1
|
King MR, Ruff KM, Lin AZ, Pant A, Farag M, Lalmansingh JM, Wu T, Fossat MJ, Ouyang W, Lew MD, Lundberg E, Vahey MD, Pappu RV. Macromolecular condensation organizes nucleolar sub-phases to set up a pH gradient. Cell 2024; 187:1889-1906.e24. [PMID: 38503281 DOI: 10.1016/j.cell.2024.02.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 01/02/2024] [Accepted: 02/22/2024] [Indexed: 03/21/2024]
Abstract
Nucleoli are multicomponent condensates defined by coexisting sub-phases. We identified distinct intrinsically disordered regions (IDRs), including acidic (D/E) tracts and K-blocks interspersed by E-rich regions, as defining features of nucleolar proteins. We show that the localization preferences of nucleolar proteins are determined by their IDRs and the types of RNA or DNA binding domains they encompass. In vitro reconstitutions and studies in cells showed how condensation, which combines binding and complex coacervation of nucleolar components, contributes to nucleolar organization. D/E tracts of nucleolar proteins contribute to lowering the pH of co-condensates formed with nucleolar RNAs in vitro. In cells, this sets up a pH gradient between nucleoli and the nucleoplasm. By contrast, juxta-nucleolar bodies, which have different macromolecular compositions, featuring protein IDRs with very different charge profiles, have pH values that are equivalent to or higher than the nucleoplasm. Our findings show that distinct compositional specificities generate distinct physicochemical properties for condensates.
Collapse
Affiliation(s)
- Matthew R King
- Department of Biomedical Engineering, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA; Center for Biomolecular Condensates, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Kiersten M Ruff
- Department of Biomedical Engineering, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA; Center for Biomolecular Condensates, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Andrew Z Lin
- Department of Biomedical Engineering, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA; Center for Biomolecular Condensates, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Avnika Pant
- Department of Biomedical Engineering, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA; Center for Biomolecular Condensates, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Mina Farag
- Department of Biomedical Engineering, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA; Center for Biomolecular Condensates, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Jared M Lalmansingh
- Department of Biomedical Engineering, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA; Center for Biomolecular Condensates, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Tingting Wu
- Center for Biomolecular Condensates, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA; Department of Electrical and Systems Engineering, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Martin J Fossat
- Department of Biomedical Engineering, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA; Center for Biomolecular Condensates, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Wei Ouyang
- Department of Bioengineering, Schools of Engineering and Medicine, Stanford University, Stanford, CA, USA; Department of Pathology, School of Medicine, Stanford University, Stanford, CA, USA; Science for Life Laboratory, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH-Royal Institute of Technology, Stockholm, Sweden
| | - Matthew D Lew
- Center for Biomolecular Condensates, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA; Department of Electrical and Systems Engineering, James F. McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Emma Lundberg
- Department of Bioengineering, Schools of Engineering and Medicine, Stanford University, Stanford, CA, USA; Department of Pathology, School of Medicine, Stanford University, Stanford, CA, USA; Science for Life Laboratory, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH-Royal Institute of Technology, Stockholm, Sweden
| | - Michael D Vahey
- Department of Biomedical Engineering, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA; Center for Biomolecular Condensates, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA
| | - Rohit V Pappu
- Department of Biomedical Engineering, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA; Center for Biomolecular Condensates, James McKelvey School of Engineering, Washington University in St. Louis, St. Louis, MO, USA.
| |
Collapse
|
2
|
Cela I, Cufaro MC, Fucito M, Pieragostino D, Lanuti P, Sallese M, Del Boccio P, Di Matteo A, Allocati N, De Laurenzi V, Federici L. Proteomic Investigation of the Role of Nucleostemin in Nucleophosmin-Mutated OCI-AML 3 Cell Line. Int J Mol Sci 2022; 23:ijms23147655. [PMID: 35886999 PMCID: PMC9317519 DOI: 10.3390/ijms23147655] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 07/07/2022] [Accepted: 07/09/2022] [Indexed: 02/06/2023] Open
Abstract
Nucleostemin (NS; a product of the GNL3 gene) is a nucleolar–nucleoplasm shuttling GTPase whose levels are high in stem cells and rapidly decrease upon differentiation. NS levels are also high in several solid and hematological neoplasms, including acute myeloid leukaemia (AML). While a role in telomere maintenance, response to stress stimuli and favoring DNA repair has been proposed in solid cancers, little or no information is available as to the role of nucleostemin in AML. Here, we investigate this issue via a proteomics approach. We use as a model system the OCI-AML 3 cell line harboring a heterozygous mutation at the NPM1 gene, which is the most frequent driver mutation in AML (approximately 30% of total AML cases). We show that NS is highly expressed in this cell line, and, contrary to what has previously been shown in other cancers, that its presence is dispensable for cell growth and viability. However, proteomics analysis of the OCI-AML 3 cell line before and after nucleostemin (NS) silencing showed several effects on different biological functions, as highlighted by ingenuity pathway analysis (IPA). In particular, we report an effect of down-regulating DNA repair through homologous recombination, and we confirmed a higher DNA damage rate in OCI-AML 3 cells when NS is depleted, which considerably increases upon stress induced by the topoisomerase II inhibitor etoposide. The data used are available via ProteomeXchange with the identifier PXD034012.
Collapse
Affiliation(s)
- Ilaria Cela
- Department of Innovative Technologies in Medicine & Dentistry, University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (I.C.); (M.F.); (D.P.); (M.S.); (N.A.); (V.D.L.)
- Center for Advanced Studies and Technology (CAST), University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (M.C.C.); (P.L.); (P.D.B.)
| | - Maria Concetta Cufaro
- Center for Advanced Studies and Technology (CAST), University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (M.C.C.); (P.L.); (P.D.B.)
