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Breunig K, Lei X, Montalbano M, Guardia GDA, Ostadrahimi S, Alers V, Kosti A, Chiou J, Klein N, Vinarov C, Wang L, Li M, Song W, Kraus WL, Libich DS, Tiziani S, Weintraub ST, Galante PAF, Penalva LOF. SERBP1 interacts with PARP1 and is present in PARylation-dependent protein complexes regulating splicing, cell division, and ribosome biogenesis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.22.586270. [PMID: 38585848 PMCID: PMC10996453 DOI: 10.1101/2024.03.22.586270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
RNA binding proteins (RBPs) containing intrinsically disordered regions (IDRs) are present in diverse molecular complexes where they function as dynamic regulators. Their characteristics promote liquid-liquid phase separation (LLPS) and the formation of membraneless organelles such as stress granules and nucleoli. IDR-RBPs are particularly relevant in the nervous system and their dysfunction is associated with neurodegenerative diseases and brain tumor development. SERBP1 is a unique member of this group, being mostly disordered and lacking canonical RNA-binding domains. Using a proteomics approach followed by functional analysis, we defined SERBP1's interactome. We uncovered novel SERBP1 roles in splicing, cell division, and ribosomal biogenesis and showed its participation in pathological stress granules and Tau aggregates in Alzheimer's disease brains. SERBP1 preferentially interacts with other G-quadruplex (G4) binders, implicated in different stages of gene expression, suggesting that G4 binding is a critical component of SERBP1 function in different settings. Similarly, we identified important associations between SERBP1 and PARP1/polyADP-ribosylation (PARylation). SERBP1 interacts with PARP1 and its associated factors and influences PARylation. Moreover, protein complexes in which SERBP1 participates contain mostly PARylated proteins and PAR binders. Based on these results, we propose a feedback regulatory model in which SERBP1 influences PARP1 function and PARylation, while PARylation modulates SERBP1 functions and participation in regulatory complexes.
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2
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Wang X, Hua X, Zhang H, Ren Y, Yang F, Zhu J. HABP4 overexpression promotes apoptosis in goat turbinate bone cells. Anim Biotechnol 2023; 34:4187-4195. [PMID: 35522841 DOI: 10.1080/10495398.2022.2062601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
Hyaluronic acid-binding protein (HABP4) plays important roles in regulating cell cycle and apoptosis. However, its functions in regulating cell apoptosis remain unclear. To reveal the effects of HABP4 on cell proliferation, cell cycle and apoptosis, the HABP4 sequence was cloned, and we investigated the gain and loss functions of HABP4 in goat turbinate bone cells. Our results showed that a 1,496-bp HABP4 sequence was cloned successfully. The interference effect of siRNA1 on HABP4 was the strongest, reducing its mRNA expression level by 83%, decreasing the cells in the G0/G1 and S phases of the cell cycle and inhibiting cell growth and apoptosis. The overexpression of HABP4 produced contrasting results. Furthermore, an HABP4 knockdown caused the up-regulated expression of genes associated with apoptosis, including Bcl-2 and BCL2L11, but the down-regulation of Caspase3, Caspase7, Bax, PARP1, SOCS2 and P53 mRNA levels. Additionally, HABP4 overexpression significantly up-regulated the expression levels of Bax, Caspase3, Caspase7, BCL2L11, P53, SOCS2 and PARP1. However, the expression of Bcl-2 was down-regulated. These data provide an important foundation for further in-depth studies of HABP4 functions.
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Affiliation(s)
- Xianjun Wang
- College of Animal & Veterinary Sciences, Southwest Minzu University, Chengdu, China
| | - Xiang Hua
- College of Animal & Veterinary Sciences, Southwest Minzu University, Chengdu, China
| | - Huanrong Zhang
- College of Animal & Veterinary Sciences, Southwest Minzu University, Chengdu, China
| | - Yupeng Ren
- College of Animal & Veterinary Sciences, Southwest Minzu University, Chengdu, China
| | - Falong Yang
- College of Animal & Veterinary Sciences, Southwest Minzu University, Chengdu, China
| | - Jiangjiang Zhu
- Qinghai-Tibetan Plateau Animal Genetic Resource Reservation and Utilization Key Laboratory of Sichuan Province, Chengdu, China
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3
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Melo-Hanchuk TD, Colleti C, Saito Â, Mendes MCS, Carvalheira JBC, Vassallo J, Kobarg J. Intracellular hyaluronic acid-binding protein 4 (HABP4): a candidate tumor suppressor in colorectal cancer. Oncotarget 2020; 11:4325-4337. [PMID: 33245729 PMCID: PMC7679031 DOI: 10.18632/oncotarget.27804] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 10/27/2020] [Indexed: 02/07/2023] Open
Abstract
Hyaluronic Acid-binding protein 4 (HABP4) is a regulatory protein of 57 kDa that is functionally involved in transcription regulation and RNA metabolism and shows several characteristics common to oncoproteins or tumor suppressors, including altered expression in cancer tissues, nucleus/cytoplasm shuttling, intrinsic lack of protein structure, complex interactomes and post translational modifications. Its gene has been found in a region on chromosome 9q22.3-31, which contains SNP haplotypes occurring in individuals with a high risk for familial colon cancer. To test a possible role of HABP4 in tumorigenesis we generated knockout mice by the CRISPR/Cas9 method and treated the animals with azoxymethane (AOM)/dextran sodium sulfate (DSS) for induction of colon tumors. HABP4-/- mice, compared to wild type mice, had more and larger tumors, and expressed more of the proliferation marker proteins Cyclin-D1, CDK4 and PCNA. Furthermore, the cells of the bottom of the colon crypts in the HABP4-/- mice divided more rapidly. Next, we generated also HABP4-/- HCT 116 cells, in cell culture and found again an increased proliferation in clonogenic assays in comparison to wild-type cells. Our study of the protein expression levels of HABP4 in human colon cancer samples, through immunohistochemistry assays, showed, that 30% of the tumors analyzed had low expression of HABP4. Our data suggest that HABP4 is involved in proliferation regulation of colon cells in vitro and in vivo and that it is a promising new candidate for a tumor suppressor protein that can be explored both in the diagnosis and possibly therapy of colon cancer.
