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Prescher N, Hänsch S, Knobbe-Thomsen CB, Stühler K, Poschmann G. The migration behavior of human glioblastoma cells is influenced by the redox-sensitive human macrophage capping protein CAPG. Free Radic Biol Med 2021; 167:81-93. [PMID: 33711419 DOI: 10.1016/j.freeradbiomed.2021.02.038] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Revised: 02/24/2021] [Accepted: 02/26/2021] [Indexed: 12/26/2022]
Abstract
The macrophage capping protein CAPG belongs to the gelsolin superfamily which modulates actin dynamics by capping the growing end of actin filaments in a Ca2+- and PIP2-dependent manner resulting in polymerization inhibition of actin filaments. In the last years, additional functions for CAPG in transcription regulation were described and higher CAPG amounts have been linked to increased invasiveness and migration behavior in different human tumor entities like e.g. glioblastoma. Nevertheless, there is a lack of knowledge how additional functions of CAPG are regulated. As CAPG contains several cysteine residues which may be accessible to oxidation we were especially interested to investigate how alterations in the cysteine oxidation state may influence the function, localization, and regulation of CAPG. In the present study, we provide strong evidence that CAPG is a redox-sensitive protein and identified two cysteines: C282 and C290 as reversibly oxidized in glioblastoma cell lines. Whereas no evidence could be found that the canonical actin capping function of CAPG is redox-regulated, our results point to a novel role of the identified cysteines in the regulation of cell migration. Along with this, we found a localization shift out of the nucleus of CAPG and RAVER1, a potential interaction partner identified in our study which might explain the observed altered cell migration properties. The newly identified redox sensitive cysteines of CAPG could perspectively be considered as new targets for controlling tumor invasive properties.
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Affiliation(s)
- Nina Prescher
- Institute of Molecular Medicine, Proteome Research, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine University Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany
| | - Sebastian Hänsch
- Department of Biology, Center for Advanced Imaging (CAi), Heinrich-Heine University Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany
| | - Christiane B Knobbe-Thomsen
- Department of Neuropathology, Heinrich-Heine University Düsseldorf and University Hospital, Universitätsstraße 1, 40225 Düsseldorf, Germany
| | - Kai Stühler
- Institute of Molecular Medicine, Proteome Research, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine University Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany; Molecular Proteomics Laboratory, Biomedical Research Centre (BMFZ), Heinrich-Heine University Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany
| | - Gereon Poschmann
- Institute of Molecular Medicine, Proteome Research, Medical Faculty and University Hospital Düsseldorf, Heinrich-Heine University Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany.
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New insights into functional roles of the polypyrimidine tract-binding protein. Int J Mol Sci 2013; 14:22906-32. [PMID: 24264039 PMCID: PMC3856098 DOI: 10.3390/ijms141122906] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2013] [Revised: 11/13/2013] [Accepted: 11/13/2013] [Indexed: 12/20/2022] Open
Abstract
Polypyrimidine Tract Binding Protein (PTB) is an intensely studied RNA binding protein involved in several post-transcriptional regulatory events of gene expression. Initially described as a pre-mRNA splicing regulator, PTB is now widely accepted as a multifunctional protein shuttling between nucleus and cytoplasm. Accordingly, PTB can interact with selected RNA targets, structural elements and proteins. There is increasing evidence that PTB and its paralog PTBP2 play a major role as repressors of alternatively spliced exons, whose transcription is tissue-regulated. In addition to alternative splicing, PTB is involved in almost all steps of mRNA metabolism, including polyadenylation, mRNA stability and initiation of protein translation. Furthermore, it is well established that PTB recruitment in internal ribosome entry site (IRES) activates the translation of picornaviral and cellular proteins. Detailed studies of the structural properties of PTB have contributed to our understanding of the mechanism of RNA binding by RNA Recognition Motif (RRM) domains. In the present review, we will describe the structural properties of PTB, its paralogs and co-factors, the role in post-transcriptional regulation and actions in cell differentiation and pathogenesis. Defining the multifunctional roles of PTB will contribute to the understanding of key regulatory events in gene expression.
