401
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Abstract
Most transcription factors specify the subset of genes that will be actively transcribed in the cell by stimulating transcription initiation at these genes, but MYC has a fundamentally different role. MYC binds E-box sites in the promoters of active genes and stimulates recruitment of the elongation factor P-TEFb and thus transcription elongation. Consequently, rather than specifying the set of genes that will be transcribed in any particular cell, MYC's predominant role is to increase the production of transcripts from active genes. This increase in the transcriptional output of the cell's existing gene expression program, called transcriptional amplification, has a profound effect on proliferation and other behaviors of a broad range of cells. Transcriptional amplification may reduce rate-limiting constraints for tumor cell proliferation and explain MYC's broad oncogenic activity among diverse tissues.
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Affiliation(s)
- Peter B Rahl
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142
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402
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Mbogning J, Nagy S, Pagé V, Schwer B, Shuman S, Fisher RP, Tanny JC. The PAF complex and Prf1/Rtf1 delineate distinct Cdk9-dependent pathways regulating transcription elongation in fission yeast. PLoS Genet 2013; 9:e1004029. [PMID: 24385927 PMCID: PMC3873232 DOI: 10.1371/journal.pgen.1004029] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Accepted: 10/31/2013] [Indexed: 11/19/2022] Open
Abstract
Cyclin-dependent kinase 9 (Cdk9) promotes elongation by RNA polymerase II (RNAPII), mRNA processing, and co-transcriptional histone modification. Cdk9 phosphorylates multiple targets, including the conserved RNAPII elongation factor Spt5 and RNAPII itself, but how these different modifications mediate Cdk9 functions is not known. Here we describe two Cdk9-dependent pathways in the fission yeast Schizosaccharomyces pombe that involve distinct targets and elicit distinct biological outcomes. Phosphorylation of Spt5 by Cdk9 creates a direct binding site for Prf1/Rtf1, a transcription regulator with functional and physical links to the Polymerase Associated Factor (PAF) complex. PAF association with chromatin is also dependent on Cdk9 but involves alternate phosphoacceptor targets. Prf1 and PAF are biochemically separate in cell extracts, and genetic analyses show that Prf1 and PAF are functionally distinct and exert opposing effects on the RNAPII elongation complex. We propose that this opposition constitutes a Cdk9 auto-regulatory mechanism, such that a positive effect on elongation, driven by the PAF pathway, is kept in check by a negative effect of Prf1/Rtf1 and downstream mono-ubiquitylation of histone H2B. Thus, optimal RNAPII elongation may require balanced action of functionally distinct Cdk9 pathways.
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Affiliation(s)
- Jean Mbogning
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Stephen Nagy
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Viviane Pagé
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
| | - Beate Schwer
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
| | - Stewart Shuman
- Molecular Biology Program, Memorial Sloan-Kettering Cancer Center, New York, New York, United States of America
| | - Robert P. Fisher
- Department of Structural and Chemical Biology, Icahn School of Medicine at Mount Sinai, New York, New York, United States of America
| | - Jason C. Tanny
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Canada
- * E-mail:
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403
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AFF1 is a ubiquitous P-TEFb partner to enable Tat extraction of P-TEFb from 7SK snRNP and formation of SECs for HIV transactivation. Proc Natl Acad Sci U S A 2013; 111:E15-24. [PMID: 24367103 DOI: 10.1073/pnas.1318503111] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The positive transcription elongation factor b (P-TEFb) stimulates RNA polymerase elongation by inducing the transition of promoter proximally paused polymerase II into a productively elongating state. P-TEFb itself is regulated by reversible association with various transcription factors/cofactors to form several multisubunit complexes [e.g., the 7SK small nuclear ribonucleoprotein particle (7SK snRNP), the super elongation complexes (SECs), and the bromodomain protein 4 (Brd4)-P-TEFb complex] that constitute a P-TEFb network controlling cellular and HIV transcription. These complexes have been thought to share no components other than the core P-TEFb subunits cyclin-dependent kinase 9 (CDK9) and cyclin T (CycT, T1, T2a, and T2b). Here we show that the AF4/FMR2 family member 1 (AFF1) is bound to CDK9-CycT and is present in all major P-TEFb complexes and that the tripartite CDK9-CycT-AFF1 complex is transferred as a single unit within the P-TEFb network. By increasing the affinity of the HIV-encoded transactivating (Tat) protein for CycT1, AFF1 facilitates Tat's extraction of P-TEFb from 7SK snRNP and the formation of Tat-SECs for HIV transcription. Our data identify AFF1 as a ubiquitous P-TEFb partner and demonstrate that full Tat transactivation requires the complete SEC.
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404
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Anders L, Guenther MG, Qi J, Fan ZP, Marineau JJ, Rahl PB, Lovén J, Sigova AA, Smith WB, Lee TI, Bradner JE, Young RA. Genome-wide localization of small molecules. Nat Biotechnol 2013; 32:92-6. [PMID: 24336317 PMCID: PMC4189815 DOI: 10.1038/nbt.2776] [Citation(s) in RCA: 148] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 11/20/2013] [Indexed: 12/28/2022]
Abstract
A vast number of small-molecule ligands, including therapeutic drugs under development and in clinical use, elicit their effects by binding specific proteins associated with the genome. An ability to map the direct interactions of a chemical entity with chromatin genome-wide could provide important insights into chemical perturbation of cellular function. Here we describe a method that couples ligand-affinity capture and massively parallel DNA sequencing (Chem-seq) to identify the sites bound by small chemical molecules throughout the human genome. We show how Chem-seq can be combined with ChIP-seq to gain unique insights into the interaction of drugs with their target proteins throughout the genome of tumor cells. These methods will be broadly useful to enhance understanding of therapeutic action and to characterize the specificity of chemical entities that interact with DNA or genome-associated proteins.
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Affiliation(s)
- Lars Anders
- 1] Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, USA. [2]
| | - Matthew G Guenther
- 1] Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, USA. [2]
| | - Jun Qi
- Department of Medical Oncology, Dana-Farber Cancer Institute, Massachusetts, USA
| | - Zi Peng Fan
- 1] Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, USA. [2] Computational and Systems Biology Program, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
| | - Jason J Marineau
- Department of Medical Oncology, Dana-Farber Cancer Institute, Massachusetts, USA
| | - Peter B Rahl
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, USA
| | - Jakob Lovén
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, USA
| | - Alla A Sigova
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, USA
| | - William B Smith
- Department of Medical Oncology, Dana-Farber Cancer Institute, Massachusetts, USA
| | - Tong Ihn Lee
- Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, USA
| | - James E Bradner
- 1] Department of Medical Oncology, Dana-Farber Cancer Institute, Massachusetts, USA. [2] Department of Medicine, Harvard Medical School, Massachusetts, USA
| | - Richard A Young
- 1] Whitehead Institute for Biomedical Research, Cambridge, Massachusetts, USA. [2] Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA
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405
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Transcription factors mediate the enzymatic disassembly of promoter-bound 7SK snRNP to locally recruit P-TEFb for transcription elongation. Cell Rep 2013; 5:1256-68. [PMID: 24316072 DOI: 10.1016/j.celrep.2013.11.003] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 10/02/2013] [Accepted: 11/02/2013] [Indexed: 12/19/2022] Open
Abstract
The transition from transcription initiation into elongation is controlled by transcription factors, which recruit positive transcription elongation factor b (P-TEFb) to promoters to phosphorylate RNA polymerase II. A fraction of P-TEFb is recruited as part of the inhibitory 7SK small nuclear ribonucleoprotein particle (snRNP), which inactivates the kinase and prevents elongation. However, it is unclear how P-TEFb is captured from the promoter-bound 7SK snRNP to activate elongation. Here, we describe a mechanism by which transcription factors mediate the enzymatic release of P-TEFb from the 7SK snRNP at promoters to trigger activation in a gene-specific manner. We demonstrate that Tat recruits PPM1G/PP2Cγ to locally disassemble P-TEFb from the 7SK snRNP at the HIV promoter via dephosphorylation of the kinase T loop. Similar to Tat, nuclear factor (NF)-κB recruits PPM1G in a stimulus-dependent manner to activate elongation at inflammatory-responsive genes. Recruitment of PPM1G to promoter-assembled 7SK snRNP provides a paradigm for rapid gene activation through transcriptional pause release.
