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Kadam R, Harish M, Dalvi K, Teni T. Novel nucleolar localization of clusterin and its associated functions in human oral cancers: An in vitro and in silico analysis. Cell Biochem Funct 2020; 39:380-391. [PMID: 33155695 DOI: 10.1002/cbf.3600] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 09/25/2020] [Accepted: 10/05/2020] [Indexed: 02/05/2023]
Abstract
Clusterin (CLU), a multifunctional chaperonic glycoprotein associated with diverse cellular functions has been shown to act as an oncogene or tumour suppressor gene in different cancers, implying a dual role in tumorigenesis. Here, we investigated the expression of CLU isoforms, their subcellular localization and functional significance in oral cancer cells. Significant downregulation of secretory CLU (sCLU) transcripts was observed in oral cancer cell lines and tumours versus normal cells while the nuclear CLU (nCLU) transcripts were undetectable. We demonstrated for the first time the nucleolar localization of sCLU, its response to different nucleolar stresses and association with cajal bodies post nucleolar stress. Functionally, knockdown of CLU revealed its negative association with ribosome biogenesis implying a possible tumour suppressor like role in oral cancers. Further, loss of sCLU in these cells also resulted in altered nuclear morphology and shrunken tubulin filaments. In addition, the levels of nucleolar Nucleophosmin 1(NPM1) and Fibrillarin, known to regulate nuclear morphology were downregulated indicating a possible role of sCLU in their stabilization. Further, an in silico docking approach to gain insights into the interaction of sCLU with nucleolar proteins NPM1, Fibrillarin, UBF and Nucleolin, revealed the involvement of a conserved region comprising of amino acid residues 140-155 of sCLU β-chain, specifically via the Phe152 residue in hydrophobic interactions with these client nucleolar proteins indicating a possible stabilizing or regulatory role of sCLU. SIGNIFICANCE OF THE STUDY: This is the first study to demonstrate the nucleolar localization of sCLU and its associated functions in oral cancer cells. Downregulation of sCLU in oral cancer tissues and cell lines, and its negative association with ribogenesis suggest its tumour suppressor like role in oral cancers. The possible role of sCLU in stabilization or regulation of different nucleolar proteins thereby impacting their functions is also implicated.
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Affiliation(s)
- Rajashree Kadam
- Teni Laboratory, Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre TMC, Navi Mumbai, India.,Homi Bhabha National Institute, Training School Complex, Mumbai, India
| | - Mahalakshmi Harish
- Protein Interactome Lab for Structural and Functional Biology, Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre TMC, Navi Mumbai, India.,Homi Bhabha National Institute, Training School Complex, Mumbai, India
| | - Kajal Dalvi
- Teni Laboratory, Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre TMC, Navi Mumbai, India
| | - Tanuja Teni
- Teni Laboratory, Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Tata Memorial Centre TMC, Navi Mumbai, India.,Homi Bhabha National Institute, Training School Complex, Mumbai, India
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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.
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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
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Mai W, Huang F, Chen H, Zhou Y, Chen Y. Nervous necrosis virus capsid protein exploits nucleolar phosphoprotein Nucleophosmin (B23) function for viral replication. Virus Res 2016; 230:1-6. [PMID: 28034778 DOI: 10.1016/j.virusres.2016.12.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2016] [Revised: 12/01/2016] [Accepted: 12/16/2016] [Indexed: 01/15/2023]
Abstract
Nucleolar proteins facilitate the replication of certain human and animal viruses through interaction with viral proteins. In this study, an interaction between nervous necrosis virus capsid protein and nucleolar phosphoprotein B23 was identified using in vitro experimental approaches. The capsid protein binds to B23 early during the viral infection and accumulates in the nucleus, particularly in the nucleolus. However, over the course of the infection B23 is redistributed from the nucleoli to the nucleoplasm. siRNA-mediated knockdown of B23 reduced viral replication and cytopathic effect. Thus, B23 targets capsid protein to the nucleus and facilitates NNV replication. The results provide the first demonstration that nucleolar protein B23 has a direct role in the nodavirus replication process.
