1
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Bahat A, Lahav O, Plotnikov A, Leshkowitz D, Dikstein R. Targeting Spt5-Pol II by Small-Molecule Inhibitors Uncouples Distinct Activities and Reveals Additional Regulatory Roles. Mol Cell 2019; 76:617-631.e4. [PMID: 31564557 DOI: 10.1016/j.molcel.2019.08.024] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2018] [Revised: 06/12/2019] [Accepted: 08/26/2019] [Indexed: 12/27/2022]
Abstract
Spt5 is a conserved and essential transcription elongation factor that promotes promoter-proximal pausing, promoter escape, elongation, and mRNA processing. Spt5 plays specific roles in the transcription of inflammation and stress-induced genes and tri-nucleotide expanded-repeat genes involved in inherited neurological pathologies. Here, we report the identification of Spt5-Pol II small-molecule inhibitors (SPIs). SPIs faithfully reproduced Spt5 knockdown effects on promoter-proximal pausing, NF-κB activation, and expanded-repeat huntingtin gene transcription. Using SPIs, we identified Spt5 target genes that responded with profoundly diverse kinetics. SPIs uncovered the regulatory role of Spt5 in metabolism via GDF15, a food intake- and body weight-inhibitory hormone. SPIs further unveiled a role for Spt5 in promoting the 3' end processing of histone genes. While several SPIs affect all Spt5 functions, a few inhibit a single one, implying uncoupling and selective targeting of Spt5 activities. SPIs expand the understanding of Spt5-Pol II functions and are potential drugs against metabolic and neurodegenerative diseases.
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Affiliation(s)
- Anat Bahat
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Or Lahav
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Alexander Plotnikov
- The Nancy and Stephen Grand Israel National Center for Personalized Medicine, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Dena Leshkowitz
- Bioinformatics Unit, Department of Life Sciences Core Facilities, The Weizmann Institute of Science, Rehovot 76100, Israel
| | - Rivka Dikstein
- Department of Biomolecular Sciences, The Weizmann Institute of Science, Rehovot 76100, Israel.
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2
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Crickard JB, Fu J, Reese JC. Biochemical Analysis of Yeast Suppressor of Ty 4/5 (Spt4/5) Reveals the Importance of Nucleic Acid Interactions in the Prevention of RNA Polymerase II Arrest. J Biol Chem 2016; 291:9853-70. [PMID: 26945063 DOI: 10.1074/jbc.m116.716001] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Indexed: 11/06/2022] Open
Abstract
RNA polymerase II (RNAPII) undergoes structural changes during the transitions from initiation, elongation, and termination, which are aided by a collection of proteins called elongation factors. NusG/Spt5 is the only elongation factor conserved in all domains of life. Although much information exists about the interactions between NusG/Spt5 and RNA polymerase in prokaryotes, little is known about how the binding of eukaryotic Spt4/5 affects the biochemical activities of RNAPII. We characterized the activities of Spt4/5 and interrogated the structural features of Spt5 required for it to interact with elongation complexes, bind nucleic acids, and promote transcription elongation. The eukaryotic specific regions of Spt5 containing the Kyrpides, Ouzounis, Woese domains are involved in stabilizing the association with the RNAPII elongation complex, which also requires the presence of the nascent transcript. Interestingly, we identify a region within the conserved NusG N-terminal (NGN) domain of Spt5 that contacts the non-template strand of DNA both upstream of RNAPII and in the transcription bubble. Mutating charged residues in this region of Spt5 did not prevent Spt4/5 binding to elongation complexes, but abrogated the cross-linking of Spt5 to DNA and the anti-arrest properties of Spt4/5, thus suggesting that contact between Spt5 (NGN) and DNA is required for Spt4/5 to promote elongation. We propose that the mechanism of how Spt5/NGN promotes elongation is fundamentally conserved; however, the eukaryotic specific regions of the protein evolved so that it can serve as a platform for other elongation factors and maintain its association with RNAPII as it navigates genomes packaged into chromatin.
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Affiliation(s)
- J Brooks Crickard
- From the Department of Biochemistry and Molecular Biology, Center for Eukaryotic Gene Regulation, Penn State University, University Park, Pennsylvania 16802 and
| | - Jianhua Fu
- the Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226
| | - Joseph C Reese
- From the Department of Biochemistry and Molecular Biology, Center for Eukaryotic Gene Regulation, Penn State University, University Park, Pennsylvania 16802 and
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3
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Laitem C, Zaborowska J, Tellier M, Yamaguchi Y, Cao Q, Egloff S, Handa H, Murphy S. CTCF regulates NELF, DSIF and P-TEFb recruitment during transcription. Transcription 2015; 6:79-90. [PMID: 26399478 PMCID: PMC4802788 DOI: 10.1080/21541264.2015.1095269] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
CTCF is a versatile transcription factor with well-established roles in chromatin organization and insulator function. Recent findings also implicate CTCF in the control of elongation by RNA polymerase (RNAP) II. Here we show that CTCF knockdown abrogates RNAP II pausing at the early elongation checkpoint of c-myc by affecting recruitment of DRB-sensitivity-inducing factor (DSIF). CTCF knockdown also causes a termination defect on the U2 snRNA genes (U2), by affecting recruitment of negative elongation factor (NELF). In addition, CTCF is required for recruitment of positive elongation factor b (P-TEFb), which phosphorylates NELF, DSIF, and Ser2 of the RNAP II CTD to activate elongation of transcription of c-myc and recognition of the snRNA gene-specific 3' box RNA processing signal. These findings implicate CTCF in a complex network of protein:protein/protein:DNA interactions and assign a key role to CTCF in controlling RNAP II transcription through the elongation checkpoint of the protein-coding c-myc and the termination site of the non-coding U2, by regulating the recruitment and/or activity of key players in these processes.