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Affiliation(s)
- Talita Diniz Melo-Hanchuk
- 2Department of Biochemistry and Tissue Biology, Institute of Biology, State University of Campinas (UNICAMP), Campinas, SP, Brazil
- *These authors contributed equally to this work
| | - Carolina Colleti
- 1School of Pharmaceutical Sciences, State University of Campinas (UNICAMP), Campinas, SP, Brazil
- *These authors contributed equally to this work
| | - Ângela Saito
- 3Brazilian Biosciences National Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, SP, Brazil
- *These authors contributed equally to this work
| | - Maria Carolina Santos Mendes
- 4Division of Oncology, Department of Internal Medicine, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - José Barreto Campello Carvalheira
- 4Division of Oncology, Department of Internal Medicine, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, SP, Brazil
| | - Jose Vassallo
- 5Laboratory of Investigative Pathology, CIPED, Faculty of Medical Sciences, State University of Campinas, Campinas, SP, Brazil
| | - Jörg Kobarg
- 1School of Pharmaceutical Sciences, State University of Campinas (UNICAMP), Campinas, SP, Brazil
- Correspondence to: Jörg Kobarg, email:
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4
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Colleti C, Melo-Hanchuk TD, da Silva FRM, Saito Â, Kobarg J. Complex interactomes and post-translational modifications of the regulatory proteins HABP4 and SERBP1 suggest pleiotropic cellular functions. World J Biol Chem 2019; 10:44-64. [PMID: 31768228 PMCID: PMC6872977 DOI: 10.4331/wjbc.v10.i3.44] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 08/30/2019] [Accepted: 10/15/2019] [Indexed: 02/05/2023] Open
Abstract
The 57 kDa antigen recognized by the Ki-1 antibody, is also known as intracellular hyaluronic acid binding protein 4 and shares 40.7% identity and 67.4% similarity with serpin mRNA binding protein 1, which is also named CGI-55, or plasminogen activator inhibitor type-1-RNA binding protein-1, indicating that they might be paralog proteins, possibly with similar or redundant functions in human cells. Through the identification of their protein interactomes, both regulatory proteins have been functionally implicated in transcriptional regulation, mRNA metabolism, specifically RNA splicing, the regulation of mRNA stability, especially, in the context of the progesterone hormone response, and the DNA damage response. Both proteins also show a complex pattern of post-translational modifications, involving Ser/Thr phosphorylation, mainly through protein kinase C, arginine methylation and SUMOylation, suggesting that their functions and locations are highly regulated. Furthermore, they show a highly dynamic cellular localization pattern with localizations in both the cytoplasm and nucleus as well as punctuated localizations in both granular cytoplasmic protein bodies, upon stress, and nuclear splicing speckles. Several reports in the literature show altered expressions of both regulatory proteins in a series of cancers as well as mutations in their genes that may contribute to tumorigenesis. This review highlights important aspects of the structure, interactome, post-translational modifications, sub-cellular localization and function of both regulatory proteins and further discusses their possible functions and their potential as tumor markers in different cancer settings.
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Affiliation(s)
- Carolina Colleti
- Faculty of Pharmaceutical Sciences, University of Campinas, Campinas 13083-871, Brazil
- Institute of Biology, Departament of Biochemistry and Tissue Biology, University of Campinas, Campinas 13083-862, Brazil
| | - Talita Diniz Melo-Hanchuk
- Institute of Biology, Departament of Biochemistry and Tissue Biology, University of Campinas, Campinas 13083-862, Brazil
| | - Flávia Regina Moraes da Silva
- Faculty of Pharmaceutical Sciences, University of Campinas, Campinas 13083-871, Brazil
- Institute of Biology, Departament of Biochemistry and Tissue Biology, University of Campinas, Campinas 13083-862, Brazil
| | - Ângela Saito
- Laboratório Nacional de Biociências, CNPEM, Campinas 13083-970, Brazil
| | - Jörg Kobarg
- Faculty of Pharmaceutical Sciences, University of Campinas, Campinas 13083-871, Brazil
- Institute of Biology, Departament of Biochemistry and Tissue Biology, University of Campinas, Campinas 13083-862, Brazil
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5
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Frankel A, Brown JI. Evaluation of kinetic data: What the numbers tell us about PRMTs. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2018; 1867:306-316. [PMID: 30342239 DOI: 10.1016/j.bbapap.2018.10.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/25/2018] [Revised: 10/10/2018] [Accepted: 10/14/2018] [Indexed: 01/06/2023]
Abstract
Protein arginine N-methyltransferase (PRMT) kinetic parameters have been catalogued over the past fifteen years for eight of the nine mammalian enzyme family members. Like the majority of methyltransferases, these enzymes employ the highly ubiquitous cofactor S-adenosyl-l-methionine as a co-substrate to methylate arginine residues in peptidic substrates with an approximately 4-μM median KM. The median values for PRMT turnover number (kcat) and catalytic efficiency (kcat/KM) are 0.0051 s-1 and 708 M-1 s-1, respectively. When comparing PRMT metrics to entries found in the BRENDA database, we find that while PRMTs exhibit high substrate affinity relative to other enzyme-substrate pairs, PRMTs display largely lower kcat and kcat/KM values. We observe that kinetic parameters for PRMTs and arginine demethylase activity from dual-functioning lysine demethylases are statistically similar, paralleling what the broader enzyme families in which they belong reveal, and adding to the evidence in support of arginine methylation reversibility.