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Affiliation(s)
- Weijun Mai
- The Institute of Life Sciences, Jiangsu University, Zhenjiang, 212013, China.
| | - Fang Huang
- The Institute of Life Sciences, Jiangsu University, Zhenjiang, 212013, China
| | - Huiqing Chen
- The Institute of Life Sciences, Jiangsu University, Zhenjiang, 212013, China
| | - Yajing Zhou
- The Institute of Life Sciences, Jiangsu University, Zhenjiang, 212013, China
| | - Yan Chen
- The Institute of Life Sciences, Jiangsu University, Zhenjiang, 212013, China
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Pirlot C, Thiry M, Trussart C, Di Valentin E, Piette J, Habraken Y. Melanoma antigen-D2: A nucleolar protein undergoing delocalization during cell cycle and after cellular stress. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2016; 1863:581-95. [DOI: 10.1016/j.bbamcr.2015.12.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2015] [Revised: 12/11/2015] [Accepted: 12/15/2015] [Indexed: 12/25/2022]
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Musinova YR, Sheval EV, Dib C, Germini D, Vassetzky YS. Functional roles of HIV-1 Tat protein in the nucleus. Cell Mol Life Sci 2016; 73:589-601. [PMID: 26507246 PMCID: PMC11108392 DOI: 10.1007/s00018-015-2077-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Revised: 09/01/2015] [Accepted: 10/16/2015] [Indexed: 02/06/2023]
Abstract
Human immunodeficiency virus-1 (HIV-1) Tat protein is one of the most important regulatory proteins for viral gene expression in the host cell and can modulate different cellular processes. In addition, Tat is secreted by the infected cell and can be internalized by neighboring cells; therefore, it affects both infected and uninfected cells. Tat can modulate cellular processes by interacting with different cellular structures and signaling pathways. In the nucleus, Tat might be localized either in the nucleoplasm or the nucleolus depending on its concentration. Here we review the distinct functions of Tat in the nucleoplasm and the nucleolus in connection with viral infection and HIV-induced oncogenesis.
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Affiliation(s)
- Yana R Musinova
- A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, 119991, Moscow, Russia
- LIA 1066 French-Russian Joint Cancer Research Laboratory, 94805, Villejuif, France
| | - Eugene V Sheval
- A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, 119991, Moscow, Russia
- LIA 1066 French-Russian Joint Cancer Research Laboratory, 94805, Villejuif, France
| | - Carla Dib
- LIA 1066 French-Russian Joint Cancer Research Laboratory, 94805, Villejuif, France
- UMR8126, Université Paris-Sud, CNRS, Institut de cancérologie Gustave Roussy, 94805, Villejuif, France
| | - Diego Germini
- LIA 1066 French-Russian Joint Cancer Research Laboratory, 94805, Villejuif, France
- UMR8126, Université Paris-Sud, CNRS, Institut de cancérologie Gustave Roussy, 94805, Villejuif, France
| | - Yegor S Vassetzky
- A.N. Belozersky Institute of Physico-Chemical Biology, M.V. Lomonosov Moscow State University, 119991, Moscow, Russia.
- LIA 1066 French-Russian Joint Cancer Research Laboratory, 94805, Villejuif, France.
- UMR8126, Université Paris-Sud, CNRS, Institut de cancérologie Gustave Roussy, 94805, Villejuif, France.