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Gautam M, Mathur A, Khan MA, Majumdar SS, Rai U. Transcriptome analysis of spermatogenically regressed, recrudescent and active phase testis of seasonally breeding wall lizards Hemidactylus flaviviridis. PLoS One 2013; 8:e58276. [PMID: 23536792 PMCID: PMC3594293 DOI: 10.1371/journal.pone.0058276] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Accepted: 02/01/2013] [Indexed: 01/24/2023] Open
Abstract
BACKGROUND Reptiles are phylogenically important group of organisms as mammals have evolved from them. Wall lizard testis exhibits clearly distinct morphology during various phases of a reproductive cycle making them an interesting model to study regulation of spermatogenesis. Studies on reptile spermatogenesis are negligible hence this study will prove to be an important resource. METHODOLOGY/PRINCIPAL FINDINGS Histological analyses show complete regression of seminiferous tubules during regressed phase with retracted Sertoli cells and spermatognia. In the recrudescent phase, regressed testis regain cellular activity showing presence of normal Sertoli cells and developing germ cells. In the active phase, testis reaches up to its maximum size with enlarged seminiferous tubules and presence of sperm in seminiferous lumen. Total RNA extracted from whole testis of regressed, recrudescent and active phase of wall lizard was hybridized on Mouse Whole Genome 8×60 K format gene chip. Microarray data from regressed phase was deemed as control group. Microarray data were validated by assessing the expression of some selected genes using Quantitative Real-Time PCR. The genes prominently expressed in recrudescent and active phase testis are cytoskeleton organization GO 0005856, cell growth GO 0045927, GTpase regulator activity GO: 0030695, transcription GO: 0006352, apoptosis GO: 0006915 and many other biological processes. The genes showing higher expression in regressed phase belonged to functional categories such as negative regulation of macromolecule metabolic process GO: 0010605, negative regulation of gene expression GO: 0010629 and maintenance of stem cell niche GO: 0045165. CONCLUSION/SIGNIFICANCE This is the first exploratory study profiling transcriptome of three drastically different conditions of any reptilian testis. The genes expressed in the testis during regressed, recrudescent and active phase of reproductive cycle are in concordance with the testis morphology during these phases. This study will pave the way for deeper insight into regulation and evolution of gene regulatory mechanisms in spermatogenesis.
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Affiliation(s)
- Mukesh Gautam
- Comparative Immuno-Endocrinology Laboratory, Department of Zoology, University of Delhi, Delhi, India
| | - Amitabh Mathur
- Comparative Immuno-Endocrinology Laboratory, Department of Zoology, University of Delhi, Delhi, India
| | - Meraj Alam Khan
- Department of Physiology, All India Institute of Medical Sciences, New Delhi, India
| | - Subeer S. Majumdar
- Cellular Endocrinology Laboratory, National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India
| | - Umesh Rai
- Comparative Immuno-Endocrinology Laboratory, Department of Zoology, University of Delhi, Delhi, India
- * E-mail:
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Hölscher M, Schäfer K, Krull S, Farhat K, Hesse A, Silter M, Lin Y, Pichler BJ, Thistlethwaite P, El-Armouche A, Maier LS, Katschinski DM, Zieseniss A. Unfavourable consequences of chronic cardiac HIF-1α stabilization. Cardiovasc Res 2012; 94:77-86. [PMID: 22258630 DOI: 10.1093/cvr/cvs014] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
AIMS The hypoxia-inducible factor-1 (HIF-1) is the master modulator of hypoxic gene expression. The effects of chronically stabilized cardiac HIF-1α and its role in the diseased heart are not precisely known. The aims of this study were as follows: (i) to elucidate consequences of HIF-1α stabilization in the heart; (ii) to analyse long-term effects of HIF-1α stabilization with ageing and the ability of the HIF-1α overexpressing hearts to respond to increased mechanical load; and (iii) to analyse HIF-1α protein levels in failing heart samples. METHODS AND RESULTS In a cardiac-specific HIF-1α transgenic mouse model, constitutive expression of HIF-1α leads to changes in capillary area and shifts the cardiac metabolism towards glycolysis with a net increase in glucose uptake. Furthermore, Ca(2+) handling is altered, with increased Ca(2)(+) transients and faster intracellular [Ca(2+)] decline. These changes are associated with decreased expression of sarcoplasmic/endoplasmic reticulum calcium ATPase 2a but elevated phosphorylation of phospholamban. HIF-1α transgenic mice subjected to transverse aortic constriction exhibited profound cardiac decompensation. Moreover, cardiomyopathy was also seen in ageing transgenic mice. In parallel, we found an increased stabilization of HIF-1α in heart samples of patients with end-stage heart failure. CONCLUSION Changes induced with transgenic cardiac HIF-1α possibly mediate beneficial effects in the short term; however, with increased mechanical load and ageing they become detrimental for cardiac function. Together with the finding of increased HIF-1α protein levels in samples from human patients with cardiomyopathy, these data indicate that chronic HIF-1α stabilization drives autonomous pathways that add to disease progression.