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Affiliation(s)
- Clélia Laitem
- a Sir William Dunn School of Pathology; University of Oxford ; Oxford , UK.,e Current address: Immunocore Limited; Milton Park , Abingdon , Oxon , UK
| | - Justyna Zaborowska
- a Sir William Dunn School of Pathology; University of Oxford ; Oxford , UK
| | - Michael Tellier
- a Sir William Dunn School of Pathology; University of Oxford ; Oxford , UK
| | - Yuki Yamaguchi
- b Graduate School of Bioscience and Biotechnology; Tokyo Institute of Technology ; Yokohama , Japan
| | - Qingfu Cao
- b Graduate School of Bioscience and Biotechnology; Tokyo Institute of Technology ; Yokohama , Japan
| | - Sylvain Egloff
- c Université de Toulouse; UPS; Laboratoire de Biologie Moléculaire Eucaryote ; Toulouse , France
| | - Hiroshi Handa
- d Department of Nanoparticle Translational Research ; Tokyo Medical University ; Tokyo , Japan
| | - Shona Murphy
- a Sir William Dunn School of Pathology; University of Oxford ; Oxford , UK
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4
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Dürr J, Lolas IB, Sørensen BB, Schubert V, Houben A, Melzer M, Deutzmann R, Grasser M, Grasser KD. The transcript elongation factor SPT4/SPT5 is involved in auxin-related gene expression in Arabidopsis. Nucleic Acids Res 2014; 42:4332-47. [PMID: 24497194 PMCID: PMC3985667 DOI: 10.1093/nar/gku096] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Revised: 12/21/2013] [Accepted: 01/09/2014] [Indexed: 11/28/2022] Open
Abstract
The heterodimeric complex SPT4/SPT5 is a transcript elongation factor (TEF) that directly interacts with RNA polymerase II (RNAPII) to regulate messenger RNA synthesis in the chromatin context. We provide biochemical evidence that in Arabidopsis, SPT4 occurs in a complex with SPT5, demonstrating that the SPT4/SPT5 complex is conserved in plants. Each subunit is encoded by two genes SPT4-1/2 and SPT5-1/2. A mutant affected in the tissue-specifically expressed SPT5-1 is viable, whereas inactivation of the generally expressed SPT5-2 is homozygous lethal. RNAi-mediated downregulation of SPT4 decreases cell proliferation and causes growth reduction and developmental defects. These plants display especially auxin signalling phenotypes. Consistently, auxin-related genes, most strikingly AUX/IAA genes, are downregulated in SPT4-RNAi plants that exhibit an enhanced auxin response. In Arabidopsis nuclei, SPT5 clearly localizes to the transcriptionally active euchromatin, and essentially co-localizes with transcribing RNAPII. Typical for TEFs, SPT5 is found over the entire transcription unit of RNAPII-transcribed genes. In SPT4-RNAi plants, elevated levels of RNAPII and SPT5 are detected within transcribed regions (including those of downregulated genes), indicating transcript elongation defects in these plants. Therefore, SPT4/SPT5 acts as a TEF in Arabidopsis, regulating transcription during the elongation stage with particular impact on the expression of certain auxin-related genes.