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Melanson VR, Kalina WV, Williams P. Ebola virus infection induces irregular dendritic cell gene expression. Viral Immunol 2015; 28:42-50. [PMID: 25493356 DOI: 10.1089/vim.2014.0091] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Filoviruses subvert the human immune system in part by infecting and replicating in dendritic cells (DCs). Using gene arrays, a phenotypic profile of filovirus infection in human monocyte-derived DCs was assessed. Monocytes from human donors were cultured in GM-CSF and IL-4 and were infected with Ebola virus Kikwit variant for up to 48 h. Extracted DC RNA was analyzed on SuperArray's Dendritic and Antigen Presenting Cell Oligo GEArray and compared to uninfected controls. Infected DCs exhibited increased expression of cytokine, chemokine, antiviral, and anti-apoptotic genes not seen in uninfected controls. Significant increases of intracellular antiviral and MHC I and II genes were also noted in EBOV-infected DCs. However, infected DCs failed to show any significant difference in co-stimulatory T-cell gene expression from uninfected DCs. Moreover, several chemokine genes were activated, but there was sparse expression of chemokine receptors that enabled activated DCs to home to lymph nodes. Overall, statistically significant expression of several intracellular antiviral genes was noted, which may limit viral load but fails to stop replication. EBOV gene expression profiling is of vital importance in understanding pathogenesis and devising novel therapeutic treatments such as small-molecule inhibitors.
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Affiliation(s)
- Vanessa R Melanson
- 1 Entomology Department, Walter Reed Army Institute of Research , Silver Spring, Maryland
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A charge-dependent mechanism is responsible for the dynamic accumulation of proteins inside nucleoli. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:101-10. [DOI: 10.1016/j.bbamcr.2014.10.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 10/02/2014] [Accepted: 10/06/2014] [Indexed: 01/19/2023]
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Identification and characterization of nuclear and nucleolar localization signals in the adeno-associated virus serotype 2 assembly-activating protein. J Virol 2014; 89:3038-48. [PMID: 25552709 DOI: 10.1128/jvi.03125-14] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
UNLABELLED Assembly-activating protein (AAP) of adeno-associated virus serotype 2 (AAV2) is a nucleolar-localizing protein that plays a critical role in transporting the viral capsid VP3 protein to the nucleolus for assembly. Here, we identify and characterize AAV2 AAP (AAP2) nuclear (NLS) and nucleolar (NoLS) localization signals near the carboxy-terminal region of AAP2 (amino acid positions 144 to 184) (AAP2(144-184)). This region contains five basic-amino-acid-rich (BR) clusters, KSKRSRR (AAP2BR1), RRR (AAP2BR2), RFR (AAP2BR3), RSTSSR (AAP2BR4), and RRIK (AAP2BR5), from the amino terminus to the carboxy terminus. We created 30 AAP2BR mutants by arginine/lysine-to-alanine mutagenesis or deletion of AAP2BRs and 8 and 1 green fluorescent protein (GFP)-AAP2BR and β-galactosidase-AAP2BR fusion proteins, respectively, and analyzed their intracellular localization in HeLa cells by immunofluorescence microscopy. The results showed that AAP2(144-184) has redundant multipartite NLSs and that any combinations of 4 AAP2BRs, but not 3 or less, can constitute a functional NLS-NoLS; AAP2BR1 and AAP2BR2 play the most influential role for nuclear localization, but either one of the two AAP2BRs is dispensable if all 4 of the other AAP2BRs are present, resulting in 3 different, overlapping NLS motifs; and the NoLS is shared redundantly among the five AAP2BRs and functions in a context-dependent manner. AAP2BR mutations not only resulted in aberrant intracellular localization, but also attenuated AAP2 protein expression to various degrees, and both of these abnormalities have a significant negative impact on capsid production. Thus, this study reveals the organization of the intermingling NLSs and NoLSs in AAP2 and provides insights into their functional roles in capsid assembly. IMPORTANCE Adeno-associated virus (AAV) has become a popular and successful vector for in vivo gene therapy; however, its biology has yet to be fully understood. In this regard, the recent discovery of the assembly-activating protein (AAP), a nonstructural, nucleolar-localizing AAV protein essential for viral capsid assembly, has provided us a new opportunity to better understand the fundamental processes required for virion formation. Here, we identify clusters of basic amino acids in the carboxy terminus of AAP from AAV serotype 2 (AAV2) that act as nuclear and nucleolar localization signals. We also demonstrate their importance in maintaining AAP expression levels and efficient production of viral capsids. Insights into the functions of AAP can elucidate the requirements and process for AAV capsid assembly, which may lead to improved vector production for use in gene therapy. This study also contributes to the growing body of work on nuclear and nucleolar localization signals.
