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Kataoka N. The Nuclear Cap-Binding Complex, a multitasking binding partner of RNA polymerase II transcripts. J Biochem 2023; 175:9-15. [PMID: 37830942 PMCID: PMC10771035 DOI: 10.1093/jb/mvad081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 09/26/2023] [Accepted: 10/03/2023] [Indexed: 10/14/2023] Open
Abstract
In eukaryotic cells, RNAs transcribed by RNA polymerase-II receive the modification at the 5' end. This structure is called the cap structure. The cap structure has a fundamental role for translation initiation by recruiting eukaryotic translation initiation factor 4F (eIF4F). The other important mediator of the cap structure is a nuclear cap-binding protein complex (CBC). CBC consists of two proteins, which are renamed as NCBP1 and NCBP2 (previously called as CBP80/NCBP and CBP20/NIP1, respectively). This review article discusses the multiple roles CBC mediates and co-ordinates in several gene expression steps in eukaryotes.
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Affiliation(s)
- Naoyuki Kataoka
- Laboratory of Cellular Biochemistry, Department of Animal Resource Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Agriculture Bldg. 7A, Room 703, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan
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2
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Huang L, Li G, Du C, Jia Y, Yang J, Fan W, Xu Y, Cheng H, Zhou Y. The polyA tail facilitates splicing of last introns with weak 3' splice sites via PABPN1. EMBO Rep 2023; 24:e57128. [PMID: 37661812 PMCID: PMC10561182 DOI: 10.15252/embr.202357128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 08/04/2023] [Accepted: 08/16/2023] [Indexed: 09/05/2023] Open
Abstract
The polyA tail of mRNAs is important for many aspects of RNA metabolism. However, whether and how it regulates pre-mRNA splicing is still unknown. Here, we report that the polyA tail acts as a splicing enhancer for the last intron via the nuclear polyA binding protein PABPN1 in HeLa cells. PABPN1-depletion induces the retention of a group of introns with a weaker 3' splice site, and they show a strong 3'-end bias and mainly locate in nuclear speckles. The polyA tail is essential for PABPN1-enhanced last intron splicing and functions in a length-dependent manner. Tethering PABPN1 to nonpolyadenylated transcripts also promotes splicing, suggesting a direct role for PABPN1 in splicing regulation. Using TurboID-MS, we construct the PABPN1 interactome, including many spliceosomal and RNA-binding proteins. Specifically, PABPN1 can recruit RBM26&27 to promote splicing by interacting with the coiled-coil and RRM domain of RBM27. PABPN1-regulated terminal intron splicing is conserved in mice. Together, our study establishes a novel mode of post-transcriptional splicing regulation via the polyA tail and PABPN1.
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Affiliation(s)
- Li Huang
- College of Life Sciences, TaiKang Center for Life and Medical Sciences, RNA InstituteWuhan UniversityWuhanChina
| | - Guangnan Li
- College of Life Sciences, TaiKang Center for Life and Medical Sciences, RNA InstituteWuhan UniversityWuhanChina
| | - Chen Du
- College of Life Sciences, TaiKang Center for Life and Medical Sciences, RNA InstituteWuhan UniversityWuhanChina
| | - Yu Jia
- College of Life Sciences, TaiKang Center for Life and Medical Sciences, RNA InstituteWuhan UniversityWuhanChina
| | - Jiayi Yang
- College of Life Sciences, TaiKang Center for Life and Medical Sciences, RNA InstituteWuhan UniversityWuhanChina
| | - Weiliang Fan
- College of Life Sciences, TaiKang Center for Life and Medical Sciences, RNA InstituteWuhan UniversityWuhanChina
| | - Yong‐Zhen Xu
- College of Life Sciences, TaiKang Center for Life and Medical Sciences, RNA InstituteWuhan UniversityWuhanChina
| | - Hong Cheng
- Key Laboratory of RNA Science and Engineering, Chinese Academy of Sciences, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of SciencesUniversity of Chinese Academy of SciencesShanghaiChina
| | - Yu Zhou
- College of Life Sciences, TaiKang Center for Life and Medical Sciences, RNA InstituteWuhan UniversityWuhanChina
- Frontier Science Center for Immunology and MetabolismWuhan UniversityWuhanChina
- Institute of Advanced StudiesWuhan UniversityWuhanChina
- State Key Laboratory of VirologyWuhan UniversityWuhanChina
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3
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Muslimov A, Tereshchenko V, Shevyrev D, Rogova A, Lepik K, Reshetnikov V, Ivanov R. The Dual Role of the Innate Immune System in the Effectiveness of mRNA Therapeutics. Int J Mol Sci 2023; 24:14820. [PMID: 37834268 PMCID: PMC10573212 DOI: 10.3390/ijms241914820] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 09/24/2023] [Accepted: 09/28/2023] [Indexed: 10/15/2023] Open
Abstract
Advances in molecular biology have revolutionized the use of messenger RNA (mRNA) as a therapeutic. The concept of nucleic acid therapy with mRNA originated in 1990 when Wolff et al. reported successful expression of proteins in target organs by direct injection of either plasmid DNA or mRNA. It took decades to bring the transfection efficiency of mRNA closer to that of DNA. The next few decades were dedicated to turning in vitro-transcribed (IVT) mRNA from a promising delivery tool for gene therapy into a full-blown therapeutic modality, which changed the biotech market rapidly. Hundreds of clinical trials are currently underway using mRNA for prophylaxis and therapy of infectious diseases and cancers, in regenerative medicine, and genome editing. The potential of IVT mRNA to induce an innate immune response favors its use for vaccination and immunotherapy. Nonetheless, in non-immunotherapy applications, the intrinsic immunostimulatory activity of mRNA directly hinders the desired therapeutic effect since it can seriously impair the target protein expression. Targeting the same innate immune factors can increase the effectiveness of mRNA therapeutics for some indications and decrease it for others, and vice versa. The review aims to present the innate immunity-related 'barriers' or 'springboards' that may affect the development of immunotherapies and non-immunotherapy applications of mRNA medicines.
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Affiliation(s)
- Albert Muslimov
- Scientific Center for Translational Medicine, Sirius University of Science and Technology, Olympic Ave 1, 354340 Sirius, Russia; (V.T.); (D.S.); (V.R.); (R.I.)
- Laboratory of Nano- and Microencapsulation of Biologically Active Substances, Peter the Great St. Petersburg Polytechnic University, Polytechnicheskaya 29, 195251 St. Petersburg, Russia;
- RM Gorbacheva Research Institute, Pavlov University, L’va Tolstogo 6-8, 197022 St. Petersburg, Russia;
| | - Valeriy Tereshchenko
- Scientific Center for Translational Medicine, Sirius University of Science and Technology, Olympic Ave 1, 354340 Sirius, Russia; (V.T.); (D.S.); (V.R.); (R.I.)
| | - Daniil Shevyrev
- Scientific Center for Translational Medicine, Sirius University of Science and Technology, Olympic Ave 1, 354340 Sirius, Russia; (V.T.); (D.S.); (V.R.); (R.I.)
| | - Anna Rogova
- Laboratory of Nano- and Microencapsulation of Biologically Active Substances, Peter the Great St. Petersburg Polytechnic University, Polytechnicheskaya 29, 195251 St. Petersburg, Russia;
- Saint-Petersburg Chemical-Pharmaceutical University, Professora Popova 14, 197376 St. Petersburg, Russia
- School of Physics and Engineering, ITMO University, Lomonosova 9, 191002 St. Petersburg, Russia
| | - Kirill Lepik
- RM Gorbacheva Research Institute, Pavlov University, L’va Tolstogo 6-8, 197022 St. Petersburg, Russia;
| | - Vasiliy Reshetnikov
- Scientific Center for Translational Medicine, Sirius University of Science and Technology, Olympic Ave 1, 354340 Sirius, Russia; (V.T.); (D.S.); (V.R.); (R.I.)
- Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Prospekt Akad. Lavrentyeva 10, 630090 Novosibirsk, Russia
| | - Roman Ivanov
- Scientific Center for Translational Medicine, Sirius University of Science and Technology, Olympic Ave 1, 354340 Sirius, Russia; (V.T.); (D.S.); (V.R.); (R.I.)
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4
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Sun H, Zhang Y, Wang G, Yang W, Xu Y. mRNA-Based Therapeutics in Cancer Treatment. Pharmaceutics 2023; 15:pharmaceutics15020622. [PMID: 36839944 PMCID: PMC9964383 DOI: 10.3390/pharmaceutics15020622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Revised: 01/28/2023] [Accepted: 01/28/2023] [Indexed: 02/15/2023] Open
Abstract
Over the past two decades, significant technological innovations have led to messenger RNA (mRNA) becoming a promising option for developing prophylactic and therapeutic vaccines, protein replacement therapies, and genome engineering. The success of the two COVID-19 mRNA vaccines has sparked new enthusiasm for other medical applications, particularly in cancer treatment. In vitro-transcribed (IVT) mRNAs are structurally designed to resemble naturally occurring mature mRNA. Delivery of IVT mRNA via delivery platforms such as lipid nanoparticles allows host cells to produce many copies of encoded proteins, which can serve as antigens to stimulate immune responses or as additional beneficial proteins for supplements. mRNA-based cancer therapeutics include mRNA cancer vaccines, mRNA encoding cytokines, chimeric antigen receptors, tumor suppressors, and other combination therapies. To better understand the current development and research status of mRNA therapies for cancer treatment, this review focused on the molecular design, delivery systems, and clinical indications of mRNA therapies in cancer.