- Department of Pharmacy, University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy
| | - Maurine Fucito
- Department of Innovative Technologies in Medicine & Dentistry, University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (I.C.); (M.F.); (D.P.); (M.S.); (N.A.); (V.D.L.)
- Center for Advanced Studies and Technology (CAST), University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (M.C.C.); (P.L.); (P.D.B.)
| | - Damiana Pieragostino
- Department of Innovative Technologies in Medicine & Dentistry, University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (I.C.); (M.F.); (D.P.); (M.S.); (N.A.); (V.D.L.)
- Center for Advanced Studies and Technology (CAST), University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (M.C.C.); (P.L.); (P.D.B.)
| | - Paola Lanuti
- Center for Advanced Studies and Technology (CAST), University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (M.C.C.); (P.L.); (P.D.B.)
- Department of Medicine and Aging Science, University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy
| | - Michele Sallese
- Department of Innovative Technologies in Medicine & Dentistry, University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (I.C.); (M.F.); (D.P.); (M.S.); (N.A.); (V.D.L.)
- Center for Advanced Studies and Technology (CAST), University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (M.C.C.); (P.L.); (P.D.B.)
| | - Piero Del Boccio
- Center for Advanced Studies and Technology (CAST), University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (M.C.C.); (P.L.); (P.D.B.)
- Department of Pharmacy, University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy
| | - Adele Di Matteo
- Institute of Molecular Biology and Pathology, National Research Council of Italy, P.le Aldo Moro 5, 00185 Rome, Italy;
| | - Nerino Allocati
- Department of Innovative Technologies in Medicine & Dentistry, University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (I.C.); (M.F.); (D.P.); (M.S.); (N.A.); (V.D.L.)
| | - Vincenzo De Laurenzi
- Department of Innovative Technologies in Medicine & Dentistry, University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (I.C.); (M.F.); (D.P.); (M.S.); (N.A.); (V.D.L.)
- Center for Advanced Studies and Technology (CAST), University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (M.C.C.); (P.L.); (P.D.B.)
| | - Luca Federici
- Department of Innovative Technologies in Medicine & Dentistry, University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (I.C.); (M.F.); (D.P.); (M.S.); (N.A.); (V.D.L.)
- Center for Advanced Studies and Technology (CAST), University “G. d’Annunzio” of Chieti-Pescara, 66100 Chieti, Italy; (M.C.C.); (P.L.); (P.D.B.)
- Correspondence:
| |
Collapse
|
3
|
Mobility of Nucleostemin in Live Cells Is Specifically Related to Transcription Inhibition by Actinomycin D and GTP-Binding Motif. Int J Mol Sci 2021; 22:ijms22158293. [PMID: 34361059 PMCID: PMC8347349 DOI: 10.3390/ijms22158293] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2021] [Revised: 07/24/2021] [Accepted: 07/29/2021] [Indexed: 12/04/2022] Open
Abstract
In vertebrates, nucleostemin (NS) is an important marker of proliferation in several types of stem and cancer cells, and it can also interact with the tumor-suppressing transcription factor p53. In the present study, the intra-nuclear diffusional dynamics of native NS tagged with GFP and two GFP-tagged NS mutants with deleted guanosine triphosphate (GTP)-binding domains were analyzed by fluorescence correlation spectroscopy. Free and slow binding diffusion coefficients were evaluated, either under normal culture conditions or under treatment with specific cellular proliferation inhibitors actinomycin D (ActD), 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), or trichostatin A (TSA). When treated with ActD, the fractional ratio of the slow diffusion was significantly decreased in the nucleoplasm. The decrease was proportional to ActD treatment duration. In contrast, DRB or TSA treatment did not affect NS diffusion. Interestingly, it was also found that the rate of diffusion of two NS mutants increased significantly even under normal conditions. These results suggest that the mobility of NS in the nucleoplasm is related to the initiation of DNA or RNA replication, and that the GTP-binding motif is also related to the large change of mobility.
Collapse
|
4
|
Gaviraghi M, Vivori C, Pareja Sanchez Y, Invernizzi F, Cattaneo A, Santoliquido BM, Frenquelli M, Segalla S, Bachi A, Doglioni C, Pelechano V, Cittaro D, Tonon G. Tumor suppressor PNRC1 blocks rRNA maturation by recruiting the decapping complex to the nucleolus. EMBO J 2018; 37:embj.201899179. [PMID: 30373810 DOI: 10.15252/embj.201899179] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 09/14/2018] [Accepted: 09/19/2018] [Indexed: 12/20/2022] Open
Abstract
Focal deletions occur frequently in the cancer genome. However, the putative tumor-suppressive genes residing within these regions have been difficult to pinpoint. To robustly identify these genes, we implemented a computational approach based on non-negative matrix factorization, NMF, and interrogated the TCGA dataset. This analysis revealed a metagene signature including a small subset of genes showing pervasive hemizygous deletions, reduced expression in cancer patient samples, and nucleolar function. Amid the genes belonging to this signature, we have identified PNRC1, a nuclear receptor coactivator. We found that PNRC1 interacts with the cytoplasmic DCP1α/DCP2 decapping machinery and hauls it inside the nucleolus. PNRC1-dependent nucleolar translocation of the decapping complex is associated with a decrease in the 5'-capped U3 and U8 snoRNA fractions, hampering ribosomal RNA maturation. As a result, PNRC1 ablates the enhanced proliferation triggered by established oncogenes such as RAS and MYC These observations uncover a previously undescribed mechanism of tumor suppression, whereby the cytoplasmic decapping machinery is hauled within nucleoli, tightly regulating ribosomal RNA maturation.