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The nucleolar phosphoprotein B23 targets Newcastle disease virus matrix protein to the nucleoli and facilitates viral replication. Virology 2014; 452-453:212-22. [PMID: 24606698 DOI: 10.1016/j.virol.2014.01.011] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Revised: 11/28/2013] [Accepted: 01/17/2014] [Indexed: 01/14/2023]
Abstract
The cellular nucleolar proteins are reported to facilitate the replication cycles of some human and animal viruses by interaction with viral proteins. In this study, a nucleolar phosphoprotein B23 was identified to interact with Newcastle disease virus (NDV) matrix (M) protein. We found that NDV M protein accumulated in the nucleolus by binding B23 early in infection, but resulted in the redistribution of B23 from the nucleoli to the nucleoplasm later in infection. In vitro binding studies utilizing deletion mutants indicated that amino acids 30-60 of M and amino acids 188-245 of B23 were required for binding. Furthermore, knockdown of B23 by siRNA or overexpression of B23 or M-binding B23-derived polypeptides remarkably reduced cytopathic effect and inhibited NDV replication. Collectively, we show that B23 facilitates NDV replication by targeting M to the nucleolus, demonstrating for the first time a direct role for nucleolar protein B23 in a paramyxovirus replication process.
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Wang Y, Xu W, Zhou D, Neckers L, Chen S. Coordinated regulation of serum- and glucocorticoid-inducible kinase 3 by a C-terminal hydrophobic motif and Hsp90-Cdc37 chaperone complex. J Biol Chem 2013; 289:4815-26. [PMID: 24379398 DOI: 10.1074/jbc.m113.518480] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Serum- and glucocorticoid-inducible kinase 3 (SGK3) mediates a variety of cellular processes including membrane transport, cell proliferation, and survival, and it has been implicated in Akt-independent signaling downstream of oncogenic PIK3CA mutations (activating mutations in the α catalytic subunit of PI3K) in human cancers. However, the regulation of SGK3 is poorly understood. Here we report that SGK3 stability and kinase activation are regulated by the Hsp90-Cdc37 chaperone complex. Hsp90-Cdc37 associates with the kinase domain of SGK3 and acts in concert with a C-terminal hydrophobic motif of SGK3 to prevent Hsp70 association and ubiquitin ligase CHIP (C terminus of Hsc70-interacting protein)-mediated degradation. Phosphorylation of hydrophobic motif triggers release of Cdc37 and concomitant association of 3-phosphoinositide dependent kinase 1 (PDK1) to activate SGK3. Our study provides new insights into regulation of SGK3 stability and activation and the rationale for application of Hsp90 inhibitors in treating SGK3-dependent cancers.
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Affiliation(s)
- Yuanzhong Wang
- From the Department of Cancer Biology, Beckman Research Institute of the City of Hope, Duarte, California 91010 and
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Kita Y, Nishiyama M, Nakayama KI. Identification of CHD7S as a novel splicing variant of CHD7 with functions similar and antagonistic to those of the full-length CHD7L. Genes Cells 2012; 17:536-47. [PMID: 22646239 DOI: 10.1111/j.1365-2443.2012.01606.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 03/21/2012] [Indexed: 01/28/2023]
Abstract
CHD7 is one of the nine members of the chromodomain helicase DNA-binding family of ATP-dependent chromatin remodeling enzymes. Mutations in CHD7 give rise to CHARGE syndrome, a human condition characterized by malformation of various organs. We have now identified a novel transcript of CHD7 that is generated by alternative splicing of exon 6. The protein encoded by this variant transcript (termed CHD7S) lacks one of the two chromodomains as well as the helicase/ATPase domain, DNA-binding domain and BRK domains of the full-length protein (CHD7L). CHD7S was found to localize specifically to the nucleolus in a manner dependent on a nucleolar localization signal. Over-expression of CHD7S, as well as that of CHD7L, resulted in an increase in 45S precursor rRNA production. Conversely, depletion of both CHD7S and CHD7L by RNA interference inhibited both 45S precursor rRNA production and cell proliferation to a greater extent than did depletion of CHD7L alone. Furthermore, we found that, like CHD7L, CHD7S binds to Sox2 in the nucleoplasm. Unexpectedly, however, whereas over-expression of CHD7L promoted Sox2-mediated transcriptional regulation, over-expression of CHD7S suppressed it. These results indicate that CHD7S functions cooperatively or antagonistically with CHD7L in the nucleolus and nucleoplasm, respectively.