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Affiliation(s)
- Han Sun
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Yu Zhang
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Ge Wang
- Department of Oral Maxillofacial & Head and Neck Oncology, National Center of Stomatology, National Clinical Research Center for Oral Disease, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, China
| | - Wen Yang
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
| | - Yingjie Xu
- Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory for Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
- Key Laboratory of Cell Differentiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China
- Correspondence:
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Jiao X, Doamekpor SK, Bird JG, Nickels BE, Tong L, Hart RP, Kiledjian M. 5' End Nicotinamide Adenine Dinucleotide Cap in Human Cells Promotes RNA Decay through DXO-Mediated deNADding. Cell 2017; 168:1015-1027.e10. [PMID: 28283058 DOI: 10.1016/j.cell.2017.02.019] [Citation(s) in RCA: 146] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 12/09/2016] [Accepted: 02/09/2017] [Indexed: 02/02/2023]
Abstract
Eukaryotic mRNAs generally possess a 5' end N7 methyl guanosine (m7G) cap that promotes their translation and stability. However, mammalian mRNAs can also carry a 5' end nicotinamide adenine dinucleotide (NAD+) cap that, in contrast to the m7G cap, does not support translation but instead promotes mRNA decay. The mammalian and fungal noncanonical DXO/Rai1 decapping enzymes efficiently remove NAD+ caps, and cocrystal structures of DXO/Rai1 with 3'-NADP+ illuminate the molecular mechanism for how the "deNADding" reaction produces NAD+ and 5' phosphate RNA. Removal of DXO from cells increases NAD+-capped mRNA levels and enables detection of NAD+-capped intronic small nucleolar RNAs (snoRNAs), suggesting NAD+ caps can be added to 5'-processed termini. Our findings establish NAD+ as an alternative mammalian RNA cap and DXO as a deNADding enzyme modulating cellular levels of NAD+-capped RNAs. Collectively, these data reveal that mammalian RNAs can harbor a 5' end modification distinct from the classical m7G cap that promotes rather than inhibits RNA decay.
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Affiliation(s)
- Xinfu Jiao
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854, USA
| | - Selom K Doamekpor
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Jeremy G Bird
- Department of Genetics and Waksman Institute, Rutgers University, Piscataway, NJ 08854, USA
| | - Bryce E Nickels
- Department of Genetics and Waksman Institute, Rutgers University, Piscataway, NJ 08854, USA
| | - Liang Tong
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Ronald P Hart
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854, USA
| | - Megerditch Kiledjian
- Department of Cell Biology and Neuroscience, Rutgers University, Piscataway, NJ 08854, USA.
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6
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The code and beyond: transcription regulation by the RNA polymerase II carboxy-terminal domain. Nat Rev Mol Cell Biol 2017; 18:263-273. [PMID: 28248323 DOI: 10.1038/nrm.2017.10] [Citation(s) in RCA: 300] [Impact Index Per Article: 42.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The carboxy-terminal domain (CTD) extends from the largest subunit of RNA polymerase II (Pol II) as a long, repetitive and largely unstructured polypeptide chain. Throughout the transcription process, the CTD is dynamically modified by post-translational modifications, many of which facilitate or hinder the recruitment of key regulatory factors of Pol II that collectively constitute the 'CTD code'. Recent studies have revealed how the physicochemical properties of the CTD promote phase separation in the presence of other low-complexity domains. Here, we discuss the intricacies of the CTD code and how the newly characterized physicochemical properties of the CTD expand the function of the CTD beyond the code.
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7
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Harlen KM, Churchman LS. Subgenic Pol II interactomes identify region-specific transcription elongation regulators. Mol Syst Biol 2017; 13:900. [PMID: 28043953 PMCID: PMC5293154 DOI: 10.15252/msb.20167279] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Transcription, RNA processing, and chromatin‐related factors all interact with RNA polymerase II (Pol II) to ensure proper timing and coordination of transcription and co‐transcriptional processes. Many transcription elongation regulators must function simultaneously to coordinate these processes, yet few strategies exist to explore the complement of factors regulating specific stages of transcription. To this end, we developed a strategy to purify Pol II elongation complexes from subgenic regions of a single gene, namely the 5′ and 3′ regions, using sequences in the nascent RNA. Applying this strategy to Saccharomyces cerevisiae, we determined the specific set of factors that interact with Pol II at precise stages during transcription. We identify many known region‐specific factors as well as determine unappreciated associations of regulatory factors during early and late stages of transcription. These data reveal a role for the transcription termination factor, Rai1, in regulating the early stages of transcription genome‐wide and support the role of Bye1 as a negative regulator of early elongation. We also demonstrate a role for the ubiquitin ligase, Bre1, in regulating Pol II dynamics during the latter stages of transcription. These data and our approach to analyze subgenic transcription elongation complexes will shed new light on the myriad factors that regulate the different stages of transcription and coordinate co‐transcriptional processes.
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Affiliation(s)
- Kevin M Harlen
- Department of Genetics, Harvard Medical School, Boston, MA, USA
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8
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Shi Y, Manley JL. The end of the message: multiple protein-RNA interactions define the mRNA polyadenylation site. Genes Dev 2015; 29:889-97. [PMID: 25934501 PMCID: PMC4421977 DOI: 10.1101/gad.261974.115] [Citation(s) in RCA: 189] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Recent studies have significantly reshaped current models for the protein–RNA interactions involved in poly(A) site recognition. Here, Shi and Manley review the recent advances in this area and provide a perspective for future studies. The key RNA sequence elements and protein factors necessary for 3′ processing of polyadenylated mRNA precursors are well known. Recent studies, however, have significantly reshaped current models for the protein–RNA interactions involved in poly(A) site recognition, painting a picture more complex than previously envisioned and also providing new insights into regulation of this important step in gene expression. Here we review the recent advances in this area and provide a perspective for future studies.
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Affiliation(s)
- Yongsheng Shi
- Department of Microbiology and Molecular Genetics, School of Medicine, University of California at Irvine, Irvine, California 92697, USA;
| | - James L Manley
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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9
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Browning KS, Bailey-Serres J. Mechanism of cytoplasmic mRNA translation. THE ARABIDOPSIS BOOK 2015; 13:e0176. [PMID: 26019692 PMCID: PMC4441251 DOI: 10.1199/tab.0176] [Citation(s) in RCA: 144] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Protein synthesis is a fundamental process in gene expression that depends upon the abundance and accessibility of the mRNA transcript as well as the activity of many protein and RNA-protein complexes. Here we focus on the intricate mechanics of mRNA translation in the cytoplasm of higher plants. This chapter includes an inventory of the plant translational apparatus and a detailed review of the translational processes of initiation, elongation, and termination. The majority of mechanistic studies of cytoplasmic translation have been carried out in yeast and mammalian systems. The factors and mechanisms of translation are for the most part conserved across eukaryotes; however, some distinctions are known to exist in plants. A comprehensive understanding of the complex translational apparatus and its regulation in plants is warranted, as the modulation of protein production is critical to development, environmental plasticity and biomass yield in diverse ecosystems and agricultural settings.
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Affiliation(s)
- Karen S. Browning
- Department of Molecular Biosciences and Institute for Cell and Molecular Biology, University of Texas at Austin, Austin TX 78712-0165
- Both authors contributed equally to this work
| | - Julia Bailey-Serres
- Department of Botany and Plant Sciences and Center for Plant Cell Biology, University of California, Riverside, CA, 92521 USA
- Both authors contributed equally to this work
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10
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Abstract
The 7mG (7-methylguanosine cap) formed on mRNA is fundamental to eukaryotic gene expression. Protein complexes recruited to 7mG mediate key processing events throughout the lifetime of the transcript. One of the most important mediators of 7mG functions is CBC (cap-binding complex). CBC has a key role in several gene expression mechanisms, including transcription, splicing, transcript export and translation. Gene expression can be regulated by signalling pathways which influence CBC function. The aim of the present review is to discuss the mechanisms by which CBC mediates and co-ordinates multiple gene expression events.
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11
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Gonatopoulos-Pournatzis T, Cowling VH. Cap-binding complex (CBC). Biochem J 2014. [PMID: 24354960 DOI: 10.1042/bj2013121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The 7mG (7-methylguanosine cap) formed on mRNA is fundamental to eukaryotic gene expression. Protein complexes recruited to 7mG mediate key processing events throughout the lifetime of the transcript. One of the most important mediators of 7mG functions is CBC (cap-binding complex). CBC has a key role in several gene expression mechanisms, including transcription, splicing, transcript export and translation. Gene expression can be regulated by signalling pathways which influence CBC function. The aim of the present review is to discuss the mechanisms by which CBC mediates and co-ordinates multiple gene expression events.
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Affiliation(s)
| | - Victoria H Cowling
- *MRC Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dow Street, Dundee DD1 5EH, U.K
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13
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A mammalian pre-mRNA 5' end capping quality control mechanism and an unexpected link of capping to pre-mRNA processing. Mol Cell 2013; 50:104-15. [PMID: 23523372 DOI: 10.1016/j.molcel.2013.02.017] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Revised: 01/24/2013] [Accepted: 02/14/2013] [Indexed: 12/27/2022]
Abstract
Recently, we reported that two homologous yeast proteins, Rai1 and Dxo1, function in a quality control mechanism to clear cells of incompletely 5' end-capped messenger RNAs (mRNAs). Here, we report that their mammalian homolog, Dom3Z (referred to as DXO), possesses pyrophosphohydrolase, decapping, and 5'-to-3' exoribonuclease activities. Surprisingly, we found that DXO preferentially degrades defectively capped pre-mRNAs in cells. Additional studies show that incompletely capped pre-mRNAs are inefficiently spliced at all introns, a fact that contrasts with current understanding, and are also poorly cleaved for polyadenylation. Crystal structures of DXO in complex with substrate mimic and products at a resolution of up to 1.5Å provide elegant insights into the catalytic mechanism and molecular basis for their three apparently distinct activities. Our data reveal a pre-mRNA 5' end capping quality control mechanism in mammalian cells, indicating DXO as the central player for this mechanism, and demonstrate an unexpected intimate link between proper 5' end capping and subsequent pre-mRNA processing.