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Affiliation(s)
- Marion Hölscher
- Department of Cardiovascular Physiology, Universitätsmedizin, Georg-August-University Göttingen, Humboldtallee 23, 37073 Göttingen, Germany
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Transcriptional regulation of the human Raver2 ribonucleoprotein gene. Gene 2011; 493:243-52. [PMID: 22146317 DOI: 10.1016/j.gene.2011.11.036] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Revised: 11/08/2011] [Accepted: 11/16/2011] [Indexed: 01/11/2023]
Abstract
Raver2 is a putative modulator of the activity of the polypyrimidine-tract binding protein (PTB), one of the most intensively studied splicing repressors. Little is known about Raver2 expression, and all current data is from mice where it shows tissue specificity. In the present study, by comparing Raver2 transcript expression in human and mouse tissues, we found that human Raver2 is ubiquitously expressed in adult tissues. In order to investigate human Raver2 transcription regulation, we identified and characterized a putative promoter region in a 1000bp region upstream of the transcription starting site of the gene. Dual luciferase reporter assays demonstrated that this region had promoter activity conferred by the first 160bp. By mutagenic analyses of putative cis-acting regulatory sequences, we identified an individual site that decreased the promoter activity by up to 40% when mutated. Together, our results suggest that regulation of human Raver2 expression involves TATA-less transcriptional activity.
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Whitman SA, Cover C, Yu L, Nelson DL, Zarnescu DC, Gregorio CC. Desmoplakin and talin2 are novel mRNA targets of fragile X-related protein-1 in cardiac muscle. Circ Res 2011; 109:262-71. [PMID: 21659647 DOI: 10.1161/circresaha.111.244244] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
RATIONALE The proper function of cardiac muscle requires the precise assembly and interactions of numerous cytoskeletal and regulatory proteins into specialized structures that orchestrate contraction and force transmission. Evidence suggests that posttranscriptional regulation is critical for muscle function, but the mechanisms involved remain understudied. OBJECTIVE To investigate the molecular mechanisms and targets of the muscle-specific fragile X mental retardation, autosomal homolog 1 (FXR1), an RNA binding protein whose loss leads to perinatal lethality in mice and cardiomyopathy in zebrafish. METHODS AND RESULTS Using RNA immunoprecipitation approaches we found that desmoplakin and talin2 mRNAs associate with FXR1 in a complex. In vitro assays indicate that FXR1 binds these mRNA targets directly and represses their translation. Fxr1 KO hearts exhibit an up-regulation of desmoplakin and talin2 proteins, which is accompanied by severe disruption of desmosome as well as costamere architecture and composition in the heart, as determined by electron microscopy and deconvolution immunofluorescence analysis. CONCLUSIONS Our findings reveal the first direct mRNA targets of FXR1 in striated muscle and support translational repression as a novel mechanism for regulating heart muscle development and function, in particular the assembly of specialized cytoskeletal structures.
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Affiliation(s)
- Samantha A Whitman
- Department of Cellular and Molecular Medicine, University of Arizona, 1656 East Mabel, Tucson, AZ 85724, USA
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Hölscher M, Silter M, Krull S, von Ahlen M, Hesse A, Schwartz P, Wielockx B, Breier G, Katschinski DM, Zieseniss A. Cardiomyocyte-specific prolyl-4-hydroxylase domain 2 knock out protects from acute myocardial ischemic injury. J Biol Chem 2011; 286:11185-94. [PMID: 21270129 DOI: 10.1074/jbc.m110.186809] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Prolylhydroxylase domain proteins (PHD) are cellular oxygen-sensing molecules that regulate the stability of the α-subunit of the transcription factor hypoxia inducible factor (HIF)-1. HIF-1 affects cardiac development as well as adaptation of the heart toward increased pressure overload or myocardial infarction. We have disrupted PHD2 in cardiomyocytes (cPhd (-/-)) using Phd2(flox/flox) mice in combination with MLCvCre mice, which resulted in HIF-1α stabilization and activation of HIF target genes in the heart. Although cPhd2(-/-) mice showed no gross abnormalities in cardiac filament structure or function, we observed a significant increased cardiac capillary area in those mice. cPhd2 (-/-) mice did not respond differently to increased mechanical load by transverse aortic constriction compared with their wild-type (wt) littermates. After ligation of the left anterior descending artery, however, the area at risk and area of necrosis were significantly smaller in the cPhd2(-/-) mice compared with Phd2 wt mice in line with the described pivotal role of HIF-1α for tissue protection in case of myocardial infarction. This correlated with a decreased number of apoptotic cells in the infarcted myocardium in the cPhd2(-/-) mice and significantly improved cardiac function 3 weeks after myocardial infarction.
