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Borkúti P, Kristó I, Szabó A, Kovács Z, Vilmos P. FERM domain-containing proteins are active components of the cell nucleus. Life Sci Alliance 2024; 7:e202302489. [PMID: 38296350 PMCID: PMC10830384 DOI: 10.26508/lsa.202302489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2023] [Revised: 01/20/2024] [Accepted: 01/22/2024] [Indexed: 02/05/2024] Open
Abstract
The FERM domain is a conserved and widespread protein module that appeared in the common ancestor of amoebae, fungi, and animals, and is therefore now found in a wide variety of species. The primary function of the FERM domain is localizing to the plasma membrane through binding lipids and proteins of the membrane; thus, for a long time, FERM domain-containing proteins (FDCPs) were considered exclusively cytoskeletal. Although their role in the cytoplasm has been extensively studied, the recent discovery of the presence and importance of cytoskeletal proteins in the nucleus suggests that FDCPs might also play an important role in nuclear function. In this review, we collected data on their nuclear localization, transport, and possible functions, which are still scattered throughout the literature, with special regard to the role of the FERM domain in these processes. With this, we would like to draw attention to the exciting, new dimension of the role of FDCPs, their nuclear activity, which could be an interesting novel direction for future research.
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Affiliation(s)
| | | | - Anikó Szabó
- HUN-REN Biological Research Centre, Szeged, Hungary
| | - Zoltán Kovács
- HUN-REN Biological Research Centre, Szeged, Hungary
- Doctoral School of Multidisciplinary Medical Science, University of Szeged, Szeged, Hungary
| | - Péter Vilmos
- HUN-REN Biological Research Centre, Szeged, Hungary
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2
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Pavani RS, Lima LP, Lima AA, Fernandes CAH, Fragoso SP, Calderano SG, Elias MC. Nuclear export of replication protein A in the nonreplicative infective forms of
Trypanosoma cruzi. FEBS Lett 2020; 594:1596-1607. [DOI: 10.1002/1873-3468.13755] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 02/04/2020] [Accepted: 02/05/2020] [Indexed: 12/17/2022]
Affiliation(s)
- Raphael S. Pavani
- Laboratório de Ciclo Celular Instituto Butantan São Paulo Brazil
- Center of Toxins, Immune Response and Cell Signaling (CeTICS) Instituto Butantan São Paulo Brazil
| | - Loyze P. Lima
- Laboratório de Ciclo Celular Instituto Butantan São Paulo Brazil
- Center of Toxins, Immune Response and Cell Signaling (CeTICS) Instituto Butantan São Paulo Brazil
| | - André A. Lima
- Laboratório de Ciclo Celular Instituto Butantan São Paulo Brazil
- Center of Toxins, Immune Response and Cell Signaling (CeTICS) Instituto Butantan São Paulo Brazil
| | - Carlos A. H. Fernandes
- Departamento de Física e Biofísica Instituto de Biociências Universidade Estadual Paulista Júlio de Mesquita Filho (UNESP) Botucatu Brazil
- Laboratorie de Biologie et Pharmacologie Appliquée Ecole Normale Supérieure Paris‐Saclay Cachan France
| | | | - Simone G. Calderano
- Center of Toxins, Immune Response and Cell Signaling (CeTICS) Instituto Butantan São Paulo Brazil
- Laboratório de Parasitologia Instituto Butantan São Paulo Brazil
| | - Maria Carolina Elias
- Laboratório de Ciclo Celular Instituto Butantan São Paulo Brazil
- Center of Toxins, Immune Response and Cell Signaling (CeTICS) Instituto Butantan São Paulo Brazil
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3
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Haniff AJN, Gam LH. Identification of urinary protein biomarkers for tobacco smoking. Biotechnol Appl Biochem 2015; 63:266-72. [DOI: 10.1002/bab.1357] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 01/23/2015] [Indexed: 01/24/2023]
Affiliation(s)
- AJ Nabill Haniff
- School of Pharmaceutical Sciences; Universiti Sains Malaysia; Penang Malaysia
| | - Lay-Harn Gam
- Doping Control Centre; Universiti Sains Malaysia; Penang Malaysia
- School of Pharmaceutical Sciences; Universiti Sains Malaysia; Penang Malaysia
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Bazzini C, Benedetti L, Civello D, Zanoni C, Rossetti V, Marchesi D, Garavaglia ML, Paulmichl M, Francolini M, Meyer G, Rodighiero S. ICln: a new regulator of non-erythroid 4.1R localisation and function. PLoS One 2014; 9:e108826. [PMID: 25295618 PMCID: PMC4189953 DOI: 10.1371/journal.pone.0108826] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2014] [Accepted: 08/27/2014] [Indexed: 01/12/2023] Open