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406
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Affiliation(s)
- Jiannan Guo
- Biochemistry Department, University of Iowa , Iowa City, Iowa 52242, United States
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407
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Coiras M, Montes M, Montanuy I, López-Huertas MR, Mateos E, Le Sommer C, Garcia-Blanco MA, Hernández-Munain C, Alcamí J, Suñé C. Transcription elongation regulator 1 (TCERG1) regulates competent RNA polymerase II-mediated elongation of HIV-1 transcription and facilitates efficient viral replication. Retrovirology 2013; 10:124. [PMID: 24165037 PMCID: PMC3874760 DOI: 10.1186/1742-4690-10-124] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 10/18/2013] [Indexed: 12/30/2022] Open
Abstract
Background Control of RNA polymerase II (RNAPII) release from pausing has been proposed as a checkpoint mechanism to ensure optimal RNAPII activity, especially in large, highly regulated genes. HIV-1 gene expression is highly regulated at the level of elongation, which includes transcriptional pausing that is mediated by both viral and cellular factors. Here, we present evidence for a specific role of the elongation-related factor TCERG1 in regulating the extent of HIV-1 elongation and viral replication in vivo. Results We show that TCERG1 depletion diminishes the basal and viral Tat-activated transcription from the HIV-1 LTR. In support of a role for an elongation mechanism in the transcriptional control of HIV-1, we found that TCERG1 modifies the levels of pre-mRNAs generated at distal regions of HIV-1. Most importantly, TCERG1 directly affects the elongation rate of RNAPII transcription in vivo. Furthermore, our data demonstrate that TCERG1 regulates HIV-1 transcription by increasing the rate of RNAPII elongation through the phosphorylation of serine 2 within the carboxyl-terminal domain (CTD) of RNAPII and suggest a mechanism for the involvement of TCERG1 in relieving pausing. Finally, we show that TCERG1 is required for HIV-1 replication. Conclusions Our study reveals that TCERG1 regulates HIV-1 transcriptional elongation by increasing the elongation rate of RNAPII and phosphorylation of Ser 2 within the CTD. Based on our data, we propose a general mechanism for TCERG1 acting on genes that are regulated at the level of elongation by increasing the rate of RNAPII transcription through the phosphorylation of Ser2. In the case of HIV-1, our evidence provides the basis for further investigation of TCERG1 as a potential therapeutic target for the inhibition of HIV-1 replication
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Affiliation(s)
| | | | | | | | | | | | | | | | | | - Carlos Suñé
- Department of Molecular Biology, Instituto de Parasitología y Biomedicina "López Neyra" (IPBLN-CSIC), Armilla, Granada 18016, Spain.
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408
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Dowen J, Bilodeau S, Orlando D, Hübner M, Abraham B, Spector D, Young R. Multiple structural maintenance of chromosome complexes at transcriptional regulatory elements. Stem Cell Reports 2013; 1:371-8. [PMID: 24286025 PMCID: PMC3841252 DOI: 10.1016/j.stemcr.2013.09.002] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 09/12/2013] [Accepted: 09/13/2013] [Indexed: 01/17/2023] Open
Abstract
Transcription factors control cell-specific gene expression programs by binding regulatory elements and recruiting cofactors and the transcription apparatus to the initiation sites of active genes. One of these cofactors is cohesin, a structural maintenance of chromosomes (SMC) complex that is necessary for proper gene expression. We report that a second SMC complex, condensin II, is also present at transcriptional regulatory elements of active genes during interphase and is necessary for normal gene activity. Both cohesin and condensin II are associated with genes in euchromatin and not heterochromatin. The two SMC complexes and the SMC loading factor NIPBL are particularly enriched at super-enhancers, and the genes associated with these regulatory elements are especially sensitive to reduced levels of these complexes. Thus, in addition to their well-established functions in chromosome maintenance during mitosis, both cohesin and condensin II make important contributions to the functions of the key transcriptional regulatory elements during interphase.
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Affiliation(s)
- Jill M. Dowen
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA
| | - Steve Bilodeau
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA
| | - David A. Orlando
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA
| | - Michael R. Hübner
- Cold Spring Harbor Laboratory, One Bungtown Road, Cold Spring Harbor, NY 11724, USA
| | - Brian J. Abraham
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA
| | - David L. Spector
- Cold Spring Harbor Laboratory, One Bungtown Road, Cold Spring Harbor, NY 11724, USA
| | - Richard A. Young
- Whitehead Institute for Biomedical Research, 9 Cambridge Center, Cambridge, MA 02142, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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409
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Abstract
Recent advances in the enzymology of transcription and chromatin regulation have led to the discovery of proteins that play a prominent role in cell differentiation and the maintenance of specialized cell functions. Knowledge about post-synthetic DNA and histone modifications as well as information about the rules that guide the formation of multimolecular chromatin-bound complexes have helped to delineate gene-regulating pathways and describe how these pathways are altered in various pathological conditions. The present review focuses on the emerging area of therapeutic interference with chromatin function for the purpose of cancer treatment and immunomodulation.
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Affiliation(s)
- Rab Prinjha
- Epinova DPU, Immuno-Inflammation Therapy Area, Medicines Research Centre, GlaxoSmithKline, Stevenage SG1 2NY, United Kingdom
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410
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Abstract
The Mediator complex is a multi-subunit assembly that appears to be required for regulating expression of most RNA polymerase II (pol II) transcripts, which include protein-coding and most non-coding RNA genes. Mediator and pol II function within the pre-initiation complex (PIC), which consists of Mediator, pol II, TFIIA, TFIIB, TFIID, TFIIE, TFIIF and TFIIH and is approximately 4.0 MDa in size. Mediator serves as a central scaffold within the PIC and helps regulate pol II activity in ways that remain poorly understood. Mediator is also generally targeted by sequence-specific, DNA-binding transcription factors (TFs) that work to control gene expression programs in response to developmental or environmental cues. At a basic level, Mediator functions by relaying signals from TFs directly to the pol II enzyme, thereby facilitating TF-dependent regulation of gene expression. Thus, Mediator is essential for converting biological inputs (communicated by TFs) to physiological responses (via changes in gene expression). In this review, we summarize an expansive body of research on the Mediator complex, with an emphasis on yeast and mammalian complexes. We focus on the basics that underlie Mediator function, such as its structure and subunit composition, and describe its broad regulatory influence on gene expression, ranging from chromatin architecture to transcription initiation and elongation, to mRNA processing. We also describe factors that influence Mediator structure and activity, including TFs, non-coding RNAs and the CDK8 module.
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Affiliation(s)
- Zachary C Poss
- Department of Chemistry and Biochemistry, University of Colorado , Boulder, CO , USA
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411
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Shimamoto N. Nanobiology of RNA polymerase: biological consequence of inhomogeneity in reactant. Chem Rev 2013; 113:8400-22. [PMID: 24074222 DOI: 10.1021/cr400006b] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Nobuo Shimamoto
- Faculty of Life Sciences, Kyoto Sangyo University , Kamigamo-Motoyama, Kita-Ku, Kyoto, 603-8555 Japan
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412
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Lewis BA. O-GlcNAcylation at promoters, nutrient sensors, and transcriptional regulation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2013; 1829:1202-6. [PMID: 24076017 DOI: 10.1016/j.bbagrm.2013.09.003] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2013] [Revised: 09/16/2013] [Accepted: 09/18/2013] [Indexed: 12/22/2022]
Abstract
Post-translational modifications play important roles in transcriptional regulation. Among the less understood PTMs is O-GlcNAcylation. Nevertheless, O-GlcNAcylation in the nucleus is found on hundreds of transcription factors and coactivators and is often found in a mutually exclusive ying-yang relationship with phosphorylation. O-GlcNAcylation also links cellular metabolism directly to the proteome, serving as a conduit of metabolic information to the nucleus. This review serves as a brief introduction to O-GlcNAcylation, emphasizing its important thematic roles in transcriptional regulation, and highlights several recent and important additions to the literature that illustrate the connections between O-GlcNAc and transcription.
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Affiliation(s)
- Brian A Lewis
- Metabolism Branch, CCR/NCI/NIH, 9000 Rockville Pike, Bethesda, MD 20892, USA.
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413
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Chu X, Qin X, Xu H, Li L, Wang Z, Li F, Xie X, Zhou H, Shen Y, Long J. Structural insights into Paf1 complex assembly and histone binding. Nucleic Acids Res 2013; 41:10619-29. [PMID: 24038468 PMCID: PMC3905892 DOI: 10.1093/nar/gkt819] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
The highly conserved Paf1 complex (PAF1C) plays critical roles in RNA polymerase II transcription elongation and in the regulation of histone modifications. It has also been implicated in other diverse cellular activities, including posttranscriptional events, embryonic development and cell survival and maintenance of embryonic stem cell identity. Here, we report the structure of the human Paf1/Leo1 subcomplex within PAF1C. The overall structure reveals that the Paf1 and Leo1 subunits form a tightly associated heterodimer through antiparallel beta-sheet interactions. Detailed biochemical experiments indicate that Leo1 binds to PAF1C through Paf1 and that the Ctr9 subunit is the key scaffold protein in assembling PAF1C. Furthermore, we show that the Paf1/Leo1 heterodimer is necessary for its binding to histone H3, the histone octamer, and nucleosome in vitro. Our results shed light on the PAF1C assembly process and substrate recognition during various PAF1C-coordinated histone modifications.