Collapse
Affiliation(s)
- Marco Gaviraghi
- Functional Genomics of Cancer Unit, Division of Experimental Oncology, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, Milan, Italy
| | - Claudia Vivori
- Functional Genomics of Cancer Unit, Division of Experimental Oncology, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, Milan, Italy
| | - Yerma Pareja Sanchez
- Science for Life Laboratory, Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Solna, Sweden
| | - Francesca Invernizzi
- Pathology Unit, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, Milan, Italy
| | - Angela Cattaneo
- Functional Proteomics Program, Istituto FIRC di Oncologia Molecolare (IFOM), Milan, Italy
| | - Benedetta Maria Santoliquido
- Functional Genomics of Cancer Unit, Division of Experimental Oncology, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, Milan, Italy
| | - Michela Frenquelli
- Functional Genomics of Cancer Unit, Division of Experimental Oncology, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, Milan, Italy
| | - Simona Segalla
- Functional Genomics of Cancer Unit, Division of Experimental Oncology, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, Milan, Italy
| | - Angela Bachi
- Functional Proteomics Program, Istituto FIRC di Oncologia Molecolare (IFOM), Milan, Italy
| | - Claudio Doglioni
- Pathology Unit, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, Milan, Italy
| | - Vicent Pelechano
- Science for Life Laboratory, Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Solna, Sweden
| | - Davide Cittaro
- Center for Translational Genomics and Bioinformatics, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, Milan, Italy
| | - Giovanni Tonon
- Functional Genomics of Cancer Unit, Division of Experimental Oncology, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, Milan, Italy .,Center for Translational Genomics and Bioinformatics, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) San Raffaele Scientific Institute, Milan, Italy
| |
Collapse
|
5
|
Tancioni I, Miller NLG, Uryu S, Lawson C, Jean C, Chen XL, Kleinschmidt EG, Schlaepfer DD. FAK activity protects nucleostemin in facilitating breast cancer spheroid and tumor growth. Breast Cancer Res 2015; 17:47. [PMID: 25880415 PMCID: PMC4407832 DOI: 10.1186/s13058-015-0551-x] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Accepted: 03/11/2015] [Indexed: 12/17/2022] Open
Abstract
Introduction Focal adhesion kinase (FAK) controls cell growth and survival downstream of integrin-matrix receptors. Upon adhesion loss or FAK inhibition, FAK can translocate to the nucleus. The nucleolus is a non-membrane nuclear structure that regulates ribosome biogenesis and cell proliferation. Nucleostemin (NS), a nucleolar-localized protein, modulates cell cycle progression, stemness, and three-dimensional tumor spheroid formation. The signaling pathways that regulate NS levels in tumors remain undefined. Methods Human breast carcinoma cells were evaluated for growth in culture (adherent and anchorage-independent spheroid) and as orthotopic tumors. FAK signaling was evaluated by pharmacological FAK inhibitor addition (PF-271, IC50 ~ 0.1 μM) and by small hairpin RNA (shRNA) knockdown followed by re-expression of FAK wildtype (WT) or a kinase-dead (KD, K454R) FAK point mutant. Immunoblotting was used to evaluate FAK, NS, nucleolar phosphoprotein B23, and nucleolin levels. Total and phosphospecific antibody imunoblotting were used to detect changes in FAK, Akt kinase (Akt also known as protein kinase B), and 4E-binding protein 1 (4E-BP1) phosphorylation, a translation repressor protein and target of the mammalian target of rapamycin (mTOR) complex. Immunohistochemical, co-immunoprecipitation, and cellular fractionation analyses were used to evaluate FAK association with nucleoli. Results Pharmacological (0.1 μM PF-271) or genetic inhibition of FAK activity prevents MDA-MB-231 and 4T1L breast carcinoma growth as spheroids and as orthotopic tumors. FAK inhibition triggers proteasome-mediated decreased NS levels but no changes in other nucleolar proteins such as B23 (nucleophosmin) or nucleolin. Active FAK was associated with purified nucleoli of anchorage-independent cells and present within nucleoli of human invasive ductal carcinoma tumor samples. FAK co-immunoprecipitated with B23 that binds NS and a complex between FAK, NS, Akt, and mTOR was detected. Constitutively-active Akt kinase promoted tumor spheroid growth, stabilized NS levels, and promoted pS65 4E-BP1 phosphorylation in the presence of inhibited FAK. Rapamycin lowered NS levels and inhibited pS65 4E-BP1 phosphorylation in cells with activated Akt-mTOR signaling. Conclusions FAK signaling occurs in the nucleolus, active FAK protects NS, and Akt-mTOR pathway regulates NS protein stability needed for breast carcinoma spheroid and tumor growth. Electronic supplementary material The online version of this article (doi:10.1186/s13058-015-0551-x) contains supplementary material, which is available to authorized users.
Collapse
Affiliation(s)
- Isabelle Tancioni
- Department of Reproductive Medicine, University of California San Diego, Moores Cancer Center, 3855 Health Sciences Dr, La Jolla, CA, 92093, USA.
| | - Nichol L G Miller
- Department of Reproductive Medicine, University of California San Diego, Moores Cancer Center, 3855 Health Sciences Dr, La Jolla, CA, 92093, USA. .,Current address: Pfizer, La Jolla, CA, 92121, USA.
| | - Sean Uryu
- Department of Reproductive Medicine, University of California San Diego, Moores Cancer Center, 3855 Health Sciences Dr, La Jolla, CA, 92093, USA.
| | - Christine Lawson
- Department of Reproductive Medicine, University of California San Diego, Moores Cancer Center, 3855 Health Sciences Dr, La Jolla, CA, 92093, USA.
| | - Christine Jean
- Department of Reproductive Medicine, University of California San Diego, Moores Cancer Center, 3855 Health Sciences Dr, La Jolla, CA, 92093, USA. .,Current address: INSERM U1037 - Cancer Research Center, Toulouse, France.
| | - Xiao Lei Chen
- Department of Reproductive Medicine, University of California San Diego, Moores Cancer Center, 3855 Health Sciences Dr, La Jolla, CA, 92093, USA.