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Affiliation(s)
- Adam Frankel
- Faculty of Pharmaceutical Sciences, University of British Columbia, 2405 Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada.
| | - Jennifer I Brown
- Faculty of Pharmaceutical Sciences, University of British Columbia, 2405 Wesbrook Mall, Vancouver, BC V6T 1Z3, Canada
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6
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Saito Â, Souza EE, Costa FC, Meirelles GV, Gonçalves KA, Santos MT, Bressan GC, McComb ME, Costello CE, Whelan SA, Kobarg J. Human Regulatory Protein Ki-1/57 Is a Target of SUMOylation and Affects PML Nuclear Body Formation. J Proteome Res 2017; 16:3147-3157. [PMID: 28695742 DOI: 10.1021/acs.jproteome.7b00001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Ki-1/57 is a nuclear and cytoplasmic regulatory protein first identified in malignant cells from Hodgkin's lymphoma. It is involved in gene expression regulation on both transcriptional and mRNA metabolism levels. Ki-1/57 belongs to the family of intrinsically unstructured proteins and undergoes phosphorylation by PKC and methylation by PRMT1. Previous characterization of its protein interaction profile by yeast two-hybrid screening showed that Ki-1/57 interacts with proteins of the SUMOylation machinery, the SUMO E2 conjugating enzyme UBC9 and the SUMO E3 ligase PIAS3, which suggested that Ki-1/57 could be involved with this process. Here we identified seven potential SUMO target sites (lysine residues) on Ki-1/57 sequence and observed that Ki-1/57 is modified by SUMO proteins in vitro and in vivo. We showed that SUMOylation of Ki-1/57 occurred on lysines 213, 276, and 336. In transfected cells expressing FLAG-Ki-1/57 wild-type, its paralog FLAG-CGI-55 wild-type, or their non-SUMOylated triple mutants, the number of PML-nuclear bodies (PML-NBs) is reduced compared with the control cells not expressing the constructs. More interestingly, after treating cells with arsenic trioxide (As2O3), the number of PML-NBs is no longer reduced when the non-SUMOylated triple mutant Ki-1/57 is expressed, suggesting that the SUMOylation of Ki-1/57 has a role in the control of As2O3-induced PML-NB formation. A proteome-wide analysis of Ki-1/57 partners in the presence of either SUMO-1 or SUMO-2 suggests that the involvement of Ki-1/57 with the regulation of gene expression is independent of the presence of either SUMO-1 or SUMO-2; however, the presence of SUMO-1 strongly influences the interaction of Ki-1/57 with proteins associated with cellular metabolism, maintenance, and cell cycle.
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Affiliation(s)
- Ângela Saito
- Laboratório Nacional de Biociências (LNBio), Centro Nacional de Pesquisa em Energia e Materiais (CNPEM) , Campinas, São Paulo 13083-970, Brazil
| | - Edmarcia E Souza
- Faculdade de Ciências Farmacêuticas, Universidade Estadual de Campinas , Campinas, São Paulo 13083-859, Brazil
| | - Fernanda C Costa
- Instituto de Física de São Carlos, Universidade de São Paulo , São Carlos, São Paulo 13563-120, Brazil
| | - Gabriela V Meirelles
- Laboratório Nacional de Biociências (LNBio), Centro Nacional de Pesquisa em Energia e Materiais (CNPEM) , Campinas, São Paulo 13083-970, Brazil
| | - Kaliandra A Gonçalves
- Laboratório Nacional de Biociências (LNBio), Centro Nacional de Pesquisa em Energia e Materiais (CNPEM) , Campinas, São Paulo 13083-970, Brazil
| | - Marcos T Santos
- ONKOS Molecular Diagnostics, Inc. , R&D Department, Ribeirão Preto, São Paulo 14056-680, Brazil
| | - Gustavo C Bressan
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Viçosa (UFV) , Viçosa, Minas Gerais 36570-000, Brazil
| | - Mark E McComb
- Center for Biomedical Mass Spectrometry, Boston University School of Medicine , Boston, Massachusetts 02118, United States
| | - Catherine E Costello
- Center for Biomedical Mass Spectrometry, Boston University School of Medicine , Boston, Massachusetts 02118, United States
| | - Stephen A Whelan
- Center for Biomedical Mass Spectrometry, Boston University School of Medicine , Boston, Massachusetts 02118, United States
| | - Jörg Kobarg
- Faculdade de Ciências Farmacêuticas, Universidade Estadual de Campinas , Campinas, São Paulo 13083-859, Brazil.,Departamento de Bioquímica e Biologia Tecidual, Programa de Pós-graduação em Biologia Funcional e Molecular, Universidade Estadual de Campinas , Campinas, São Paulo 13083-862, Brazil
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7
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Bolger GB. The RNA-binding protein SERBP1 interacts selectively with the signaling protein RACK1. Cell Signal 2017; 35:256-263. [PMID: 28267599 DOI: 10.1016/j.cellsig.2017.03.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2016] [Revised: 02/23/2017] [Accepted: 03/02/2017] [Indexed: 12/19/2022]
Abstract
The RACK1 protein interacts with numerous proteins involved in signal transduction, the cytoskeleton, and mRNA splicing and translation. We used the 2-hybrid system to identify additional proteins interacting with RACK1 and isolated the RNA-binding protein SERBP1. SERPB1 shares amino acid sequence homology with HABP4 (also known as Ki-1/57), a component of the RNA spicing machinery that has been shown previously to interact with RACK1. Several different isoforms of SERBP1, generated by alternative mRNA splicing, interacted with RACK1 with indistinguishable interaction strength, as determined by a 2-hybrid beta-galactosidase assay. Analysis of deletion constructs of SERBP1 showed that the C-terminal third of the SERBP1 protein, which contains one of its two substrate sites for protein arginine N-methyltransferase 1 (PRMT1), is necessary and sufficient for it to interact with RACK1. Analysis of single amino acid substitutions in RACK1, identified in a reverse 2-hybrid screen, showed very substantial overlap with those implicated in the interaction of RACK1 with the cAMP-selective phosphodiesterase PDE4D5. These data are consistent with SERBP1 interacting selectively with RACK1, mediated by an extensive interaction surface on both proteins.