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Rehfeld A, Plass M, Krogh A, Friis-Hansen L. Alterations in polyadenylation and its implications for endocrine disease. Front Endocrinol (Lausanne) 2013; 4:53. [PMID: 23658553 PMCID: PMC3647115 DOI: 10.3389/fendo.2013.00053] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Accepted: 04/22/2013] [Indexed: 12/17/2022] Open
Abstract
INTRODUCTION Polyadenylation is the process in which the pre-mRNA is cleaved at the poly(A) site and a poly(A) tail is added - a process necessary for normal mRNA formation. Genes with multiple poly(A) sites can undergo alternative polyadenylation (APA), producing distinct mRNA isoforms with different 3' untranslated regions (3' UTRs) and in some cases different coding regions. Two thirds of all human genes undergo APA. The efficiency of the polyadenylation process regulates gene expression and APA plays an important part in post-transcriptional regulation, as the 3' UTR contains various cis-elements associated with post-transcriptional regulation, such as target sites for micro-RNAs and RNA-binding proteins. Implications of alterations in polyadenylation for endocrine disease: Alterations in polyadenylation have been found to be causative of neonatal diabetes and IPEX (immune dysfunction, polyendocrinopathy, enteropathy, X-linked) and to be associated with type I and II diabetes, pre-eclampsia, fragile X-associated premature ovarian insufficiency, ectopic Cushing syndrome, and many cancer diseases, including several types of endocrine tumor diseases. PERSPECTIVES Recent developments in high-throughput sequencing have made it possible to characterize polyadenylation genome-wide. Antisense elements inhibiting or enhancing specific poly(A) site usage can induce desired alterations in polyadenylation, and thus hold the promise of new therapeutic approaches. SUMMARY This review gives a detailed description of alterations in polyadenylation in endocrine disease, an overview of the current literature on polyadenylation and summarizes the clinical implications of the current state of research in this field.
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Affiliation(s)
- Anders Rehfeld
- Genomic Medicine, Rigshospitalet, Copenhagen University HospitalCopenhagen, Denmark
| | - Mireya Plass
- Department of Biology, The Bioinformatics Centre, University of CopenhagenCopenhagen, Denmark
| | - Anders Krogh
- Department of Biology, The Bioinformatics Centre, University of CopenhagenCopenhagen, Denmark
| | - Lennart Friis-Hansen
- Genomic Medicine, Rigshospitalet, Copenhagen University HospitalCopenhagen, Denmark
- *Correspondence: Lennart Friis-Hansen, Genomic Medicine, Rigshospitalet, Copenhagen University Hospital, 4113, Blegdamsvej 9, DK2100 Copenhagen, Denmark. e-mail:
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Abstract
In eukaryotic cells, introns are spliced from pre-mRNAs by the spliceosome. Both the composition and the structure of the spliceosome are highly dynamic, and eight DExD/H RNA helicases play essential roles in controlling conformational rearrangements. There is evidence that the various helicases are functionally and physically connected with each other and with many other factors in the spliceosome. Understanding the dynamics of those interactions is essential to comprehend the mechanism and regulation of normal as well as of pathological splicing. This review focuses on recent advances in the characterization of the splicing helicases and their interactions, and highlights the deep integration of splicing helicases in global mRNP biogenesis pathways.
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Affiliation(s)
- Olivier Cordin
- Wellcome Trust Centre for Cell Biology, University of Edinburgh, Edinburgh, UK
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Bartkowiak B, Mackellar AL, Greenleaf AL. Updating the CTD Story: From Tail to Epic. GENETICS RESEARCH INTERNATIONAL 2011; 2011:623718. [PMID: 22567360 PMCID: PMC3335468 DOI: 10.4061/2011/623718] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Accepted: 08/10/2011] [Indexed: 12/03/2022]
Abstract
Eukaryotic RNA polymerase II (RNAPII) not only synthesizes mRNA but also coordinates transcription-related processes via its unique C-terminal repeat domain (CTD). The CTD is an RNAPII-specific protein segment consisting of repeating heptads with the consensus sequence Y1S2P3T4S5P6S7 that has been shown to be extensively post-transcriptionally modified in a coordinated, but complicated, manner. Recent discoveries of new modifications, kinases, and binding proteins have challenged previously established paradigms. In this paper, we examine results and implications of recent studies related to modifications of the CTD and the respective enzymes; we also survey characterizations of new CTD-binding proteins and their associated processes and new information regarding known CTD-binding proteins. Finally, we bring into focus new results that identify two additional CTD-associated processes: nucleocytoplasmic transport of mRNA and DNA damage and repair.
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Affiliation(s)
- Bartlomiej Bartkowiak
- Department of Biochemistry and Center for RNA Biology, Duke University Medical Center, Durham, NC 27710, USA
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Nucleophosmin deposition during mRNA 3' end processing influences poly(A) tail length. EMBO J 2011; 30:3994-4005. [PMID: 21822216 DOI: 10.1038/emboj.2011.272] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Accepted: 07/04/2011] [Indexed: 12/12/2022] Open
Abstract
During polyadenylation, the multi-functional protein nucleophosmin (NPM1) is deposited onto all cellular mRNAs analysed to date. Premature termination of poly(A) tail synthesis in the presence of cordycepin abrogates deposition of the protein onto the mRNA, indicating natural termination of poly(A) addition is required for NPM1 binding. NPM1 appears to be a bona fide member of the complex involved in 3' end processing as it is associated with the AAUAAA-binding CPSF factor and can be co-immunoprecipitated with other polyadenylation factors. Furthermore, reduction in the levels of NPM1 results in hyperadenylation of mRNAs, consistent with alterations in poly(A) tail chain termination. Finally, knockdown of NPM1 results in retention of poly(A)(+) RNAs in the cell nucleus, indicating that NPM1 influences mRNA export. Collectively, these data suggest that NPM1 has an important role in poly(A) tail length determination and may help network 3' end processing with other aspects of nuclear mRNA maturation.
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Lahudkar S, Shukla A, Bajwa P, Durairaj G, Stanojevic N, Bhaumik SR. The mRNA cap-binding complex stimulates the formation of pre-initiation complex at the promoter via its interaction with Mot1p in vivo. Nucleic Acids Res 2010; 39:2188-209. [PMID: 21075799 PMCID: PMC3064766 DOI: 10.1093/nar/gkq1029] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The cap-binding complex (CBC) binds to the cap structure of mRNA to protect it from exonucleases as well as to regulate downstream post-transcriptional events, translational initiation and nonsense-mediated mRNA decay. However, its role in regulation of the upstream transcriptional events such as initiation or elongation remains unknown. Here, using a formaldehyde-based in vivo cross-linking and chromatin immunoprecipitation assay in conjunction with transcriptional, mutational and co-immunoprecipitational analyses, we show that CBC is recruited to the body of yeast gene, and then stimulates the formation of pre-initiation complex (PIC) at several yeast promoters through its interaction with Mot1p (modifier of transcription). Mot1p is recruited to these promoters, and enhances the PIC formation. We find that CBC promotes the recruitment of Mot1p which subsequently stimulates PIC formation at these promoters. Furthermore, the formation of PIC is essential for recruitment of CBC. Thus, our study presents an interesting observation that an mRNA binding factor exhibits a reciprocal synergistic effect on formation of PIC (and hence transcriptional initiation) at the promoter, revealing a new pathway of eukaryotic gene regulation in vivo.
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Affiliation(s)
| | | | | | | | | | - Sukesh R. Bhaumik
- *To whom correspondence should be addressed. Tel: +1 618 453 6479; Fax: +1 618 453 6440;
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19
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Risk JM, Laurie RE, Macknight RC, Day CL. FRIGIDA and related proteins have a conserved central domain and family specific N- and C- terminal regions that are functionally important. PLANT MOLECULAR BIOLOGY 2010; 73:493-505. [PMID: 20405310 DOI: 10.1007/s11103-010-9635-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2010] [Accepted: 04/05/2010] [Indexed: 05/08/2023]
Abstract
Arabidopsis accessions are either winter-annuals, which require cold winter temperatures for spring flowering, or rapid-cycling summer annuals. Typically, winter annual accessions have functional FRIGIDA (FRI) and FRIGIDA-LIKE 1 (FRL1) proteins that promote high expression of FLOWERING LOCUS C (FLC), which prevents flowering until after winter. In contrast, many rapid-cycling accessions have low FLC levels because FRI is inactive. Using biochemical, functional and bioinformatic approaches, we show that FRI and FRL1 contain a stable, central domain that is conserved across the FRI superfamily. This core domain is monomeric in solution and primarily alpha-helical. We analysed the ability of several FRI deletion constructs to function in Arabidopsis plants. Our findings suggest that the C-terminus, which is predicted to be disordered, is required for FRI to promote FLC expression and may mediate protein:protein interactions. The contribution of the FRI N-terminus appears to be limited, as constructs missing these residues retained significant activity when expressed at high levels. The important N- and C-terminal regions differ between members of the FRI superfamily and sequence analysis identified five FRI families with distinct expression patterns in Arabidopsis, suggesting the families have separate biological roles.
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Affiliation(s)
- Joanna M Risk
- Biochemistry Department, University of Otago, Dunedin 9054, New Zealand
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20
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Millevoi S, Vagner S. Molecular mechanisms of eukaryotic pre-mRNA 3' end processing regulation. Nucleic Acids Res 2009; 38:2757-74. [PMID: 20044349 PMCID: PMC2874999 DOI: 10.1093/nar/gkp1176] [Citation(s) in RCA: 294] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Messenger RNA (mRNA) 3′ end formation is a nuclear process through which all eukaryotic primary transcripts are endonucleolytically cleaved and most of them acquire a poly(A) tail. This process, which consists in the recognition of defined poly(A) signals of the pre-mRNAs by a large cleavage/polyadenylation machinery, plays a critical role in gene expression. Indeed, the poly(A) tail of a mature mRNA is essential for its functions, including stability, translocation to the cytoplasm and translation. In addition, this process serves as a bridge in the network connecting the different transcription, capping, splicing and export machineries. It also participates in the quantitative and qualitative regulation of gene expression in a variety of biological processes through the selection of single or alternative poly(A) signals in transcription units. A large number of protein factors associates with this machinery to regulate the efficiency and specificity of this process and to mediate its interaction with other nuclear events. Here, we review the eukaryotic 3′ end processing machineries as well as the comprehensive set of regulatory factors and discuss the different molecular mechanisms of 3′ end processing regulation by proposing several overlapping models of regulation.