| | - Elizabeth G Kleinschmidt
- Department of Reproductive Medicine, University of California San Diego, Moores Cancer Center, 3855 Health Sciences Dr, La Jolla, CA, 92093, USA.
| | - David D Schlaepfer
- Department of Reproductive Medicine, University of California San Diego, Moores Cancer Center, 3855 Health Sciences Dr, La Jolla, CA, 92093, USA.
| |
Collapse
|
6
|
Lo D, Zhang Y, Dai MS, Sun XX, Zeng SX, Lu H. Nucleostemin stabilizes ARF by inhibiting the ubiquitin ligase ULF. Oncogene 2014; 34:1688-97. [PMID: 24769896 PMCID: PMC4212020 DOI: 10.1038/onc.2014.103] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2013] [Revised: 02/02/2014] [Accepted: 03/13/2014] [Indexed: 12/18/2022]
Abstract
Up-regulated expression of nucleolar GTPase Nucleostemin (NS) has been associated with increased cellular proliferation potential and tumor malignancy during cancer development. Recent reports attribute the growth regulatory effects of NS protein to its role in facilitating ribosome production. However, the oncogenic potential of NS remains unclear since imbalanced levels of NS have been reported to exert growth inhibitory effect by modulating p53 tumor suppressor activity. It also remains in questions if aberrant NS levels might play a p53-independent role in regulation of cell proliferation and growth. In this study, we performed affinity purification and mass spectrometry analysis to explore protein-protein interactions influencing NS growth regulatory properties independently of p53 tumor suppressor. We identified the Alternative Reading Frame (ARF) protein as a key protein associating with NS and further verified the interaction through in vitro and in vivo assays. We demonstrated that NS is able to regulate cell cycle progression by regulating the stability of the ARF tumor suppressor. Furthermore, overexpression of NS suppressed ARF polyubiquitination by its E3 ligase ULF and elongated its half-life, while knockdown of NS led to the decrease of ARF levels. Also, we found that NS can enhance NPM stabilization of ARF. Thus, we propose that in the absence of p53, ARF can be stabilized by NS and NPM to serve as an alternative tumor suppressor surveillance, preventing potential cellular transformation resulting from the growth inducing effects of NS overexpression.
Collapse
Affiliation(s)
- D Lo
- Department of Biochemistry and Molecular Biology, Tulane Cancer Center, Tulane University School of Medicine, New Orleans, LA, USA
| | - Y Zhang
- Department of Biochemistry and Molecular Biology, Tulane Cancer Center, Tulane University School of Medicine, New Orleans, LA, USA
| | - M-S Dai
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, OR, USA
| | - X-X Sun
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, OR, USA
| | - S X Zeng
- Department of Biochemistry and Molecular Biology, Tulane Cancer Center, Tulane University School of Medicine, New Orleans, LA, USA
| | - H Lu
- Department of Biochemistry and Molecular Biology, Tulane Cancer Center, Tulane University School of Medicine, New Orleans, LA, USA
| |
Collapse
|
7
|
Hein N, Hannan KM, George AJ, Sanij E, Hannan RD. The nucleolus: an emerging target for cancer therapy. Trends Mol Med 2013; 19:643-54. [PMID: 23953479 DOI: 10.1016/j.molmed.2013.07.005] [Citation(s) in RCA: 181] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2013] [Revised: 07/10/2013] [Accepted: 07/15/2013] [Indexed: 02/07/2023]
Abstract
For over 100 years, pathologists have utilised an increase in size and number of nucleoli, the subnuclear site of ribosome synthesis, as a marker of aggressive tumours. Despite this, the contribution of the nucleolus and ribosomal RNA synthesis to cancer has been largely overlooked. This concept has recently changed with the demonstration that the nucleolus indirectly controls numerous other cellular functions, in particular, the cellular activity of the critical tumour suppressor protein, p53. Moreover, selective inhibition of ribosomal gene transcription in the nucleolus has been shown to be an effective therapeutic strategy to promote cancer-specific activation of p53. This article reviews the largely untapped potential of the nucleolus and ribosomal gene transcription as exciting new targets for cancer therapy.
Collapse
Affiliation(s)
- Nadine Hein
- Division of Cancer Research, Peter MacCallum Cancer Centre, East Melbourne, 3002, Victoria, Australia; Sir Peter MacCallum Department of Oncology, The University of Melbourne, Parkville, 3010, Victoria, Australia
| | | | | | | | | |
Collapse
|
8
|
Abstract
HeLa cells engineered with the fluorescent ubiquitinylation-based cell cycle indicator are used to study the connection between nucleolar stress and cell cycle progression. The results demonstrate a feedforward mechanism that leads to G2 arrest and identify ATR and Chk1 as molecular agents of the requisite checkpoint. We report experiments on the connection between nucleolar stress and cell cycle progression, using HeLa cells engineered with the fluorescent ubiquitinylation-based cell cycle indicator. Nucleolar stress elicited by brief exposure of cells to a low concentration of actinomycin D that selectively inhibits rRNA synthesis had no effect on traverse of G1 or S, but stalled cells in very late interphase. Additional experiments revealed that a switch occurs during a specific temporal window during nucleolar stress and that the subsequent cell cycle arrest is not triggered simply by the stress-induced decline in the synthesis of rRNA or by a ribosome starvation phenomenon. Further experiments revealed that this nucleolus stress-induced cell cycle arrest involves the action of a G2 checkpoint mediated by the ataxia telangiectasia and Rad3-related protein (ATR)–checkpoint kinase 1 (Chk1) pathway. Based on analysis of the cell cycle stages at which this nucleolar stress effect is put into action, to become manifest later, our results demonstrate a feedforward mechanism that leads to G2 arrest and identify ATR and Chk1 as molecular agents of the requisite checkpoint.
