendly interface offers various data-mining features including co-regulation search, network generation and regulatory enrichment testing. Gene expression profiles for many tissues and cell lines can be also combined with these analyses to display only the interactions possible in the system under study. AURA 2 aims at becoming a valuable toolbox for PTR studies and at tracing the road for how PTR network-building tools should be designed. AURA 2 is available at http://aura.science.unitn.it.
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Affiliation(s)
- Erik Dassi
- Laboratory of Translational Genomics; Centre for Integrative Biology; University of Trento; Trento, Italy
| | - Angela Re
- Laboratory of Translational Genomics; Centre for Integrative Biology; University of Trento; Trento, Italy
| | - Sara Leo
- Laboratory of Translational Genomics; Centre for Integrative Biology; University of Trento; Trento, Italy
| | - Toma Tebaldi
- Laboratory of Translational Genomics; Centre for Integrative Biology; University of Trento; Trento, Italy
| | - Luigi Pasini
- Laboratory of Translational Genomics; Centre for Integrative Biology; University of Trento; Trento, Italy
| | - Daniele Peroni
- Laboratory of Translational Genomics; Centre for Integrative Biology; University of Trento; Trento, Italy
| | - Alessandro Quattrone
- Laboratory of Translational Genomics; Centre for Integrative Biology; University of Trento; Trento, Italy
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146
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Ribosome profiling: new views of translation, from single codons to genome scale. Nat Rev Genet 2014; 15:205-13. [PMID: 24468696 DOI: 10.1038/nrg3645] [Citation(s) in RCA: 435] [Impact Index Per Article: 39.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Genome-wide analyses of gene expression have so far focused on the abundance of mRNA species as measured either by microarray or, more recently, by RNA sequencing. However, neither approach provides information on protein synthesis, which is the true end point of gene expression. Ribosome profiling is an emerging technique that uses deep sequencing to monitor in vivo translation. Studies using ribosome profiling have already provided new insights into the identity and the amount of proteins that are produced by cells, as well as detailed views into the mechanism of protein synthesis itself.
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147
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Ingolia NT, Brar GA, Rouskin S, McGeachy AM, Weissman JS. Genome-wide annotation and quantitation of translation by ribosome profiling. CURRENT PROTOCOLS IN MOLECULAR BIOLOGY 2014; Chapter 4:4.18.1-4.18.19. [PMID: 23821443 DOI: 10.1002/0471142727.mb0418s103] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Recent studies highlight the importance of translational control in determining protein abundance, underscoring the value of measuring gene expression at the level of translation. A protocol for genome-wide, quantitative analysis of in vivo translation by deep sequencing is presented here. This ribosome-profiling approach maps the exact positions of ribosomes on transcripts by nuclease footprinting. The nuclease-protected mRNA fragments are converted into a DNA library suitable for deep sequencing using a strategy that minimizes bias. The abundance of different footprint fragments in deep sequencing data reports on the amount of translation of a gene. Additionally, footprints reveal the exact regions of the transcriptome that are translated. To better define translated reading frames, an adaptation that reveals the sites of translation initiation by pre-treating cells with harringtonine to immobilize initiating ribosomes is described. The protocol described requires 5 to 7 days to generate a completed ribosome profiling sequencing library. Sequencing and data analysis requires an additional 4 to 5 days.
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Affiliation(s)
- Nicholas T Ingolia
- Department of Cellular and Molecular Pharmacology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
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148
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Arias C, Weisburd B, Stern-Ginossar N, Mercier A, Madrid AS, Bellare P, Holdorf M, Weissman JS, Ganem D. KSHV 2.0: a comprehensive annotation of the Kaposi's sarcoma-associated herpesvirus genome using next-generation sequencing reveals novel genomic and functional features. PLoS Pathog 2014; 10:e1003847. [PMID: 24453964 PMCID: PMC3894221 DOI: 10.1371/journal.ppat.1003847] [Citation(s) in RCA: 241] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 10/20/2013] [Indexed: 01/08/2023] Open
Abstract
Productive herpesvirus infection requires a profound, time-controlled remodeling of the viral transcriptome and proteome. To gain insights into the genomic architecture and gene expression control in Kaposi's sarcoma-associated herpesvirus (KSHV), we performed a systematic genome-wide survey of viral transcriptional and translational activity throughout the lytic cycle. Using mRNA-sequencing and ribosome profiling, we found that transcripts encoding lytic genes are promptly bound by ribosomes upon lytic reactivation, suggesting their regulation is mainly transcriptional. Our approach also uncovered new genomic features such as ribosome occupancy of viral non-coding RNAs, numerous upstream and small open reading frames (ORFs), and unusual strategies to expand the virus coding repertoire that include alternative splicing, dynamic viral mRNA editing, and the use of alternative translation initiation codons. Furthermore, we provide a refined and expanded annotation of transcription start sites, polyadenylation sites, splice junctions, and initiation/termination codons of known and new viral features in the KSHV genomic space which we have termed KSHV 2.0. Our results represent a comprehensive genome-scale image of gene regulation during lytic KSHV infection that substantially expands our understanding of the genomic architecture and coding capacity of the virus. Kaposi's sarcoma-associated herpesvirus (KSHV) is a cancer-causing agent in immunocompromised patients that establishes long-lasting infections in its hosts. Initially described in 1994 and extensively studied ever since, KSHV molecular biology is understood in broad outline, but many detailed questions are still to be resolved. After almost two decades, specific aspects pertaining to the organization of the KSHV genome as well as the fate of the viral transcripts during the productive stages of infection remain unexplored. Here we use a systematic genome-wide approach to investigate changes in gene and protein expression during the productive stage of infection known as the lytic cycle. We found that the viral genome has a large coding capacity, capable of generating at least 45% more products than initially anticipated by bioinformatic analyses alone, and that it uses multiple strategies to expand its coding capacity well beyond what is determined solely by the DNA sequence of its genome. We also provide an expanded and highly detailed annotation of known and new genomic features in KSHV. We have termed this new architectural and functional annotation KSHV 2.0. Our results indicate that viral genomes are more complex than anticipated, and that they are subject to tight mechanisms of regulation to ensure correct gene expression.
