1
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Pillet B, Méndez-Godoy A, Murat G, Favre S, Stumpe M, Falquet L, Kressler D. Dedicated chaperones coordinate co-translational regulation of ribosomal protein production with ribosome assembly to preserve proteostasis. eLife 2022; 11:74255. [PMID: 35357307 PMCID: PMC8970588 DOI: 10.7554/elife.74255] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 02/22/2022] [Indexed: 12/17/2022] Open
Abstract
The biogenesis of eukaryotic ribosomes involves the ordered assembly of around 80 ribosomal proteins. Supplying equimolar amounts of assembly-competent ribosomal proteins is complicated by their aggregation propensity and the spatial separation of their location of synthesis and pre-ribosome incorporation. Recent evidence has highlighted that dedicated chaperones protect individual, unassembled ribosomal proteins on their path to the pre-ribosomal assembly site. Here, we show that the co-translational recognition of Rpl3 and Rpl4 by their respective dedicated chaperone, Rrb1 or Acl4, reduces the degradation of the encoding RPL3 and RPL4 mRNAs in the yeast Saccharomyces cerevisiae. In both cases, negative regulation of mRNA levels occurs when the availability of the dedicated chaperone is limited and the nascent ribosomal protein is instead accessible to a regulatory machinery consisting of the nascent-polypeptide-associated complex and the Caf130-associated Ccr4-Not complex. Notably, deregulated expression of Rpl3 and Rpl4 leads to their massive aggregation and a perturbation of overall proteostasis in cells lacking the E3 ubiquitin ligase Tom1. Taken together, we have uncovered an unprecedented regulatory mechanism that adjusts the de novo synthesis of Rpl3 and Rpl4 to their actual consumption during ribosome assembly and, thereby, protects cells from the potentially detrimental effects of their surplus production. Living cells are packed full of molecules known as proteins, which perform many vital tasks the cells need to survive and grow. Machines called ribosomes inside the cells use template molecules called messenger RNAs (or mRNAs for short) to produce proteins. The newly-made proteins then have to travel to a specific location in the cell to perform their tasks. Some newly-made proteins are prone to forming clumps, so cells have other proteins known as chaperones that ensure these clumps do not form. The ribosomes themselves are made up of several proteins, some of which are also prone to clumping as they are being produced. To prevent this from happening, cells control how many ribosomal proteins they make, so there are just enough to form the ribosomes the cell needs at any given time. Previous studies found that, in yeast, two ribosomal proteins called Rpl3 and Rpl4 each have their own dedicated chaperone to prevent them from clumping. However, it remained unclear whether these chaperones are also involved in regulating the levels of Rpl3 and Rpl4. To address this question, Pillet et al. studied both of these dedicated chaperones in yeast cells. The experiments showed that the chaperones bound to their target proteins (either units of Rpl3 or Rpl4) as they were being produced on the ribosomes. This protected the template mRNAs the ribosomes were using to produce these proteins from being destroyed, thus allowing further units of Rpl3 and Rpl4 to be produced. When enough Rpl3 and Rpl4 units were made, there were not enough of the chaperones to bind them all, leaving the mRNA templates unprotected. This led to the destruction of the mRNA templates, which decreased the numbers of Rpl3 and Rpl4 units being produced. The work of Pillet et al. reveals a feedback mechanism that allows yeast to tightly control the levels of Rpl3 and Rpl4. In the future, these findings may help us understand diseases caused by defects in ribosomal proteins, such as Diamond-Blackfan anemia, and possibly also neurodegenerative diseases caused by clumps of proteins forming in cells. The next step will be to find out whether the mechanism uncovered by Pillet et al. also exists in human and other mammalian cells.