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Affiliation(s)
- Yasuyuki Kita
- Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan
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Pérez-Castro AJ, Freire R. Rad9B responds to nucleolar stress through ATR and JNK signalling, and delays the G1-S transition. J Cell Sci 2012; 125:1152-64. [PMID: 22399810 DOI: 10.1242/jcs.091124] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The complex formed by Rad9, Rad1 and Hus1 (9-1-1) protects against genomic instability by activating DNA damage checkpoint and DNA damage repair pathways, mainly in response to replication fork collapse and UV lesions. Here we compare the role of Rad9A (also known as Rad9) with the human paralogue Rad9B. Unlike Rad9A, overexpression of Rad9B delays cells in G1 phase. Moreover, Rad9B migrates to nucleoli after nucleolar stress in an ATR- and JNK-dependent manner, in a newly described nucleolar domain structure containing p21. Analysis of chimeras of Rad9A and Rad9B demonstrate that localisation to nucleoli and the block in G1 phase upon overexpression crucially depend on the Rad9B C-terminal tail. Taken together, data presented here show a relationship between Rad9B and pathways for checkpoints, stress response and nucleolar function.
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Affiliation(s)
- Antonio Jesús Pérez-Castro
- Unidad de Investigación, Hospital Universitario de Canarias, Instituto de Tecnologías Biomédicas, Ofra s/n, La Laguna, Tenerife, Spain
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Koiwai K, Noma S, Takahashi Y, Hayano T, Maezawa S, Kouda K, Matsumoto T, Suzuki M, Furuichi M, Koiwai O. TdIF2 is a nucleolar protein that promotes rRNA gene promoter activity. Genes Cells 2011; 16:748-64. [PMID: 21668587 DOI: 10.1111/j.1365-2443.2011.01524.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Terminal deoxynucleotidyltransferase (TdT) interacting factor 2 (TdIF2) is an acidic protein that binds to TdT. TdIF2 binds to DNA and core histones and contains an acidic-amino acid-rich region in its C-terminus. It has therefore been suggested to function as a histone chaperone within the nucleus. TdIF2 localized within the nucleolus in HEK 293T cells, and its N-terminal (residues 1-234) and C-terminal (residues 606-756) regions were crucial for the nucleolar localization. A chromatin immunoprecipitation (ChIP) assay showed that TdIF2 associated with the promoter of human ribosomal RNA genes (hrDNAP), and an in vitro luciferase assay system showed that it promoted hrDNAP activity. Using the yeast two-hybrid system with TdIF2 as the bait, we isolated the cDNA encoding HIV Tat interactive protein 60 (Tip60), which has histone acetyltransferase (HAT) activity, as a TdIF2-binding protein. TdIF2 bound to Tip60 in vitro and in vivo, inhibited the Tip60 HAT activity in vitro and co-localized with Tip60 within the nucleolus. In addition, TdIF2 promotes upstream binding factor (UBF) acetylation in vivo. Thus, TdIF2 might promote hrDNAP activity by suppressing Tip60's HAT activity and promoting UBF acetylation.
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Affiliation(s)
- Kotaro Koiwai
- Department of Applied Biological Science, Tokyo University of Science, Noda, Chiba, Japan.
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