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Affiliation(s)
- Xinlei Chu
- State Key Laboratory of Medicinal Chemical Biology, Nankai University, 94 Weijin Road, Tianjin 300071, China, College of Life Sciences, Nankai University, 94 Weijin Road, Tianjin 300071, China and Synergetic Innovation Center of Chemical Science and Engineering, 94 Weijin Road, Tianjin 300071, China
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414
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Abstract
Elongation is becoming increasingly recognized as a critical step in eukaryotic transcriptional regulation. Although traditional genetic and biochemical studies have identified major players of transcriptional elongation, our understanding of the importance and roles of these factors is evolving rapidly through the recent advances in genome-wide and single-molecule technologies. Here, we focus on how elongation can modulate the transcriptional outcome through the rate-liming step of RNA polymerase II (Pol II) pausing near promoters and how the participating factors were identified. Among the factors we describe are the pausing factors--NELF (negative elongation factor) and DSIF (DRB sensitivity-inducing factor)--and P-TEFb (positive elongation factor b), which is the key player in pause release. We also describe the high-resolution view of Pol II pausing and propose nonexclusive models for how pausing is achieved. We then discuss Pol II elongation through the bodies of genes and the roles of FACT and SPT6, factors that allow Pol II to move through nucleosomes.
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Affiliation(s)
- Hojoong Kwak
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14853-2703; ,
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415
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Affiliation(s)
- Dirk Eick
- Department of Molecular Epigenetics, Helmholtz Center Munich and Center for Integrated Protein Science Munich (CIPSM), Marchioninistrasse 25, 81377 Munich,
Germany
| | - Matthias Geyer
- Center of Advanced European Studies and Research, Group Physical Biochemistry,
Ludwig-Erhard-Allee 2, 53175 Bonn, Germany
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416
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Proserpio V, Fittipaldi R, Ryall JG, Sartorelli V, Caretti G. The methyltransferase SMYD3 mediates the recruitment of transcriptional cofactors at the myostatin and c-Met genes and regulates skeletal muscle atrophy. Genes Dev 2013; 27:1299-312. [PMID: 23752591 DOI: 10.1101/gad.217240.113] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Elucidating the epigenetic mechanisms underlying muscle mass determination and skeletal muscle wasting holds the potential of identifying molecular pathways that constitute possible drug targets. Here, we report that the methyltransferase SMYD3 modulates myostatin and c-Met transcription in primary skeletal muscle cells and C2C12 myogenic cells. SMYD3 targets the myostatin and c-Met genes and participates in the recruitment of the bromodomain protein BRD4 to their regulatory regions through protein-protein interaction. By recruiting BRD4, SMYD3 favors chromatin engagement of the pause-release factor p-TEFb (positive transcription elongation factor) and elongation of Ser2-phosphorylated RNA polymerase II (PolIISer2P). Reducing SMYD3 decreases myostatin and c-Met transcription, thus protecting from glucocorticoid-induced myotube atrophy. Supporting functional relevance of the SMYD3/BRD4 interaction, BRD4 pharmacological blockade by the small molecule JQ1 prevents dexamethasone-induced myostatin and atrogene up-regulation and spares myotube atrophy. Importantly, in a mouse model of dexamethasone-induced skeletal muscle atrophy, SMYD3 depletion prevents muscle loss and fiber size decrease. These findings reveal a mechanistic link between SMYD3/BRD4-dependent transcriptional regulation, muscle mass determination, and skeletal muscle atrophy and further encourage testing of small molecules targeting specific epigenetic regulators in animal models of muscle wasting.
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417
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Adamik J, Wang KZQ, Unlu S, Su AJA, Tannahill GM, Galson DL, O’Neill LA, Auron PE. Distinct mechanisms for induction and tolerance regulate the immediate early genes encoding interleukin 1β and tumor necrosis factor α. PLoS One 2013; 8:e70622. [PMID: 23936458 PMCID: PMC3731334 DOI: 10.1371/journal.pone.0070622] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Accepted: 06/19/2013] [Indexed: 12/16/2022] Open
Abstract
Interleukin-1β and Tumor Necrosis Factor α play related, but distinct, roles in immunity and disease. Our study revealed major mechanistic distinctions in the Toll-like receptor (TLR) signaling-dependent induction for the rapidly expressed genes (IL1B and TNF) coding for these two cytokines. Prior to induction, TNF exhibited pre-bound TATA Binding Protein (TBP) and paused RNA Polymerase II (Pol II), hallmarks of poised immediate-early (IE) genes. In contrast, unstimulated IL1B displayed very low levels of both TBP and paused Pol II, requiring the lineage-specific Spi-1/PU.1 (Spi1) transcription factor as an anchor for induction-dependent interaction with two TLR-activated transcription factors, C/EBPβ and NF-κB. Activation and DNA binding of these two pre-expressed factors resulted in de novo recruitment of TBP and Pol II to IL1B in concert with a permissive state for elongation mediated by the recruitment of elongation factor P-TEFb. This Spi1-dependent mechanism for IL1B transcription, which is unique for a rapidly-induced/poised IE gene, was more dependent upon P-TEFb than was the case for the TNF gene. Furthermore, the dependence on phosphoinositide 3-kinase for P-TEFb recruitment to IL1B paralleled a greater sensitivity to the metabolic state of the cell and a lower sensitivity to the phenomenon of endotoxin tolerance than was evident for TNF. Such differences in induction mechanisms argue against the prevailing paradigm that all IE genes possess paused Pol II and may further delineate the specific roles played by each of these rapidly expressed immune modulators.
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Affiliation(s)
- Juraj Adamik
- Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania, United States of America
| | - Kent Z. Q. Wang
- Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania, United States of America
| | - Sebnem Unlu
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - An-Jey A. Su
- Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania, United States of America
| | | | - Deborah L. Galson
- Division of Hematology/Oncology, Department of Medicine, University of Pittsburgh Cancer Institute, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Luke A. O’Neill
- School of Biochemistry and Immunology, Trinity College Dublin, Dublin, Ireland
| | - Philip E. Auron
- Department of Biological Sciences, Duquesne University, Pittsburgh, Pennsylvania, United States of America
- Department of Microbiology and Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- * E-mail:
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418
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Bowman EA, Bowman CR, Ahn JH, Kelly WG. Phosphorylation of RNA polymerase II is independent of P-TEFb in the C. elegans germline. Development 2013; 140:3703-13. [PMID: 23903194 DOI: 10.1242/dev.095778] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
RNA polymerase II (Pol II) elongation in metazoans is thought to require phosphorylation of serine 2 (Ser2-P) of the Pol II C-terminal domain (CTD) by the P-TEFb complex, CDK-9/cyclin T. Another Ser2 kinase complex, CDK-12/cyclin K, which requires upstream CDK-9 activity has been identified in Drosophila and human cells. We show that regulation of Ser2-P in C. elegans soma is similar to other metazoan systems, but Ser2-P in the germline is independent of CDK-9, and largely requires only CDK-12. The observed differences are not due to differential tissue expression as both kinases and their cyclin partners are ubiquitously expressed. Surprisingly, loss of CDK-9 from germ cells has little effect on Ser2-P, yet CDK-9 is essential for germline development. By contrast, loss of CDK-12 and Ser2-P specifically from germ cells has little impact on germline development or function, although significant loss of co-transcriptional H3K36 trimethylation is observed. These results show a reduced requirement for Pol II Ser2-P in germline development and suggest that generating Ser2-P is not the essential role of CDK-9 in these cells. Transcriptional elongation in the C. elegans germline thus appears to be uniquely regulated, which may be a novel facet of germline identity.
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419
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Harvey R, Schuster E, Jennings BH. Pleiohomeotic interacts with the core transcription elongation factor Spt5 to regulate gene expression in Drosophila. PLoS One 2013; 8:e70184. [PMID: 23894613 PMCID: PMC3718797 DOI: 10.1371/journal.pone.0070184] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2013] [Accepted: 06/17/2013] [Indexed: 11/26/2022] Open
Abstract
The early elongation checkpoint regulated by Positive Transcription Elongation Factor b (P-TEFb) is a critical control point for the expression of many genes. Spt5 interacts directly with RNA polymerase II and has an essential role in establishing this checkpoint, and also for further transcript elongation. Here we demonstrate that Drosophila Spt5 interacts both physically and genetically with the Polycomb Group (PcG) protein Pleiohomeotic (Pho), and the majority of Pho binding sites overlap with Spt5 binding sites across the genome in S2 cells. Our results indicate that Pho can interact with Spt5 to regulate transcription elongation in a gene specific manner.