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Affiliation(s)
- Benjamin Pillet
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | | | - Guillaume Murat
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Sébastien Favre
- Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Michael Stumpe
- Department of Biology, University of Fribourg, Fribourg, Switzerland.,Metabolomics and Proteomics Platform, Department of Biology, University of Fribourg, Fribourg, Switzerland
| | - Laurent Falquet
- Department of Biology, University of Fribourg, Fribourg, Switzerland.,Swiss Institute of Bioinformatics, University of Fribourg, Fribourg, Switzerland
| | - Dieter Kressler
- Department of Biology, University of Fribourg, Fribourg, Switzerland
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2
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Lee ES, Wolf EJ, Ihn SSJ, Smith HW, Emili A, Palazzo AF. TPR is required for the efficient nuclear export of mRNAs and lncRNAs from short and intron-poor genes. Nucleic Acids Res 2021; 48:11645-11663. [PMID: 33091126 PMCID: PMC7672458 DOI: 10.1093/nar/gkaa919] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 09/21/2020] [Accepted: 10/02/2020] [Indexed: 12/14/2022] Open
Abstract
While splicing has been shown to enhance nuclear export, it has remained unclear whether mRNAs generated from intronless genes use specific machinery to promote their export. Here, we investigate the role of the major nuclear pore basket protein, TPR, in regulating mRNA and lncRNA nuclear export in human cells. By sequencing mRNA from the nucleus and cytosol of control and TPR-depleted cells, we provide evidence that TPR is required for the efficient nuclear export of mRNAs and lncRNAs that are generated from short transcripts that tend to have few introns, and we validate this with reporter constructs. Moreover, in TPR-depleted cells reporter mRNAs generated from short transcripts accumulate in nuclear speckles and are bound to Nxf1. These observations suggest that TPR acts downstream of Nxf1 recruitment and may allow mRNAs to leave nuclear speckles and properly dock with the nuclear pore. In summary, our study provides one of the first examples of a factor that is specifically required for the nuclear export of intronless and intron-poor mRNAs and lncRNAs.
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Affiliation(s)
- Eliza S Lee
- University of Toronto, Department of Biochemistry, Canada
| | - Eric J Wolf
- University of Toronto, Department of Molecular Genetics, Canada
| | - Sean S J Ihn
- University of Toronto, Department of Biochemistry, Canada
| | | | - Andrew Emili
- University of Toronto, Department of Molecular Genetics, Canada.,Boston University School of Medicine, Department of Biochemistry, Boston, MA, USA
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3
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Suresh HG, Pascoe N, Andrews B. The structure and function of deubiquitinases: lessons from budding yeast. Open Biol 2020; 10:200279. [PMID: 33081638 PMCID: PMC7653365 DOI: 10.1098/rsob.200279] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Protein ubiquitination is a key post-translational modification that regulates diverse cellular processes in eukaryotic cells. The specificity of ubiquitin (Ub) signalling for different bioprocesses and pathways is dictated by the large variety of mono-ubiquitination and polyubiquitination events, including many possible chain architectures. Deubiquitinases (DUBs) reverse or edit Ub signals with high sophistication and specificity, forming an integral arm of the Ub signalling machinery, thus impinging on fundamental cellular processes including DNA damage repair, gene expression, protein quality control and organellar integrity. In this review, we discuss the many layers of DUB function and regulation, with a focus on insights gained from budding yeast. Our review provides a framework to understand key aspects of DUB biology.
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Affiliation(s)
- Harsha Garadi Suresh
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada M5S 3E1
| | - Natasha Pascoe
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada M5S 3E1.,Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada M5S 3E1
| | - Brenda Andrews
- Donnelly Centre for Cellular and Biomolecular Research, University of Toronto, Toronto, Ontario, Canada M5S 3E1.,Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada M5S 3E1
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4
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Cornelio-Parra DV, Goswami R, Costanzo K, Morales-Sosa P, Mohan RD. Function and regulation of the Spt-Ada-Gcn5-Acetyltransferase (SAGA) deubiquitinase module. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2020; 1864:194630. [PMID: 32911111 DOI: 10.1016/j.bbagrm.2020.194630] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 08/31/2020] [Accepted: 09/01/2020] [Indexed: 12/27/2022]
Abstract
The Spt-Ada-Gcn5 Acetyltransferase (SAGA) chromatin modifying complex is a critical regulator of gene expression and is highly conserved across species. Subunits of SAGA arrange into discrete modules with lysine aceyltransferase and deubiquitinase activities housed separately. Mutation of the SAGA deubiquitinase module can lead to substantial biological misfunction and diseases such as cancer, neurodegeneration, and blindness. Here, we review the structure and functions of the SAGA deubiquitinase module and regulatory mechanisms acting to control these.