Collapse
Affiliation(s)
- Hanhui Ma
- Department of Biochemistry and Molecular Pharmacology and Program in Cell and Developmental Dynamics, University of Massachusetts Medical School, Worcester, MA 01605, USA.
| | | |
Collapse
|
9
|
Nucleolar protein GLTSCR2 stabilizes p53 in response to ribosomal stresses. Cell Death Differ 2012; 19:1613-22. [PMID: 22522597 DOI: 10.1038/cdd.2012.40] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
p53 is a key regulator of cell growth and death by controlling cell cycle progression and apoptosis under conditions of stress such as DNA damage or oncogenic stimulation. As these processes are critical for cell function and inhibition of tumor development, p53 regulatory pathways are strictly monitored in cells. Recently, it was recognized that nucleolar proteins, including nucleophosmin/B23, ribosomal protein L11, and alternate reading frame (ARF), form the nucleolus-ARF-murine double minute 2 (MDM2) axis in p53 regulatory pathways, which increases p53 stability by suppressing the activity of MDM2. In this work, we show that nucleolar protein glioma tumor-suppressor candidate region gene 2 (GLTSCR2) translocates to the nucleoplasm under ribosomal stress, where it interacts with and stabilizes p53 and inhibits cell cycle progression without the involvement of the major upstream p53 regulator, ARF. Furthermore, ectopic expression of GLTSCR2 significantly suppressed growth of cancer cells in a xenograft animal model via p53-dependent pathway. Our data identify GLTSCR2 as a new member of the nucleolus-nucleoplasmic axis for p53 regulation. ARF-independent direct regulation of p53 by GLTSCR2 may be a key mechanism and therapeutic target for cell death or growth inhibition when nucleolus-ARF-p53 pathways are inactivated by genetic or epigenetic modifications of ARF, which are the second most common types of genetic change observed in human cancers.
Collapse
|
10
|
Pan ZG, Wang YY, Fan L, Qian W, Song YH, Zhu LR. RNAi-mediated down-regulation of expression of nucleostemin in human colorectal carcinoma cell line SW480. Shijie Huaren Xiaohua Zazhi 2012; 20:70-73. [DOI: 10.11569/wcjd.v20.i1.70] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the effect of transfection of nucleostemin-specific small interfering RNA (siRNA) on nucleostemin expression and cell proliferation in human colorectal carcinoma cell line SW480.
METHODS: A plasmid containing siRNA targeting the nucleostemin gene was constructed and transfected into SW480 cells with Lipofectamine2000 Reagent. After transfection, nucleostemin expression was detected by real-time PCR and Western blot, and cell proliferation was determined by MTT assay.
RESULTS: Compared to the control groups, the levels of the nucleostemin mRNA and protein were obviously reduced in cells transfected with nucleostemin-specific RNA (protein: 1.069 ± 0.368, 1.003 ± 0.313 vs 1.901 ± 0.817, both P < 0.05; mRNA: 1.069 ± 0.368, 1.003 ± 0.313 vs 2.035 ± 0.665, both P < 0.05). There were no significant differences in the expression of nucleostemin mRNA and protein between the two control groups (both P > 0.05). SiRNA-mediated inhibition of nucleostemin expression significantly suppressed the proliferation of SW480 cells.
CONCLUSION: SiRNA-mediated inhibition of nucleostemin expression significantly suppressed the proliferation of SW480 cells.
Collapse
|
11
|
Huna A, Salmina K, Jascenko E, Duburs G, Inashkina I, Erenpreisa J. Self-Renewal Signalling in Presenescent Tetraploid IMR90 Cells. J Aging Res 2011; 2011:103253. [PMID: 21629737 PMCID: PMC3100543 DOI: 10.4061/2011/103253] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 02/22/2011] [Accepted: 02/25/2011] [Indexed: 12/22/2022] Open
Abstract
Endopolyploidy and genomic instability are shared features of both stress-induced cellular senescence and malignant growth. Here, we examined these facets in the widely used normal human fibroblast model of senescence, IMR90. At the presenescence stage, a small (2–7%) proportion of cells overcome the 4n-G1 checkpoint, simultaneously inducing self-renewal (NANOG-positivity), the DNA damage response (DDR; γ-H2AX-positive foci), and senescence (p16inka4a- and p21CIP1-positivity) signalling, some cells reach octoploid DNA content and divide. All of these markers initially appear and partially colocalise in the perinucleolar compartment. Further, with development of senescence and accumulation of p16inka4a and p21CIP1, NANOG is downregulated in most cells. The cells increasingly arrest in the 4n-G1 fraction, completely halt divisions and ultimately degenerate. A positive link between DDR, self-renewal, and senescence signalling is initiated in the cells overcoming the tetraploidy barrier, indicating that cellular and molecular context of induced tetraploidy during this period of presenescence is favourable for carcinogenesis.
Collapse
Affiliation(s)
- Anda Huna
- Latvian Biomedical Research and Study Centre, Ratsupites 1, 1067 Riga, Latvia
| | | | | | | | | | | |
Collapse
|
12
|
Nucleolar stress is an early response to myocardial damage involving nucleolar proteins nucleostemin and nucleophosmin. Proc Natl Acad Sci U S A 2011; 108:6145-50. [PMID: 21444791 DOI: 10.1073/pnas.1017935108] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Nucleolar stress, characterized by loss of nucleolar integrity, has not been described in the cardiac context. In addition to ribosome biogenesis, nucleoli are critical for control of cell proliferation and stress responses. Our group previously demonstrated induction of the nucleolar protein nucleostemin (NS) in response to cardiac pathological insult. NS interacts with nucleophosmin (NPM), a marker of nucleolar stress with cytoprotective properties. The dynamic behavior of NS and NPM reveal that nucleolar disruption is an early event associated with stress response in cardiac cells. Rapid translocation of NS and NPM to the nucleoplasm and suppression of new preribosomal RNA synthesis occurs in both neonatal rat cardiomyocytes (NRCM) and cardiac progenitor cells (CPC) upon exposure to doxorubicin or actinomycin D. Silencing of NS significantly increases cell death resulting from doxorubicin treatment in CPC, whereas NPM knockdown alone induces cell death. Overexpression of either NS or NPM significantly decreases caspase 8 activity in cultured cardiomyocytes challenged with doxorubicin. The presence of altered nucleolar structures resulting from myocardial infarction in mice supports the model of nucleolar stress as a general response to pathological injury. Collectively, these findings serve as the initial description of myocardial nucleolar stress and establish the postulate that nucleoli acts as sensors of stress, regulating the cellular response to pathological insults.