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Affiliation(s)
- Graeme B Bolger
- Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294-3300, USA; Department of Pharmacology, University of Alabama at Birmingham, Birmingham, AL 35294-3300, USA.
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8
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Ahn JW, Kim S, Na W, Baek SJ, Kim JH, Min K, Yeom J, Kwak H, Jeong S, Lee C, Kim SY, Choi CY. SERBP1 affects homologous recombination-mediated DNA repair by regulation of CtIP translation during S phase. Nucleic Acids Res 2015; 43:6321-33. [PMID: 26068472 PMCID: PMC4513868 DOI: 10.1093/nar/gkv592] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2014] [Revised: 05/13/2015] [Accepted: 05/24/2015] [Indexed: 11/12/2022] Open
Abstract
DNA double-strand breaks (DSBs) are the most severe type of DNA damage and are primarily repaired by non-homologous end joining (NHEJ) and homologous recombination (HR) in the G1 and S/G2 phase, respectively. Although CtBP-interacting protein (CtIP) is crucial in DNA end resection during HR following DSBs, little is known about how CtIP levels increase in an S phase-specific manner. Here, we show that Serpine mRNA binding protein 1 (SERBP1) regulates CtIP expression at the translational level in S phase. In response to camptothecin-mediated DNA DSBs, CHK1 and RPA2 phosphorylation, which are hallmarks of HR activation, was abrogated in SERBP1-depleted cells. We identified CtIP mRNA as a binding target of SERBP1 using RNA immunoprecipitation-coupled RNA sequencing, and confirmed SERBP1 binding to CtIP mRNA in S phase. SERBP1 depletion resulted in reduction of polysome-associated CtIP mRNA and concomitant loss of CtIP expression in S phase. These effects were reversed by reconstituting cells with wild-type SERBP1, but not by SERBP1 ΔRGG, an RNA binding defective mutant, suggesting regulation of CtIP translation by SERBP1 association with CtIP mRNA. These results indicate that SERBP1 affects HR-mediated DNA repair in response to DNA DSBs by regulation of CtIP translation in S phase.
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Affiliation(s)
- Jang-Won Ahn
- Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746, Republic of Korea
| | - Sunjik Kim
- Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746, Republic of Korea
| | - Wooju Na
- Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746, Republic of Korea
| | - Su-Jin Baek
- Human Genomics Research Center, KRIBB, Daejeon 305-806, Republic of Korea Department of Functional Genomics, University of Science of Technology, Daejeon 305-350, Republic of Korea
| | - Jeong-Hwan Kim
- Human Genomics Research Center, KRIBB, Daejeon 305-806, Republic of Korea
| | - Keehong Min
- Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746, Republic of Korea
| | - Jeonghun Yeom
- Center for Theragnosis, Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea Department of Biological Chemistry, University of Science and Technology, Daejeon 305-333, Republic of Korea
| | - Hoyun Kwak
- Department of Molecular Biology, Dankook University, Yongin 448-701, Republic of Korea
| | - Sunjoo Jeong
- Department of Molecular Biology, Dankook University, Yongin 448-701, Republic of Korea
| | - Cheolju Lee
- Center for Theragnosis, Korea Institute of Science and Technology, Seoul 136-791, Republic of Korea Department of Biological Chemistry, University of Science and Technology, Daejeon 305-333, Republic of Korea
| | - Seon-Young Kim
- Human Genomics Research Center, KRIBB, Daejeon 305-806, Republic of Korea Department of Functional Genomics, University of Science of Technology, Daejeon 305-350, Republic of Korea
| | - Cheol Yong Choi
- Department of Biological Sciences, Sungkyunkwan University, Suwon 440-746, Republic of Korea
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Kaehler C, Guenther A, Uhlich A, Krobitsch S. PRMT1-mediated arginine methylation controls ATXN2L localization. Exp Cell Res 2015; 334:114-25. [PMID: 25748791 DOI: 10.1016/j.yexcr.2015.02.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 02/20/2015] [Accepted: 02/25/2015] [Indexed: 01/02/2023]
Abstract
Arginine methylation is a posttranslational modification that is of importance in diverse cellular processes. Recent proteomic mass spectrometry studies reported arginine methylation of ataxin-2-like (ATXN2L), the paralog of ataxin-2, a protein that is implicated in the neurodegenerative disorder spinocerebellar ataxia type 2. Here, we investigated the methylation state of ATXN2L and its significance for ATXN2L localization. We first confirmed that ATXN2L is asymmetrically dimethylated in vivo, and observed that the nuclear localization of ATXN2L is altered under methylation inhibition. We further discovered that ATXN2L associates with the protein arginine-N-methyltransferase 1 (PRMT1). Finally, we showed that neither mutation of the arginine-glycine-rich motifs of ATXN2L nor methylation inhibition alters ATXN2L localization to stress granules, suggesting that methylation of ATXN2L is probably not mandatory.
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Affiliation(s)
- Christian Kaehler
- Max Planck Institute for Molecular Genetics, Ihnestrasse 63-73, 14195 Berlin, Germany
| | - Anika Guenther
- Max Planck Institute for Molecular Genetics, Ihnestrasse 63-73, 14195 Berlin, Germany
| | - Anja Uhlich
- Max Planck Institute for Molecular Genetics, Ihnestrasse 63-73, 14195 Berlin, Germany
| | - Sylvia Krobitsch
- Max Planck Institute for Molecular Genetics, Ihnestrasse 63-73, 14195 Berlin, Germany.