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Affiliation(s)
- Robert Harvey
- Transcriptional Regulation Group, UCL Cancer Institute, University College London, London, United Kingdom
| | - Eugene Schuster
- Department of Genetics, Evolution and Environment, University College London, London, United Kingdom
| | - Barbara H. Jennings
- Transcriptional Regulation Group, UCL Cancer Institute, University College London, London, United Kingdom
- * E-mail:
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420
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Smith E, Shilatifard A. Transcriptional elongation checkpoint control in development and disease. Genes Dev 2013; 27:1079-88. [PMID: 23699407 DOI: 10.1101/gad.215137.113] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Transcriptional elongation control by RNA polymerase II and its associated factors has taken center stage as a process essential for the regulation of gene expression throughout development. In this review, we analyze recent findings on the identification of factors functioning in the regulation of the transcriptional elongation checkpoint control (TECC) stage of gene expression and how the factors' misregulation is associated with disease pathogenesis, including cancer.
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Affiliation(s)
- Edwin Smith
- Stowers Institute for Medical Research, Kansas City, Missouri 64110, USA
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421
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Ji X, Zhou Y, Pandit S, Huang J, Li H, Lin CY, Xiao R, Burge CB, Fu XD. SR proteins collaborate with 7SK and promoter-associated nascent RNA to release paused polymerase. Cell 2013; 153:855-68. [PMID: 23663783 DOI: 10.1016/j.cell.2013.04.028] [Citation(s) in RCA: 244] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Revised: 03/14/2013] [Accepted: 04/15/2013] [Indexed: 10/26/2022]
Abstract
RNAP II is frequently paused near gene promoters in mammals, and its transition to productive elongation requires active recruitment of P-TEFb, a cyclin-dependent kinase for RNAP II and other key transcription elongation factors. A fraction of P-TEFb is sequestered in an inhibitory complex containing the 7SK noncoding RNA, but it has been unclear how P-TEFb is switched from the 7SK complex to RNAP II during transcription activation. We report that SRSF2 (also known as SC35, an SR-splicing factor) is part of the 7SK complex assembled at gene promoters and plays a direct role in transcription pause release. We demonstrate RNA-dependent, coordinated release of SRSF2 and P-TEFb from the 7SK complex and transcription activation via SRSF2 binding to promoter-associated nascent RNA. These findings reveal an unanticipated SR protein function, a role for promoter-proximal nascent RNA in gene activation, and an analogous mechanism to HIV Tat/TAR for activating cellular genes.
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Affiliation(s)
- Xiong Ji
- State Key Laboratory of Virology, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China
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422
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Balancing chromatin remodeling and histone modifications in transcription. Trends Genet 2013; 29:621-9. [PMID: 23870137 DOI: 10.1016/j.tig.2013.06.006] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 05/29/2013] [Accepted: 06/18/2013] [Indexed: 11/24/2022]
Abstract
Chromatin remodelers use the energy of ATP hydrolysis to reposition or evict nucleosomes or to replace canonical histones with histone variants. By regulating nucleosome dynamics, remodelers gate access to the underlying DNA for replication, repair, and transcription. Nucleosomes are subject to extensive post-translational modifications that can recruit regulatory proteins or alter the local chromatin structure. Just as extensive crosstalk has been observed between different histone post-translational modifications, there is growing evidence for both coordinated and antagonistic functional relations between nucleosome remodeling and modifying machineries. Defining the combined functions of the complexes that alter nucleosome interactions, position, and stability is key to understanding processes that require access to DNA, particularly with growing appreciation of their contributions to human health and disease. Here, we highlight recent advances in the interactions between histone modifications and the imitation-switch (ISWI) and chromodomain helicase DNA-binding protein 1 (CHD1) chromatin remodelers from studies in budding yeast, fission yeast, flies, and mammalian cells, with a focus on yeast.
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423
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Jeronimo C, Bataille AR, Robert F. The Writers, Readers, and Functions of the RNA Polymerase II C-Terminal Domain Code. Chem Rev 2013; 113:8491-522. [DOI: 10.1021/cr4001397] [Citation(s) in RCA: 89] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Célia Jeronimo
- Institut de recherches cliniques de Montréal, Montréal, Québec,
Canada H2W 1R7
| | - Alain R. Bataille
- Institut de recherches cliniques de Montréal, Montréal, Québec,
Canada H2W 1R7
| | - François Robert
- Institut de recherches cliniques de Montréal, Montréal, Québec,
Canada H2W 1R7
- Département
de Médecine,
Faculté de Médecine, Université de Montréal, Montréal, Québec,
Canada H3T 1J4
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424
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Kawauchi J, Inoue M, Fukuda M, Uchida Y, Yasukawa T, Conaway RC, Conaway JW, Aso T, Kitajima S. Transcriptional properties of mammalian elongin A and its role in stress response. J Biol Chem 2013; 288:24302-15. [PMID: 23828199 DOI: 10.1074/jbc.m113.496703] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Elongin A was shown previously to be capable of potently activating the rate of RNA polymerase II (RNAPII) transcription elongation in vitro by suppressing transient pausing by the enzyme at many sites along DNA templates. The role of Elongin A in RNAPII transcription in mammalian cells, however, has not been clearly established. In this report, we investigate the function of Elongin A in RNAPII transcription. We present evidence that Elongin A associates with the IIO form of RNAPII at sites of newly transcribed RNA and is relocated to dotlike domains distinct from those containing RNAPII when cells are treated with the kinase inhibitor 5,6-dichloro-1-β-d-ribofuranosylbenzimidazole. Significantly, Elongin A is required for maximal induction of transcription of the stress response genes ATF3 and p21 in response to several stimuli. Evidence from structure-function studies argues that Elongin A transcription elongation activity, but not its ubiquitination activity, is most important for its function in induction of transcription of ATF3 and p21. Taken together, our data provide new insights into the function of Elongin A in RNAPII transcription and bring to light a previously unrecognized role for Elongin A in the regulation of stress response genes.
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Affiliation(s)
- Junya Kawauchi
- Department of Biochemical Genetics, Medical Research Institute, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
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425
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Cks1 enhances transcription efficiency at the GAL1 locus by linking the Paf1 complex to the 19S proteasome. EUKARYOTIC CELL 2013; 12:1192-201. [PMID: 23825181 DOI: 10.1128/ec.00151-13] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Cks1 was originally identified based on genetic interactions with CDC28, the gene that encodes Cdk1 in the budding yeast Saccharomyces cerevisiae. Subsequent work has shown that Cks1 binds Cdc28 and modulates its activity against certain substrates. However, the Cks1/Cdc28 complex also has a role in transcriptional chromatin remodeling not related to kinase activity. In order to elucidate protein networks associated with Cks1 transcriptional functions, proteomic analysis was performed on immunoaffinity-purified Cks1, identifying a physical interaction with the Paf1 complex. Specifically, we found that the Paf1 complex component Rtf1 interacts directly with Cks1 and that this interaction is essential for efficient recruitment of Cks1 to chromatin in the context of GAL1 gene induction. We further found that Cks1 in this capacity serves as an adaptor allowing Rtf1 to recruit 19S proteasome particles, shown to be required for efficient RNA production from some rapidly inducible genes such as GAL1.
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426
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Lu H, Li Z, Xue Y, Zhou Q. Viral-host interactions that control HIV-1 transcriptional elongation. Chem Rev 2013; 113:8567-82. [PMID: 23795863 DOI: 10.1021/cr400120z] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Huasong Lu
- School of Pharmaceutical Sciences, Xiamen University , Xiamen, Fujian 361005, China
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427
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Nayak D, Voss M, Windgassen T, Mooney RA, Landick R. Cys-pair reporters detect a constrained trigger loop in a paused RNA polymerase. Mol Cell 2013; 50:882-93. [PMID: 23769674 DOI: 10.1016/j.molcel.2013.05.015] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 04/10/2013] [Accepted: 05/07/2013] [Indexed: 01/22/2023]
Abstract
Transcriptional pausing, which regulates transcript elongation in both prokaryotes and eukaryotes, is thought to involve formation of alternative RNA polymerase conformations in which nucleotide addition is inhibited in part by restriction of trigger loop (TL) folding. The polymorphous TL must convert from a random coil to a helical hairpin that contacts the nucleotide triphosphate (NTP) substrate to allow rapid nucleotide addition. Understanding the distribution of TL conformations in different enzyme states is made difficult by the TL's small size and sensitive energetics. Here, we report a Cys-pair reporter strategy to elucidate the relative occupancies of different TL conformations in E. coli RNA polymerase based on the ability of Cys residues engineered into the TL and surrounding regions to form disulfide bonds. Our results indicate that a paused complex stabilized by a nascent RNA hairpin favors nonproductive TL conformations that persist after NTP binding but can be reversed by the elongation factor RfaH.