Collapse
|
13
|
Abstract
When cells are observed by phase contrast microscopy, nucleoli are among the most conspicuous structures. The nucleolus was formally described between 1835 and 1839, but it was another century before it was discovered to be associated with a specific chromosomal locus, thus defining it as a cytogenetic entity. Nucleoli were first isolated in the 1950s, from starfish oocytes. Then, in the early 1960s, a boomlet of studies led to one of the epochal discoveries in the modern era of genetics and cell biology: that the nucleolus is the site of ribosomal RNA synthesis and nascent ribosome assembly. This epistemologically repositioned the nucleolus as not merely an aspect of nuclear anatomy but rather as a cytological manifestation of gene action-a major heuristic advance. Indeed, the finding that the nucleolus is the seat of ribosome production constitutes one of the most vivid confluences of form and function in the history of cell biology. This account presents the nucleolus in both historical and contemporary perspectives. The modern era has brought the unanticipated discovery that the nucleolus is plurifunctional, constituting a paradigm shift.
Collapse
Affiliation(s)
- Thoru Pederson
- Program in Cell and Developmental Dynamics, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, 01605, USA.
| |
Collapse
|
14
|
Park JH, Sihn CR, Lee YS, Lee SJ, Kim SH. Depletion of Neuroguidin/CANu1 sensitizes human osteosarcoma U2OS cells to doxorubicin. BMB Rep 2011; 44:46-51. [DOI: 10.5483/bmbrep.2011.44.1.46] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
|
15
|
NPM1/B23: A Multifunctional Chaperone in Ribosome Biogenesis and Chromatin Remodeling. Biochem Res Int 2010; 2011:195209. [PMID: 21152184 PMCID: PMC2989734 DOI: 10.1155/2011/195209] [Citation(s) in RCA: 226] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 08/29/2010] [Indexed: 12/21/2022] Open
Abstract
At a first glance, ribosome biogenesis and chromatin remodeling are quite different processes, but they share a common problem involving interactions between charged nucleic acids and small basic proteins that may result in unwanted intracellular aggregations. The multifunctional nuclear acidic chaperone NPM1 (B23/nucleophosmin) is active in several stages of ribosome biogenesis, chromatin remodeling, and mitosis as well as in DNA repair, replication and transcription. In addition, NPM1 plays an important role in the Myc-ARF-p53 pathway as well as in SUMO regulation. However, the relative importance of NPM1 in these processes remains unclear. Provided herein is an update on the expanding list of the diverse activities and interacting partners of NPM1. Mechanisms of NPM1 nuclear export functions of NPM1 in the nucleolus and at the mitotic spindle are discussed in relation to tumor development. It is argued that the suggested function of NPM1 as a histone chaperone could explain several, but not all, of the effects observed in cells following changes in NPM1 expression. A future challenge is to understand how NPM1 is activated, recruited, and controlled to carry out its functions.
Collapse
|
16
|
Wang G, Pan Y, Ahmad KA, Ahmed K. Protein B23/nucleophosmin/numatrin nuclear dynamics in relation to protein kinase CK2 and apoptotic activity in prostate cells. Biochemistry 2010; 49:3842-52. [PMID: 20387789 DOI: 10.1021/bi9021928] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Protein B23/nucleophosmin/numatrin (B23) is a key nucleolar/nuclear matrix-associated protein required for cell growth-related functions, such as rRNA synthesis. Protein kinase CK2 (CK2) (formerly casein kinase 2, a protein Ser/Thr kinase signal that is involved in cell growth and cell death) mediates phosphorylation of B23, thereby influencing its functional activity. Here we have delineated the dynamics of B23 and its link to CK2 status in response to altered growth stimuli and induction of apoptosis in cultured prostate cells and in rat prostate cells in vivo. Our studies employing PC-3 and ALVA-41 prostate cancer cells demonstrated colocalization of CK2 and B23 in the nucleus. Further, CK2 and B23 underwent coordinate modulation in the nucleus related to their nucleocytoplasmic shuttling in response to induction of apoptotic activity in cells caused by downregulation of CK2 or by treatment with other apoptosis-inducing agents. These alterations in nuclear association of B23 occurred in the absence of a significant change in the level of cytoplasmic B23. Similar studies in the in vivo model of rat prostate epithelial cells subjected to androgen deprivation (that resulted in loss of nuclear CK2 and induction of apoptosis) demonstrated dynamic modulation of nuclear matrix-associated B23 without a significant change in its cytoplasmic level. These changes were reversed by androgen-mediated growth response in the prostate. Our results suggest that CK2-mediated phosphorylation of B23 is essential for its retention in the nucleus and that coordinated nuclear localization of B23 and CK2 is dynamically regulated in response to altered growth status in the cell.