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10
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Costa FC, Saito A, Gonçalves KA, Vidigal PM, Meirelles GV, Bressan GC, Kobarg J. Ki-1/57 and CGI-55 ectopic expression impact cellular pathways involved in proliferation and stress response regulation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1843:2944-56. [PMID: 25205453 DOI: 10.1016/j.bbamcr.2014.08.016] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 08/27/2014] [Accepted: 08/28/2014] [Indexed: 10/24/2022]
Abstract
Ki-1/57 (HABP4) and CGI-55 (SERBP1) are regulatory proteins and paralogs with 40.7% amino acid sequence identity and 67.4% similarity. Functionally, they have been implicated in the regulation of gene expression on both the transcriptional and mRNA metabolism levels. A link with tumorigenesis is suggested, since both paralogs show altered expression levels in tumor cells and the Ki-1/57 gene is found in a region of chromosome 9q that represents a haplotype for familiar colon cancer. However, the target genes regulated by Ki-1/57 and CGI-55 are unknown. Here, we analyzed the alterations of the global transcriptome profile after Ki-1/57 or CGI-55 overexpression in HEK293T cells by DNA microchip technology. We were able to identify 363 or 190 down-regulated and 50 or 27 up-regulated genes for Ki-1/57 and CGI-55, respectively, of which 20 were shared between both proteins. Expression levels of selected genes were confirmed by qRT-PCR both after protein overexpression and siRNA knockdown. The majority of the genes with altered expression were associated to proliferation, apoptosis and cell cycle control processes, prompting us to further explore these contexts experimentally. We observed that overexpression of Ki-1/57 or CGI-55 results in reduced cell proliferation, mainly due to a G1 phase arrest, whereas siRNA knockdown of CGI-55 caused an increase in proliferation. In the case of Ki-1/57 overexpression, we found protection from apoptosis after treatment with the ER-stress inducer thapsigargin. Together, our data give important new insights that may help to explain these proteins putative involvement in tumorigenic events.
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Affiliation(s)
- Fernanda C Costa
- Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, Campinas, São Paulo, Brasil.
| | - Angela Saito
- Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, Campinas, São Paulo, Brasil; Departamento de Bioquímica-Programa de Pós-graduação em Biologia Funcional e Molecular, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brasil.
| | - Kaliandra A Gonçalves
- Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, Campinas, São Paulo, Brasil; Departamento de Bioquímica-Programa de Pós-graduação em Biologia Funcional e Molecular, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brasil.
| | - Pedro M Vidigal
- Laboratório de Bioinformática, Instituto de Biotecnologia Aplicada à Agropecuária-BIOAGRO, Universidade Federal de Viçosa, Viçosa, Minas Gerais, Brasil.
| | - Gabriela V Meirelles
- Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, Campinas, São Paulo, Brasil.
| | - Gustavo C Bressan
- Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, Campinas, São Paulo, Brasil; Departamento de Bioquímica-Programa de Pós-graduação em Biologia Funcional e Molecular, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brasil.
| | - Jörg Kobarg
- Laboratório Nacional de Biociências, Centro Nacional de Pesquisa em Energia e Materiais, Campinas, São Paulo, Brasil; Departamento de Bioquímica-Programa de Pós-graduação em Biologia Funcional e Molecular, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brasil; Departamento de Genética, Evolução e Bioagentes - Programa de Pós-graduação em Genética e Biologia Molecular, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, São Paulo, Brasil.
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11
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Lau HT, Lewis KA, Ong SE. Quantifying in vivo, site-specific changes in protein methylation with SILAC. Methods Mol Biol 2014; 1188:161-175. [PMID: 25059611 DOI: 10.1007/978-1-4939-1142-4_12] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Interest in protein methylation has grown rapidly in recent years. Mass spectrometry-based proteomics is ideally suited to characterize protein modifications, but the multiplicity of methylated residues and the lack of efficient methods to enrich methylated proteins have limited the proteomic identification of protein methylation sites. In this protocol, we compare two metabolic labeling approaches, stable isotope labeling by amino acids in cell culture (SILAC) and its variant heavy methyl SILAC, for studying protein methylation. Instead of heavy lysine and arginine in the typical SILAC experiment, heavy methyl SILAC uses (13)C, (2)H methionine as the labeling amino acid. As cells convert methionine to S-adenosylmethionine, heavy methyl SILAC encodes a 4 Da mass tag for each methyl group, distinguishing between degrees of methylation is possible from mass difference alone. We provide a protocol for SILAC-based analyses of protein methylation and highlight the strengths and weaknesses of each method for targeted and proteomic analyses.