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Affiliation(s)
- Dhananjaya Nayak
- Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706, USA
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428
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Flajollet S, Rachez C, Ploton M, Schulz C, Gallais R, Métivier R, Pawlak M, Leray A, Issulahi AA, Héliot L, Staels B, Salbert G, Lefebvre P. The elongation complex components BRD4 and MLLT3/AF9 are transcriptional coactivators of nuclear retinoid receptors. PLoS One 2013; 8:e64880. [PMID: 23762261 PMCID: PMC3677938 DOI: 10.1371/journal.pone.0064880] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2013] [Accepted: 04/18/2013] [Indexed: 12/20/2022] Open
Abstract
Nuclear all-trans retinoic acid receptors (RARs) initiate early transcriptional events which engage pluripotent cells to differentiate into specific lineages. RAR-controlled transactivation depends mostly on agonist-induced structural transitions in RAR C-terminus (AF-2), thus bridging coactivators or corepressors to chromatin, hence controlling preinitiation complex assembly. However, the contribution of other domains of RAR to its overall transcriptional activity remains poorly defined. A proteomic characterization of nuclear proteins interacting with RAR regions distinct from the AF-2 revealed unsuspected functional properties of the RAR N-terminus. Indeed, mass spectrometry fingerprinting identified the Bromodomain-containing protein 4 (BRD4) and ALL1-fused gene from chromosome 9 (AF9/MLLT3), known to associate with and regulates the activity of Positive Transcription Elongation Factor b (P-TEFb), as novel RAR coactivators. In addition to promoter sequences, RAR binds to genomic, transcribed regions of retinoid-regulated genes, in association with RNA polymerase II and as a function of P-TEFb activity. Knockdown of either AF9 or BRD4 expression affected differentially the neural differentiation of stem cell-like P19 cells. Clusters of retinoid-regulated genes were selectively dependent on BRD4 and/or AF9 expression, which correlated with RAR association to transcribed regions. Thus RAR establishes physical and functional links with components of the elongation complex, enabling the rapid retinoid-induced induction of genes required for neuronal differentiation. Our data thereby extends the previously known RAR interactome from classical transcriptional modulators to components of the elongation machinery, and unravel a functional role of RAR in transcriptional elongation.
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Affiliation(s)
- Sébastien Flajollet
- European Genomic Institute for Diabetes (EGID), FR 3508, Lille, France
- INSERM UMR1011, Lille, France
- Univ Lille 2, Lille, France
- Institut Pasteur de Lille, Lille, France
| | - Christophe Rachez
- Unité de Régulation Epigénétique, URA 2578 du CNRS, Département de Biologie du Développement, Institut Pasteur, Paris, France
| | - Maheul Ploton
- European Genomic Institute for Diabetes (EGID), FR 3508, Lille, France
- INSERM UMR1011, Lille, France
- Univ Lille 2, Lille, France
- Institut Pasteur de Lille, Lille, France
| | - Céline Schulz
- Interdisciplinary Research Institute, Univ Lille 1, USR 3078 CNRS, Biophotonique Cellulaire Fonctionnelle, Villeneuve d’Ascq, France
| | - Rozenn Gallais
- Equipe SPARTE, UMR CNRS 6026-Université Rennes 1, Rennes, France
| | - Raphaël Métivier
- Equipe SPARTE, UMR CNRS 6026-Université Rennes 1, Rennes, France
| | - Michal Pawlak
- European Genomic Institute for Diabetes (EGID), FR 3508, Lille, France
- INSERM UMR1011, Lille, France
- Univ Lille 2, Lille, France
- Institut Pasteur de Lille, Lille, France
| | - Aymeric Leray
- Interdisciplinary Research Institute, Univ Lille 1, USR 3078 CNRS, Biophotonique Cellulaire Fonctionnelle, Villeneuve d’Ascq, France
| | - Al Amine Issulahi
- Interdisciplinary Research Institute, Univ Lille 1, USR 3078 CNRS, Biophotonique Cellulaire Fonctionnelle, Villeneuve d’Ascq, France
| | - Laurent Héliot
- Interdisciplinary Research Institute, Univ Lille 1, USR 3078 CNRS, Biophotonique Cellulaire Fonctionnelle, Villeneuve d’Ascq, France
| | - Bart Staels
- European Genomic Institute for Diabetes (EGID), FR 3508, Lille, France
- INSERM UMR1011, Lille, France
- Univ Lille 2, Lille, France
- Institut Pasteur de Lille, Lille, France
| | - Gilles Salbert
- Equipe SPARTE, UMR CNRS 6026-Université Rennes 1, Rennes, France
| | - Philippe Lefebvre
- European Genomic Institute for Diabetes (EGID), FR 3508, Lille, France
- INSERM UMR1011, Lille, France
- Univ Lille 2, Lille, France
- Institut Pasteur de Lille, Lille, France
- * E-mail:
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429
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Direct protein interactions are responsible for Ikaros-GATA and Ikaros-Cdk9 cooperativeness in hematopoietic cells. Mol Cell Biol 2013; 33:3064-76. [PMID: 23732910 DOI: 10.1128/mcb.00296-13] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ikaros (Ik) is a critical regulator of hematopoietic gene expression. Here, we established that the Ik interactions with GATA transcription factors and cyclin-dependent kinase 9 (Cdk9), a component of the positive transcription elongation factor b (P-TEFb), are required for transcriptional activation of Ik target genes. A detailed dissection of Ik-GATA and Ik-Cdk9 protein interactions indicated that the C-terminal zinc finger domain of Ik interacts directly with the C-terminal zinc fingers of GATA1, GATA2, and GATA3, whereas the N-terminal zinc finger domain of Ik is required for interaction with the kinase and T-loop domains of Cdk9. The relevance of these interactions was demonstrated in vivo in COS-7 and primary hematopoietic cells, in which Ik facilitated Cdk9 and GATA protein recruitment to gene promoters and transcriptional activation. Moreover, the oncogenic isoform Ik6 did not efficiently interact with Cdk9 or GATA proteins in vivo and perturbed Cdk9/P-TEFb recruitment to Ik target genes, thereby affecting transcription elongation. Finally, characterization of a novel nuclear Ik isoform revealed that Ik exon 6 is dispensable for interactions with Mi2 and GATA proteins but is essential for the Cdk9 interaction. Thus, Ik is central to the Ik-GATA-Cdk9 regulatory network, which is broadly utilized for gene regulation in hematopoietic cells.
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430
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Tian B, Zhao Y, Kalita M, Edeh CB, Paessler S, Casola A, Teng MN, Garofalo RP, Brasier AR. CDK9-dependent transcriptional elongation in the innate interferon-stimulated gene response to respiratory syncytial virus infection in airway epithelial cells. J Virol 2013; 87:7075-92. [PMID: 23596302 PMCID: PMC3676079 DOI: 10.1128/jvi.03399-12] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Accepted: 04/08/2013] [Indexed: 12/20/2022] Open
Abstract
Respiratory syncytial virus (RSV) is a negative-sense single-stranded RNA virus responsible for lower respiratory tract infections. During infection, the presence of double-stranded RNA (dsRNA) activates the interferon (IFN) regulatory factor 3 (IRF3) transcription factor, an event triggering expression of immediate early, IFN-stimulated genes (ISGs). We examine the role of transcriptional elongation in control of IRF3-dependent ISG expression. RSV infection induces ISG54, ISG56, and CIG5 gene expression in an IRF3-dependent manner demonstrated by IRF3 small interfering RNA (siRNA) silencing in both A549 epithelial cells and IRF3(-/-) MEFs. ISG expression was mediated by the recruitment of IRF3, CDK9, polymerase II (Pol II), and phospho-Ser(2) carboxy-terminal domain (CTD) Pol II to the IFN-stimulated response element (ISRE) binding sites of the IRF3-dependent ISG promoters in native chromatin. We find that RSV infection enhances the activated fraction of cyclin-dependent kinase 9 (CDK9) by promoting its association with bromodomain 4 (BRD4) and disrupting its association with the inhibitory 7SK small nuclear RNA. The requirement of CDK9 activity for ISG expression was shown by siRNA-mediated silencing of CDK9 and by a selective CDK9 inhibitor in A549 cells. In contrast, RSV-induced beta interferon (IFN-β) expression is not influenced by CDK9 inhibition. Using transcript-selective quantitative real-time reverse transcription-PCR (Q-RT-PCR) assays for the ISG54 gene, we observed that RSV induces transition from short to fully spliced mRNA transcripts and that this transition is blocked by CDK9 inhibition in both A549 and primary human small airway epithelial cells. These data indicate that transcription elongation plays a major role in RSV-induced ISG expression and is mediated by IRF3-dependent recruitment of activated CDK9. CDK9 activity may be a target for immunomodulation in RSV-induced lung disease.