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Affiliation(s)
- Julius Dürr
- Department of Cell Biology & Plant Biochemistry, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany, Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany and Institute for Biochemistry I, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany
| | - Ihab B. Lolas
- Department of Cell Biology & Plant Biochemistry, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany, Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany and Institute for Biochemistry I, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany
| | - Brian B. Sørensen
- Department of Cell Biology & Plant Biochemistry, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany, Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany and Institute for Biochemistry I, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany
| | - Veit Schubert
- Department of Cell Biology & Plant Biochemistry, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany, Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany and Institute for Biochemistry I, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany
| | - Andreas Houben
- Department of Cell Biology & Plant Biochemistry, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany, Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany and Institute for Biochemistry I, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany
| | - Michael Melzer
- Department of Cell Biology & Plant Biochemistry, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany, Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany and Institute for Biochemistry I, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany
| | - Rainer Deutzmann
- Department of Cell Biology & Plant Biochemistry, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany, Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany and Institute for Biochemistry I, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany
| | - Marion Grasser
- Department of Cell Biology & Plant Biochemistry, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany, Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany and Institute for Biochemistry I, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany
| | - Klaus D. Grasser
- Department of Cell Biology & Plant Biochemistry, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany, Department of Biotechnology, Chemistry and Environmental Engineering, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark, Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany and Institute for Biochemistry I, Biochemie-Zentrum Regensburg (BZR), University of Regensburg, Universitätsstrasse 31, D-93053 Regensburg, Germany
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5
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Han B, Xie R, Li L, Zhu L, Wang S. A heuristic biomarker selection approach based on professional tennis player ranking strategy. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2013; 113:186-201. [PMID: 24184113 DOI: 10.1016/j.cmpb.2013.10.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2013] [Revised: 10/07/2013] [Accepted: 10/07/2013] [Indexed: 06/02/2023]
Abstract
Extracting significant features from high-dimension and small sample size biological data is a challenging problem. Recently, Michał Draminski proposed the Monte Carlo feature selection (MC) algorithm, which was able to search over large feature spaces and achieved better classification accuracies. However in MC the information of feature rank variations is not utilized and the ranks of features are not dynamically updated. Here, we propose a novel feature selection algorithm which integrates the ideas of the professional tennis players ranking, such as seed players and dynamic ranking, into Monte Carlo simulation. Seed players make the feature selection game more competitive and selective. The strategy of dynamic ranking ensures that it is always the current best players to take part in each competition. The proposed algorithm is tested on 8 biological datasets. Results demonstrate that the proposed method is computationally efficient, stable and has favorable performance in classification.
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Affiliation(s)
- Bin Han
- College of Life Information Science and Instrument Engineering, Hangzhou Dianzi University, Hangzhou, People's Republic of China.
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6
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Kang MS, Yu SL, Kim HY, Lim HS, Lee SK. SPT4 increases UV-induced mutagenesis in yeast through impaired nucleotide excision repair. Mol Cell Toxicol 2013. [DOI: 10.1007/s13273-013-0006-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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7
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Prabhakaran M, Kelley RL. Mutations in the transcription elongation factor SPT5 disrupt a reporter for dosage compensation in Drosophila. PLoS Genet 2012; 8:e1003073. [PMID: 23209435 PMCID: PMC3510053 DOI: 10.1371/journal.pgen.1003073] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Accepted: 09/22/2012] [Indexed: 12/04/2022] Open
Abstract
In Drosophila, the MSL (Male Specific Lethal) complex up regulates transcription of active genes on the single male X-chromosome to equalize gene expression between sexes. One model argues that the MSL complex acts upon the elongation step of transcription rather than initiation. In an unbiased forward genetic screen for new factors required for dosage compensation, we found that mutations in the universally conserved transcription elongation factor Spt5 lower MSL complex dependent expression from the miniwhite reporter gene in vivo. We show that SPT5 interacts directly with MSL1 in vitro and is required downstream of MSL complex recruitment, providing the first mechanistic data corroborating the elongation model of dosage compensation. Drosophila males hypertranscribe most of the genes along their single X chromosome to match the output of females with two X chromosomes. It had been difficult to imagine how the MSL dosage compensation complex could impose a modest, but essential, ∼two-fold increase by interacting with hundreds of different factors that control transcription initiation for such a diverse collection of genes. An alternative model proposed that dosage compensation instead acted at some step of transcription elongation common to all genes. We performed a genetic screen for mutations that subtly reduce dosage compensation and recovered mutations in the Spt5 gene that encodes a universally conserved elongation factor. SPT5 closes the RNA polymerase II clamp around the DNA template to prevent pausing or premature termination. We find that the dosage compensation complex genetically and physically interacts with SPT5 on actively transcribed genes providing direct molecular support for the elongation model of dosage compensation.
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Affiliation(s)
- Mahalakshmi Prabhakaran
- Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Richard L. Kelley
- Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas, United States of America
- * E-mail:
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8
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Hartzog GA, Fu J. The Spt4-Spt5 complex: a multi-faceted regulator of transcription elongation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1829:105-15. [PMID: 22982195 DOI: 10.1016/j.bbagrm.2012.08.007] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2012] [Revised: 08/21/2012] [Accepted: 08/29/2012] [Indexed: 10/27/2022]
Abstract
In all domains of life, elongating RNA polymerases require the assistance of accessory factors to maintain their processivity and regulate their rate. Among these elongation factors, the Spt5/NusG factors stand out. Members of this protein family appear to be the only transcription accessory proteins that are universally conserved across all domains of life. In archaea and eukaryotes, Spt5 associates with a second protein, Spt4. In addition to regulating elongation, the eukaryotic Spt4-Spt5 complex appears to couple chromatin modification states and RNA processing to transcription elongation. This review discusses the experimental bases for our current understanding of Spt4-Spt5 function and recent studies that are beginning to elucidate the structure of Spt4-Spt5/RNA polymerase complexes and mechanism of Spt4-Spt5 action. This article is part of a Special Issue entitled: RNA polymerase II Transcript Elongation.