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5
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Nuño-Cabanes C, Rodríguez-Navarro S. The promiscuity of the SAGA complex subunits: Multifunctional or moonlighting proteins? BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2020; 1864:194607. [PMID: 32712338 DOI: 10.1016/j.bbagrm.2020.194607] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 04/27/2020] [Revised: 07/09/2020] [Accepted: 07/13/2020] [Indexed: 12/15/2022]
Abstract
Gene expression, the decoding of DNA information into accessible instructions for protein synthesis, is a complex process in which multiple steps, including transcription, mRNA processing and mRNA export, are regulated by different factors. One of the first steps in this process involves chemical and structural changes in chromatin to allow transcription. For such changes to occur, histone tail and DNA epigenetic modifications foster the binding of transcription factors to promoter regions. The SAGA coactivator complex plays a crucial role in this process by mediating histone acetylation through Gcn5, and histone deubiquitination through Ubp8 enzymes. However, most SAGA subunits interact physically with other proteins beyond the SAGA complex. These interactions could represent SAGA-independent functions or a mechanism to widen SAGA multifunctionality. Among the different mechanisms to perform more than one function, protein moonlighting defines unrelated molecular activities for the same polypeptide sequence. Unlike pleiotropy, where a single gene can affect different phenotypes, moonlighting necessarily involves separate functions of a protein at the molecular level. In this review we describe in detail some of the alternative physical interactions of several SAGA subunits. In some cases, the alternative role constitutes a clear moonlighting function, whereas in most of them the lack of molecular evidence means that we can only define these interactions as promiscuous that require further work to verify if these are moonlighting functions.
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Affiliation(s)
- Carme Nuño-Cabanes
- Gene Expression and RNA Metabolism Laboratory, Instituto de Biomedicina de Valencia (CSIC), Jaume Roig, 11, E-46010 Valencia, Spain
| | - Susana Rodríguez-Navarro
- Gene Expression and RNA Metabolism Laboratory, Instituto de Biomedicina de Valencia (CSIC), Jaume Roig, 11, E-46010 Valencia, Spain.
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6
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Martín-Villanueva S, Fernández-Pevida A, Kressler D, de la Cruz J. The Ubiquitin Moiety of Ubi1 Is Required for Productive Expression of Ribosomal Protein eL40 in Saccharomyces cerevisiae. Cells 2019; 8:cells8080850. [PMID: 31394841 PMCID: PMC6721733 DOI: 10.3390/cells8080850] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 08/02/2019] [Accepted: 08/06/2019] [Indexed: 01/01/2023] Open
Abstract
Ubiquitin is a highly conserved small eukaryotic protein. It is generated by proteolytic cleavage of precursor proteins in which it is fused either to itself, constituting a polyubiquitin precursor of head-to-tail monomers, or as a single N-terminal moiety to ribosomal proteins. Understanding the role of the ubiquitin fused to ribosomal proteins becomes relevant, as these proteins are practically invariably eS31 and eL40 in the different eukaryotes. Herein, we used the amenable yeast Saccharomyces cerevisiae to study whether ubiquitin facilitates the expression of the fused eL40 (Ubi1 and Ubi2 precursors) and eS31 (Ubi3 precursor) ribosomal proteins. We have analyzed the phenotypic effects of a genomic ubi1∆ub-HA ubi2∆ mutant, which expresses a ubiquitin-free HA-tagged eL40A protein as the sole source of cellular eL40. This mutant shows a severe slow-growth phenotype, which could be fully suppressed by increased dosage of the ubi1∆ub-HA allele, or partially by the replacement of ubiquitin by the ubiquitin-like Smt3 protein. While expression levels of eL40A-HA from ubi1∆ub-HA are low, eL40A is produced practically at normal levels from the Smt3-S-eL40A-HA precursor. Finally, we observed enhanced aggregation of eS31-HA when derived from a Ubi3∆ub-HA precursor and reduced aggregation of eL40A-HA when expressed from a Smt3-S-eL40A-HA precursor. We conclude that ubiquitin might serve as a cis-acting molecular chaperone that assists in the folding and synthesis of the fused eL40 and eS31 ribosomal proteins.
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Affiliation(s)
- Sara Martín-Villanueva
- Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocio/CSIC/Universidad de Sevilla, E-41013 Seville, Spain
- Departamento de Genética, Universidad de Sevilla, E-41012 Seville, Spain
| | - Antonio Fernández-Pevida
- Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocio/CSIC/Universidad de Sevilla, E-41013 Seville, Spain
- Departamento de Genética, Universidad de Sevilla, E-41012 Seville, Spain
| | - Dieter Kressler
- Unit of Biochemistry, Department of Biology, University of Fribourg, CH-1700 Fribourg, Switzerland.
| | - Jesús de la Cruz
- Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocio/CSIC/Universidad de Sevilla, E-41013 Seville, Spain.