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Affiliation(s)
| | - Yingxin Zhao
- Department of Internal Medicine,
- Institute for Translational Sciences,
- Sealy Center for Molecular Medicine,
| | | | | | | | - Antonella Casola
- Institute for Translational Sciences,
- Sealy Center for Molecular Medicine,
- Pediatrics, University of Texas Medical Branch, Galveston, Texas, USA
| | - Michael N. Teng
- Joy McCann Culverhouse Airway Disease Research Center, Department of Internal Medicine, University of South Florida Morsani College of Medicine, Tampa, Florida, USA
| | - Roberto P. Garofalo
- Institute for Translational Sciences,
- Pediatrics, University of Texas Medical Branch, Galveston, Texas, USA
| | - Allan R. Brasier
- Department of Internal Medicine,
- Institute for Translational Sciences,
- Sealy Center for Molecular Medicine,
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431
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Abstract
Synthetic nucleic acid analogues have profoundly advanced our knowledge of DNA and RNA, as well as the complex biological processes that involve nucleic acids. As a pivotal enzyme, eukaryotic RNA polymerase II (Pol II) is responsible for transcribing DNA into messenger RNA, which serves as a template to direct protein synthesis. Chemically modified nucleic acid analogues have greatly facilitated the structural elucidation of RNA Pol II elongation complex and understanding the key chemical interactions governing RNA Pol II transcriptional fidelity. This review addresses major progress in RNA polymerase II mechanistic studies using modified nucleic acid analogues in recent years.
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Affiliation(s)
- Su Zhang
- University of California, San Diego, Skaggs School of Pharmacy & Pharmaceutical Sciences
| | - Dong Wang
- University of California, San Diego, Skaggs School of Pharmacy & Pharmaceutical Sciences
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432
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Eilebrecht S, Schwartz C, Rohr O. Non-coding RNAs: novel players in chromatin-regulation during viral latency. Curr Opin Virol 2013; 3:387-93. [PMID: 23660570 DOI: 10.1016/j.coviro.2013.04.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 04/01/2013] [Indexed: 10/26/2022]
Abstract
Chromatin structure plays an essential role during gene expression regulation not only in the case of the host cellular genome, but also during the viral life cycle. Epigenetic chromatin marks thereby define, whether a gene promoter is accessible for the transcription machinery or whether a repressive heterochromatin state is established. The heterochromatin-mediated repression of lytic viral genes results in viral latency, enabling the virus to persist dormant without being recognized by the host immune system, but keeping the potential for reactivation. Arising new systems biology approaches are starting to uncover an unexpected multiplicity and variety of non-coding (nc)RNAs playing important roles during chromatin structure control, likely constituting a novel layer in epigenetic regulation. In this review we give an overview of chromatin-regulatory viral and host cellular ncRNAs and their links to viral latency.
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Affiliation(s)
- Sebastian Eilebrecht
- Vaccine Research Institute, INSERM U955, 8 rue du Général Sarrail, 94010 Créteil, France.
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433
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Bywater MJ, Pearson RB, McArthur GA, Hannan RD. Dysregulation of the basal RNA polymerase transcription apparatus in cancer. Nat Rev Cancer 2013; 13:299-314. [PMID: 23612459 DOI: 10.1038/nrc3496] [Citation(s) in RCA: 166] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mutations that directly affect transcription by RNA polymerases rank among the most central mediators of malignant transformation, but the frequency of new anticancer drugs that selectively target defective transcription apparatus entering the clinic has been limited. This is because targeting the large protein-protein and protein-DNA interfaces that control both generic and selective aspects of RNA polymerase transcription has proved extremely difficult. However, recent technological advances have led to a 'quantum leap' in our comprehension of the structure and function of the core RNA polymerase components, how they are dysregulated in a broad range of cancers and how they may be targeted for 'transcription therapy'.
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Affiliation(s)
- Megan J Bywater
- Division of Cancer Research, Peter MacCallum Cancer Centre, Melbourne 8006, Victoria, Australia
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434
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Jennings BH. Pausing for thought: disrupting the early transcription elongation checkpoint leads to developmental defects and tumourigenesis. Bioessays 2013; 35:553-60. [PMID: 23575664 PMCID: PMC3698693 DOI: 10.1002/bies.201200179] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Accepted: 03/04/2013] [Indexed: 12/30/2022]
Abstract
Factors affecting transcriptional elongation have been characterized extensively in in vitro, single cell (yeast) and cell culture systems; however, data from the context of multicellular organisms has been relatively scarce. While studies in homogeneous cell populations have been highly informative about the underlying molecular mechanisms and prevalence of polymerase pausing, they do not reveal the biological impact of perturbing this regulation in an animal. The core components regulating pausing are expressed in all animal cells and are recruited to the majority of genes, however, disrupting their function often results in discrete phenotypic effects. Mutations in genes encoding key regulators of transcriptional pausing have been recovered from several genetic screens for specific phenotypes or interactions with specific factors in mice, zebrafish and flies. Analysis of these mutations has revealed that control of transcriptional pausing is critical for a diverse range of biological pathways essential for animal development and survival.
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435
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Taube R, Peterlin BM. Lost in transcription: molecular mechanisms that control HIV latency. Viruses 2013; 5:902-27. [PMID: 23518577 PMCID: PMC3705304 DOI: 10.3390/v5030902] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 03/15/2013] [Accepted: 03/18/2013] [Indexed: 02/06/2023] Open
Abstract
Highly active antiretroviral therapy (HAART) has limited the replication and spread of the human immunodeficiency virus (HIV). However, despite treatment, HIV infection persists in latently infected reservoirs, and once therapy is interrupted, viral replication rebounds quickly. Extensive efforts are being directed at eliminating these cell reservoirs. This feat can be achieved by reactivating latent HIV while administering drugs that prevent new rounds of infection and allow the immune system to clear the virus. However, current approaches to HIV eradication have not been effective. Moreover, as HIV latency is multifactorial, the significance of each of its molecular mechanisms is still under debate. Among these, transcriptional repression as a result of reduced levels and activity of the positive transcription elongation factor b (P-TEFb: CDK9/cyclin T) plays a significant role. Therefore, increasing levels of P-TEFb expression and activity is an excellent strategy to stimulate viral gene expression. This review summarizes the multiple steps that cause HIV to enter into latency. It positions the interplay between transcriptionally active and inactive host transcriptional activators and their viral partner Tat as valid targets for the development of new strategies to reactivate latent viral gene expression and eradicate HIV.
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Affiliation(s)
- Ran Taube
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva, 84105, Israel
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +972-8-6479858; Fax: +972-8-6479953
| | - Boris Matija Peterlin
- Department of Medicine, Microbiology and Immunology, Rosalind Russell Medical Research Center, University of California at San Francisco, San Francisco, CA 94143, USA; E-Mail:
- Department of Virology, Haartman Institute, University of Helsinki, 00014 Helsinki, Finland
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436
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Abstract
The gene expression programs that establish and maintain specific cell states in humans are controlled by thousands of transcription factors, cofactors, and chromatin regulators. Misregulation of these gene expression programs can cause a broad range of diseases. Here, we review recent advances in our understanding of transcriptional regulation and discuss how these have provided new insights into transcriptional misregulation in disease.
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Affiliation(s)
- Tong Ihn Lee
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
| | - Richard A. Young
- Whitehead Institute for Biomedical Research, Cambridge, MA 02142, USA
- Department of Biology, Massachusetts
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437
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Muniz L, Egloff S, Kiss T. RNA elements directing in vivo assembly of the 7SK/MePCE/Larp7 transcriptional regulatory snRNP. Nucleic Acids Res 2013; 41:4686-98. [PMID: 23471002 PMCID: PMC3632141 DOI: 10.1093/nar/gkt159] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Through controlling the nuclear level of active positive transcription elongation factor b (P-TEFb), the 7SK small nuclear RNA (snRNA) functions as a key regulator of RNA polymerase II transcription. Together with hexamethylene bisacetamide-inducible proteins 1/2 (HEXIM1/2), the 7SK snRNA sequesters P-TEFb into transcriptionally inactive ribonucleoprotein (RNP). In response to transcriptional stimulation, the 7SK/HEXIM/P-TEFb RNP releases P-TEFb to promote polymerase II-mediated messenger RNA synthesis. Besides transiently associating with HEXIM1/2 and P-TEFb, the 7SK snRNA stably interacts with the La-related protein 7 (Larp7) and the methylphosphate capping enzyme (MePCE). In this study, we used in vivo RNA–protein interaction assays to determine the sequence and structural elements of human 7SK snRNA directing assembly of the 7SK/MePCE/Larp7 core snRNP. MePCE interacts with the short 5′-terminal G1-U4/U106-G111 helix-tail motif and Larp7 binds to the 3′-terminal hairpin and the following U-rich tail of 7SK. The overall RNA structure and some particular nucleotides provide the information for specific binding of MePCE and Larp7. We also demonstrate that binding of Larp7 to 7SK is a prerequisite for in vivo recruitment of P-TEFb, indicating that besides providing stability for 7SK, Larp7 directly participates in P-TEFb regulation. Our results provide further explanation for the frequently observed link between Larp7 mutations and cancer development.