Abstract
To optimise the efficiency of cell machinery, cells can use the same protein (often called a hub protein) to participate in different cell functions by simply changing its target molecules. There are large data sets describing protein-protein interactions (“interactome”) but they frequently fail to consider the functional significance of the interactions themselves. We studied the interaction between two potential hub proteins, ICln and 4.1R (in the form of its two splicing variants 4.1R80 and 4.1R135), which are involved in such crucial cell functions as proliferation, RNA processing, cytoskeleton organisation and volume regulation. The sub-cellular localisation and role of native and chimeric 4.1R over-expressed proteins in human embryonic kidney (HEK) 293 cells were examined. ICln interacts with both 4.1R80 and 4.1R135 and its over-expression displaces 4.1R from the membrane regions, thus affecting 4.1R interaction with ß-actin. It was found that 4.1R80 and 4.1R135 are differently involved in regulating the swelling activated anion current (ICl,swell) upon hypotonic shock, a condition under which both isoforms are dislocated from the membrane region and thus contribute to ICl,swell current regulation. Both 4.1R isoforms are also differently involved in regulating cell morphology, and ICln counteracts their effects. The findings of this study confirm that 4.1R plays a role in cell volume regulation and cell morphology and indicate that ICln is a new negative regulator of 4.1R functions.
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Affiliation(s)
- Claudia Bazzini
- Department of Biosciences, University of Milan, Milan, Italy
| | - Lorena Benedetti
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy
- Fondazione Filarete for Biosciences and Innovation, Milan, Italy
| | - Davide Civello
- Department of Biosciences, University of Milan, Milan, Italy
| | - Chiara Zanoni
- Pharmaceutical Sciences Department (DISFARM), University of Milan, Milan, Italy
| | | | - Davide Marchesi
- Fondazione Filarete for Biosciences and Innovation, Milan, Italy
| | | | - Markus Paulmichl
- Institute of Pharmacology and Toxicology, Paracelsus Medical University, Salzburg, Austria
| | - Maura Francolini
- Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy
- Fondazione Filarete for Biosciences and Innovation, Milan, Italy
| | - Giuliano Meyer
- Department of Biosciences, University of Milan, Milan, Italy
| | - Simona Rodighiero
- Fondazione Filarete for Biosciences and Innovation, Milan, Italy
- * E-mail:
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5
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Rolly protein (ROLP)-Epb4.1/3: a potential protein-protein interaction relevant for the maintenance of cell adhesion. Int J Mol Sci 2009; 10:2054-2065. [PMID: 19564939 PMCID: PMC2695267 DOI: 10.3390/ijms10052054] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Accepted: 05/11/2009] [Indexed: 11/17/2022] Open
Abstract
We recently described Rolly Protein (ROLP), a small protein synthesized by substrate-adherent cells in a broad range of tissues. In a first set of experiments performed taking advantage of bone forming tibial cartilage as an experimental model we showed that ROLP transcription is associated to cells in an active proliferation state, whereas its downregulation is observed when cell proliferation decreases. Taking advantage of siRNA technology we also documented the expression modulation of some apoptosis-related genes in ROLP-silenced cells. In this work we search for the possible molecular interactors of ROLP by using both the antibody array approach as well as the co-immunoprecipitation approach. Results suggest the occurrence of an interaction of ROLP with Erythrocyte membrane Protein Band 4.1/3 (Epb4.1/3), an oncosuppressor downregulated in tumor development and in metastatic tissues; in addition we report experimental results that keep in line also with a potential interaction of ROLP with other PDZ-containing proteins. We also present experimental evidences supporting a role played by ROLP in cell adhesion thus supporting the existence of a biologically relevant link between ROLP and Epb4.1/3. We here suggest that ROLP might exert its biological role cooperating with Epb4.1/3, a protein that is involved in biological pathways that are often inhibited in tumor metastasis. Given the role of Epb4.1/3 in contrasting cancerogenesis we think that its cooperation with ROLP might be relevant in cancer studies and deserves further investigation.