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Affiliation(s)
- Ho-Tak Lau
- Department of Pharmacology, University of Washington, 1959 NE Pacific Street, 357280, Seattle, WA, 98195, USA
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12
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Lee YJ, Wei HM, Chen LY, Li C. Localization of SERBP1 in stress granules and nucleoli. FEBS J 2013; 281:352-64. [DOI: 10.1111/febs.12606] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2013] [Accepted: 11/06/2013] [Indexed: 12/24/2022]
Affiliation(s)
- Yu-Jen Lee
- Institute of Biochemistry and Biotechnology; Chung Shan Medical University; Taichung Taiwan
| | - Hung-Ming Wei
- Department of Biomedical Sciences; Chung Shan Medical University; Taichung Taiwan
| | - Ling-Yun Chen
- Institute of Biochemistry and Biotechnology; Chung Shan Medical University; Taichung Taiwan
| | - Chuan Li
- Department of Biomedical Sciences; Chung Shan Medical University; Taichung Taiwan
- Department of Medical Research; Chung Shan Medical University Hospital; Taichung Taiwan
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Chew TG, Peaston A, Lim AK, Lorthongpanich C, Knowles BB, Solter D. A tudor domain protein SPINDLIN1 interacts with the mRNA-binding protein SERBP1 and is involved in mouse oocyte meiotic resumption. PLoS One 2013; 8:e69764. [PMID: 23894536 PMCID: PMC3718791 DOI: 10.1371/journal.pone.0069764] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2013] [Accepted: 06/12/2013] [Indexed: 12/11/2022] Open
Abstract
Mammalian oocytes are arrested at prophase I of meiosis, and resume meiosis prior to ovulation. Coordination of meiotic arrest and resumption is partly dependent on the post-transcriptional regulation of maternal transcripts. Here, we report that, SPINDLIN1 (SPIN1), a maternal protein containing Tudor-like domains, interacts with a known mRNA-binding protein SERBP1, and is involved in regulating maternal transcripts to control meiotic resumption. Mouse oocytes deficient for Spin1 undergo normal folliculogenesis, but are defective in resuming meiosis. SPIN1, via its Tudor-like domain, forms a ribonucleoprotein complex with SERBP1, and regulating mRNA stability and/or translation. The mRNA for the cAMP-degrading enzyme, PDE3A, is reduced in Spin1 mutant oocytes, possibly contributing to meiotic arrest. Our study demonstrates that Spin1 regulates maternal transcripts post-transcriptionally and is involved in meiotic resumption.
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Affiliation(s)
- Ting Gang Chew
- Mammalian Development Laboratory, Institute of Medical Biology, A-STAR, Singapore, Singapore.
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14
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Identification of a novel lipin homologue from the parasitic protozoan Trypanosoma brucei. BMC Microbiol 2013; 13:101. [PMID: 23656927 PMCID: PMC3654991 DOI: 10.1186/1471-2180-13-101] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 05/06/2013] [Indexed: 02/03/2023] Open
Abstract
Background Arginine methylation is a post-translational modification that expands the functional diversity of proteins. Kinetoplastid parasites contain a relatively large group of protein arginine methyltransferases (PRMTs) compared to other single celled eukaryotes. Several T. brucei proteins have been shown to serve as TbPRMT substrates in vitro, and a great number of proteins likely to undergo methylation are predicted by the T. brucei genome. This indicates that a large number of proteins whose functions are modulated by arginine methylation await discovery in trypanosomes. Here, we employed a yeast two-hybrid screen using as bait the major T. brucei type I PRMT, TbPRMT1, to identify potential substrates of this enzyme. Results We identified a protein containing N-LIP and C-LIP domains that we term TbLpn. These domains are usually present in a family of proteins known as lipins, and involved in phospholipid biosynthesis and gene regulation. Far western and co-immunoprecipitation assays confirmed the TbPRMT1-TbLpn interaction. We also demonstrated that TbLpn is localized mainly to the cytosol, and is methylated in vivo. In addition, we showed that, similar to mammalian and yeast proteins with N-LIP and C-LIP domains, recombinant TbLpn exhibits phosphatidic acid phosphatase activity, and that two conserved aspartic acid residues present in the C-LIP domain are critical for its enzymatic activity. Conclusions This study reports the characterization of a novel trypanosome protein and provides insight into its enzymatic activity and function in phospholipid biosynthesis. It also indicates that TbLpn functions may be modulated by arginine methylation.
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A Y2H-seq approach defines the human protein methyltransferase interactome. Nat Methods 2013; 10:339-42. [PMID: 23455924 DOI: 10.1038/nmeth.2397] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Accepted: 01/15/2013] [Indexed: 11/09/2022]
Abstract
To accelerate high-density interactome mapping, we developed a yeast two-hybrid interaction screening approach involving short-read second-generation sequencing (Y2H-seq) with improved sensitivity and a quantitative scoring readout allowing rapid interaction validation. We applied Y2H-seq to investigate enzymes involved in protein methylation, a largely unexplored post-translational modification. The reported network of 523 interactions involving 22 methyltransferases or demethylases is comprehensively annotated and validated through coimmunoprecipitation experiments and defines previously undiscovered cellular roles of nonhistone protein methylation.
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Lee YJ, Hsieh WY, Chen LY, Li C. Protein arginine methylation of SERBP1 by protein arginine methyltransferase 1 affects cytoplasmic/nuclear distribution. J Cell Biochem 2012; 113:2721-8. [PMID: 22442049 DOI: 10.1002/jcb.24151] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Protein arginine methylation regulates a broad array of cellular processes. SERBP1 implicated in tumor progression through its putative involvement in the plaminogen activator protease cascade, is an RNA-binding protein containing an RG-rich domain and an RGG box domain that might be methylated by protein arginine N-methyltransferases (PRMTs). Asymmetric dimethylarginine (aDMA) was detected in SERBP1 and an indirect methyltransferase inhibitor adenosine dialdehyde (AdOx) significantly reduced the methylation signals. Arginines in the middle RG and C-terminal RGG region of SERBP1 are methylated based on the analyses of different deletion constructs. The predominant type I protein arginine methyltransferase PRMT1 co-immunoprecipitated with SERBP1 and the level of bound PRMT1 decreased upon the addition of AdOx. Recombinant PRMT1 methylated SERBP1 and knockdown of PRMT1 significantly reduced the aDMA level of SERBP1, indicating that SERBP1 is specifically methylated by PRMT1. Immunofluorescent analyses of endogenous SERBP1 showed predominant cytoplasmic localization of SERBP1. Treatment of AdOx or PRMT1 siRNA increased the nuclear localization of SERBP1. Analyses of different deletions indicated that the middle RG region is important for the nuclear localization while both N- and C- terminus are required for nuclear export. Low methylation of the C-terminal RGG region also favors nuclear localization. In conclusion, the RG-rich and RGG box of SERBP1 is asymmetrically dimethylated by PRMT1 and the modification affects protein interaction and intracellular localization of the protein. These findings provide the basis for dissecting the roles of SERBP1.