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Affiliation(s)
- Lisa Muniz
- Laboratoire de Biologie Moléculaire Eucaryote du CNRS, UMR5099, IFR109 CNRS, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex 9, France
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438
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Schulze-Gahmen U, Upton H, Birnberg A, Bao K, Chou S, Krogan NJ, Zhou Q, Alber T. The AFF4 scaffold binds human P-TEFb adjacent to HIV Tat. eLife 2013; 2:e00327. [PMID: 23471103 PMCID: PMC3589825 DOI: 10.7554/elife.00327] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2012] [Accepted: 01/16/2013] [Indexed: 02/05/2023] Open
Abstract
Human positive transcription elongation factor b (P-TEFb) phosphorylates RNA polymerase II and regulatory proteins to trigger elongation of many gene transcripts. The HIV-1 Tat protein selectively recruits P-TEFb as part of a super elongation complex (SEC) organized on a flexible AFF1 or AFF4 scaffold. To understand this specificity and determine if scaffold binding alters P-TEFb conformation, we determined the structure of a tripartite complex containing the recognition regions of P-TEFb and AFF4. AFF4 meanders over the surface of the P-TEFb cyclin T1 (CycT1) subunit but makes no stable contacts with the CDK9 kinase subunit. Interface mutations reduced CycT1 binding and AFF4-dependent transcription. AFF4 is positioned to make unexpected direct contacts with HIV Tat, and Tat enhances P-TEFb affinity for AFF4. These studies define the mechanism of scaffold recognition by P-TEFb and reveal an unanticipated intersubunit pocket on the AFF4 SEC that potentially represents a target for therapeutic intervention against HIV/AIDS. DOI:http://dx.doi.org/10.7554/eLife.00327.001.
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Affiliation(s)
- Ursula Schulze-Gahmen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Heather Upton
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Andrew Birnberg
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Katherine Bao
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Seemay Chou
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Nevan J Krogan
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States
- California Institute for Quantitative Biosciences, QB3, Berkeley, United States
- J David Gladstone Institutes, San Francisco, United States
| | - Qiang Zhou
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Tom Alber
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
- California Institute for Quantitative Biosciences, QB3, Berkeley, United States
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439
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Hole A, Baumli S, Shao H, Shi S, Huang S, Pepper C, Fischer P, Wang S, Endicott JA, Noble ME. Comparative structural and functional studies of 4-(thiazol-5-yl)-2-(phenylamino)pyrimidine-5-carbonitrile CDK9 inhibitors suggest the basis for isotype selectivity. J Med Chem 2013; 56:660-70. [PMID: 23252711 PMCID: PMC3579457 DOI: 10.1021/jm301495v] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Indexed: 01/08/2023]
Abstract
Cyclin-dependent kinase 9/cyclin T, the protein kinase heterodimer that constitutes positive transcription elongation factor b, is a well-validated target for treatment of several diseases, including cancer and cardiac hypertrophy. In order to aid inhibitor design and rationalize the basis for CDK9 selectivity, we have studied the CDK-binding properties of six different members of a 4-(thiazol-5-yl)-2-(phenylamino)pyrimidine-5-carbonitrile series that bind to both CDK9/cyclin T and CDK2/cyclin A. We find that for a given CDK, the melting temperature of a CDK/cyclin/inhibitor complex correlates well with inhibitor potency, suggesting that differential scanning fluorimetry (DSF) is a useful orthogonal measure of inhibitory activity for this series. We have used DSF to demonstrate that the binding of these compounds is independent of the presence or absence of the C-terminal tail region of CDK9, unlike the binding of the CDK9-selective inhibitor 5,6-dichlorobenzimidazone-1-β-d-ribofuranoside (DRB). Finally, on the basis of 11 cocrystal structures bound to CDK9/cyclin T or CDK2/cyclin A, we conclude that selective inhibition of CDK9/cyclin T by members of the 4-(thiazol-5-yl)-2-(phenylamino)pyrimidine-5-carbonitrile series results from the relative malleability of the CDK9 active site rather than from the formation of specific polar contacts.
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Affiliation(s)
- Alison
J. Hole
- Department
of Biochemistry, University of Oxford,
South Parks Road, Oxford OX1
3QU, U.K
| | - Sonja Baumli
- Department
of Biochemistry, University of Oxford,
South Parks Road, Oxford OX1
3QU, U.K
| | - Hao Shao
- School of Pharmacy
and Centre
for Biomolecular Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, U.K
| | - Shenhua Shi
- School of Pharmacy
and Centre
for Biomolecular Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, U.K
| | - Shiliang Huang
- School of Pharmacy
and Centre
for Biomolecular Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, U.K
| | - Chris Pepper
- Institute of Cancer and Genetics,
School of Medicine, Cardiff University,
Heath Park, Cardiff CF14 4XN, U.K
| | - Peter
M. Fischer
- School of Pharmacy
and Centre
for Biomolecular Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, U.K
| | - Shudong Wang
- School of Pharmacy
and Centre
for Biomolecular Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, U.K
- School of Pharmacy and Medical
Sciences, University of South Australia, Adelaide SA 5001, Australia
| | - Jane A. Endicott
- Department
of Biochemistry, University of Oxford,
South Parks Road, Oxford OX1
3QU, U.K
| | - Martin E. Noble
- Department
of Biochemistry, University of Oxford,
South Parks Road, Oxford OX1
3QU, U.K
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440
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Lee KM, Tarn WY. Coupling pre-mRNA processing to transcription on the RNA factory assembly line. RNA Biol 2013; 10:380-90. [PMID: 23392244 DOI: 10.4161/rna.23697] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
It has been well-documented that nuclear processing of primary transcripts of RNA polymerase II occurs co-transcriptionally and is functionally coupled to transcription. Moreover, increasing evidence indicates that transcription influences pre-mRNA splicing and even several post-splicing RNA processing events. In this review, we discuss the issues of how RNA polymerase II modulates co-transcriptional RNA processing events via its carboxyl terminal domain, and the protein domains involved in coupling of transcription and RNA processing events. In addition, we describe how transcription influences the expression or stability of mRNAs through the formation of distinct mRNP complexes. Finally, we delineate emerging findings that chromatin modifications function in the regulation of RNA processing steps, especially splicing, in addition to transcription. Overall, we provide a comprehensive view that transcription could integrate different control systems, from epigenetic to post-transcriptional control, for efficient gene expression.
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Affiliation(s)
- Kuo-Ming Lee
- Institute of Biomedical Sciences; Academia Sinica; Taipei, Taiwan
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441
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Singh M, Choi CP, Feigon J. xRRM: a new class of RRM found in the telomerase La family protein p65. RNA Biol 2013; 10:353-9. [PMID: 23328630 DOI: 10.4161/rna.23608] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Genuine La and La-related proteins group 7 (LARP7) bind to the non-coding RNAs transcribed by RNA polymerase III (RNAPIII), which end in UUU-3'OH. The La motif and RRM1 of these proteins (the La module) cooperate to bind the UUU-3'OH, protecting the RNA from degradation, while other domains may be important for RNA folding or other functions. Among the RNAPIII transcripts is ciliate telomerase RNA (TER). p65, a member of the LARP7 family, is an integral Tetrahymena thermophila telomerase holoenzyme protein required for TER biogenesis and telomerase RNP assembly. p65, together with TER and telomerase reverse transcriptase (TERT), form the Tetrahymena telomerase RNP catalytic core. p65 has an N-terminal domain followed by a La module and a C-terminal domain, which binds to the TER stem 4. We recently showed that the p65 C-terminal domain harbors a cryptic, atypical RRM, which uses a unique mode of single- and double-strand RNA binding and is required for telomerase RNP catalytic core assembly. This domain, which we named xRRM, appears to be present in and unique to genuine La and LARP7 proteins. Here we review the structure of the xRRM, discuss how this domain could recognize diverse substrates of La and LARP7 proteins and discuss the functional implications of the xRRM as an RNP chaperone.
