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Tang JC, Li Y, Wang YL, Zhang ZP, Jiang YH, Feng JJ, Zou PF. TRAF5 splicing variants associate with TRAF3 and RIP1 in NF-κB and type I IFN signaling in large yellow croaker Larimichthys crocea. FISH & SHELLFISH IMMUNOLOGY 2022; 130:418-427. [PMID: 36152803 DOI: 10.1016/j.fsi.2022.09.042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 08/28/2022] [Accepted: 09/16/2022] [Indexed: 06/16/2023]
Abstract
As a member of the tumor necrosis factor receptor-associated factor (TRAF) family, TRAF5 acts as a crucial adaptor molecule and plays important roles in the host innate immune responses. In the present study, the typical form and a splicing variant of TRAF5, termed Lc-TRAF5_tv1 and Lc-TRAF5_tv2 were characterized in large yellow croaker (Larimichthys crocea). The putative Lc-TRAF5_tv1 protein is constituted of 577 aa, contains a RING finger domain, two zinc finger domains, a coiled-coil domain, and a MATH domain, whereas Lc-TRAF5_tv2 protein is constituted of 236 aa and only contains a RING finger domain due to a premature stop resulted from the intron retention. Subcellular localization analysis revealed that both of Lc-TRAF5_tv1 and Lc-TRAF5_tv2 were localized in the cytoplasm, with Lc-TRAF5_tv2 found to aggregate around the nucleus. It was revealed that Lc-TRAF5_tv1 mRNA was broadly expressed in examined organs/tissues and showed extremely higher level than that of Lc-TRAF5_tv2, and both of them could be up-regulated under poly I:C, LPS, PGN, and Pseudomonas plecoglossicida stimulations in vivo. Interestingly, overexpression of Lc-TRAF5_tv1 and Lc-TRAF5_tv2 could significantly induce NF-κB but not IFN1 activation, whereas co-expression of them remarkably induced IFN1 activation but impaired NF-κB activation. In addition, both Lc-TRAF5_tv1 and Lc-TRAF5_tv2 were associated with TRAF3 and RIP1 in IFN1 activation, whereas only Lc-TRAF5_tv1 cooperated with TRAF3 and RIP1 in NF-κB activation. These results collectively indicated that the splicing variant together with the typical form of TRAF5 function importantly in the regulation of host immune signaling in teleosts.
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Affiliation(s)
- Jun Chun Tang
- Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture and Rural Affairs, Ornamental Aquarium Engineering Research Centre in University of Fujian Province, Fisheries College, Jimei University, Xiamen, Fujian Province, 361021, China
| | - Ying Li
- Key Laboratory of Estuarine Ecological Security and Environmental Health, Tan Kah Kee College, Xiamen University, Zhangzhou, Fujian Province, 363105, China.
| | - Yi Lei Wang
- Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture and Rural Affairs, Ornamental Aquarium Engineering Research Centre in University of Fujian Province, Fisheries College, Jimei University, Xiamen, Fujian Province, 361021, China; State Key Laboratory of Large Yellow Croaker Breeding, Ningde Fufa Fisheries Company Limited, Ningde, Fujian Province, 352103, China
| | - Zi Ping Zhang
- State Key Laboratory of Large Yellow Croaker Breeding, Ningde Fufa Fisheries Company Limited, Ningde, Fujian Province, 352103, China; College of Marine Science, Fujian Agriculture and Forestry University, Fuzhou, Fujian Province, 350002, China
| | - Yong Hua Jiang
- Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture and Rural Affairs, Ornamental Aquarium Engineering Research Centre in University of Fujian Province, Fisheries College, Jimei University, Xiamen, Fujian Province, 361021, China
| | - Jian Jun Feng
- Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture and Rural Affairs, Ornamental Aquarium Engineering Research Centre in University of Fujian Province, Fisheries College, Jimei University, Xiamen, Fujian Province, 361021, China
| | - Peng Fei Zou
- Key Laboratory of Healthy Mariculture for the East China Sea, Ministry of Agriculture and Rural Affairs, Ornamental Aquarium Engineering Research Centre in University of Fujian Province, Fisheries College, Jimei University, Xiamen, Fujian Province, 361021, China.