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Affiliation(s)
- Grant A Hartzog
- Department of MCD Biology, University of California, Santa Cruz, CA 95064, USA.
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9
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McKay SL, Johnson TL. An investigation of a role for U2 snRNP spliceosomal components in regulating transcription. PLoS One 2011; 6:e16077. [PMID: 21283673 PMCID: PMC3025917 DOI: 10.1371/journal.pone.0016077] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Accepted: 12/04/2010] [Indexed: 11/18/2022] Open
Abstract
There is mounting evidence to suggest that the synthesis of pre-mRNA transcripts and their subsequent splicing are coordinated events. Previous studies have implicated the mammalian spliceosomal U2 snRNP as having a novel role in stimulating transcriptional elongation in vitro through interactions with the elongation factors P-TEFb and Tat-SF1; however, the mechanism remains unknown [1]. These factors are conserved in Saccharomyces cerevisiae, a fact that suggests that a similar interaction may occur in yeast to stimulate transcriptional elongation in vivo. To address this possibility we have looked for evidence of a role for the yeast Tat-SF1 homolog, Cus2, and the U2 snRNA in regulating transcription. Specifically, we have performed a genetic analysis to look for functional interactions between Cus2 or U2 snRNA and the P-TEFb yeast homologs, the Bur1/2 and Ctk1/2/3 complexes. In addition, we have analyzed Cus2-deleted or -overexpressing cells and U2 snRNA mutant cells to determine if they show transcription-related phenotypes similar to those displayed by the P-TEFb homolog mutants. In no case have we been able to observe phenotypes consistent with a role for either spliceosomal factor in transcription elongation. Furthermore, we did not find evidence for physical interactions between the yeast U2 snRNP factors and the P-TEFb homologs. These results suggest that in vivo, S. cerevisiae do not exhibit functional or physical interactions similar to those exhibited by their mammalian counterparts in vitro. The significance of the difference between our in vivo findings and the previously published in vitro results remains unclear; however, we discuss the potential importance of other factors, including viral proteins, in mediating the mammalian interactions.
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Affiliation(s)
- Susannah L. McKay
- Molecular Biology Section, Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
| | - Tracy L. Johnson
- Molecular Biology Section, Division of Biological Sciences, University of California San Diego, La Jolla, California, United States of America
- * E-mail:
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10
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Abstract
Until recently, it was generally assumed that essentially all regulation of transcription takes place via regions adjacent to the coding region of a gene--namely promoters and enhancers--and that, after recruitment to the promoter, the polymerase simply behaves like a machine, quickly "reading the gene." However, over the past decade a revolution in this thinking has occurred, culminating in the idea that transcript elongation is extremely complex and highly regulated and, moreover, that this process significantly affects both the organization and integrity of the genome. This review addresses basic aspects of transcript elongation by RNA polymerase II (RNAPII) and how it relates to other DNA-related processes.
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Affiliation(s)
- Luke A Selth
- Mechanisms of Transcription Laboratory, Clare Hall Laboratories, Cancer Research UK London Research Institute, South Mimms, Hertfordshire EN6 3LD, United Kingdom
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11
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Schwer B, Schneider S, Pei Y, Aronova A, Shuman S. Characterization of the Schizosaccharomyces pombe Spt5-Spt4 complex. RNA (NEW YORK, N.Y.) 2009; 15:1241-50. [PMID: 19460865 PMCID: PMC2704081 DOI: 10.1261/rna.1572709] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The Spt5-Spt4 complex regulates early transcription elongation by RNA polymerase II and has an imputed role in pre-mRNA processing via its physical association with mRNA capping enzymes. Here we characterize the Schizosaccharomyces pombe core Spt5-Spt4 complex as a heterodimer and map a trypsin-resistant Spt4-binding domain within the Spt5 subunit. A genetic analysis of Spt4 in S. pombe revealed it to be inessential for growth at 25 degrees C-30 degrees C but critical at 37 degrees C. These results echo the conditional spt4Delta growth phenotype in budding yeast, where we find that Saccharomyces cerevisiae and S. pombe Spt4 are functionally interchangeable. Complementation of S. cerevisiae spt4Delta and a two-hybrid assay for Spt4-Spt5 interaction provided a readout of the effects of 33 missense and truncation mutations on S. pombe Spt4 function in vivo, which were interpreted in light of the recent crystal structure of S. cerevisiae Spt4 fused to a fragment of Spt5. Our results highlight the importance of the Spt4 Zn2+-binding residues--Cys12, Cys15, Cys29, and Asp32--and of Ser57, a conserved constituent of the Spt4-Spt5 interface. The 990-amino acid S. pombe Spt5 protein has an exceptionally regular carboxyl-terminal domain (CTD) composed of 18 nonapeptide repeats. We find that as few as three nonamer repeats sufficed for S. pombe growth, but only when Spt4 was present. Synthetic lethality of the spt5(1-835) spt4Delta double mutant at 34 degrees C suggests that interaction of Spt4 with the central domain of Spt5 overlaps functionally with the Spt5 CTD.