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Affiliation(s)
- Carolina Arias
- Novartis Institute for Biomedical Research, Department of Infectious Diseases, Emeryville, California, United States of America
- * E-mail:
| | - Ben Weisburd
- Novartis Vaccines and Diagnostics, Bioinformatics, Emeryville, California, United States of America
| | - Noam Stern-Ginossar
- Department of Cellular and Molecular Pharmacology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, California, United States of America
| | - Alexandre Mercier
- Novartis Institute for Biomedical Research, Department of Infectious Diseases, Emeryville, California, United States of America
| | - Alexis S. Madrid
- Novartis Institute for Biomedical Research, Department of Infectious Diseases, Emeryville, California, United States of America
| | - Priya Bellare
- Novartis Institute for Biomedical Research, Department of Infectious Diseases, Emeryville, California, United States of America
| | - Meghan Holdorf
- Novartis Institute for Biomedical Research, Department of Infectious Diseases, Emeryville, California, United States of America
| | - Jonathan S. Weissman
- Department of Cellular and Molecular Pharmacology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, California, United States of America
| | - Don Ganem
- Novartis Institute for Biomedical Research, Department of Infectious Diseases, Emeryville, California, United States of America
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149
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von Arnim AG, Jia Q, Vaughn JN. Regulation of plant translation by upstream open reading frames. PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2014; 214:1-12. [PMID: 24268158 DOI: 10.1016/j.plantsci.2013.09.006] [Citation(s) in RCA: 145] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Revised: 09/08/2013] [Accepted: 09/10/2013] [Indexed: 05/08/2023]
Abstract
We review the evidence that upstream open reading frames (uORFs) function as RNA sequence elements for post-transcriptional control of gene expression, specifically translation. uORFs are highly abundant in the genomes of angiosperms. Their negative effect on translation is often attenuated by ribosomal translation reinitiation, a process whose molecular biochemistry is still being investigated. Certain uORFs render translation responsive to small molecules, thus offering a path for metabolic control of gene expression in evolution and synthetic biology. In some cases, uORFs form modular logic gates in signal transduction. uORFs thus provide eukaryotes with a functionality analogous to, or comparable to, riboswitches and attenuators in prokaryotes. uORFs exist in many genes regulating development and point toward translational control of development. While many uORFs appear to be poorly conserved, and the number of genes with conserved-peptide uORFs is modest, many mRNAs have a conserved pattern of uORFs. Evolutionarily, the gain and loss of uORFs may be a widespread mechanism that diversifies gene expression patterns. Last but not least, this review includes a dedicated uORF database for Arabidopsis.
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Affiliation(s)
- Albrecht G von Arnim
- Department of Biochemistry, Cellular and Molecular Biology, The University of Tennessee, Knoxville, TN 37996-0840, USA; Graduate School of Genome Science and Technology, The University of Tennessee, Knoxville, TN 37996-0840, USA.
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150
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Dunn JG, Foo CK, Belletier NG, Gavis ER, Weissman JS. Ribosome profiling reveals pervasive and regulated stop codon readthrough in Drosophila melanogaster. eLife 2013; 2:e01179. [PMID: 24302569 PMCID: PMC3840789 DOI: 10.7554/elife.01179] [Citation(s) in RCA: 277] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Ribosomes can read through stop codons in a regulated manner, elongating rather than terminating the nascent peptide. Stop codon readthrough is essential to diverse viruses, and phylogenetically predicted to occur in a few hundred genes in Drosophila melanogaster, but the importance of regulated readthrough in eukaryotes remains largely unexplored. Here, we present a ribosome profiling assay (deep sequencing of ribosome-protected mRNA fragments) for Drosophila melanogaster, and provide the first genome-wide experimental analysis of readthrough. Readthrough is far more pervasive than expected: the vast majority of readthrough events evolved within D. melanogaster and were not predicted phylogenetically. The resulting C-terminal protein extensions show evidence of selection, contain functional subcellular localization signals, and their readthrough is regulated, arguing for their importance. We further demonstrate that readthrough occurs in yeast and humans. Readthrough thus provides general mechanisms both to regulate gene expression and function, and to add plasticity to the proteome during evolution. DOI: http://dx.doi.org/10.7554/eLife.01179.001.
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Affiliation(s)
- Joshua G Dunn
- California Institute of Quantitative Biosciences, San Francisco, United States
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