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6
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Pérez-Ferreiro CM, Lospitao E, Correas I. Protein 4.1R self-association: identification of the binding domain. Biochem J 2006; 400:457-65. [PMID: 16881872 PMCID: PMC1698608 DOI: 10.1042/bj20060644] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Erythroid protein 4.1 (4.1R) stabilizes the spectrin-actin network and anchors it to the plasma membrane. To contribute to the characterization of non-erythroid protein 4.1R, we used sedimentation, pull-down and co-immunoprecipitation assays to investigate the ability of protein 4.1R to establish inter-/intra-molecular associations. We demonstrated that the small 4.1R isoforms of 60 kDa (4.1R60), but not the larger isoforms of 80 and 135 kDa (4.1R80 and 4.1R135), were self-associated, and that a domain contained in all 4.1R isoforms, the core region, was responsible for 4.1R self-association. Results from denaturing-renaturing experiments, in which an initially non-self-associated 4.1R80 isoform became self-associated, suggested that an initially hidden core region was subsequently exposed. This hypothesis was supported by results from pull-down assays, which showed that the core region interacted with the N-terminal end of the FERM (4.1, ezrin, radixin, moesin) domain that is present in 4.1R80 and 4.1R135 isoforms but absent from 4.1R60 isoforms. Consistently, 4.1R80 isoforms bound neither to each other nor to 4.1R60 isoforms. We propose that 4.1R60 isoforms are constitutively self-associated, whereas 4.1R80 and 4.1R135 self-association is prevented by intramolecular interactions.
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Affiliation(s)
- Carmen M Pérez-Ferreiro
- Departamento de Biología Molecular, CBMSO (Centro de Biología Molecular Severo Ochoa), UAM/CSIC, Cantoblanco, E-28049 Madrid, Spain.
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7
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González-Mariscal L, Ponce A, Alarcón L, Jaramillo BE. The tight junction protein ZO-2 has several functional nuclear export signals. Exp Cell Res 2006; 312:3323-35. [PMID: 16920099 DOI: 10.1016/j.yexcr.2006.07.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2005] [Revised: 07/05/2006] [Accepted: 07/06/2006] [Indexed: 11/27/2022]
Abstract
The tight junction (TJ) protein ZO-2 changes its subcellular distribution according to the state of confluency of the culture. Thus in confluent monolayers, it localizes at the TJ region whereas in sparse cultures it concentrates at the nucleus. The canine sequence of ZO-2 displays four putative nuclear export signals (NES), two at the second PDZ domain (NES-0 and NES-1) and the rest at the GK region (NES-2 and NES-3). The functionality of NES-0 and NES-3 was unknown, hence here we have explored it with a nuclear export assay, injecting into the nucleus of MDCK cells peptides corresponding to the ZO-2 NES sequences chemically coupled to ovalbumin. We show that both NES-0 and NES-3 are functional and sensitive to leptomycin B. We also demonstrate that NES-1, previously characterized as a non functional NES, is rendered capable of nuclear export upon the acquisition of a negative charge at its Ser369 residue. Experiments performed injecting at the nucleus WT and mutated ZO-2-GST fusion proteins revealed the need of both NES-0 and NES-1, and NES-2 and NES-3 for attaining an efficient nuclear exit of the respective amino and middle segments of ZO-2. Moreover, the transfection of MDCK cells with full-length ZO-2 revealed that the mutation of any of the NES present in the molecule was sufficient to induce nuclear accumulation of the protein.
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Affiliation(s)
- Lorenza González-Mariscal
- Department of Physiology, Biophysics and Neuroscience, Center for Research and Advanced Studies (CINVESTAV), Ave. Instituto Politécnico Nacional 2508, México, D.F., 07360, México.