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Affiliation(s)
- Beate Schwer
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York 10065, USA.
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12
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Guo M, Xu F, Yamada J, Egelhofer T, Gao Y, Hartzog GA, Teng M, Niu L. Core structure of the yeast spt4-spt5 complex: a conserved module for regulation of transcription elongation. Structure 2009; 16:1649-58. [PMID: 19000817 DOI: 10.1016/j.str.2008.08.013] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2008] [Revised: 08/20/2008] [Accepted: 08/20/2008] [Indexed: 11/30/2022]
Abstract
The Spt4-Spt5 complex is an essential RNA polymerase II elongation factor found in all eukaryotes and important for gene regulation. We report here the crystal structure of Saccharomyces cerevisiae Spt4 bound to the NGN domain of Spt5. This structure reveals that Spt4-Spt5 binding is governed by an acid-dipole interaction between Spt5 and Spt4. Mutations that disrupt this interaction disrupt the complex. Residues forming this pivotal interaction are conserved in the archaeal homologs of Spt4 and Spt5, which we show also form a complex. Even though bacteria lack a Spt4 homolog, the NGN domains of Spt5 and its bacterial homologs are structurally similar. Spt4 is located at a position that may help to maintain the functional conformation of the following KOW domains in Spt5. This structural and evolutionary perspective of the Spt4-Spt5 complex and its homologs suggest that it is an ancient, core component of the transcription elongation machinery.
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Affiliation(s)
- Min Guo
- Hefei National Laboratory for Physical Sciences at Microscale and Key Laboratory of Structural Biology, School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230027, China
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13
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Wenzel S, Schweimer K, Rösch P, Wöhrl BM. The small hSpt4 subunit of the human transcription elongation factor DSIF is a Zn-finger protein with α/β type topology. Biochem Biophys Res Commun 2008; 370:414-8. [DOI: 10.1016/j.bbrc.2008.03.080] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2008] [Accepted: 03/19/2008] [Indexed: 10/22/2022]
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14
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Kobayashi MS, Asai S, Ishikawa K, Nishida Y, Nagata T, Takahashi Y. Global profiling of influence of intra-ischemic brain temperature on gene expression in rat brain. ACTA ACUST UNITED AC 2008; 58:171-91. [PMID: 18440647 DOI: 10.1016/j.brainresrev.2008.03.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2007] [Revised: 02/08/2008] [Accepted: 03/08/2008] [Indexed: 12/20/2022]
Abstract
Mild to moderate differences in brain temperature are known to greatly affect the outcome of cerebral ischemia. The impact of brain temperature on ischemic disorders has been mainly evaluated through pathological analysis. However, no comprehensive analyses have been conducted at the gene expression level. Using a high-density oligonucleotide microarray, we screened 24000 genes in the hippocampus under hypothermic (32 degrees C), normothermic (37 degrees C), and hyperthermic (39 degrees C) conditions in a rat ischemia-reperfusion model. When the ischemic group at each intra-ischemic brain temperature was compared to a sham-operated control group, genes whose expression levels changed more than three-fold with statistical significance could be detected. In our screening condition, thirty-three genes (some of them novel) were obtained after screening, and extensive functional surveys and literature reviews were subsequently performed. In the hypothermic condition, many neuroprotective factor genes were obtained, whereas cell death- and cell damage-associated genes were detected as the brain temperature increased. At all intra-ischemic brain temperatures, multiple molecular chaperone genes were obtained. The finding that intra-ischemic brain temperature affects the expression level of many genes related to neuroprotection or neurotoxicity coincides with the different pathological outcomes at different brain temperatures, demonstrating the utility of the genetic approach.
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Affiliation(s)
- Megumi Sugahara Kobayashi
- Division of Genomic Epidemiology and Clinical Trials, Advanced Medical Research Center, Nihon University School of Medicine, Oyaguchi-Kami Machi, Itabashi-ku, Tokyo 173-8610, Japan
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15
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Zhu W, Wada T, Okabe S, Taneda T, Yamaguchi Y, Handa H. DSIF contributes to transcriptional activation by DNA-binding activators by preventing pausing during transcription elongation. Nucleic Acids Res 2007; 35:4064-75. [PMID: 17567605 PMCID: PMC1919491 DOI: 10.1093/nar/gkm430] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The transcription elongation factor 5,6-dichloro-1-β-d-ribofuranosylbenzimidazole (DRB) sensitivity-inducing factor (DSIF) regulates RNA polymerase II (RNAPII) processivity by promoting, in concert with negative elongation factor (NELF), promoter-proximal pausing of RNAPII. DSIF is also reportedly involved in transcriptional activation. However, the role of DSIF in transcriptional activation by DNA-binding activators is unclear. Here we show that DSIF acts cooperatively with a DNA-binding activator, Gal4-VP16, to promote transcriptional activation. In the absence of DSIF, Gal4-VP16-activated transcription resulted in frequent pausing of RNAPII during elongation in vitro. The presence of DSIF reduced pausing, thereby supporting Gal4-VP16-mediated activation. We found that DSIF exerts its positive effects within a short time-frame from initiation to elongation, and that NELF does not affect the positive regulatory function of DSIF. Knockdown of the gene encoding the large subunit of DSIF, human Spt5 (hSpt5), in HeLa cells reduced Gal4-VP16-mediated activation of a reporter gene, but had no effect on expression in the absence of activator. Together, these results provide evidence that higher-level transcription has a stronger requirement for DSIF, and that DSIF contributes to efficient transcriptional activation by preventing RNAPII pausing during transcription elongation.