Collapse
Affiliation(s)
- Guixia Wang
- Cellular and Molecular Biochemistry Research Laboratory (151), Minneapolis Veterans Affairs Medical Center, and Department of Laboratory Medicine and Pathology and Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota 55417, USA
| | | | | | | |
Collapse
|
17
|
Nalabothula N, Indig FE, Carrier F. The Nucleolus Takes Control of Protein Trafficking Under Cellular Stress. MOLECULAR AND CELLULAR PHARMACOLOGY 2010; 2:203-212. [PMID: 21499571 PMCID: PMC3076688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The nucleolus is a highly dynamic nuclear substructure that was originally described as the site of ribosome biogenesis. The advent of proteomic analysis has now allowed the identification of over 4500 nucleolus associated proteins with only about 30% of them associated with ribogenesis (1). The great number of nucleolar proteins not associated with traditionally accepted nucleolar functions indicates a role for the nucleolus in other cellular functions such as mitosis, cell-cycle progression, cell proliferation and many forms of stress response including DNA repair (2). A number of recent reviews have addressed the pivotal role of the nucleolus in the cellular stress response (1, 3, 4). Here, we will focus on the role of Nucleolin and Nucleophosmin, two major components of the nucleolus, in response to genotoxic stress. Due to space constraint only a limited number of studies are cited. We thus apologize to all our colleagues whose works are not referenced here.
Collapse
Affiliation(s)
- Narasimharao Nalabothula
- Marlene and Stewart Greenebaum Cancer Center, University of Maryland, Baltimore, School of Medicine, Department of Radiation Oncology, Baltimore, Maryland
| | - Fred E. Indig
- National Institute on Aging, National Institutes of Health, Baltimore, Maryland
| | - France Carrier
- Marlene and Stewart Greenebaum Cancer Center, University of Maryland, Baltimore, School of Medicine, Department of Radiation Oncology, Baltimore, Maryland
| |
Collapse
|
18
|
Politz JCR, Hogan EM, Pederson T. MicroRNAs with a nucleolar location. RNA (NEW YORK, N.Y.) 2009; 15:1705-15. [PMID: 19628621 PMCID: PMC2743059 DOI: 10.1261/rna.1470409] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2008] [Accepted: 06/18/2009] [Indexed: 05/03/2023]
Abstract
There is increasing evidence that noncoding RNAs play a functional role in the nucleus. We previously reported that the microRNA (miRNA), miR-206, is concentrated in the nucleolus of rat myoblasts, as well as in the cytoplasm as expected. Here we have extended this finding. We show by cell/nuclear fractionation followed by microarray analysis that a number of miRNAs can be detected within the nucleolus of rat myoblasts, some of which are significantly concentrated there. Pronounced nucleolar localization is a specific phenomenon since other miRNAs are present at only very low levels in the nucleolus and occur at much higher levels in the nucleoplasm and/or the cytoplasm. We have further characterized a subset of these miRNAs using RT-qPCR and in situ hybridization, and the results suggest that some miRNAs are present in the nucleolus in precursor form while others are present as mature species. Furthermore, we have found that these miRNAs are clustered in specific sites within the nucleolus that correspond to the classical granular component. One of these miRNAs is completely homologous to a portion of a snoRNA, suggesting that it may be processed from it. In contrast, the other nucleolar-concentrated miRNAs do not show homology with any annotated rat snoRNAs and thus appear to be present in the nucleolus for other reasons, such as modification/processing, or to play roles in the late stages of ribosome biosynthesis or in nonribosomal functions that have recently been ascribed to the granular component of the nucleolus.
Collapse
Affiliation(s)
- Joan C Ritland Politz
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
| | | | | |
Collapse
|
19
|
Rosby R, Cui Z, Rogers E, deLivron MA, Robinson VL, DiMario PJ. Knockdown of the Drosophila GTPase nucleostemin 1 impairs large ribosomal subunit biogenesis, cell growth, and midgut precursor cell maintenance. Mol Biol Cell 2009; 20:4424-34. [PMID: 19710426 DOI: 10.1091/mbc.e08-06-0592] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Mammalian nucleostemin (NS) is a nucleolar guanosine triphosphate-binding protein implicated in cell cycle progression, stem cell proliferation, and ribosome assembly. Drosophila melanogaster contains a four-member nucleostemin family (NS1-4). NS1 is the closest orthologue to human NS; it shares 33% identity and 67% similarity with human NS. We show that NS1 has intrinsic GTPase and ATPase activity and that it is present within nucleoli of most larval and adult cells. Endogenous NS1 and lightly expressed green fluorescent protein (GFP)-NS1 enrich within the nucleolar granular regions as expected, whereas overexpressed GFP-NS1 localized throughout the nucleolus and nucleoplasm, and to several transcriptionally active interbands of polytene chromosomes. Severe overexpression correlated with the appearance of melanotic tumors and larval/pupal lethality. Depletion of 60% of NS1 transcripts also lead to larval and pupal lethality. NS1 protein depletion>95 correlated with the loss of imaginal island (precursor) cells in the larval midgut and to an apparent block in the nucleolar release of large ribosomal subunits in terminally differentiated larval midgut polyploid cells. Ultrastructural examination of larval Malpighian tubule cells depleted for NS1 showed a loss of cytoplasmic ribosomes and a concomitant appearance of cytoplasmic preautophagosomes and lysosomes. We interpret the appearance of these structures as indicators of cell stress response.