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Affiliation(s)
- Stefania Millevoi
- Institut National de la Santé et de la Recherche Médicale U563, Toulouse, F-31000, France.
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21
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Raczynska KD, Simpson CG, Ciesiolka A, Szewc L, Lewandowska D, McNicol J, Szweykowska-Kulinska Z, Brown JWS, Jarmolowski A. Involvement of the nuclear cap-binding protein complex in alternative splicing in Arabidopsis thaliana. Nucleic Acids Res 2009; 38:265-78. [PMID: 19864257 PMCID: PMC2800227 DOI: 10.1093/nar/gkp869] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
The nuclear cap-binding protein complex (CBC) participates in 5′ splice site selection of introns that are proximal to the mRNA cap. However, it is not known whether CBC has a role in alternative splicing. Using an RT–PCR alternative splicing panel, we analysed 435 alternative splicing events in Arabidopsis thaliana genes, encoding mainly transcription factors, splicing factors and stress-related proteins. Splicing profiles were determined in wild type plants, the cbp20 and cbp80(abh1) single mutants and the cbp20/80 double mutant. The alternative splicing events included alternative 5′ and 3′ splice site selection, exon skipping and intron retention. Significant changes in the ratios of alternative splicing isoforms were found in 101 genes. Of these, 41% were common to all three CBC mutants and 15% were observed only in the double mutant. The cbp80(abh1) and cbp20/80 mutants had many more changes in alternative splicing in common than did cbp20 and cbp20/80 suggesting that CBP80 plays a more significant role in alternative splicing than CBP20, probably being a platform for interactions with other splicing factors. Cap-binding proteins and the CBC are therefore directly involved in alternative splicing of some Arabidopsis genes and in most cases influenced alternative splicing of the first intron, particularly at the 5′ splice site.
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22
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Kierzkowski D, Kmieciak M, Piontek P, Wojtaszek P, Szweykowska-Kulinska Z, Jarmolowski A. The Arabidopsis CBP20 targets the cap-binding complex to the nucleus, and is stabilized by CBP80. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2009; 59:814-25. [PMID: 19453442 DOI: 10.1111/j.1365-313x.2009.03915.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The cap-binding protein complex (CBC) binds to the caps of all RNA polymerase II transcripts, and plays an important role in RNA metabolism. We characterized interactions, localization and nuclear-cytoplasmic transport of two subunits of the Arabidopsis thaliana cap-binding protein complex (AtCBC): AtCBP20 and AtCBP80. Using CFP/YFP-tagged proteins, we show that transport of AtCBC from the cytoplasm to the nucleus in the plant cell is different from that described in other eukaryotic cells. We show that the smaller subunit of the complex, AtCBP20, plays a crucial role in the nuclear import of AtCBC. The C-terminal part of AtCBP20 contains two functionally independent nuclear localization signals (NLSs). At least one of these two NLSs is required for the import of CBC into the plant nucleus. The interaction between the A. thaliana CBP20 and CBP80 was also analyzed in detail, using the yeast two-hybrid system and fluorescence resonance energy transfer (FRET) assays. The N-terminal part of AtCBP20 is essential for interaction with AtCBP80. Furthermore, AtCBP80 is important for the protein stability of the smaller subunit of CBC. Based on these data, we propose a model for the nuclear-cytoplasmic trafficking of the CBC complex in plants.
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Affiliation(s)
- Daniel Kierzkowski
- Department of Molecular and Cellular Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska, Poland
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23
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Rigo F, Martinson HG. Polyadenylation releases mRNA from RNA polymerase II in a process that is licensed by splicing. RNA (NEW YORK, N.Y.) 2009; 15:823-36. [PMID: 19304926 PMCID: PMC2673064 DOI: 10.1261/rna.1409209] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
When transcription is coupled to pre-mRNA processing in HeLa nuclear extracts nascent transcripts become attached to RNA polymerase II during assembly of the cleavage/polyadenylation apparatus (CPA), and are not released even after cleavage at the poly(A) site. Here we show that these cleaved transcripts are anchored to the polymerase at their 3' ends by the CPA or, when introns are present, by the larger 3'-terminal exon definition complex (EDC), which consists of splicing factors complexed with the CPA. Poly(A) addition releases the RNA from the polymerase when the RNA is anchored only by the CPA. When anchored by the EDC, poly(A) addition remains a requirement, but it triggers release only after being licensed by splicing. The process by which RNA must first be attached to the polymerase by the EDC, and then can only be released following dual inputs from splicing and polyadenylation, provides an obvious opportunity for surveillance as the RNA enters the transport pathway.
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Affiliation(s)
- Frank Rigo
- Department of Chemistry and Biochemistry, University of California at Los Angeles, Los Angeles, California 90095-1569, USA
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24
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Friend K, Lovejoy AF, Steitz JA. U2 snRNP binds intronless histone pre-mRNAs to facilitate U7-snRNP-dependent 3' end formation. Mol Cell 2008; 28:240-52. [PMID: 17964263 PMCID: PMC2149891 DOI: 10.1016/j.molcel.2007.09.026] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Revised: 08/08/2007] [Accepted: 09/14/2007] [Indexed: 11/17/2022]
Abstract
In metazoa, pre-mRNA 3' end formation occurs via two pathways: cleavage/polyadenylation for the majority of RNA polymerase II transcripts and U7-snRNP-dependent cleavage for replication-dependent histone pre-mRNAs. An RNA element derived from a replication-dependent histone gene affects multiple steps of pre-mRNA processing. Here, we demonstrate that a portion of this RNA element, present in the majority of histone mRNAs, stimulates U7-snRNP-dependent cleavage. Surprisingly, this element binds U2 snRNP, although it is derived from an intronless mRNA. Specifically, SF3b, a U2 and U12-snRNP component, contacts the RNA element both in vitro and in vivo in conjunction with hPrp43, a DEAH-box helicase. Tethering either U2 or U12 snRNP to histone pre-mRNA substrates stimulates U7-snRNP-dependent cleavage in vitro and in vivo. Finally, we show that U2 snRNP associates with histone pre-mRNAs in vivo. We conclude that U2 snRNP plays a nonsplicing role in histone mRNA maturation.
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Affiliation(s)
- Kyle Friend
- Howard Hughes Medical Institute, Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
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25
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Blechingberg J, Lykke-Andersen S, Jensen TH, Jørgensen AL, Nielsen AL. Regulatory mechanisms for 3'-end alternative splicing and polyadenylation of the Glial Fibrillary Acidic Protein, GFAP, transcript. Nucleic Acids Res 2007; 35:7636-50. [PMID: 17981838 PMCID: PMC2190720 DOI: 10.1093/nar/gkm931] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The glial fibrillary acidic protein, GFAP, forms the intermediate cytoskeleton in cells of the glial lineage. Besides the common GFAPα transcript, the GFAPε and GFAPκ transcripts are generated by alternative mRNA 3′-end processing. Here we use a GFAP minigene to characterize molecular mechanisms participating in alternative GFAP expression. Usage of a polyadenylation signal within the alternatively spliced exon 7a is essential to generate the GFAPκ and GFAPκ transcripts. The GFAPκ mRNA is distinct from GFAPε mRNA given that it also includes intron 7a. Polyadenylation at the exon 7a site is stimulated by the upstream splice site. Moreover, exon 7a splice enhancer motifs supported both exon 7a splicing and polyadenylation. SR proteins increased the usage of the exon 7a polyadenylation signal but not the exon 7a splicing, whereas the polypyrimidine tract binding (PTB) protein enhanced both exon 7a polyadenylation and exon 7a splicing. Finally, increasing transcription by the VP16 trans-activator did not affect the frequency of use of the exon 7a polyadenylation signal whereas the exon 7a splicing frequency was decreased. Our data suggest a model with the selection of the exon 7a polyadenylation site being the essential and primary event for regulating GFAP alternative processing.
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Affiliation(s)
- Jenny Blechingberg
- Institute of Human Genetics, The Bartholin Building, University of Aarhus, DK-8000 Aarhus C, Denmark
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26
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Luo Z, Chen Z. Improperly terminated, unpolyadenylated mRNA of sense transgenes is targeted by RDR6-mediated RNA silencing in Arabidopsis. THE PLANT CELL 2007; 19:943-58. [PMID: 17384170 PMCID: PMC1867362 DOI: 10.1105/tpc.106.045724] [Citation(s) in RCA: 167] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
RNA silencing can be induced by highly transcribed transgenes through a pathway dependent on RNA-DEPENDENT RNA POLYMERASE6 (RDR6) and may function as a genome protection mechanism against excessively expressed genes. Whether all transcripts or just aberrant transcripts activate this protection mechanism is unclear. Consistent RNA silencing induced by a transgene with three direct repeats of the beta-glucuronidase (GUS) open reading frame (ORF) is associated with high levels of truncated, unpolyadenylated transcripts, probably from abortive transcription elongation. Truncated, unpolyadenylated transcripts from triple GUS ORF repeats were degraded in the wild type but accumulated in an rdr6 mutant, suggesting targeting for degradation by RDR6-mediated RNA silencing. A GUS transgene without a 3' transcription terminator produced unpolyadenylated readthrough mRNA and consistent RDR6-dependent RNA silencing. Both GUS triple repeats and terminator-less GUS transgenes silenced an expressed GUS transgene in trans in the wild type but not in the rdr6 mutant. Placing two 3' terminators in the GUS transgene 3' reduced mRNA 3' readthrough, decreased GUS-specific small interfering RNA accumulation, and enhanced GUS gene expression. Moreover, RDR6 was localized in the nucleus. We propose that improperly terminated, unpolyadenylated mRNA from transgene transcription is subject to RDR6-mediated RNA silencing, probably by acting as templates for the RNA polymerase, in Arabidopsis thaliana.