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Affiliation(s)
- Wenyan Zhu
- Graduate School of Bioscience and Biotechnology and Integrated Research Institute, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan
| | - Tadashi Wada
- Graduate School of Bioscience and Biotechnology and Integrated Research Institute, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan
- *To whom correspondence should be addressed. +81-45-924-5798+81-45-924-5834,
| | - Sachiko Okabe
- Graduate School of Bioscience and Biotechnology and Integrated Research Institute, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan
| | - Takuya Taneda
- Graduate School of Bioscience and Biotechnology and Integrated Research Institute, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan
| | - Yuki Yamaguchi
- Graduate School of Bioscience and Biotechnology and Integrated Research Institute, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan
| | - Hiroshi Handa
- Graduate School of Bioscience and Biotechnology and Integrated Research Institute, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan
- *To whom correspondence should be addressed. +81-45-924-5798+81-45-924-5834,
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16
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Yang Y, Liu W, Zou W, Wang H, Zong H, Jiang J, Wang Y, Gu J. Ubiquitin-dependent proteolysis of trihydrophobin 1 (TH1) by the human papilloma virus E6-associated protein (E6-AP). J Cell Biochem 2007; 101:167-80. [PMID: 17131388 DOI: 10.1002/jcb.21164] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Human Papilloma virus E6-associated protein (E6-AP), which is known as an E3 ubiquitin ligase, mediates ubiquitination and subsequent degradation of a series of cellular proteins. In this paper, we identify here trihydrophobin 1 (TH1), an integral subunit of the human negative transcription elongation factor (NELF) complex, as a novel E6-AP interaction protein and a target of E6-AP-mediated degradation. Overexpression of E6-AP results in degradation of TH1 in a dose-dependent manner, whereas knock-down of endogenous E6-AP elevates the TH1 protein level. TH1 protein turnover is substantially faster, compared to controls, in cells that overexpressed E6-AP. Wild-type E6-AP promotes the ubiquitination of TH1, while a catalytically inactive point mutant of E6-AP abolishes its ubiquitination. Furthermore, in vitro ubiquitination assay also demonstrates that TH1 can be ubiquitinated by E6-AP. The degradation is blocked by treatment with proteasome inhibitor MG132. Herein, we provide strong evidence that TH1 is a specific substrate that is targeted for degradation through E6-AP-catalyzed polyubiquitination.
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Affiliation(s)
- Yanzhong Yang
- Key Laboratory of Medical Molecular Virology Ministry of Education and Health, Gene Research Center, Shanghai Medical College and Institutes of Biomedical Science of Fudan University, Shanghai 200032, P.R. China
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17
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Yamada T, Yamaguchi Y, Inukai N, Okamoto S, Mura T, Handa H. P-TEFb-mediated phosphorylation of hSpt5 C-terminal repeats is critical for processive transcription elongation. Mol Cell 2006; 21:227-37. [PMID: 16427012 DOI: 10.1016/j.molcel.2005.11.024] [Citation(s) in RCA: 282] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2005] [Revised: 09/12/2005] [Accepted: 11/29/2005] [Indexed: 11/17/2022]
Abstract
Human DSIF, a heterodimer composed of hSpt4 and hSpt5, plays opposing roles in transcription elongation by RNA polymerase II (RNA Pol II). Here, we describe an evolutionarily conserved repetitive heptapeptide motif (consensus = G-S-R/Q-T-P) in the C-terminal region (CTR) of hSpt5, which, like the C-terminal domain (CTD) of RNA Pol II, is highly phosphorylated by P-TEFb. Thr-4 residues of the CTR repeats are functionally important phosphorylation sites. In vitro, Thr-4 phosphorylation is critical for the elongation activation activity of DSIF, but not to its elongation repression activity. In vivo, Thr-4 phosphorylation is critical for epidermal growth factor (EGF)-inducible transcription of c-fos and for efficient progression of RNA Pol II along the gene. We consider this phosphorylation to be a switch that converts DSIF from a repressor to an activator. We propose the "mini-CTD" hypothesis, in which phosphorylated CTR is thought to function in a manner analogous to phosphorylated CTD, serving as an additional code for active elongation complexes.