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8
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Pérez-Ferreiro CM, Vernos I, Correas I. Protein 4.1R regulates interphase microtubule organization at the centrosome. J Cell Sci 2005; 117:6197-206. [PMID: 15564380 DOI: 10.1242/jcs.01544] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In human red blood cells, protein 4.1 (4.1R) stabilizes the spectrin-actin network and anchors it to the plasma membrane. To contribute to the characterization of functional roles of 4.1R in nonerythroid cells, we analysed the effect of ectopic expression of 4.1R isoforms on interphase microtubules in fibroblastic cells. We found that specific 4.1R isoforms disturbed the microtubule architecture but not the actin cytoskeleton. Biochemical sedimentation and/or confocal microscopy analyses showed that the pericentriolar components gamma-tubulin and pericentrin remained at centrosomes, whereas the distributions of proteins p150Glued and the dynein intermediate chain were altered. Remarkably, 4.1R was displaced from the centrosome. In microtubule depolymerizing-repolymerizing assays, 4.1R-transfected cells showed an ability to depolymerize and nucleate microtubules that was similar to that of untransfected cells; however, microtubules became disorganized soon after regrowth. In microtubule-depolymerized transfected cells and during the initial steps of microtubule regrowth, centrosomal 4.1R localized with gamma-tubulin but did not when microtubules became disorganized. To learn more about centrosomal 4.1R function, isolated centrosomes were examined by confocal microscopy, western blot and in vitro microtubule aster-assembly assays. The experiments showed that 4.1R was present in isolated centrosome preparations, that it remained in the center of in-vitro-assembled microtubule asters and that more asters were assembled by the addition of protein 4.1R fused to glutathione-S-transferase. Together, these results indicate that 4.1R plays a key role at the centrosome, contributing to the maintenance of a radial microtubule organization.
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Affiliation(s)
- Carmen M Pérez-Ferreiro
- Departamento de Biología Molecular, Centro de Biología Molecular 'Severo Ochoa' (UAM/CSIC), Universidad Autónoma de Madrid, 28049 Madrid, Spain
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9
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Gruenbaum Y, Margalit A, Goldman RD, Shumaker DK, Wilson KL. The nuclear lamina comes of age. Nat Rev Mol Cell Biol 2005; 6:21-31. [PMID: 15688064 DOI: 10.1038/nrm1550] [Citation(s) in RCA: 693] [Impact Index Per Article: 36.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Many nuclear proteins form lamin-dependent complexes, including LEM-domain proteins, nesprins and SUN-domain proteins. These complexes have roles in chromatin organization, gene regulation and signal transduction. Some link the nucleoskeleton to cytoskeletal structures, ensuring that the nucleus and centrosome assume appropriate intracellular positions. These complexes provide new insights into cell architecture, as well as a foundation for the understanding of the molecular mechanisms that underlie the human laminopathies - clinical disorders that range from Emery-Dreifuss muscular dystrophy to the accelerated ageing seen in Hutchinson-Gilford progeria syndrome.
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Affiliation(s)
- Yosef Gruenbaum
- Department of Genetics, The Institute of Life Sciences, The Hebrew University of Jerusalem, Givat Ram, Jerusalem, 91904 Israel.
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10
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Gascard P, Parra MK, Zhao Z, Calinisan VR, Nunomura W, Rivkees SA, Mohandas N, Conboy JG. Putative tumor suppressor protein 4.1B is differentially expressed in kidney and brain via alternative promoters and 5' alternative splicing. ACTA ACUST UNITED AC 2004; 1680:71-82. [PMID: 15488987 DOI: 10.1016/j.bbaexp.2004.08.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2004] [Revised: 08/03/2004] [Accepted: 08/10/2004] [Indexed: 10/26/2022]
Abstract
Protein 4.1B has been reported as a tumor suppressor in brain, but not in kidney, despite high expression in both tissues. Here we demonstrate that N-terminal variability in kidney and brain 4.1B isoforms arises through an unusual coupling of RNA processing events in the 5' region of the gene. We describe two transcriptional promoters at far upstream alternative exons 1A and 1B, and show that their respective transcripts splice differentially to exon 2'/2 in a manner that determines mRNA coding capacity. The consequence of this unique processing is that exon 1B transcripts initiate translation at AUG1 (in exon 2') and encode larger 4.1B isoforms with an N-terminal extension; exon 1A transcripts initiate translation at AUG2 (in exon 4) and encode smaller 4.1B isoforms. Tissue-specific differences in promoter utilization may thus explain the abundance of larger 4.1B isoforms in brain but not in kidney. In cell studies, differentiation of PC12 cells was accompanied by translocation of large protein 4.1B isoforms into the nucleus. We propose that first exon specification is coupled to downstream splicing events, generating 4.1B isoforms with diverse roles in kidney and brain physiology, and potentially unique functions in cell proliferation and tumor suppression.