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Affiliation(s)
- Zhenghua Luo
- Department of Botany and Plant Pathology, Purdue University, West Lafayette, Indiana 47907-2054, USA
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27
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Millevoi S, Loulergue C, Dettwiler S, Karaa SZ, Keller W, Antoniou M, Vagner S. An interaction between U2AF 65 and CF I(m) links the splicing and 3' end processing machineries. EMBO J 2006; 25:4854-64. [PMID: 17024186 PMCID: PMC1618107 DOI: 10.1038/sj.emboj.7601331] [Citation(s) in RCA: 150] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2006] [Accepted: 07/31/2006] [Indexed: 11/08/2022] Open
Abstract
The protein factor U2 snRNP Auxiliary Factor (U2AF) 65 is an essential component required for splicing and involved in the coupling of splicing and 3' end processing of vertebrate pre-mRNAs. Here we have addressed the mechanisms by which U2AF 65 stimulates pre-mRNA 3' end processing. We identify an arginine/serine-rich region of U2AF 65 that mediates an interaction with an RS-like alternating charge domain of the 59 kDa subunit of the human cleavage factor I (CF I(m)), an essential 3' processing factor that functions at an early step in the recognition of the 3' end processing signal. Tethered functional analysis shows that the U2AF 65/CF I(m) 59 interaction stimulates in vitro 3' end cleavage and polyadenylation. These results therefore uncover a direct role of the U2AF 65/CF I(m) 59 interaction in the functional coordination of splicing and 3' end processing.
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Affiliation(s)
- Stefania Millevoi
- INSERM U563, Toulouse, France
- Institut Claudius Regaud, Toulouse, France
- Université Toulouse III Paul Sabatier, Toulouse, France
| | - Clarisse Loulergue
- INSERM U563, Toulouse, France
- Institut Claudius Regaud, Toulouse, France
- Université Toulouse III Paul Sabatier, Toulouse, France
- Nuclear Biology Group, Department of Medical and Molecular Genetics, King's College London School of Medicine, Guy's Campus, Guy's Hospital, London, UK
| | - Sabine Dettwiler
- Department of Cell Biology, Biozentrum, University of Basel, Basel, Switzerland
| | - Sarah Zeïneb Karaa
- INSERM U563, Toulouse, France
- Université Toulouse III Paul Sabatier, Toulouse, France
| | - Walter Keller
- Department of Cell Biology, Biozentrum, University of Basel, Basel, Switzerland
| | - Michael Antoniou
- Nuclear Biology Group, Department of Medical and Molecular Genetics, King's College London School of Medicine, Guy's Campus, Guy's Hospital, London, UK
| | - Stéphan Vagner
- INSERM U563, Toulouse, France
- Institut Claudius Regaud, Toulouse, France
- Université Toulouse III Paul Sabatier, Toulouse, France
- INSERM U563, Institut Claudius Régaud, 20–24 Rue du Pont St Pierre, Toulouse 31052, France. Tel.: +33 5 67 69 63 11; Fax: +33 5 61 42 46 31; E-mail:
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28
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Kyburz A, Friedlein A, Langen H, Keller W. Direct interactions between subunits of CPSF and the U2 snRNP contribute to the coupling of pre-mRNA 3' end processing and splicing. Mol Cell 2006; 23:195-205. [PMID: 16857586 DOI: 10.1016/j.molcel.2006.05.037] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2006] [Revised: 04/13/2006] [Accepted: 05/22/2006] [Indexed: 10/24/2022]
Abstract
Eukaryotic pre-mRNAs are capped at their 5' ends, polyadenylated at their 3' ends, and spliced before being exported from the nucleus to the cytoplasm. Although the three processing reactions can be studied separately in vitro, they are coupled in vivo. We identified subunits of the U2 snRNP in highly purified CPSF and showed that the two complexes physically interact. We therefore tested whether this interaction contributes to the coupling of 3' end processing and splicing. We found that CPSF is necessary for efficient splicing activity in coupled assays and that mutations in the pre-mRNA binding site of the U2 snRNP resulted in impaired splicing and in much reduced cleavage efficiency. Moreover, we showed that efficient cleavage required the presence of the U2 snRNA in coupled assays. We therefore propose that the interaction between CPSF and the U2 snRNP contributes to the coupling of splicing and 3' end formation.
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Affiliation(s)
- Andrea Kyburz
- Department of Cell Biology, Biozentrum, University of Basel, CH-4056 Basel, Switzerland
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29
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Rush M, Zhao X, Schwartz S. A splicing enhancer in the E4 coding region of human papillomavirus type 16 is required for early mRNA splicing and polyadenylation as well as inhibition of premature late gene expression. J Virol 2005; 79:12002-15. [PMID: 16140776 PMCID: PMC1212645 DOI: 10.1128/jvi.79.18.12002-12015.2005] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Successful inhibition of human papillomavirus type 16 (HPV-16) late gene expression early in the life cycle is essential for persistence of infection, the highest risk factor for cervical cancer. Our study aimed to locate regulatory RNA elements in the early region of HPV-16 that influence late gene expression. For this purpose, subgenomic HPV-16 expression plasmids under control of the strong human cytomegalovirus immediate early promoter were used. An exonic splicing enhancer that firmly supported the use of the E4 3' splice site at position 3358 in the early region of the HPV-16 genome was identified. The enhancer was mapped to a 65-nucleotide AC-rich sequence located approximately 100 nucleotides downstream of the position 3358 3' splice site. Deletion of the enhancer caused loss of both splicing at the upstream position 3358 3' splice site and polyadenylation at the early polyadenylation signal, pAE. Direct splicing occurred at the competing L1 3' splice site at position 5639 in the late region. Optimization of the position 3358 3' splice site restored splicing to that site and polyadenylation at pAE. Additionally, a sequence of 40 nucleotides with a negative effect on late mRNA production was located immediately downstream of the enhancer. As the E4 3' splice site is employed by both early and late mRNAs, the enhancer constitutes a key regulator of temporal HPV-16 gene expression, which is required for early mRNA production as well as for the inhibition of premature late gene expression.
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Affiliation(s)
- Margaret Rush
- Department of Medical Biochemistry and Microbiology, Uppsala University, Biomedical Centre, Husargatan 3, Box 582, 75123 Uppsala, Sweden
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30
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Puget N, Knowlton M, Scully R. Molecular analysis of sister chromatid recombination in mammalian cells. DNA Repair (Amst) 2005; 4:149-61. [PMID: 15590323 PMCID: PMC2967438 DOI: 10.1016/j.dnarep.2004.08.010] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2004] [Indexed: 01/19/2023]
Abstract
Sister chromatid recombination (SCR) is a potentially error-free pathway for the repair of double-strand breaks arising during replication and is thought to be important for the prevention of genomic instability and cancer. Analysis of sister chromatid recombination at a molecular level has been limited by the difficulty of selecting specifically for these events. To overcome this, we have developed a novel "nested intron" reporter that allows the positive selection in mammalian cells of "long tract" gene conversion events arising between sister chromatids. We show that these events arise spontaneously in cycling cells and are strongly induced by a site-specific double-strand break (DSB) caused by the restriction endonuclease, I-SceI. Notably, some I-SceI-induced sister chromatid recombination events entailed multiple rounds of gene amplification within the reporter, with the generation of a concatemer of amplified gene segments. Thus, there is an intimate relationship between sister chromatid recombination control and certain types of gene amplification. Dysregulated sister chromatid recombination may contribute to cancer progression, in part, by promoting gene amplification.
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Affiliation(s)
| | | | - Ralph Scully
- Corresponding author. Tel.: +1 617 667 4252; fax: +1 617 667 0980. (R. Scully)
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31
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Zheng ZM, Tao M, Yamanegi K, Bodaghi S, Xiao W. Splicing of a cap-proximal human Papillomavirus 16 E6E7 intron promotes E7 expression, but can be restrained by distance of the intron from its RNA 5' cap. J Mol Biol 2004; 337:1091-108. [PMID: 15046980 DOI: 10.1016/j.jmb.2004.02.023] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2003] [Revised: 02/05/2004] [Accepted: 02/09/2004] [Indexed: 11/24/2022]
Abstract
Human papillomavirus 16 (HPV16) E6E7 pre-mRNA is bicistronic and has an intron in the E6 coding region with one 5' splice site and two alternative 3' splice sites, which produce E6(*)I and E6(*)II, respectively. If this intron remains unspliced, the resulting E6E7 mRNA expresses oncogenic E6. We found for the first time that the E6E7 pre-mRNA was efficiently spliced in vitro only when capped and that cellular cap-binding factors were involved in the splicing. The cap-dependent splicing of the E6E7 pre-mRNA was extremely efficient in cervical cancer-derived cells, producing mostly E6(*)I, but inefficient in cells transfected with a common retrovirus expression vector, pLXSN16E6E7, due to the large size of this vector's exon 1. Further studies showed that efficient splicing of the E6E7 pre-mRNA depends on the distance of the cap-proximal intron from the RNA 5' cap, with an optimal distance of less than 307nt in order to facilitate better association of U1 small nuclear RNA with the intron 5' splice site. The same was true for splicing of human beta-globin RNA. Splicing of the E6E7 RNA provided more E7 RNA templates and promoted E7 translation, whereas a lack of RNA splicing produced a low level of E7 translation. Together, our data indicate that the distance between the RNA 5' cap and cap-proximal intron is rate limiting for RNA splicing. HPV16 E6E7 pre-mRNA takes advantage of its small cap-proximal exon to confer efficient splicing for better E7 expression.