- Departamento de Genética, Universidad de Sevilla, E-41012 Seville, Spain.
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7
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Xiao C, Yu Q, Zhang B, Li J, Zhang D, Li M. Role of the mRNA export factor Sus1 in oxidative stress tolerance in Candida albicans. Biochem Biophys Res Commun 2018; 496:253-259. [DOI: 10.1016/j.bbrc.2018.01.044] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Accepted: 01/06/2018] [Indexed: 10/18/2022]
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8
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Raices M, D'Angelo MA. Nuclear pore complexes and regulation of gene expression. Curr Opin Cell Biol 2017; 46:26-32. [PMID: 28088069 DOI: 10.1016/j.ceb.2016.12.006] [Citation(s) in RCA: 81] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Revised: 12/09/2016] [Accepted: 12/21/2016] [Indexed: 12/31/2022]
Abstract
Nuclear pore complexes (NPCs), are large multiprotein channels that penetrate the nuclear envelope connecting the nucleus to the cytoplasm. Accumulating evidence shows that besides their main role in regulating the exchange of molecules between these two compartments, NPCs and their components also play important transport-independent roles, including gene expression regulation, chromatin organization, DNA repair, RNA processing and quality control, and cell cycle control. Here, we will describe the recent findings about the role of these structures in the regulation of gene expression.
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Affiliation(s)
- Marcela Raices
- Sanford Burnham Prebys Medical Discovery Institute, Development, Aging and Regeneration Program, 10901 N. Torrey Pines Road, La Jolla, 92037 CA, United States
| | - Maximiliano A D'Angelo
- Sanford Burnham Prebys Medical Discovery Institute, Development, Aging and Regeneration Program, 10901 N. Torrey Pines Road, La Jolla, 92037 CA, United States.
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9
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Sakaguchi N, Maeda K. Germinal Center B-Cell-Associated Nuclear Protein (GANP) Involved in RNA Metabolism for B Cell Maturation. Adv Immunol 2016; 131:135-86. [PMID: 27235683 DOI: 10.1016/bs.ai.2016.02.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Germinal center B-cell-associated nuclear protein (GANP) is upregulated in germinal center B cells against T-cell-dependent antigens in mice and humans. In mice, GANP depletion in B cells impairs antibody affinity maturation. Conversely, its transgenic overexpression augments the generation of high-affinity antigen-specific B cells. GANP associates with AID in the cytoplasm, shepherds AID into the nucleus, and augments its access to the rearranged immunoglobulin (Ig) variable (V) region of the genome in B cells, thereby precipitating the somatic hypermutation of V region genes. GANP is also upregulated in human CD4(+) T cells and is associated with APOBEC3G (A3G). GANP interacts with A3G and escorts it to the virion cores to potentiate its antiretroviral activity by inactivating HIV-1 genomic cDNA. Thus, GANP is characterized as a cofactor associated with AID/APOBEC cytidine deaminase family molecules in generating diversity of the IgV region of the genome and genetic alterations of exogenously introduced viral targets. GANP, encoded by human chromosome 21, as well as its mouse equivalent on chromosome 10, contains a region homologous to Saccharomyces Sac3 that was characterized as a component of the transcription/export 2 (TREX-2) complex and was predicted to be involved in RNA export and metabolism in mammalian cells. The metabolism of RNA during its maturation, from the transcription site at the chromosome within the nucleus to the cytoplasmic translation apparatus, needs to be elaborated with regard to acquired and innate immunity. In this review, we summarize the current knowledge on GANP as a component of TREX-2 in mammalian cells.
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Affiliation(s)
- N Sakaguchi
- WPI Immunology Frontier Research Center (IFReC), Osaka University, Suita, Osaka, Japan; Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan.