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2
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Boudreault S, Roy P, Lemay G, Bisaillon M. Viral modulation of cellular RNA alternative splicing: A new key player in virus-host interactions? WILEY INTERDISCIPLINARY REVIEWS-RNA 2019; 10:e1543. [PMID: 31034770 PMCID: PMC6767064 DOI: 10.1002/wrna.1543] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/13/2018] [Revised: 03/25/2019] [Accepted: 04/08/2019] [Indexed: 12/26/2022]
Abstract
Upon viral infection, a tug of war is triggered between host cells and viruses to maintain/gain control of vital cellular functions, the result of which will ultimately dictate the fate of the host cell. Among these essential cellular functions, alternative splicing (AS) is an important RNA maturation step that allows exons, or parts of exons, and introns to be retained in mature transcripts, thereby expanding proteome diversity and function. AS is widespread in higher eukaryotes, as it is estimated that nearly all genes in humans are alternatively spliced. Recent evidence has shown that upon infection by numerous viruses, the AS landscape of host‐cells is affected. In this review, we summarize recent advances in our understanding of how virus infection impacts the AS of cellular transcripts. We also present various molecular mechanisms allowing viruses to modulate cellular AS. Finally, the functional consequences of these changes in the RNA splicing signatures during virus–host interactions are discussed. This article is categorized under:RNA in Disease and Development > RNA in Disease RNA Processing > Splicing Regulation/Alternative Splicing
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Affiliation(s)
- Simon Boudreault
- Département de biochimie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Patricia Roy
- Département de biochimie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Guy Lemay
- Département de microbiologie, infectiologie et immunologie, Faculté de médecine, Université de Montréal, Montréal, Québec, Canada
| | - Martin Bisaillon
- Département de biochimie, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, Québec, Canada
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3
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Wei X, Qian W, Sizhu S, Li Y, Guo K, Jin M, Zhou H. Negative Regulation of Interferon-β Production by Alternative Splicing of Tumor Necrosis Factor Receptor-Associated Factor 3 in Ducks. Front Immunol 2018; 9:409. [PMID: 29599773 PMCID: PMC5863512 DOI: 10.3389/fimmu.2018.00409] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2017] [Accepted: 02/14/2018] [Indexed: 02/06/2023] Open
Abstract
Tumor necrosis factor receptor-associated factor 3 (TRAF3), an intracellular signal transducer, is identified as an important component of Toll-like receptors and RIG-I-like receptors induced type I interferon (IFN) signaling pathways. Previous studies have clarified TRAF3 function in mammals, but little is known about the role of TRAF3 in ducks. Here, we cloned and characterized the full-length duck TRAF3 (duTRAF3) gene and an alternatively spliced isoform of duTRAF3 (duTRAF3-S) lacking the fragment encoding amino acids 217–319, from duck embryo fibroblasts (DEFs). We found that duTRAF3 and duTRAF3-S played different roles in regulating IFN-β production in DEFs. duTRAF3 through its TRAF domain interacted with duMAVS or duTRIF, leading to the production of IFN-β. However, duTRAF3-S, containing the TRAF domain, was unable to bind duMAVS or duTRIF due to the intramolecular binding between the N- and C-terminal of duTRAF3-S that blocked the function of its TRAF domain. Further analysis identified that duTRAF3-S competed with duTRAF3 itself for binding to duTRAF3, perturbing duTRAF3 self-association, which impaired the assembly of duTRAF3-duMAVS/duTRIF complex, ultimately resulted in a reduced production of IFN-β. These findings suggest that duTRAF3 is an important regulator of duck innate immune signaling and reveal a novel mechanism for the negative regulation of IFN-β production via changing the formation of the homo-oligomerization of wild molecules, implying a novel regulatory role of truncated proteins.
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Affiliation(s)
- Xiaoqin Wei
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,Department of Animal Science, XiZang Agriculture and Animal Husbandry College, Linzhi, China
| | - Wei Qian
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Suolang Sizhu
- Department of Animal Science, XiZang Agriculture and Animal Husbandry College, Linzhi, China
| | - Yongtao Li
- College of Animal Husbandry & Veterinary Science, Henan Agricultural University, Zhengzhou, China
| | - Kelei Guo
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China
| | - Meilin Jin
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
| | - Hongbo Zhou
- State Key Laboratory of Agricultural Microbiology, College of Veterinary Medicine, Huazhong Agricultural University, Wuhan, China.,Key Laboratory of Preventive Veterinary Medicine in Hubei Province, The Cooperative Innovation Center for Sustainable Pig Production, Wuhan, China
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4
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López-Urrutia E, Campos-Parra A, Herrera LA, Pérez-Plasencia C. Alternative splicing regulation in tumor necrosis factor-mediated inflammation. Oncol Lett 2017; 14:5114-5120. [PMID: 29113151 PMCID: PMC5656035 DOI: 10.3892/ol.2017.6905] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2016] [Accepted: 07/07/2017] [Indexed: 02/06/2023] Open
Abstract
It is generally accepted that alternative splicing has an effect on disease when it leads to conspicuous changes in relevant proteins, but that the combinatorial effect of several small modifications can have marked outcomes as well. Inflammation is a complex process involving numerous signaling pathways, among which the tumor necrosis factor (TNF) pathway is one of the most studied. Signaling pathways are commonly represented as intricate cascades of molecular interactions that eventually lead to the activation of one or several genes. Alternative splicing is a common means of controlling protein expression in time and space; therefore, it can modulate the outcome of signaling pathways through small changes in their elements. Notably, the overall process is tightly regulated, which is easily overlooked when analyzing the pathway as a whole. The present review summarizes recent studies of the alternative splicing of key players of the TNF pathway leading to inflammation, and hypothesizes on the cumulative results of those modifications and the impact on cancer development.