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Affiliation(s)
- Zhi-Ming Zheng
- HIV and AIDS Malignancy Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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32
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Wu C, Alwine JC. Secondary structure as a functional feature in the downstream region of mammalian polyadenylation signals. Mol Cell Biol 2004; 24:2789-96. [PMID: 15024068 PMCID: PMC371127 DOI: 10.1128/mcb.24.7.2789-2796.2004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Secondary structure within the downstream region of mammalian polyadenylation signals has been proposed to perform important functions. The simian virus 40 late polyadenylation signal (SVLPA) forms alternate secondary structures in equilibrium. Their formation correlates with cleavage-polyadenylation efficiency (H. Hans and J. C. Alwine, Mol. Cell. Biol. 20:2926-2932, 2000; M. I. Zarudnaya, I. M. Kolomiets, A. L. Potyahaylo, and D. M. Hovorun, Nucleic Acids Res. 3:1375-1386, 2003), and oligonucleotides that disrupt the secondary structure inhibit in vitro cleavage. To define the important features of downstream secondary structure, we first minimized the SVLPA by deletion, forming a downstream region with fewer, and more stable, stem-loop structures. Specific mutagenesis showed that both stem stability and loop size are important functional features of the downstream region. Stabilization of the stem, thus minimizing alternative structures, decreased cleavage efficiency both in vitro and in vivo. This was most deleterious when the stem was stabilized at the base of the loop, constraining loop size by inhibiting breathing of the stem. The significance of loop size was supported by mutants that showed increased cleavage efficiency with increased loop size and vice versa. A loop of at least 12 nucleotides promoted cleavage; U richness in the loop also promoted cleavage and was particularly important when the stem was stabilized. A mutation designed to eliminate downstream secondary structure still formed many relatively weak alternative structures in equilibrium and retained function. The data suggest that although the downstream region is very important, its structure is quite malleable and is able to tolerate significant mutation within a wide range of primary and secondary structural features. We propose that this malleability is due to the enhanced ability of GU- and U-rich downstream elements to easily form secondary structures with surrounding sequences.
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Affiliation(s)
- Chunxiao Wu
- Department of Cancer Biology, Abramson Family Cancer Research Institute School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6142, USA
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Abstract
The mature mRNA always carries nucleotide sequences that faithfully mirror the protein product according to the niles of the genetic code. However, in the chromosome, the nucleotide sequence that represents a certain protein is interrupted by additional sequences. Therefore, most eukaryotic genes are longer than their final mRNA products. The human genome project revealed that only a tiny portion of sequences serves as protein-coding region and almost one quarter of the genome is occupied by non-coding intervening sequences. The elimination of these non-coding regions from the precursor RNA in a process termed splicing must be extremely precise, because even a single nucleotide mistake may cause a fatal error. At present, two types of intervening sequences have been identified in protein-coding genes. One of them, the U2-dependent or major-class is prevalent and represents 99% of known sequences. The other one, the so-called U12-dependent or minor-class of introns, occurs in much lesser amounts in the genome. The basic problem of nuclear splicing concerns i/ the molecular mechanisms, which ensure that the coding regions are correctly recognized and spliced together: ii/ the principles and mechanisms that guarantee the high fidelity of the splicing system; iii/ the differences in the excision mechanisms of the two classes of introns. We are going to present models explaining how intervening sequences are accurately removed and the coding regions correctly juxtaposed. The two splicing mechanisms will also be compared.
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Affiliation(s)
- T Rauch
- Institute of Biochemistry, Biological Research Center of the Hungarian Academy of Sciences, PO Box 521, H-6701 Szeged, Hungary
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34
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Howe KJ. RNA polymerase II conducts a symphony of pre-mRNA processing activities. BIOCHIMICA ET BIOPHYSICA ACTA 2002; 1577:308-24. [PMID: 12213660 DOI: 10.1016/s0167-4781(02)00460-8] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
RNA polymerase II (RNAP II) and its associated factors interact with a diverse collection of nuclear proteins during the course of precursor messenger RNA synthesis. This growing list of known contacts provides compelling evidence for the existence of large multifunctional complexes, a.k.a. transcriptosomes, within which the biosynthesis of mature mRNAs is coordinated. Recent studies have demonstrated that the unique carboxy-terminal domain (CTD) of the largest subunit of RNAP II plays an important role in recruiting many of these activities to the transcriptional machinery. Throughout the transcription cycle the CTD undergoes a variety of covalent and structural modifications which can, in turn, modulate the interactions and functions of processing factors during transcription initiation, elongation and termination. New evidence suggests that the possibility that interaction of some of these processing factors with the polymerase can affect its elongation rate. Besides the CTD, proteins involved in pre-mRNA processing can interact with general transcription factors (GTFs) and transcriptional activators, which associate with polymerase at promoters. This suggests a mechanism for the recruitment of specific processing activities to different transcription units. This harmonic integration of transcriptional and post-transcriptional activities, many of which once were considered to be functionally isolated within the cell, supports a general model for the coordination of gene expression by RNAP II within the nucleus.
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Affiliation(s)
- Kenneth James Howe
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA.
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35
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Cooke C, Alwine JC. Characterization of specific protein-RNA complexes associated with the coupling of polyadenylation and last-intron removal. Mol Cell Biol 2002; 22:4579-86. [PMID: 12052867 PMCID: PMC133901 DOI: 10.1128/mcb.22.13.4579-4586.2002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Polyadenylation and splicing are highly coordinated on substrate RNAs capable of coupled polyadenylation and splicing. Individual elements of both splicing and polyadenylation signals are required for the in vitro coupling of the processing reactions. In order to understand more about the coupling mechanism, we examined specific protein-RNA complexes formed on RNA substrates, which undergo coupled splicing and polyadenylation. We hypothesized that formation of a coupling complex would be adversely affected by mutations of either splicing or polyadenylation elements known to be required for coupling. We defined three specific complexes (A(C)', A(C), and B(C)) that form rapidly on a coupled splicing and polyadenylation substrate, well before the appearance of spliced and/or polyadenylated products. The A(C)' complex is formed by 30 s after mixing, the A(C) complex is formed between 1 and 2 min after mixing, and the B(C) complex is formed by 2 to 3 min after mixing. A(C)' is a precursor of A(C), and the A(C)' and/or A(C) complex is a precursor of B(C). Of the three complexes, B(C) appears to be a true coupling complex in that its formation was consistently diminished by mutations or experimental conditions known to disrupt coupling. The characteristics of the A(C)' complex suggest that it is analogous to the spliceosomal A complex, which forms on splicing-only substrates. Formation of the A(C)' complex is dependent on the polypyrimidine tract. The transition from A(C)' to A(C) appears to require an intact 3'-splice site. Formation of the B(C) complex requires both splicing elements and the polyadenylation signal. A unique polyadenylation-specific complex formed rapidly on substrates containing only the polyadenylation signal. This complex, like the A(C)' complex, formed very transiently on the coupled splicing and polyadenylation substrate; we suggest that these two complexes coordinate, resulting in the B(C) complex. We also suggest a model in which the coupling mechanism may act as a dominant checkpoint in which aberrant definition of one exon overrides the normal processing at surrounding wild-type sites.
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Affiliation(s)
- Charles Cooke
- Department of Microbiology, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6142, USA
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36
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Zieler H, Huynh CQ. Intron-dependent stimulation of marker gene expression in cultured insect cells. INSECT MOLECULAR BIOLOGY 2002; 11:87-95. [PMID: 11841506 DOI: 10.1046/j.0962-1075.2001.00312.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We tested in a systematic fashion the effect of an intron on the level of luciferase expression in cultured C6/36 Aedes albopictus cells. The intron was inserted in both orientations, upstream and downstream of the luciferase coding region in two different luciferase expression vectors. The two parental luciferase expression vectors differed only in their promoters, one containing the Drosophila melanogaster actin5C promoter and the other the Autographa californica nuclear polyhedrosis virus hr5/ie1 enhancer/promoter. All resulting intron-containing constructs were tested for their ability to express luciferase in transient assays following electroporation into C6/36 cells. We found that the introns stimulate luciferase expression between twelve and sixtyfold, depending on the promoter. Enhanced expression was only seen when the intron was present in the correct orientation upstream of the luciferase ORF. When the 3' splice sites of the enhanced intron-containing constructs were mutated, the expression level dropped back to below the level of the intronless parental constructs, suggesting that the intron-dependent stimulation of luciferase expression is depending on splicing and is not due to other effects the intron may have on transcription or translation. The luciferase transcripts of all constructs were analysed by reverse transcription, PCR amplification and sequencing, and the results show a perfect correlation between efficient splicing of the intron and elevated levels of luciferase expression. Our findings have the potential to be very useful for boosting expression of foreign proteins in the widely used baculoviral or non-viral systems in insect cells.