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Affiliation(s)
- Yu-Jen Lee
- Institute of Biochemistry and Biotechnology, Chung Shan Medical University, Taichung, Taiwan
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Gonçalves KDA, Bressan GC, Saito A, Morello LG, Zanchin NIT, Kobarg J. Evidence for the association of the human regulatory protein Ki-1/57 with the translational machinery. FEBS Lett 2011; 585:2556-60. [PMID: 21771594 DOI: 10.1016/j.febslet.2011.07.010] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2011] [Revised: 07/04/2011] [Accepted: 07/04/2011] [Indexed: 02/06/2023]
Abstract
Ki-1/57 is a cytoplasmic and nuclear protein of 57 kDa first identified in malignant cells from Hodgkin's lymphoma. Based on yeast-two hybrid protein interaction we found out that Ki-1/57 interacts with adaptor protein RACK1 (receptor of activated kinase 1), CIRP (cold-inducible RNA-binding protein), RPL38 (ribosomal protein L38) and FXR1 (fragile X mental retardation-related protein 1). Since these proteins are involved in the regulation of translation we suspected that Ki-1/57 may have a role in it. We show by immunoprecipitation the association of Ki-1/57 with FMRP. Confocal microscopy revealed that Ki-1/57 colocalizes with FMRP/FXR1/2 to stress granules. Furthermore Ki-1/57 cosediments with free ribosomal particles and enhances translation, when tethered to a reporter mRNA, suggesting that Ki-1/57 may be involved in translational regulation.
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Affiliation(s)
- Kaliandra de Almeida Gonçalves
- Laboratório Nacional de Biociências (LNBio), Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), Campinas, São Paulo, Brazil
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Gonçalves KA, Borges JC, Silva JC, Papa PF, Bressan GC, Torriani IL, Kobarg J. Solution structure of the human signaling protein RACK1. BMC STRUCTURAL BIOLOGY 2010; 10:15. [PMID: 20529362 PMCID: PMC2896345 DOI: 10.1186/1472-6807-10-15] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Accepted: 06/08/2010] [Indexed: 01/09/2023]
Abstract
Background The adaptor protein RACK1 (receptor of activated kinase 1) was originally identified as an anchoring protein for protein kinase C. RACK1 is a 36 kDa protein, and is composed of seven WD repeats which mediate its protein-protein interactions. RACK1 is ubiquitously expressed and has been implicated in diverse cellular processes involving: protein translation regulation, neuropathological processes, cellular stress, and tissue development. Results In this study we performed a biophysical analysis of human RACK1 with the aim of obtaining low resolution structural information. Small angle X-ray scattering (SAXS) experiments demonstrated that human RACK1 is globular and monomeric in solution and its low resolution structure is strikingly similar to that of an homology model previously calculated by us and to the crystallographic structure of RACK1 isoform A from Arabidopsis thaliana. Both sedimentation velocity and sedimentation equilibrium analytical ultracentrifugation techniques showed that RACK1 is predominantly a monomer of around 37 kDa in solution, but also presents small amounts of oligomeric species. Moreover, hydrodynamic data suggested that RACK1 has a slightly asymmetric shape. The interaction of RACK1 and Ki-1/57 was tested by sedimentation equilibrium. The results suggested that the association between RACK1 and Ki-1/57(122-413) follows a stoichiometry of 1:1. The binding constant (KB) observed for RACK1-Ki-1/57(122-413) interaction was of around (1.5 ± 0.2) × 106 M-1 and resulted in a dissociation constant (KD) of (0.7 ± 0.1) × 10-6 M. Moreover, the fluorescence data also suggests that the interaction may occur in a cooperative fashion. Conclusion Our SAXS and analytical ultracentrifugation experiments indicated that RACK1 is predominantly a monomer in solution. RACK1 and Ki-1/57(122-413) interact strongly under the tested conditions.
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Affiliation(s)
- Kaliandra A Gonçalves
- Laboratório Nacional de Biociências (LNBio), Centro de Pesquisa em Energia e Materiais (CNPEM), Campinas, SP, Brazil
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Arginine methylation analysis of the splicing-associated SR protein SFRS9/SRP30C. Cell Mol Biol Lett 2009; 14:657-69. [PMID: 19557313 PMCID: PMC6275941 DOI: 10.2478/s11658-009-0024-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Accepted: 06/10/2009] [Indexed: 11/20/2022] Open
Abstract
The human SFRS9/SRp30c belongs to the SR family of splicing regulators. Despite evidence that members of this protein family may be targeted by arginine methylation, this has yet to be experimentally addressed. In this study, we found that SFRS9 is a target for PRMT1-mediated arginine methylation in vitro, and that it is immunoprecipitated from HEK-293 lysates by antibodies that recognize both mono- and dimethylated arginines. We further observed that upon treatment with the methylation inhibitor Adox, the fluorescent EGFP-SFRS9 re-localizes to dot-like structures in the cell nucleus. In subsequent confocal analyses, we found that EGFP-SFRS9 localizes to nucleoli in Adox-treated cells. Our findings indicate the importance of arginine methylation for the subnuclear localization of SFRS9.