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Affiliation(s)
- Eduardo López-Urrutia
- Genomics Laboratory, UBIMED, Faculty of Higher Studies-Iztacala, National Autonomous University, Tlalnepantla, 54090 State of Mexico, Mexico
| | - Alma Campos-Parra
- Genomics Laboratory, National Cancer Institute of Mexico, Tlalpan, 14680 Mexico City, Mexico
| | - Luis Alonso Herrera
- Epigenetics Laboratory, National Cancer Institute of Mexico, Tlalpan, 14680 Mexico City, Mexico
| | - Carlos Pérez-Plasencia
- Genomics Laboratory, UBIMED, Faculty of Higher Studies-Iztacala, National Autonomous University, Tlalnepantla, 54090 State of Mexico, Mexico.,Genomics Laboratory, National Cancer Institute of Mexico, Tlalpan, 14680 Mexico City, Mexico
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5
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Miliara S, Gkouskou KK, Sharp TV, Eliopoulos AG. SUMOylation is required for optimal TRAF3 signaling capacity. PLoS One 2013; 8:e80470. [PMID: 24260396 PMCID: PMC3832365 DOI: 10.1371/journal.pone.0080470] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 10/03/2013] [Indexed: 12/15/2022] Open
Abstract
TNF receptor-associated factors (TRAFs) are multifunctional adaptor proteins involved in temporal and spatial coordination of signals necessary for normal immune function. Here, we report that TRAF3, a TRAF family member with a key role in Toll-like and TNF family receptor signaling and suppressor of lymphomagenesis, is post-translationally modified by the small ubiquitin-related modifier (SUMO). Through yeast two-hybrid and co-immunoprecipitation assays we have identified Ubc9, the SUMO conjugating enzyme, as a novel TRAF3-interacting protein. We show that Ubc9-dependent SUMOylation of TRAF3 modulates optimal association with the CD40 receptor, thereby influencing TRAF3 degradation and non-canonical NF-κB activation upon CD40 triggering. Collectively, our findings describe a novel post-translational modification of a TRAF family member and reveal a link between SUMOylation and TRAF-mediated signal transduction.
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Affiliation(s)
- Sophia Miliara
- Molecular and Cellular Biology Laboratory, University of Crete School of Medicine, Heraklion, Greece
- Laboratory of Cancer Biology, Institute of Molecular Biology and Biotechnology, Foundation of Research and Technology Hellas, Heraklion, Greece
| | - Kalliopi K. Gkouskou
- Molecular and Cellular Biology Laboratory, University of Crete School of Medicine, Heraklion, Greece
- Laboratory of Cancer Biology, Institute of Molecular Biology and Biotechnology, Foundation of Research and Technology Hellas, Heraklion, Greece
| | - Tyson V. Sharp
- Barts Cancer Institute, Queen Mary University of London, London, United Kingdom
| | - Aristides G. Eliopoulos
- Molecular and Cellular Biology Laboratory, University of Crete School of Medicine, Heraklion, Greece
- Laboratory of Cancer Biology, Institute of Molecular Biology and Biotechnology, Foundation of Research and Technology Hellas, Heraklion, Greece
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6
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Leeman JR, Gilmore TD. Alternative splicing in the NF-kappaB signaling pathway. Gene 2008; 423:97-107. [PMID: 18718859 DOI: 10.1016/j.gene.2008.07.015] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2008] [Revised: 07/08/2008] [Accepted: 07/09/2008] [Indexed: 10/21/2022]
Abstract
Activation of transcription factor NF-kappaB can affect the expression of several hundred genes, many of which are involved in inflammation and immunity. The proper NF-kappaB transcriptional response is primarily regulated by post-translational modification of NF-kappaB signaling constituents. Herein, we review the accumulating evidence suggesting that alternative splicing of NF-kappaB signaling components is another means of controlling NF-kappaB signaling. Several alternative splicing events in both the tumor necrosis factor and Toll/interleukin-1 NF-kappaB signaling pathways can inhibit the NF-kappaB response, whereas others enhance NF-kappaB signaling. Alternative splicing of mRNAs encoding some NF-kappaB signaling components can be induced by prolonged exposure to an NF-kappaB-activating signal, such as lipopolysaccharide, suggesting a mechanism for negative feedback to dampen excessive NF-kappaB signaling. Moreover, some NF-kappaB alternative splicing events appear to be specific for certain diseases, and could serve as therapeutic targets or biomarkers.