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Affiliation(s)
- Tomoko Yamada
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama 226-8501, Japan
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18
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Xiao Y, Yang YH, Burckin TA, Shiue L, Hartzog GA, Segal MR. Analysis of a splice array experiment elucidates roles of chromatin elongation factor Spt4-5 in splicing. PLoS Comput Biol 2005; 1:e39. [PMID: 16172632 PMCID: PMC1214541 DOI: 10.1371/journal.pcbi.0010039] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2005] [Accepted: 08/08/2005] [Indexed: 11/19/2022] Open
Abstract
Splicing is an important process for regulation of gene expression in eukaryotes, and it has important functional links to other steps of gene expression. Two examples of these linkages include Ceg1, a component of the mRNA capping enzyme, and the chromatin elongation factors Spt4-5, both of which have recently been shown to play a role in the normal splicing of several genes in the yeast Saccharomyces cerevisiae. Using a genomic approach to characterize the roles of Spt4-5 in splicing, we used splicing-sensitive DNA microarrays to identify specific sets of genes that are mis-spliced in ceg1, spt4, and spt5 mutants. In the context of a complex, nested, experimental design featuring 22 dye-swap array hybridizations, comprising both biological and technical replicates, we applied five appropriate statistical models for assessing differential expression between wild-type and the mutants. To refine selection of differential expression genes, we then used a robust model-synthesizing approach, Differential Expression via Distance Synthesis, to integrate all five models. The resultant list of differentially expressed genes was then further analyzed with regard to select attributes: we found that highly transcribed genes with long introns were most sensitive to spt mutations. QPCR confirmation of differential expression was established for the limited number of genes evaluated. In this paper, we showcase splicing array technology, as well as powerful, yet general, statistical methodology for assessing differential expression, in the context of a real, complex experimental design. Our results suggest that the Spt4-Spt5 complex may help coordinate splicing with transcription under conditions that present kinetic challenges to spliceosome assembly or function.
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Affiliation(s)
- Yuanyuan Xiao
- Department of Epidemiology and Biostatistics, Center for Bioinformatics and Molecular Biostatistics, University of California, San Francisco, California, United States of America
| | - Yee H Yang
- Department of Medicine, Center for Bioinformatics and Molecular Biostatistics, University of California, San Francisco, California, United States of America
| | - Todd A Burckin
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California, United States of America
| | - Lily Shiue
- Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California, United States of America
| | - Grant A Hartzog
- Department of Molecular, Cell, and Developmental Biology, University of California, Santa Cruz, California, United States of America
| | - Mark R Segal
- Department of Epidemiology and Biostatistics, Center for Bioinformatics and Molecular Biostatistics, University of California, San Francisco, California, United States of America
- * To whom correspondence should be addressed. E-mail:
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Bucheli ME, Buratowski S. Npl3 is an antagonist of mRNA 3' end formation by RNA polymerase II. EMBO J 2005; 24:2150-60. [PMID: 15902270 PMCID: PMC1150882 DOI: 10.1038/sj.emboj.7600687] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2005] [Accepted: 04/28/2005] [Indexed: 11/09/2022] Open
Abstract
Proper 3' end formation is critical for the production of functional mRNAs. Termination by RNA polymerase II is linked to mRNA cleavage and polyadenylation, but it is less clear whether earlier stages of mRNA production also contribute to transcription termination. We performed a genetic screen to identify mutations that decreased transcriptional readthrough of a defective GAL10 poly(A) terminator. A partial deletion of the GAL10 downstream region leads to transcription through the downstream GAL7 promoter, resulting in the inability of cells to grow on galactose. Mutations in elongation factors Spt4 and Spt6 suppress the readthrough phenotype, presumably by decreasing the amount of polymerase transcribing through the downstream GAL7 promoter. Interestingly, mutations in the mRNA-binding protein Npl3 improve transcription termination. Both in vivo and in vitro experiments suggest that Npl3 can antagonize 3' end formation by competing for RNA binding with polyadenylation/termination factors. These results suggest that elongation rate and mRNA packaging can influence polyadenylation and termination.
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Affiliation(s)
- Miriam E Bucheli
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
| | - Stephen Buratowski
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA, USA
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA. Tel.: +1 617 432 0696; Fax: +1 617 738 0516; E-mail:
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20
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Ping YH, Chu CY, Cao H, Jacque JM, Stevenson M, Rana TM. Modulating HIV-1 replication by RNA interference directed against human transcription elongation factor SPT5. Retrovirology 2004; 1:46. [PMID: 15620346 PMCID: PMC545048 DOI: 10.1186/1742-4690-1-46] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2004] [Accepted: 12/27/2004] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Several cellular positive and negative elongation factors are involved in regulating RNA polymerase II processivity during transcription elongation in human cells. In recruiting several of these regulatory factors to the 5' long terminal repeat (LTR) promoter during transcription elongation, HIV-1 modulates replication of its genome in a process mediated by the virus-encoded transactivator Tat. One particular cellular regulatory factor, DSIF subunit human SPT5 (hSpt5), has been implicated in both positively and negatively regulating transcriptional elongation but its role in Tat transactivation in vivo and in HIV-1 replication has not been completely elucidated. RESULTS To understand the in vivo function of hSpt5 and define its role in Tat transactivation and HIV-1 replication, we used RNA interference (RNAi) to specifically knockdown hSpt5 expression by degrading hSpt5 mRNA. Short-interfering RNA (siRNA) designed to target hSpt5 for RNAi successfully resulted in knockdown of both hSpt5 mRNA and protein levels, and did not significantly affect cell viability. In contrast to hSpt5 knockdown, siRNA-mediated silencing of human mRNA capping enzyme, a functionally important hSpt5-interacting cellular protein, was lethal and showed a significant increase in cell death over the course of the knockdown experiment. In addition, hSpt5 knockdown led to significant decreases in Tat transactivation and inhibited HIV-1 replication, indicating that hSpt5 was required for mediating Tat transactivation and HIV-1 replication. CONCLUSIONS The findings presented here showed that hSpt5 is a bona fide positive regulator of Tat transactivation and HIV-1 replication in vivo. These results also suggest that hSpt5 function in transcription regulation and mRNA capping is essential for a subset of cellular and viral genes and may not be required for global gene expression.