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Affiliation(s)
- H Zieler
- Medical Entomology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
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37
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Kmieciak M, Simpson CG, Lewandowska D, Brown JWS, Jarmolowski A. Cloning and characterization of two subunits of Arabidopsis thaliana nuclear cap-binding complex. Gene 2002; 283:171-83. [PMID: 11867224 DOI: 10.1016/s0378-1119(01)00859-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In this report we characterize two Arabidopsis thaliana proteins, named AtCBP20 and AtCBP80, that are homologues of human subunits of a nuclear cap-binding protein complex (CBC). AtCBP20 has a calculated molecular mass of 29.9 kDa, and AtCBP80 is a 96.5 kDa protein. AtCBP20 exhibits 68% identity and 82% similarity to human CBP20. Like its human homologue, AtCBP20 contains a canonical RNA binding domain (RBD) with single RNP2 and RNP1 motifs. In addition to the N-terminal part, which is similar to the human protein, AtCBP20 has a long C-terminus rich in arginine, glycine and aspartate residues. The second subunit of the Arabidopsis cap-binding complex, AtCBP80, shows 28% identity and 50% similarity to its homologue from HeLa cells. The protein contains a MIF4G domain at its N-terminus, the feature characteristic to all analyzed CBP80s. This domain, described also in eIF4G and NMD2 proteins, is thought to be involved in protein-protein and also in protein--RNA interactions. Both proteins AtCBP20 and AtCBP80 are encoded by single-copy genes in the A. thaliana genome. The AtCBP20 gene is located on chromosome V, and the AtCBP80 gene is encoded by chromosome II. Among introns identified in the AtCBP20 gene, we discovered an U12 type intervening sequence (an AT-AC intron). This intron is spliced out very efficiently in plants, but when isolated and tested for splicing in tobacco protoplasts, the efficiency of the U12 intron excision was low. Splicing efficiency of the U12 intron is improved by the addition of exon and intron sequences upstream or downstream of the U12 intron. AtCBP20 and AtCBP80 are constitutively expressed in all examined organs of A. thaliana, including roots, stems, leaves and flowers. Interestingly, the steady-state level of both transcripts seem to be very similar in all tissues analyzed.
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Affiliation(s)
- Maciej Kmieciak
- Department of Gene Expression, Adam Mickiewicz University, Miedzychodzka 5, 60-371, Poznan, Poland
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38
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Ahuja D, Karow DS, Kilpatrick JE, Imperiale MJ. RNA polymerase II-dependent positional effects on mRNA 3' end processing in the adenovirus major late transcription unit. J Biol Chem 2001; 276:41825-31. [PMID: 11551915 DOI: 10.1074/jbc.m104709200] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
During the early phase of adenovirus infection, the promoter-proximal L1 poly(A) site in the major late transcription unit is used preferentially despite the fact that the distal L3 poly(A) site is stronger (i.e. it competes better for processing factors and is cleaved at a faster rate, in vitro). Previous work had established that this was due at least in part to the stable binding of the processing factor, cleavage and polyadenylation specificity factor, to the L1 poly(A) site as mediated by specific regulatory sequences. It is now demonstrated that in addition, the L1 poly(A) site has a positional advantage because of its 5' location in the transcription unit. We also show that preferential processing of a particular poly(A) site in a complex transcription unit is dependent on RNA polymerase II. Our results are consistent with recent reports demonstrating that the processing factors cleavage and polyadenylation specificity factor and cleavage stimulatory factor are associated with the RNA polymerase II holoenzyme; thus, processing at a weak poly(A) site like L1 can be enhanced by virtue of its being the first site to be transcribed.
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Affiliation(s)
- D Ahuja
- Department of Microbiology and Immunology and Comprehensive Cancer Center, University of Michigan Medical School, Ann Arbor, Michigan 48109, USA
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39
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Fong N, Bentley DL. Capping, splicing, and 3' processing are independently stimulated by RNA polymerase II: different functions for different segments of the CTD. Genes Dev 2001; 15:1783-95. [PMID: 11459828 PMCID: PMC312735 DOI: 10.1101/gad.889101] [Citation(s) in RCA: 180] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2001] [Accepted: 05/25/2001] [Indexed: 12/24/2022]
Abstract
Capping, splicing, and cleavage/polyadenylation of pre-mRNAs are interdependent events that are all stimulated in vivo by the carboxy-terminal domain (CTD) of RNA Pol II. We show that the CTD independently enhances splicing and 3' processing and that stimulation of splicing by enhancers is facilitated by the CTD. We provide evidence that stimulation of 3' processing by the CTD requires contact with the 50-kD subunit of the cleavage stimulation factor, CstF. Overexpression of the CTD-binding domain of CstF p50 had a dominant-negative effect on 3' processing without disrupting the CstF complex. The CTD comprises 52 heptad repeats. The CTD carboxyl terminus including heptads 27-52 supported capping, splicing, and 3' processing but the amino terminus supported only capping. We conclude that the CTD independently stimulates all three major pre-mRNA processing steps and that different regions of the CTD can serve distinct functions in pre-mRNA processing.
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Affiliation(s)
- N Fong
- Department of Biochemistry and Molecular Genetics, University of Colorado Health Science Center (UCHSC), Denver, Colorado 80262, USA
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40
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Stover C, Endo Y, Takahashi M, Lynch NJ, Constantinescu C, Vorup-Jensen T, Thiel S, Friedl H, Hankeln T, Hall R, Gregory S, Fujita T, Schwaeble W. The human gene for mannan-binding lectin-associated serine protease-2 (MASP-2), the effector component of the lectin route of complement activation, is part of a tightly linked gene cluster on chromosome 1p36.2-3. Genes Immun 2001; 2:119-27. [PMID: 11426320 DOI: 10.1038/sj.gene.6363745] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2000] [Accepted: 02/01/2001] [Indexed: 11/08/2022]
Abstract
The proteases of the lectin pathway of complement activation, MASP-1 and MASP-2, are encoded by two separate genes. The MASP1 gene is located on chromosome 3q27, the MASP2 gene on chromosome 1p36.23-31. The genes for the classical complement activation pathway proteases, C1r and C1s, are linked on chromosome 12p13. We have shown that the MASP2 gene encodes two gene products, the 76 kDa MASP-2 serine protease and a plasma protein of 19 kDa, termed MAp19 or sMAP. Both gene products are components of the lectin pathway activation complex. We present the complete primary structure of the human MASP2 gene and the tight cluster that this locus forms with non-complement genes. A comparison of the MASP2 gene with the previously characterised C1s gene revealed identical positions of introns separating orthologous coding sequences, underlining the hypothesis that the C1s and MASP2 genes arose by exon shuffling from one ancestral gene.
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Affiliation(s)
- C Stover
- Department of Microbiology and Immunology, University of Leicester, Leicester, UK
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41
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Ellison KS, Rice SA, Verity R, Smiley JR. Processing of alpha-globin and ICP0 mRNA in cells infected with herpes simplex virus type 1 ICP27 mutants. J Virol 2000; 74:7307-19. [PMID: 10906184 PMCID: PMC112251 DOI: 10.1128/jvi.74.16.7307-7319.2000] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Herpes simplex virus (HSV) ICP27 is an essential and multifunctional regulator of viral gene expression that modulates RNA splicing, polyadenylation, and nuclear export. We have previously reported that ICP27 causes the cytoplasmic accumulation of unspliced alpha-globin pre-mRNA. Here we examined the effects of a series of ICP27 mutations that alter important functional regions of the protein on the processing and nuclear transport of alpha-globin and HSV ICP0 RNA. The results demonstrate that ICP27 mutants that are impaired for growth in noncomplementing cells, including mutants in the N- and C-terminal regions, are defective in the accumulation of alpha-globin pre-mRNA. Unexpectedly, several mutants that are competent to repress the expression of reporter genes in transient transfection assays failed to accumulate unspliced RNA, implying that different mechanisms are responsible for transrepression and pre-mRNA accumulation. Several mutants caused a marked increase in the length and heterogeneity of the alpha-globin mRNA poly(A) tail, suggesting that ICP27 may directly or indirectly affect the regulation of poly(A) polymerase. ICP27 was also required for the accumulation of multiple ICP0 intron-bearing transcripts, but this effect displayed a mutational sensitivity profile different from that of accumulation of unspliced alpha-globin RNA. Moreover, unlike spliced and unspliced alpha-globin RNAs, which were efficiently exported to the cytoplasm, spliced and intron-containing ICP0 transcripts were predominantly nuclear in localization, and ICP27 was not required for nuclear retention of the spliced message. We propose that these transcript- and ICP27 allele-specific differences may be explained by the presence of a strong cis-acting ICP27 response element in the alpha-globin transcript.
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Affiliation(s)
- K S Ellison
- Department of Medical Microbiology and Immunology, University of Alberta, Edmonton, Alberta, Canada T6G 2H7
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42
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Bond GL, Prives C, Manley JL. Poly(A) polymerase phosphorylation is dependent on novel interactions with cyclins. Mol Cell Biol 2000; 20:5310-20. [PMID: 10866687 PMCID: PMC85980 DOI: 10.1128/mcb.20.14.5310-5320.2000] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have previously shown that poly(A) polymerase (PAP) is negatively regulated by cyclin B-cdc2 kinase hyperphosphorylation in the M phase of the cell cycle. Here we show that cyclin B(1) binds PAP directly, and we demonstrate further that this interaction is mediated by a stretch of amino acids in PAP with homology to the cyclin recognition motif (CRM), a sequence previously shown in several cell cycle regulators to target specifically G(1)-phase-type cyclins. We find that PAP interacts with not only G(1)- but also G(2)-type cyclins via the CRM and is a substrate for phosphorylation by both types of cyclin-cdk pairs. PAP's CRM shows novel, concentration-dependent effects when introduced as an 8-mer peptide into binding and kinase assays. While higher concentrations of PAP's CRM block PAP-cyclin binding and phosphorylation, lower concentrations induce dramatic stimulation of both activities. Our data not only support the notion that PAP is directly regulated by cyclin-dependent kinases throughout the cell cycle but also introduce a novel type of CRM that functionally interacts with both G(1)- and G(2)-type cyclins in an unexpected way.
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Affiliation(s)
- G L Bond
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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43
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Abstract
Structures visible within the eukaryotic nucleus have fascinated generations of biologists. Recent data show that these structures form in response to gene expression and are highly dynamic in living cells. RNA processing and assembly require many factors but the nucleus apparently lacks any active transport system to deliver these to the RNAs. Instead, processing factors move by diffusion but are concentrated by transient association with functionally related components. At sites of high activity this gives rise to visible structures, with components in dynamic equilibrium with the surrounding nucleoplasm. Processing factors are recruited from this pool by cooperative binding to RNA substrates.