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Affiliation(s)
- Philippe Gascard
- Life Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Mail stop 74-157, Berkeley CA 94720, USA
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Batchelor CL, Woodward AM, Crouch DH. Nuclear ERM (ezrin, radixin, moesin) proteins: regulation by cell density and nuclear import. Exp Cell Res 2004; 296:208-22. [PMID: 15149851 DOI: 10.1016/j.yexcr.2004.02.010] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2003] [Revised: 12/22/2003] [Indexed: 12/21/2022]
Abstract
The highly conserved ERM (ezrin-radixin-moesin) family of proteins function as molecular linkers between the actin cytoskeleton and transmembrane receptors. We now provide unequivocal evidence that full-length endogenous ezrin and moesin also localise to the nucleus in two independent mammalian cell lines. All three ERM family members can localise to the nucleus upon exogenous expression of their GFP-tagged counterparts, suggesting a common family trend. Furthermore, Dmoesin, the Drosophila ERM homologue, is present in the nucleus of an insect cell line and can localise to the nucleus when exogenously expressed in MDCK cells. The nuclear localisation of endogenous ezrin and moesin is regulated by cell density and is resistant to detergent extraction, suggesting tight association with nuclear structures. Furthermore, phosphorylation in the actin-binding domain is not a prerequisite for nuclear localisation. We have identified a specific nuclear localisation sequence, which is conserved and functional in all ERM family members, implying specific regulated nuclear import. Although the precise nuclear function of the ERM proteins is unknown, these data provide further evidence that an increasing number of cytoskeletal components directly link the plasma membrane with nuclear events.
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Affiliation(s)
- Clare L Batchelor
- Biomedical Research Centre, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK
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12
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Jensik PJ, Huggenvik JI, Collard MW. Identification of a nuclear export signal and protein interaction domains in deformed epidermal autoregulatory factor-1 (DEAF-1). J Biol Chem 2004; 279:32692-9. [PMID: 15161925 DOI: 10.1074/jbc.m400946200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Deformed epidermal autoregulatory factor-1 (DEAF-1) is a DNA-binding protein required for embryonic development and linked to clinical depression and suicidal behavior in humans. Although primarily nuclear, cytoplasmic localization of DEAF-1 has been observed, and this suggests the presence of a nuclear export signal (NES). Using a series of fluorescent fusion proteins, an NES with a novel spacing of leucines (LXLX(6)LLX(5)LX(2)L) was identified near the COOH-terminal MYND domain at amino acids 454-476. The NES was leptomycin B-sensitive and mutation of the leucine residues decreased or eliminated nuclear export activity. In vitro pull downs and an in vivo fluorescent protein interaction assay identified a DEAF-1/DEAF-1 protein interaction domain within the NES region. DNA binding had been previously mapped to a positively charged surface patch in the novel DNA binding fold called the "SAND" domain. A second protein-protein interaction domain was identified at amino acids 243-306 that contains the DNA-binding SAND domain and also an adjacent zinc binding motif and a monopartite nuclear localization signal (NLS). Deletion of these adjacent sequences or mutation of the conserved cysteines or histidine in the zinc binding motif not only inhibits protein interaction but also eliminates DNA binding, demonstrating that DEAF-1 protein-protein interaction is required for DNA recognition. The identification of an NES and NLS provides a basis for the control of DEAF-1 subcellular localization and function, whereas the requirement of protein-protein interaction by the SAND domain appears to be unique among this class of transcription factors.