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Affiliation(s)
- Yueh-Hsin Ping
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
- Department and Institute of Pharmacology National Yang-Ming University Shih-Pai, Taipei 11221 Taiwan
| | - Chia-ying Chu
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Hong Cao
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
| | - Jean-Marc Jacque
- Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA 01605, USA
| | - Mario Stevenson
- Program in Molecular Medicine, University of Massachusetts Medical School, 373 Plantation Street, Worcester, MA 01605, USA
| | - Tariq M Rana
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA
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Endoh M, Zhu W, Hasegawa J, Watanabe H, Kim DK, Aida M, Inukai N, Narita T, Yamada T, Furuya A, Sato H, Yamaguchi Y, Mandal SS, Reinberg D, Wada T, Handa H. Human Spt6 stimulates transcription elongation by RNA polymerase II in vitro. Mol Cell Biol 2004; 24:3324-36. [PMID: 15060154 PMCID: PMC381665 DOI: 10.1128/mcb.24.8.3324-3336.2004] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Recent studies have suggested that Spt6 participates in the regulation of transcription by RNA polymerase II (RNAPII). However, its underlying mechanism remains largely unknown. One possibility, which is supported by genetic and biochemical studies of Saccharomyces cerevisiae, is that Spt6 affects chromatin structure. Alternatively, Spt6 directly controls transcription by binding to the transcription machinery. In this study, we establish that human Spt6 (hSpt6) is a classic transcription elongation factor that enhances the rate of RNAPII elongation. hSpt6 is capable of stimulating transcription elongation both individually and in concert with DRB sensitivity-inducing factor (DSIF), comprising human Spt5 and human Spt4. We also provide evidence showing that hSpt6 interacts with RNAPII and DSIF in human cells. Thus, in vivo, hSpt6 may regulate multiple steps of mRNA synthesis through its interaction with histones, elongating RNAPII, and possibly other components of the transcription machinery.
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Affiliation(s)
- Masaki Endoh
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8501, Japan
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22
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Mellor J, Morillon A. ISWI complexes in Saccharomyces cerevisiae. ACTA ACUST UNITED AC 2004; 1677:100-12. [PMID: 15020051 DOI: 10.1016/j.bbaexp.2003.10.014] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2003] [Revised: 10/23/2003] [Accepted: 10/23/2003] [Indexed: 10/26/2022]
Abstract
The imitation switch (ISWI) class of chromatin remodeling ATPase is ubiquitous in eukaryotes. It is becoming clear that these enzymes exist as part of larger complexes and the nature of the associated proteins dictate the function associated with a complex both in biochemical assays and in the cell. Much progress has been made in understanding these relationships in the budding yeast Saccharomyces cerevisiae, containing two ATPases, Isw1p and Isw2p. This has been aided by the ease of genetic manipulation, by a number of systematic screens designed to specifically detect ISWI function and by the plethora of data generated from a number of global screens for function. At present, many functions for yeast Isw1p and Isw2p are related to effects on RNA levels and are associated with the controlled repression of gene expression that crudely fall into three types: displacement of the basal transcription machinery to repress or silence transcription of genes (Isw2 complex and Isw1/Ioc3 complex); control of the activation of expression leading to coordination of transcription elongation; and efficient termination of transcription (Isw1/Ioc4/Ioc2 complex). The latter two functions are regulated by specific phosphorylation of residues within the carboxy terminal domain (CTD) of the largest subunit of RNA polymerase II (RNAPII). Other functions may relate to the ability of ISWI complex to displace transcription factors or enzymes from the template. Other ISWI-containing complexes that have yet to be characterized indicate that much remains to be learnt about yeast ISWI itself and importantly, how the various forms cooperate with different classes of chromatin remodeling ATPase, complexes containing histone acetylases, deacetylases, methylases and both DNA and RNA polymerases.
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Affiliation(s)
- Jane Mellor
- Department of Biochemistry, Microbiology Unit, University of Oxford, South Parks Road, Oxford OX1 3QU, UK.
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