| | - K Maeda
- WPI Immunology Frontier Research Center (IFReC), Osaka University, Suita, Osaka, Japan; Laboratory of Host Defense, Research Institute for Microbial Diseases, Osaka University, Suita, Japan
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10
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AbuQattam A, Gallego J, Rodríguez-Navarro S. An intronic RNA structure modulates expression of the mRNA biogenesis factor Sus1. RNA (NEW YORK, N.Y.) 2016; 22:75-86. [PMID: 26546116 PMCID: PMC4691836 DOI: 10.1261/rna.054049.115] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 10/03/2015] [Indexed: 06/05/2023]
Abstract
Sus1 is a conserved protein involved in chromatin remodeling and mRNA biogenesis. Unlike most yeast genes, the SUS1 pre-mRNA of Saccharomyces cerevisiae contains two introns and is alternatively spliced, retaining one or both introns in response to changes in environmental conditions. SUS1 splicing may allow the cell to control Sus1 expression, but the mechanisms that regulate this process remain unknown. Using in silico analyses together with NMR spectroscopy, gel electrophoresis, and UV thermal denaturation experiments, we show that the downstream intron (I2) of SUS1 forms a weakly stable, 37-nucleotide stem-loop structure containing the branch site near its apical loop and the 3' splice site after the stem terminus. A cellular assay revealed that two of four mutants containing altered I2 structures had significantly impaired SUS1 expression. Semiquantitative RT-PCR experiments indicated that all mutants accumulated unspliced SUS1 pre-mRNA and/or induced distorted levels of fully spliced mRNA relative to wild type. Concomitantly, Sus1 cellular functions in histone H2B deubiquitination and mRNA export were affected in I2 hairpin mutants that inhibited splicing. This work demonstrates that I2 structure is relevant for SUS1 expression, and that this effect is likely exerted through modulation of splicing.
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Affiliation(s)
- Ali AbuQattam
- Gene Expression and RNA Metabolism Laboratory, Centro de Investigación Príncipe Felipe, Valencia 46012, Spain Facultad de Medicina, Universidad Católica de Valencia, Valencia 46001, Spain
| | - José Gallego
- Facultad de Medicina, Universidad Católica de Valencia, Valencia 46001, Spain
| | - Susana Rodríguez-Navarro
- Gene Expression and RNA Metabolism Laboratory, Centro de Investigación Príncipe Felipe, Valencia 46012, Spain
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11
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Abstract
Aneuploidy, the unbalanced segregation of chromosomes during cell division, is recurrent in many tumors and the cause of birth defects and genetic diseases. Centromeric chromatin represents the chromosome attachment site to the mitotic spindle, marked by specialized nucleosomes containing a specific histone variant, CEN-H3/Cse4, in yeast. Mislocalization of Cse4 outside the centromere is deleterious and may cause aberrant chromosome behavior and mitotic loss. For this reason, ubiquitylation by the E3-ubiquitin ligase Psh1 and subsequent proteolysis tightly regulates its restricted localization. Among multiproteic machineries, the SAGA complex is not merely engaged in acetylation but also directly involved in deubiquitylation. In this study, we investigated the role of SAGA-DUB’s Ubp8-driven deubiquitylation of the centromeric histone variant Cse4 in budding yeast. We found that Ubp8 works in concert with the E3-ubiquitin ligase Psh1, and that its loss causes defective deubiquitylation and the accumulation of a short ubiquitin oligomer on Cse4. We also show that lack of Ubp8 and defective deubiquitylation increase mitotic instability, cause faster Cse4 proteolysis and induce mislocalization of the centromeric histone outside the centromere. Our data provide evidence for a fundamental role of DUB-Ubp8 in deubiquitylation and the stability of the centromeric histone in budding yeast.
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12
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Durairaj G, Sen R, Uprety B, Shukla A, Bhaumik SR. Sus1p facilitates pre-initiation complex formation at the SAGA-regulated genes independently of histone H2B de-ubiquitylation. J Mol Biol 2014; 426:2928-2941. [PMID: 24911582 DOI: 10.1016/j.jmb.2014.05.028] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 04/29/2014] [Accepted: 05/31/2014] [Indexed: 12/23/2022]
Abstract
Sus1p is a common component of transcriptional co-activator, SAGA (Spt-Ada-Gcn5-Acetyltransferase), and mRNA export complex, TREX-2 (Transcription-export 2), and is involved in promoting transcription and mRNA export. However, it is not clearly understood how Sus1p promotes transcription. Here, we show that Sus1p is predominantly recruited to the upstream activating sequence of a SAGA-dependent gene, GAL1, under transcriptionally active conditions as a component of SAGA to promote the formation of pre-initiation complex (PIC) at the core promoter and, consequently, transcriptional initiation. Likewise, Sus1p promotes the PIC formation at other SAGA-dependent genes and hence transcriptional initiation. Such function of Sus1p in promoting PIC formation and transcriptional initiation is not mediated via its role in regulation of SAGA's histone H2B de-ubiquitylation activity. However, Sus1p's function in regulation of histone H2B ubiquitylation is associated with transcriptional elongation, DNA repair and replication. Collectively, our results support that Sus1p promotes PIC formation (and hence transcriptional initiation) at the SAGA-regulated genes independently of histone H2B de-ubiquitylation and further controls transcriptional elongation, DNA repair and replication via orchestration of histone H2B ubiquitylation, thus providing distinct functional insights of Sus1p in regulation of DNA transacting processes.