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Affiliation(s)
- Marion Hölscher
- Department of Cardiovascular Physiology, Universitätsmedizin Göttingen, Georg-August University Göttingen, Göttingen, Germany
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A helix replacement mechanism directs metavinculin functions. PLoS One 2010; 5:e10679. [PMID: 20502710 PMCID: PMC2873289 DOI: 10.1371/journal.pone.0010679] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Accepted: 04/15/2010] [Indexed: 11/25/2022] Open
Abstract
Cells require distinct adhesion complexes to form contacts with their neighbors or the extracellular matrix, and vinculin links these complexes to the actin cytoskeleton. Metavinculin, an isoform of vinculin that harbors a unique 68-residue insert in its tail domain, has distinct actin bundling and oligomerization properties and plays essential roles in muscle development and homeostasis. Moreover, patients with sporadic or familial mutations in the metavinculin-specific insert invariably develop fatal cardiomyopathies. Here we report the high resolution crystal structure of the metavinculin tail domain, as well as the crystal structures of full-length human native metavinculin (1,134 residues) and of the full-length cardiomyopathy-associated ΔLeu954 metavinculin deletion mutant. These structures reveal that an α-helix (H1′) and extended coil of the metavinculin insert replace α-helix H1 and its preceding extended coil found in the N-terminal region of the vinculin tail domain to form a new five-helix bundle tail domain. Further, biochemical analyses demonstrate that this helix replacement directs the distinct actin bundling and oligomerization properties of metavinculin. Finally, the cardiomyopathy associated ΔLeu954 and Arg975Trp metavinculin mutants reside on the replaced extended coil and the H1′ α-helix, respectively. Thus, a helix replacement mechanism directs metavinculin's unique functions.
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A conserved peptide motif in Raver2 mediates its interaction with the polypyrimidine tract-binding protein. Exp Cell Res 2010; 316:966-79. [DOI: 10.1016/j.yexcr.2009.11.023] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2009] [Revised: 11/23/2009] [Accepted: 11/29/2009] [Indexed: 12/29/2022]
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Lee JH, Rangarajan ES, Yogesha SD, Izard T. Raver1 interactions with vinculin and RNA suggest a feed-forward pathway in directing mRNA to focal adhesions. Structure 2009; 17:833-42. [PMID: 19523901 DOI: 10.1016/j.str.2009.04.010] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Revised: 04/09/2009] [Accepted: 04/10/2009] [Indexed: 10/20/2022]
Abstract
The translational machinery of the cell relocalizes to focal adhesions following the activation of integrin receptors. This response allows for rapid, local production of components needed for adhesion complex assembly and signaling. Vinculin links focal adhesions to the actin cytoskeleton following its activation by integrin signaling, which severs intramolecular interactions of vinculin's head and tail (Vt) domains. Our vinculin:raver1 crystal structures and binding studies show that activated Vt selectively interacts with one of the three RNA recognition motifs of raver1, that the vinculin:raver1 complex binds to F-actin, and that raver1 binds selectively to RNA, including a sequence found in vinculin mRNA. Further, mutation of residues that mediate interaction of raver1 with vinculin abolish their colocalization in cells. These findings suggest a feed-forward model where vinculin activation at focal adhesions provides a scaffold for recruitment of raver1 and its mRNA cargo to facilitate the production of components of adhesion complexes.
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Affiliation(s)
- Jun Hyuck Lee
- Cell Adhesion Laboratory, Department of Cancer Biology, The Scripps Research Institute, Jupiter, FL 33458, USA
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A role for polypyrimidine tract binding protein in the establishment of focal adhesions. Mol Cell Biol 2009; 29:5564-77. [PMID: 19667078 DOI: 10.1128/mcb.00590-09] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Polypyrimidine tract binding protein (PTB) is a widely expressed RNA binding protein. In the nucleus PTB regulates the splicing of alternative exons, while in the cytoplasm it can affect mRNA stability, translation, and localization. Here we demonstrate that PTB transiently localizes to the cytoplasm and to protrusions in the cellular edge of mouse embryo fibroblasts during adhesion to fibronectin and the early stages of cell spreading. This cytoplasmic PTB is associated with transcripts encoding the focal adhesion scaffolding proteins vinculin and alpha-actinin 4. We demonstrate that vinculin mRNA colocalizes with PTB to cytoplasmic protrusions and that PTB depletion reduces vinculin mRNA at the cellular edge and limits the size of focal adhesions. The loss of PTB also alters cell morphology and limits the ability of cells to spread after adhesion. These data indicate that during the initial stages of cell adhesion, PTB shuttles from the nucleus to the cytoplasm and influences focal adhesion formation through coordinated control of scaffolding protein mRNAs.