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Affiliation(s)
- Joshua R Leeman
- Department of Biology, Boston University, 5 Cummington Street, Boston, MA 02215, USA
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7
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Qian Y, Zhao Z, Jiang Z, Li X. Role of NF kappa B activator Act1 in CD40-mediated signaling in epithelial cells. Proc Natl Acad Sci U S A 2002; 99:9386-91. [PMID: 12089335 PMCID: PMC123150 DOI: 10.1073/pnas.142294499] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
CD40, a cell surface receptor in the tumor necrosis factor receptor family, first identified and functionally characterized on B lymphocytes, is also expressed on epithelial and other cells and is now thought to play a more general role in immune regulation. Overexpression of the NF kappa B activator 1 (Act1) leads to the activation of both NF kappa B and Jun kinase in epithelial cell lines. Endogenous Act1 is recruited to the CD40 receptor in human intestinal (HT29) and cervical (HeLa) epithelial cells upon stimulation with CD40 ligand, indicating that Act1 is involved in this signaling pathway. Act1 also interacts with tumor necrosis factor receptor-associated factor 3, a component involved in CD40-activated pathway. Furthermore, transfection of Act1 into C33A cervical epithelial cells, which do not express it, renders these cells sensitive to CD40 ligand-induced NF kappa B activation and protects them from CD40 ligand-induced apoptosis. We conclude that Act1 plays an important role in CD40-mediated signaling in epithelial cells.
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Affiliation(s)
- Youcun Qian
- Department of Immunology, Lerner Research Institute, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA
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8
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Iseli C, Stevenson BJ, de Souza SJ, Samaia HB, Camargo AA, Buetow KH, Strausberg RL, Simpson AJG, Bucher P, Jongeneel CV. Long-range heterogeneity at the 3' ends of human mRNAs. Genome Res 2002; 12:1068-74. [PMID: 12097343 PMCID: PMC186619 DOI: 10.1101/gr.62002] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The publication of a draft of the human genome and of large collections of transcribed sequences has made it possible to study the complex relationship between the transcriptome and the genome. In the work presented here, we have focused on mapping mRNA 3' ends onto the genome by use of the raw data generated by the expressed sequence tag (EST) sequencing projects. We find that at least half of the human genes encode multiple transcripts whose polyadenylation is driven by multiple signals. The corresponding transcript 3' ends are spread over distances in the kilobase range. This finding has profound implications for our understanding of gene expression regulation and of the diversity of human transcripts, for the design of cDNA microarray probes, and for the interpretation of gene expression profiling experiments.
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Affiliation(s)
- Christian Iseli
- Office of Information Technology, Ludwig Institute for Cancer Research, Switzerland
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9
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Gamper C, Omene CO, van Eyndhoven WG, Glassman GD, Lederman S. Expression and function of TRAF-3 splice-variant isoforms in human lymphoma cell lines. Hum Immunol 2001; 62:1167-77. [PMID: 11600226 DOI: 10.1016/s0198-8859(01)00284-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
TRAF-3 gene products are signaling adaptor molecules required for lymphocytes to mediate T-dependent antibody responses in vivo. Previous work identified 8 splice-variant TRAF-3 mRNA species by RT-PCR that have the potential to encode novel isoforms, seven of which induce NF-kappaB activation when over-expressed in 293 cells. Here, their expression was characterized by RNAse protection assay, which showed the T cell line Jurkat D1.1 and the B cell lines BJAB, Daudi, and Raji each expressed mRNA encoding TRAF-3 splice-variants in approximately the same rank order (from highest to lowest); TRAF-3 Delta103aa, Delta83aa, full-length, Delta25aa, Delta52aa, Delta56aa, Delta27aa, and Delta221aa mRNA. The TRAF-3 Delta130aa mRNA was not detectable in any of the cell lines examined. The functional effect of over-expressing each TRAF-3 splice-variant on NF-kappaB activation was studied in the TRAF-5-responsive B cell line, BJAB. Of the seven TRAF-3 splice-variant isoforms that induce NF-kappaB activation in 293 cells, only TRAF-3 Delta27aa, Delta103aa, or Delta130aa induce NF-kappaB activation in BJAB cells. Together, these data indicate that a number of TRAF-3 splice-variant mRNAs are expressed and function in B and T lymphoma lines, which suggests that certain TRAF-3 splice-variant isoforms may participate in mediating the known functions of the TRAF-3 gene in lymphocytes.