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Bressan GC, Quaresma AJC, Moraes EC, Manfiolli AO, Passos DO, Gomes MD, Kobarg J. Functional association of human Ki-1/57 with pre-mRNA splicing events. FEBS J 2009; 276:3770-83. [PMID: 19523114 DOI: 10.1111/j.1742-4658.2009.07092.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The cytoplasmic and nuclear protein Ki-1/57 was first identified in malignant cells from Hodgkin's lymphoma. Despite studies showing its phosphorylation, arginine methylation, and interaction with several regulatory proteins, the functional role of Ki-1/57 in human cells remains to be determined. Here, we investigated the relationship of Ki-1/57 with RNA functions. Through immunoprecipitation assays, we verified the association of Ki-1/57 with the endogenous splicing proteins hnRNPQ and SFRS9 in HeLa cell extracts. We also found that recombinant Ki-1/57 was able to bind to a poly-U RNA probe in electrophoretic mobility shift assays. In a classic splicing test, we showed that Ki-1/57 can modify the splicing site selection of the adenoviral E1A minigene in a dose-dependent manner. Further confocal and fluorescence microscopy analysis revealed the localization of enhanced green fluorescent proteinKi-1/57 to nuclear bodies involved in RNA processing and or small nuclear ribonucleoprotein assembly, depending on the cellular methylation status and its N-terminal region. In summary, our findings suggest that Ki-1/57 is probably involved in cellular events related to RNA functions, such as pre-mRNA splicing.
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Lei NZ, Zhang XY, Chen HZ, Wang Y, Zhan YY, Zheng ZH, Shen YM, Wu Q. A feedback regulatory loop between methyltransferase PRMT1 and orphan receptor TR3. Nucleic Acids Res 2008; 37:832-48. [PMID: 19095693 PMCID: PMC2647306 DOI: 10.1093/nar/gkn941] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
PRMT1, an arginine methyltransferase, plays an important role in numerous cellular processes. In this study, we demonstrate a feedback regulatory loop between PRMT1 and the orphan receptor TR3. Unlike another orphan receptor HNF4, TR3 is not methylated by PRMT1 although they physically interact with each other. By delaying the TR3 protein degradation, PRMT1 binding leads to the elevation of TR3 cellular protein level, thereby enhances the DNA binding and transactivation activity of TR3 in a non-methyltransferase manner. Another coactivator SRC-2 acts synergistically with PRMT1 to regulate TR3 functions. In turn, TR3 binding to the catalytic domain of PRMT1 causes an inhibition of the PRMT1 methyltransferase activity. This repression results in the functional changes in some of PRMT1 substrates, including STAT3 and Sam68. The negative regulation of PRMT1 by TR3 was further confirmed in both TR3-knockdown cells and TR3-knockout mice with the use of an agonist for TR3. Taken together, our study not only identifies a regulatory role of PRMT1, independent on methyltransferase activity, in TR3 transactivation, but also characterizes a novel function of TR3 in the repression of PRMT1 methyltransferase activity.
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Affiliation(s)
- Na-zi Lei
- Key Laboratory of the Ministry of Education for Cell Biology and Tumor Cell Engineering, School of Life Sciences, Xiamen University, Xiamen 361005, Fujian Province, China
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Corley SM, Gready JE. Identification of the RGG box motif in Shadoo: RNA-binding and signaling roles? Bioinform Biol Insights 2008; 2:383-400. [PMID: 19812790 PMCID: PMC2735946 DOI: 10.4137/bbi.s1075] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Using comparative genomics and in-silico analyses, we previously identified a new member of the prion-protein (PrP) family, the gene SPRN, encoding the protein Shadoo (Sho), and suggested its functions might overlap with those of PrP. Extended bioinformatics and conceptual biology studies to elucidate Sho’s functions now reveal Sho has a conserved RGG-box motif, a well-known RNA-binding motif characterized in proteins such as FragileX Mental Retardation Protein. We report a systematic comparative analysis of RGG-box containing proteins which highlights the motif’s functional versatility and supports the suggestion that Sho plays a dual role in cell signaling and RNA binding in brain. These findings provide a further link to PrP, which has well-characterized RNA-binding properties.
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Affiliation(s)
- Susan M Corley
- Computational Proteomics and Therapy Design Group, Division of Molecular Bioscience, John Curtin School of Medical Research, Australian National University, PO Box 334, Canberra ACT 2601, Australia
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Bressan GC, Silva JC, Borges JC, Dos Passos DO, Ramos CHI, Torriani IL, Kobarg J. Human regulatory protein Ki-1/57 has characteristics of an intrinsically unstructured protein. J Proteome Res 2008; 7:4465-74. [PMID: 18788774 DOI: 10.1021/pr8005342] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The human protein Ki-1/57 was first identified through the cross reactivity of the anti-CD30 monoclonal antibody Ki-1, in Hodgkin lymphoma cells. The expression of Ki-1/57 in diverse cancer cells and its phosphorylation in peripheral blood leukocytes after mitogenic activation suggested its possible role in cell signaling. Ki-1/57 interacts with several other regulatory proteins involved in cellular signaling, transcriptional regulation and RNA metabolism, suggesting it may have pleiotropic functions. In a previous spectroscopic analysis, we observed a low content of secondary structure for Ki-1/57 constructs. Here, Circular dichroism experiments, in vitro RNA binding analysis, and limited proteolysis assays of recombinant Ki-1/57(122-413) and proteolysis assays of endogenous full length protein from human HEK293 cells suggested that Ki-1/57 has characteristics of an intrinsically unstructured protein. Small-angle X-ray scattering (SAXS) experiments were performed with the C-terminal fragment Ki-1/57(122-413). These results indicated an elongated shape and a partially unstructured conformation of the molecule in solution, confirming the characteristics of an intrinsically unstructured protein. Experimental curves together with ab initio modeling approaches revealed an extended and flexible molecule in solution. An elongated shape was also observed by analytical gel filtration. Furthermore, sedimentation velocity analysis suggested that Ki-1/57 is a highly asymmetric protein. These findings may explain the functional plasticity of Ki-1/57, as suggested by the wide array of proteins with which it is capable of interacting in yeast two-hybrid interaction assays.
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Affiliation(s)
- Gustavo C Bressan
- National Synchrotron Light Laboratory - LNLS, 13083-970, Campinas, SP, Brazil
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