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Gooding C, Smith CWJ. Tropomyosin exons as models for alternative splicing. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 644:27-42. [PMID: 19209811 DOI: 10.1007/978-0-387-85766-4_3] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Three of the four mammalian tropomyosin (Tm) genes are alternatively spliced, most commonly by mutually exclusive selection from pairs of internal or 3' end exons. Alternative splicing events in the TPM1, 2 and 3 genes have been analysed experimentally in various levels ofdetail. In particular, mutually exclusive exon pairs in the betaTm (TPM2) and alphaTm (TPM1) genes are among the most intensively studied models for striated and smooth muscle specific alternative splicing, respectively. Analysis of these model systems has provided important insights into general mechanisms and strategies of splicing regulation.
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Affiliation(s)
- Clare Gooding
- Department of Biochemistry, University of Cambridge, CB2 1GA, UK
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Lahmann I, Fabienke M, Henneberg B, Pabst O, Vauti F, Minge D, Illenberger S, Jockusch BM, Korte M, Arnold HH. The hnRNP and cytoskeletal protein raver1 contributes to synaptic plasticity. Exp Cell Res 2007; 314:1048-60. [PMID: 18061163 DOI: 10.1016/j.yexcr.2007.10.022] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2007] [Revised: 10/26/2007] [Accepted: 10/31/2007] [Indexed: 12/18/2022]
Abstract
Raver1 is an hnRNP protein that interacts with the ubiquitous splicing regulator PTB and binds to cytoskeletal components like alpha-actinin and vinculin/metavinculin. Cell culture experiments suggested that raver1 functions as corepressor in PTB-regulated splicing reactions and may thereby increase proteome complexity. To determine the role of raver1 in vivo, we inactivated the gene by targeted disruption in the mouse. Here we report that raver1-deficient mice develop regularly to adulthood and show no obvious anatomical or behavioral defects. In keeping with this notion, cells from raver1-null mice were indistinguishable from wild type cells and displayed normal growth, motility, and cytoskeletal architecture in culture. Moreover, alternative splicing of exons, including the model exon 3 of alpha-tropomyosin, was not markedly changed in mutant mice, suggesting that the role of raver1 for PTB-mediated exon repression is not absolutely required to generate splice variants during mouse development. Interestingly however, loss of raver1 caused significantly reduced plasticity of synapses on acute hippocampal slices, as elicited by electrophysiological measurements of markedly lower LTP and LTD in mutant neurons. Our results provide evidence that raver1 may play an important role for the regulation of neuronal synaptic plasticity, possibly by controlling especially the late LTP via posttranscriptional mechanisms.
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Affiliation(s)
- Ines Lahmann
- Cell and Molecular Biology, Institute for Biochemistry and Biotechnology, Technical University of Braunschweig, Braunschweig, Germany
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Functional characterization of the ribonucleoprotein, PTB-binding 1/Raver1 promoter region. Gene 2007; 405:79-87. [PMID: 17931803 DOI: 10.1016/j.gene.2007.09.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2007] [Revised: 09/03/2007] [Accepted: 09/06/2007] [Indexed: 11/22/2022]
Abstract
Raver1 is a ribonucleoprotein, evolutionarily conserved in mammals, which acts as a polypyrimidine tract-binding protein (PTB/hnRNPI) co-repressor in regulating alternative splicing events. The mouse homologue has been identified as a dual compartment protein that interacts with PTB within perinucleolar structures, and localizes at microfilament plasma membrane attachment sites in fibroblasts, epithelial and muscle cells. Human Raver1 gene is localized on chromosome 19p13.2 and encodes for an inferred 756 amino acid protein sharing 87% similarity with the mouse orthologue. The human Raver1 gene expression has not been previously investigated. Here we report the mRNA expression profile of human Raver1 gene and the molecular characterization of its promoter region. From the in silico analysis of 1542 bp of the Raver1 5'-flanking region (GC content=61%), no canonical TATA or CAAT boxes can be highlighted, whereas several consensus Sp1 putative binding sequences can be predicted within 1 kb from the transcription start site (TSS) that we determined by 5'-RACE. Functional analyses established a minimal region involved in the regulation of the human Raver1 promoter activity. Mutational analyses and transfection studies indicated that a GGGAGCTCCC sequence at -531 represents a putative cis signal acting as a negative regulator element of the promoter function. Altogether, our results indicate that human Raver1 gene promoter region shares common features of ubiquitously expressed gene with the interacting splicing regulator PTB.
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