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Affiliation(s)
- J D Lewis
- Wellcome Trust Centre for Cell Biology, ICMB, King's Buildings, The University of Edinburgh, Edinburgh EH9 3JR, Scotland, UK
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44
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Cheung P, Ellison KS, Verity R, Smiley JR. Herpes simplex virus ICP27 induces cytoplasmic accumulation of unspliced polyadenylated alpha-globin pre-mRNA in infected HeLa cells. J Virol 2000; 74:2913-9. [PMID: 10684311 PMCID: PMC111785 DOI: 10.1128/jvi.74.6.2913-2919.2000] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcripts of most intron-bearing cellular genes must be processed by the splicing machinery in order to efficiently accumulate and gain access to the cytoplasm. However, we found that herpes simplex virus induces cytoplasmic accumulation of both spliced and unspliced polyadenylated alpha-globin RNAs in infected HeLa cells. Accumulation of the unspliced RNA required the immediate-early protein ICP27, and ICP27 was sufficient (in combination with ICP4) to produce this effect in a transient-transfection assay. However, expression of ICP27 did not markedly alter the levels of fully spliced alpha-globin transcripts in infected cells. These data demonstrate that the previously documented effects of ICP27 on the cellular splicing apparatus do not greatly inhibit splicing of alpha-globin RNA and argue that ICP27 induces a splicing-independent pathway for alpha-globin RNA accumulation and nuclear export.
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Affiliation(s)
- P Cheung
- Departments of Biology, McMaster University, Hamilton, Ontario L8N 3Z5
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45
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Gao M, Fritz DT, Ford LP, Wilusz J. Interaction between a poly(A)-specific ribonuclease and the 5' cap influences mRNA deadenylation rates in vitro. Mol Cell 2000; 5:479-88. [PMID: 10882133 PMCID: PMC2811581 DOI: 10.1016/s1097-2765(00)80442-6] [Citation(s) in RCA: 139] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We have used an in vitro system that reproduces in vivo aspects of mRNA turnover to elucidate mechanisms of deadenylation. DAN, the major enzyme responsible for poly(A) tail shortening in vitro, specifically interacts with the 5' cap structure of RNA substrates, and this interaction is greatly stimulated by a poly(A) tail. Several observations suggest that cap-DAN interactions are functionally important for the networking between regulated mRNA stability and translation. First, uncapped RNA substrates are inefficiently deadenylated. Second, a stem-loop structure in the 5' UTR dramatically reduces deadenylation by interfering with cap-DAN interactions. Third, the addition of cap binding protein eIF4E inhibits deadenylation in vitro. These data provide insights into the early steps of substrate recognition that target an mRNA for degradation.
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46
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Vagner S, Vagner C, Mattaj IW. The carboxyl terminus of vertebrate poly(A) polymerase interacts with U2AF 65 to couple 3'-end processing and splicing. Genes Dev 2000; 14:403-13. [PMID: 10691733 PMCID: PMC316384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
Although it has been established that the processing factors involved in pre-mRNA splicing and 3'-end formation can influence each other positively, the molecular basis of this coupling interaction was not known. Stimulation of pre-mRNA splicing by an adjacent cis-linked cleavage and polyadenylation site in HeLa cell nuclear extract is shown to occur at an early step in splicing, the binding of U2AF 65 to the pyrimidine tract of the intron 3' splice site. The carboxyl terminus of poly(A) polymerase (PAP) previously has been implicated indirectly in the coupling process. We demonstrate that a fusion protein containing the 20 carboxy-terminal amino acids of PAP, when tethered downstream of an intron, increases splicing efficiency and, like the entire 3'-end formation machinery, stimulates U2AF 65 binding to the intron. The carboxy-terminal domain of PAP makes a direct and specific interaction with residues 17-47 of U2AF 65, implicating this interaction in the coupling of splicing and 3'-end formation.
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Affiliation(s)
- S Vagner
- European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
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47
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Vagner S, Vagner C, Mattaj IW. The carboxyl terminus of vertebrate poly(A) polymerase interacts with U2AF 65 to couple 3′-end processing and splicing. Genes Dev 2000. [DOI: 10.1101/gad.14.4.403] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Although it has been established that the processing factors involved in pre-mRNA splicing and 3′-end formation can influence each other positively, the molecular basis of this coupling interaction was not known. Stimulation of pre-mRNA splicing by an adjacentcis-linked cleavage and polyadenylation site in HeLa cell nuclear extract is shown to occur at an early step in splicing, the binding of U2AF 65 to the pyrimidine tract of the intron 3′ splice site. The carboxyl terminus of poly(A) polymerase (PAP) previously has been implicated indirectly in the coupling process. We demonstrate that a fusion protein containing the 20 carboxy-terminal amino acids of PAP, when tethered downstream of an intron, increases splicing efficiency and, like the entire 3′-end formation machinery, stimulates U2AF 65 binding to the intron. The carboxy-terminal domain of PAP makes a direct and specific interaction with residues 17–47 of U2AF 65, implicating this interaction in the coupling of splicing and 3′-end formation.
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48
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Vagner S, Rüegsegger U, Gunderson SI, Keller W, Mattaj IW. Position-dependent inhibition of the cleavage step of pre-mRNA 3'-end processing by U1 snRNP. RNA (NEW YORK, N.Y.) 2000; 6:178-188. [PMID: 10688357 PMCID: PMC1369904 DOI: 10.1017/s1355838200991854] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The 3' ends of most eukaryotic pre-mRNAs are generated by 3' endonucleolytic cleavage and subsequent polyadenylation. 3'-end formation can be influenced positively or negatively by various factors. In particular, U1 snRNP acts as an inhibitor when bound to a 5' splice site located either upstream of the 3'-end formation signals of bovine papilloma virus (BPV) late transcripts or downstream of the 3'-end processing signals in the 5' LTR of the HIV-1 provirus. Previous work showed that in BPV it is not the first step, 3' cleavage, that is affected by U1 snRNP, but rather the second step, polyadenylation, that is inhibited. Since in HIV-1 the biological requirement is to produce transcripts that read through the 5' LTR cleavage site rather than being cleaved there, this mechanism seemed unlikely to apply. The obvious difference between the two examples was the relative orientation of the 3'-end formation signals and the U1 snRNP-binding site. In vitro assays were therefore used to assess the effect of U1 snRNP bound at various locations relative to a cleavage/polyadenylation site on the 3' cleavage reaction. U1 snRNP was found to inhibit cleavage when bound to a 5' splice site downstream of the cleavage/polyadenylation site, as in the HIV-1 LTR. U1 snRNP binding at this location was shown not to affect the recruitment of multiple cleavage/polyadenylation factors to the cleavage substrate, indicating that inhibition is unlikely to be due to steric hindrance. Interactions between U1A, U1 70K, and poly(A) polymerase, which mediate the effect of U1 snRNP on polyadenylation of other pre-mRNAs, were shown not to be required for cleavage inhibition. Therefore, U1 snRNP bound to a 5' splice site can inhibit cleavage and polyadenylation in two mechanistically different ways depending on whether the 5' splice site is located upstream or downstream of the cleavage site.
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Affiliation(s)
- S Vagner
- European Molecular Biology Laboratory, Heidelberg, Germany
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49
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Abstract
This chapter focuses on the history of the discovery of cap and an update of research on viral and cellular-messenger RNA (mRNA) capping. Cap structures of the type m7 GpppN(m)pN(m)p are present at the 5′ ends of nearly all eukaryotic cellular and viral mRNAs. A cap is added to cellular mRNA precursors and to the transcripts of viruses that replicate in the nucleus during the initial phases of transcription and before other processing events, including internal N6A methylation, 3′-poly (A) addition, and exon splicing. Despite the variations on the methylation theme, the important biological consequences of a cap structure appear to correlate with the N7-methyl on the 5′-terminal G and the two pyrophosphoryl bonds that connect m7G in a 5′–5′ configuration to the first nucleotide of mRNA. In addition to elucidating the biochemical mechanisms of capping and the downstream effects of this 5′- modification on gene expression, the advent of gene cloning has made available an ever-increasing amount of information on the proteins responsible for producing caps and the functional effects of other cap-related interactions. Genetic approaches have demonstrated the lethal consequences of cap failure in yeasts, and complementation studies have shown the evolutionary functional conservation of capping from unicellular to metazoan organisms.
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Affiliation(s)
- Y Furuichi
- AGENE Research Institute, Kamakura, Japan
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50
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Fortes P, Kufel J, Fornerod M, Polycarpou-Schwarz M, Lafontaine D, Tollervey D, Mattaj IW. Genetic and physical interactions involving the yeast nuclear cap-binding complex. Mol Cell Biol 1999; 19:6543-53. [PMID: 10490594 PMCID: PMC84624 DOI: 10.1128/mcb.19.10.6543] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/1999] [Accepted: 07/12/1999] [Indexed: 11/20/2022] Open
Abstract
Yeast strains lacking the yeast nuclear cap-binding complex (yCBC) are viable, although impaired in growth. We have taken advantage of this observation to carry out a genetic screen for components that show synthetic lethality (SL) with a cbp20-Delta cbp80-Delta double mutation. One set of SL interactions was due to mutations that were complemented by components of U1 small nuclear RNP (snRNP) and the yeast splicing commitment complex. These interactions confirm the role of yCBC in commitment complex formation. Physical interaction of yCBC with the commitment complex components Mud10p and Mud2p, which may directly mediate yCBC function, was demonstrated. Unexpectedly, we identified multiple SL mutations that were complemented by Cbf5p and Nop58p. These are components of the two major classes of yeast small nucleolar RNPs, which function in the maturation of rRNA precursors. Mutants lacking yCBC were found to be defective in rRNA processing. Analysis of the yCBC deletion phenotype suggests that this is likely to be due to a defect in the splicing of a subset of ribosomal protein mRNA precursors.
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Affiliation(s)
- P Fortes
- European Molecular Biology Laboratory, D-69117 Heidelberg, Germany
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