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Affiliation(s)
- Geetha Durairaj
- Department of Biochemistry and Molecular Biology Southern Illinois University School of Medicine Carbondale, IL-62901 USA
| | - Rwik Sen
- Department of Biochemistry and Molecular Biology Southern Illinois University School of Medicine Carbondale, IL-62901 USA
| | - Bhawana Uprety
- Department of Biochemistry and Molecular Biology Southern Illinois University School of Medicine Carbondale, IL-62901 USA
| | - Abhijit Shukla
- Department of Biochemistry and Molecular Biology Southern Illinois University School of Medicine Carbondale, IL-62901 USA
| | - Sukesh R Bhaumik
- Department of Biochemistry and Molecular Biology Southern Illinois University School of Medicine Carbondale, IL-62901 USA
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13
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Stancheva I, Schirmer EC. Nuclear Envelope: Connecting Structural Genome Organization to Regulation of Gene Expression. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2014; 773:209-44. [DOI: 10.1007/978-1-4899-8032-8_10] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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14
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González-Aguilera C, Tous C, Babiano R, de la Cruz J, Luna R, Aguilera A. Nab2 functions in the metabolism of RNA driven by polymerases II and III. Mol Biol Cell 2011; 22:2729-40. [PMID: 21680710 PMCID: PMC3145548 DOI: 10.1091/mbc.e11-01-0055] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The hnRNP Nab2 is associated with actively transcribed RNAPII and RNAPIII genes. Nab2 has a function in RNAPII transcription and participates in tRNA metabolism and ribosomal subunit export, and, as a consequence, nab2 mutations confer translation defects. Results support Nab2 as a key regulator of gene expression. Gene expression in eukaryotes is an essential process that includes transcription, RNA processing, and export. One important player in this interface is the poly(A)+-RNA–binding protein Nab2, which regulates the mRNA poly(A)+-tail length and export. Here we show that Nab2 has additional roles during mRNA transcription, tRNA metabolism, and ribosomal subunit export. Nab2 is associated with the entire open reading frame of actively transcribed RNA polymerase (RNAP) II and III genes. As a consequence, nab2 mutations confer translation defects that are detected by polysome profiling. Genome-wide analysis of expression of a conditional degron nab2 mutant shows that the role of Nab2 in RNAPII transcription and RNAPIII metabolism is direct. Taken together, our results identify novel functions for Nab2 in transcription and metabolism of most types of RNAs, indicating that Nab2 function is more ubiquitous than previously anticipated, and that it is a central player in the general and coordinated control of gene expression from transcription to translation.
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Affiliation(s)
- Cristina González-Aguilera
- Centro Andaluz de Biología Molecular y Medicina Regenerativa, Universidad de Sevilla-Consejo Superior de Investigaciones Científicas, 41092 Seville, Spain
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15
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Abstract
Messenger RNAs undergo 5' capping, splicing, 3'-end processing, and export before translation in the cytoplasm. It has become clear that these mRNA processing events are tightly coupled and have a profound effect on the fate of the resulting transcript. This processing is represented by modifications of the pre-mRNA and loading of various protein factors. The sum of protein factors that stay with the mRNA as a result of processing is modified over the life of the transcript, conferring significant regulation to its expression.
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Affiliation(s)
- Sami Hocine
- Department for Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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16
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The nuclear pore complex: bridging nuclear transport and gene regulation. Nat Rev Mol Cell Biol 2010; 11:490-501. [DOI: 10.1038/nrm2928] [Citation(s) in RCA: 390] [Impact Index Per Article: 27.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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17
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The interface between transcription and mRNP export: from THO to THSC/TREX-2. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2010; 1799:533-8. [PMID: 20601280 DOI: 10.1016/j.bbagrm.2010.06.002] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Revised: 06/10/2010] [Accepted: 06/14/2010] [Indexed: 11/20/2022]
Abstract
Eukaryotic gene expression is a multilayer process covering transcription to post-translational protein modifications. As the nascent pre-mRNA emerges from the RNA polymerase II (RNAPII), it is packed in a messenger ribonucleoparticle (mRNP) whose optimal configuration is critical for the normal pre-mRNA processing and mRNA export, mRNA integrity as well as for transcription elongation efficiency. The interplay between transcription and mRNP formation feeds forward and backward and involves a number of conserved factors, from THO to THSC/TREX-2, which in addition have a unique impact on transcription-dependent genome instability. Here we review our actual knowledge of the role that these factors play at the interface between transcription and mRNA export in the model organism Saccharomyces cerevisiae.