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Affiliation(s)
- Philip J Jensik
- Department of Physiology, Southern Illinois University School of Medicine, Carbondale, Illinois 62901, USA
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Kittiniyom K, Mastronardi M, Roemer M, Wells WA, Greenberg ER, Titus-Ernstoff L, Newsham IF. Allele-specific loss of heterozygosity at theDAL-1/4.1B (EPB41L3) tumor-suppressor gene locus in the absence of mutation. Genes Chromosomes Cancer 2004; 40:190-203. [PMID: 15138999 DOI: 10.1002/gcc.20034] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
DAL-1/4.1B (EPB41L3)is a member of the protein 4.1 superfamily, which encompasses structural proteins that play important roles in membrane processes via interactions with actin, spectrin, and the cytoplasmic domains of integral membrane proteins. DAL-1/4.1B localizes within chromosomal region 18p11.3, which is affected by loss of heterozygosity (LOH) in various adult tumors. Reintroduction of this protein into DAL-1/4.1B-null lung and breast tumor cell lines significantly reduced the number of cells, providing functional evidence that this protein possesses a growth suppressor function not confined to a single cell type. For characterization of the mutational mechanisms responsible for loss of DAL-1/4.1B function in tumors, the exon-intron structure of DAL-1/4.1B was examined for mutations in 15 normal/tumor pairs of non-small cell lung carcinoma by single-strand conformation polymorphism analysis. These studies revealed that small intragenic mutations are uncommon in DAL-1/4.1B. Furthermore, LOH analysis on 129 informative early-stage breast tumors utilizing a new intragenic C/T single-nucleotide polymorphism in exon 14 revealed that LOH resulted in preferential retention of the C-containing allele, suggesting that allele-specific loss is occurring. These studies indicate that mechanisms such as imprinting or monoallelic expression in combination with loss of heterozygosity may be responsible for loss of the DAL-1/4.1B protein in early breast disease.
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Affiliation(s)
- Kanokwan Kittiniyom
- David and Doreen Hermelin Laboratory of Molecular Oncogenetics, Hermelin Brain Tumor Center and Department of Neurosurgery, Henry Ford Hospital, Detroit, Michigan 48202, USA
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14
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Krauss SW, Chen C, Penman S, Heald R. Nuclear actin and protein 4.1: essential interactions during nuclear assembly in vitro. Proc Natl Acad Sci U S A 2003; 100:10752-7. [PMID: 12960380 PMCID: PMC196875 DOI: 10.1073/pnas.1934680100] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Structural protein 4.1, which has crucial interactions within the spectrin-actin lattice of the human red cell membrane skeleton, also is widely distributed at diverse intracellular sites in nucleated cells. We previously showed that 4.1 is essential for assembly of functional nuclei in vitro and that the capacity of 4.1 to bind actin is required. Here we report that 4.1 and actin colocalize in mammalian cell nuclei using fluorescence microscopy and, by higher-resolution detergent-extracted cell whole-mount electron microscopy, are associated on nuclear filaments. We also devised a cell-free assay using Xenopus egg extract containing fluorescent actin to follow actin during nuclear assembly. By directly imaging actin under nonperturbing conditions, the total nuclear actin population is retained and visualized in situ relative to intact chromatin. We detected actin initially when chromatin and nuclear pores began assembling. As nuclear lamina assembled, but preceding DNA synthesis, actin distributed in a reticulated pattern throughout the nucleus. Protein 4.1 epitopes also were detected when actin began to accumulate in nuclei, producing a diffuse coincident pattern. As nuclei matured, actin was detected both coincident with and also independent of 4.1 epitopes. To test whether acquisition of nuclear actin is required for nuclear assembly, the actin inhibitor latrunculin A was added to Xenopus egg extracts during nuclear assembly. Latrunculin A strongly perturbed nuclear assembly and produced distorted nuclear structures containing neither actin nor protein 4.1. Our results suggest that actin as well as 4.1 is necessary for nuclear assembly and that 4.1-actin interactions may be critical.
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Affiliation(s)
- Sharon Wald Krauss
- Department of Subcellular Structure, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720, USA.
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