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Affiliation(s)
- C Gamper
- Laboratory of Molecular Immunology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA
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10
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Grammer AC, Lipsky PE. CD40-mediated regulation of immune responses by TRAF-dependent and TRAF-independent signaling mechanisms. Adv Immunol 2001; 76:61-178. [PMID: 11079098 DOI: 10.1016/s0065-2776(01)76019-1] [Citation(s) in RCA: 71] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- A C Grammer
- Intramural Research Program of National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland, USA
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11
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Affiliation(s)
- S Lederman
- Laboratory of Molecular Immunology, Columbia University, New York, New York, USA
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12
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Lederman S, Suciu-Foca N. Antigen presenting cells integrate opposing signals from CD4+ and CD8+ regulatory T lymphocytes to arbitrate the outcomes of immune responses. Hum Immunol 1999; 60:533-61. [PMID: 10426271 DOI: 10.1016/s0198-8859(99)00045-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
An individual's set of polymorphic HLA class II and I molecules is known to select the T cell repertoire in the thymus and to present processed antigenic peptides (pAg) to mature peripheral CD4+ T helper (Th) and CD8+ T cytotoxic (Th) cells in the periphery. This review highlights new studies which address how antigen presenting cells (APC) integrate the responses of cognate Th and T suppressor (Ts) cells to determine the outcome of immune responses. Together with other findings, these studies emphasize that understanding the mechanism of immune processes requires consideration of HLA molecules in the context of the peptides they bind, the antigen presenting cells (APC) that express them and the T lymphocytes that recognize them. The activities of lymphocyte and APC surface structures are becoming integrated into a physiological understanding of the cellular interactions between regulatory and effector T cells with APC.
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Affiliation(s)
- S Lederman
- Department of Medicine and Pathology, Columbia University, New York, NY 10032, USA.
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13
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van Eyndhoven WG, Gamper CJ, Cho E, Mackus WJ, Lederman S. TRAF-3 mRNA splice-deletion variants encode isoforms that induce NF-kappaB activation. Mol Immunol 1999; 36:647-58. [PMID: 10509816 DOI: 10.1016/s0161-5890(99)00079-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Although TRAF-3 gene products are required for signaling in T-B cell collaboration, full-length TRAF-3 appears to lack signaling function in transient transfection assays that measure NF-kappaB activation. However, the TRAF-3 gene also encodes at least three mRNA splice-deletion variants that predict protein isoforms (delta25aa, delta52aa and delta56aa) with altered zinc (Zn) finger domains and unknown functional capacities. To determine whether TRAF-3 splice-deletion variants may transmit activating receptor signals to the nucleus, cDNAs for five additional splice-variant isoforms (delta27aa, delta83aa, delta103aa, delta130aa and delta221aa) were cloned from a TRAF-3+ lymphoma and the expression and function of each of the eight TRAF-3 splice-deletion variants was analyzed. Among the splice-deletion variants, TRAF-3 delta130 mRNA is expressed by tonsillar B cells and by each of a panel of B and T cell lines. TRAF-3 delta221 protein is expressed by tonsillar B cells and by each of the lymphocytic lines. The functional effect of over-expressing each TRAF-3 splice-deletion variant on NF-kappaB activation was studied in 293 T cells. Seven of the TRAF-3 splice-deletion variants, such as TRAF-3 delta130, induce substantial NF-kappaB-driven luciferase activity (80-500 fold). In contrast, TRAF-3 delta221 (in which the complete Zn finger domain is absent) fails to induce NF-kappaB activation. Although full-length TRAF-3 alone is inactive, it augments the functional effects of the seven activating TRAF-3 splice-deletion variants (1.4-5 fold). These data indicate that alterations of the Zn finger domains render the TRAF-3 splice-deletion variants capable of inducing NF-kappaB activation and that full-length TRAF-3 augments their signaling.
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Affiliation(s)
- W G van Eyndhoven
- Laboratory of Molecular Immunology, Columbia University, New York, NY 10032, USA
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