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Ellisdon AM, Jani D, Köhler A, Hurt E, Stewart M. Structural basis for the interaction between yeast Spt-Ada-Gcn5 acetyltransferase (SAGA) complex components Sgf11 and Sus1. J Biol Chem 2009; 285:3850-3856. [PMID: 20007317 PMCID: PMC2823527 DOI: 10.1074/jbc.m109.070839] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Sus1 is a central component of the yeast gene gating machinery, the process by which actively transcribing genes such as GAL1 become associated with nuclear pore complexes. Sus1 is a component of both the SAGA transcriptional co-activator complex and the TREX-2 complex that binds to nuclear pore complexes. TREX-2 contains two Sus1 chains that have an articulated helical hairpin fold, enabling them to wrap around an extended α-helix in Sac3, following a helical hydrophobic stripe. In SAGA, Sus1 binds to Sgf11 and has been proposed to provide a link between SAGA and TREX-2. We present here the crystal structure of the complex between Sus1 and the N-terminal region of Sgf11 that forms an extended α-helix around which Sus1 wraps in a manner that shares some similarities with the Sus1-Sac3 interface in TREX-2. However, the Sus1-binding site on Sgf11 is somewhat shorter than on Sac3 and is based on a narrower hydrophobic stripe. Engineered mutants that disrupt the Sgf11-Sus1 interaction in vitro confirm the importance of the hydrophobic helical stripe in molecular recognition. Helix α1 of the Sus1-articulated hairpin does not bind directly to Sgf11 and adopts a wide range of conformations within and between crystal forms, consistent with the presence of a flexible hinge and also with results from previous extensive mutagenesis studies (Klöckner, C., Schneider, M., Lutz, S., Jani, D., Kressler, D., Stewart, M., Hurt, E., and Köhler, A. (2009) J. Biol. Chem. 284, 12049–12056). A single Sus1 molecule cannot bind Sgf11 and Sac3 simultaneously and this, combined with the structure of the Sus1-Sgf11 complex, indicates that Sus1 forms separate subcomplexes within SAGA and TREX-2.
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Affiliation(s)
- Andrew M Ellisdon
- From the Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, United Kingdom and
| | - Divyang Jani
- From the Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, United Kingdom and
| | - Alwin Köhler
- Biochemie-Zentrum der Universität Heidelberg, INF328, D-69120 Heidelberg, Germany
| | - Ed Hurt
- Biochemie-Zentrum der Universität Heidelberg, INF328, D-69120 Heidelberg, Germany
| | - Murray Stewart
- From the Medical Research Council Laboratory of Molecular Biology, Hills Road, Cambridge CB2 0QH, United Kingdom and.
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Rodríguez-Navarro S. Insights into SAGA function during gene expression. EMBO Rep 2009; 10:843-50. [PMID: 19609321 DOI: 10.1038/embor.2009.168] [Citation(s) in RCA: 116] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2009] [Accepted: 06/17/2009] [Indexed: 12/26/2022] Open
Abstract
Histone modifications are a crucial source of epigenetic control. SAGA (Spt-Ada-Gcn5 acetyltransferase) is a chromatin-modifying complex that contains two distinct enzymatic activities, Gcn5 and Ubp8, through which it acetylates and deubiquitinates histone residues, respectively, thereby enforcing a pattern of modifications that is decisive in regulating gene expression. Here, I discuss the latest contributions to understanding the roles of the SAGA complex, highlighting the characterization of the SAGA-deubiquitination module, and emphasizing the functions newly ascribed to SAGA during transcription elongation and messenger-RNA export. These findings suggest that a crosstalk exists between chromatin remodelling, transcription and messenger-RNA export, which could constitute a checkpoint for accurate gene expression. I focus particularly on the new components of human SAGA, which was recently discovered and confirms the conservation of the SAGA complex throughout evolution.
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