Collapse
Affiliation(s)
- Raphyel Rosby
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803-1715, USA
| | | | | | | | | | | |
Collapse
|
20
|
Romanova L, Kellner S, Katoku-Kikyo N, Kikyo N. Novel role of nucleostemin in the maintenance of nucleolar architecture and integrity of small nucleolar ribonucleoproteins and the telomerase complex. J Biol Chem 2009; 284:26685-94. [PMID: 19648109 DOI: 10.1074/jbc.m109.013342] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nucleostemin (NS) is a nucleolar protein involved in the regulation of cell proliferation. Both overexpression and knockdown of NS increase the activity of the tumor suppressor protein p53, resulting in cell cycle arrest. In addition, NS regulates processing of pre-rRNA and consequently the level of total protein synthesis. Here, we describe a previously uncharacterized function of NS in the maintenance of the tripartite nucleolar structure as well as the integrity of small nucleolar ribonucleoproteins (snoRNPs). NS is also necessary to maintain the telomerase complex which shares common protein subunits with the H/ACA box snoRNPs. First, immunofluorescence microscopy and electron microscopy demonstrated that knockdown of NS disorganized the nucleolar architecture, in particular, the dense fibrillar component where snoRNPs are localized. Second, gel filtration chromatography and immunoprecipitation indicated that NS depletion leads to dissociation of the components of snoRNPs and the telomerase complex. Third, NS depletion reduced both telomerase activity and the cellular level of pseudouridine, an H/ACA snoRNP-mediated modification of rRNA and other RNAs that are important for their folding and stability. These morphological, biochemical and functional studies demonstrate that NS plays an important role to maintain nucleolar structure and function on a more fundamental level than previously thought.
Collapse
Affiliation(s)
- Liudmila Romanova
- Division of Hematology, Department of Medicine, Stem Cell Institute, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | | | | | | |
Collapse
|
21
|
Mercier I, Casimiro MC, Zhou J, Wang C, Plymire C, Bryant KG, Daumer KM, Sotgia F, Bonuccelli G, Witkiewicz AK, Lin J, Tran TH, Milliman J, Frank PG, Jasmin JF, Rui H, Pestell RG, Lisanti MP. Genetic ablation of caveolin-1 drives estrogen-hypersensitivity and the development of DCIS-like mammary lesions. THE AMERICAN JOURNAL OF PATHOLOGY 2009; 174:1172-90. [PMID: 19342371 DOI: 10.2353/ajpath.2009.080882] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Caveolin-1 (Cav-1) loss-of-function mutations are exclusively associated with estrogen receptor-positive (ER(+)) human breast cancers. To dissect the role of Cav-1 loss-of-function in the pathogenesis of human breast cancers, we used Cav-1(-/-) null mice as a model system. First, we demonstrated that Cav-1(-/-) mammary epithelia overexpress two well-established ER co-activator genes, CAPER and Foxa1, in addition to ER-alpha. Thus, the functional loss of Cav-1 may be sufficient to confer estrogen-hypersensitivity in the mammary gland. To test this hypothesis directly, we subjected Cav-1(-/-) mice to ovariectomy and estrogen supplementation. As predicted, Cav-1(-/-) mammary glands were hyper-responsive to estrogen and developed dysplastic mammary lesions with adjacent stromal angiogenesis that resemble human ductal carcinoma in situ. Based on an extensive biomarker analysis, these Cav-1(-/-) mammary lesions contain cells that are hyperproliferative and stain positively with nucleolar (B23/nucleophosmin) and stem/progenitor cell markers (SPRR1A and beta-catenin). Genome-wide transcriptional profiling identified many estrogen-related genes that were over-expressed in Cav-1(-/-) mammary glands, including CAPER--an ER co-activator gene and putative stem/progenitor cell marker. Analysis of human breast cancer samples revealed that CAPER is overexpressed and undergoes a cytoplasmic-to-nuclear shift during the transition from pre-malignancy to ductal carcinoma in situ. Thus, Cav-1(-/-) null mice are a new preclinical model for studying the molecular paradigm of estrogen hypersensitivity and the development of estrogen-dependent ductal carcinoma in situ lesions.
Collapse
Affiliation(s)
- Isabelle Mercier
- Department of Cancer Biology, Kimmel Cancer Center, Thomas Jefferson University, 233 South 10th Street, Philadelphia, PA 19107, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Pederson T, Tsai RY. In search of nonribosomal nucleolar protein function and regulation. J Cell Biol 2009; 184:771-6. [PMID: 19289796 PMCID: PMC2699146 DOI: 10.1083/jcb.200812014] [Citation(s) in RCA: 126] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Accepted: 01/30/2009] [Indexed: 01/15/2023] Open
Abstract
The life of the nucleolus has proven to be more colorful and multifaceted than had been envisioned a decade ago. A large number of proteins found in this subnuclear compartment have no identifiable tie either to the ribosome biosynthetic pathway or to the other newly established activities occurring within the nucleolus. The questions of how and why these proteins end up in this subnuclear compartment remain unanswered and are the focus of intense current interest. This review discusses our thoughts on the discovery of nonribosomal proteins in the nucleolus.
Collapse
Affiliation(s)
- Thoru Pederson
- Program in Cell Dynamics, Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Robert Y.L. Tsai
- Center for Cancer and Stem Cell Biology, Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, TX 77030
| |
Collapse
|
23
|
Ma H, Pederson T. Nucleostemin: a multiplex regulator of cell-cycle progression. Trends Cell Biol 2008; 18:575-9. [PMID: 18951797 DOI: 10.1016/j.tcb.2008.09.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2008] [Revised: 09/16/2008] [Accepted: 09/18/2008] [Indexed: 11/15/2022]
Abstract
Nucleostemin (NS) is a protein concentrated in the nucleolus of most stem cells and also in many tumor cells, which has been implicated in cell-cycle progression owing to its ability to modulate p53. Depletion of NS causes G(1) cell-cycle arrest, but its overexpression does so as well. Recently, this paradox has been clarified. NS overexpression causes a sequestration of murine double minute 2 (MDM2), preventing the destruction of p53. A recent study has demonstrated that loss of NS promotes the interaction of L5 and L11 ribosomal proteins with MDM2 and, thus, also prevents p53 degradation. This new finding expands our understanding of the multiple modes of NS action and reinforces the concept that the nucleolus has key roles in cell-cycle progression.
Collapse
Affiliation(s)
- Hanhui Ma
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01609, USA.
| | | |
Collapse
|