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Affiliation(s)
- Mahavir Singh
- Department of Chemistry and Biochemistry and the Molecular Biology Institute; University of California; Los Angeles, CA USA
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442
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Abstract
Immune response to pathogens depends on coordinated regulation of numerous genes that contribute collectively to pathogen elimination and restoration of the integrity of the affected tissue. The pathogen-induced gene expression is governed largely by the signal-induced posttranslational histone modifications that facilitate assembly of the functionally distinct chromatin complexes. In this review, we describe the principles of chromatin-based gene regulation during innate immune responses. We discuss the ability of pathogens to hijack the host response by interfering with various arms of transcriptional machinery involved in the responses. In particular, we discuss the phenomenon of the histone mimicry where interaction between histones and transcriptional regulators is targeted by pathogens that carry the histone-like sequences (histone mimics). We show how the principle of isotone mimicry as an efficient way to control host gene expression has been sued for the development of novel anti-inflammatory pharmacological approaches.
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443
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Gu B, Eick D, Bensaude O. CTD serine-2 plays a critical role in splicing and termination factor recruitment to RNA polymerase II in vivo. Nucleic Acids Res 2012; 41:1591-603. [PMID: 23275552 PMCID: PMC3561981 DOI: 10.1093/nar/gks1327] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Co-transcriptional pre-mRNA processing relies on reversible phosphorylation of the carboxyl-terminal domain (CTD) of Rpb1, the largest subunit of RNA polymerase II (RNAP II). In this study, we replaced in live cells the endogenous Rpb1 by S2A Rpb1, where the second serines (Ser2) in the CTD heptapeptide repeats were switched to alanines, to prevent phosphorylation. Although slower, S2A RNAP II was able to transcribe. However, it failed to recruit splicing components such as U2AF65 and U2 snRNA to transcription sites, although the recruitment of U1 snRNA was not affected. As a consequence, co-transcriptional splicing was impaired. Interestingly, the magnitude of the S2A RNAP II splicing defect was promoter dependent. In addition, S2A RNAP II showed an impaired recruitment of the cleavage factor PCF11 to pre-mRNA and a defect in 3'-end RNA cleavage. These results suggest that CTD Ser2 plays critical roles in co-transcriptional pre-mRNA maturation in vivo: It likely recruits U2AF65 to ensure an efficient co-transcriptional splicing and facilitates the recruitment of pre-mRNA 3'-end processing factors to enhance 3'-end cleavage.
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Affiliation(s)
- Bo Gu
- Ecole Normale Supérieure, IBENS, 46, rue d'Ulm, Paris 75005, France
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444
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Lin CY, Lovén J, Rahl PB, Paranal RM, Burge CB, Bradner JE, Lee TI, Young RA. Transcriptional amplification in tumor cells with elevated c-Myc. Cell 2012; 151:56-67. [PMID: 23021215 DOI: 10.1016/j.cell.2012.08.026] [Citation(s) in RCA: 1120] [Impact Index Per Article: 93.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Revised: 05/29/2012] [Accepted: 08/08/2012] [Indexed: 12/12/2022]
Abstract
Elevated expression of the c-Myc transcription factor occurs frequently in human cancers and is associated with tumor aggression and poor clinical outcome. The effect of high levels of c-Myc on global gene regulation is poorly understood but is widely thought to involve newly activated or repressed "Myc target genes." We report here that in tumor cells expressing high levels of c-Myc the transcription factor accumulates in the promoter regions of active genes and causes transcriptional amplification, producing increased levels of transcripts within the cell's gene expression program. Thus, rather than binding and regulating a new set of genes, c-Myc amplifies the output of the existing gene expression program. These results provide an explanation for the diverse effects of oncogenic c-Myc on gene expression in different tumor cells and suggest that transcriptional amplification reduces rate-limiting constraints for tumor cell growth and proliferation.
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Affiliation(s)
- Charles Y Lin
- Whitehead Institute for Biomedical Research, Cambridge Center, MA 02142, USA
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445
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Transcription elongation factors DSIF and NELF: promoter-proximal pausing and beyond. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012. [PMID: 23202475 DOI: 10.1016/j.bbagrm.2012.11.007] [Citation(s) in RCA: 123] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
DRB sensitivity-inducing factor (DSIF) and negative elongation factor (NELF) were originally identified as factors responsible for transcriptional inhibition by 5,6-dichloro-1-beta-d-ribofuranosyl-benzimidazole (DRB) and were later found to control transcription elongation, together with P-TEFb, at the promoter-proximal region. Although there is ample evidence that these factors play roles throughout the genome, other data also suggest gene- or tissue-specific roles for these factors. In this review, we discuss how these apparently conflicting data can be reconciled. In light of recent findings, we also discuss the detailed mechanism by which these factors control the elongation process at the molecular level. This article is part of a Special Issue entitled: RNA polymerase II Transcript Elongation.
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446
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Gracey Maniar LE, Maniar JM, Chen ZY, Lu J, Fire AZ, Kay MA. Minicircle DNA vectors achieve sustained expression reflected by active chromatin and transcriptional level. Mol Ther 2012. [PMID: 23183534 DOI: 10.1038/mt.2012.244] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Current efforts in nonviral gene therapy are plagued by a pervasive difficulty in sustaining therapeutic levels of delivered transgenes. Minicircles (plasmid derivatives with the same expression cassette but lacking a bacterial backbone) show sustained expression and hold promise for therapeutic use where persistent transgene expression is required. To characterize the widely-observed silencing process affecting expression of foreign DNA in mammals, we used a system in which mouse liver presented with either plasmid or minicircle consistently silences plasmid but not minicircle expression. We found that preferential silencing of plasmid DNA occurs at a nuclear stage that precedes transport of mRNA to the cytoplasm, evident from a consistent >25-fold minicircle/plasmid transcript difference observed in both nuclear and total RNA. Among possible mechanisms of nuclear silencing, our data favor chromatin-linked transcriptional blockage rather than targeted degradation, aberrant processing, or compromised mRNA transport. In particular, we observe dramatic enrichment of H3K27 trimethylation on plasmid sequences. Also, it appears that Pol II can engage the modified plasmid chromatin, potentially in a manner that is not productive in the synthesis of high levels of new transcript. We outline a scenario in which sustained differences at the chromatin level cooperate to determine the activity of foreign DNA.
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Affiliation(s)
- Lia E Gracey Maniar
- Department of Genetics, Stanford University School of Medicine, Stanford, California, USA
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447
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Lenasi T, Barboric M. Mutual relationships between transcription and pre-mRNA processing in the synthesis of mRNA. WILEY INTERDISCIPLINARY REVIEWS-RNA 2012. [PMID: 23184646 DOI: 10.1002/wrna.1148] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The generation of messenger RNA (mRNA) in eukaryotes is achieved by transcription from the DNA template and pre-mRNA processing reactions of capping, splicing, and polyadenylation. Although RNA polymerase II (RNAPII) catalyzes the synthesis of pre-mRNA, it also serves as a principal coordinator of the processing reactions in the course of transcription. In this review, we focus on the interplay between transcription and cotranscriptional pre-mRNA maturation events, mediated by the recruitment of RNA processing factors to differentially phosphorylated C-terminal domain of Rbp1, the largest subunit of RNAPII. Furthermore, we highlight the bidirectional nature of the interplay by discussing the impact of RNAPII kinetics on pre-mRNA processing as well as how the processing events reach back to different phases of gene transcription.
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Affiliation(s)
- Tina Lenasi
- Institute of Biomedicine, Biochemistry and Developmental Biology, University of Helsinki, Helsinki, Finland.
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448
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Herz HM, Mohan M, Garruss AS, Liang K, Takahashi YH, Mickey K, Voets O, Verrijzer CP, Shilatifard A. Enhancer-associated H3K4 monomethylation by Trithorax-related, the Drosophila homolog of mammalian Mll3/Mll4. Genes Dev 2012; 26:2604-20. [PMID: 23166019 DOI: 10.1101/gad.201327.112] [Citation(s) in RCA: 285] [Impact Index Per Article: 23.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Monomethylation of histone H3 on Lys 4 (H3K4me1) and acetylation of histone H3 on Lys 27 (H3K27ac) are histone modifications that are highly enriched over the body of actively transcribed genes and on enhancers. Although in yeast all H3K4 methylation patterns, including H3K4me1, are implemented by Set1/COMPASS (complex of proteins associated with Set1), there are three classes of COMPASS-like complexes in Drosophila that could carry out H3K4me1 on enhancers: dSet1, Trithorax, and Trithorax-related (Trr). Here, we report that Trr, the Drosophila homolog of the mammalian Mll3/4 COMPASS-like complexes, can function as a major H3K4 monomethyltransferase on enhancers in vivo. Loss of Trr results in a global decrease of H3K4me1 and H3K27ac levels in various tissues. Assays with the cut wing margin enhancer implied a functional role for Trr in enhancer-mediated processes. A genome-wide analysis demonstrated that Trr is required to maintain the H3K4me1 and H3K27ac chromatin signature that resembles the histone modification patterns described for enhancers. Furthermore, studies in the mammalian system suggested a role for the Trr homolog Mll3 in similar processes. Since Trr and mammalian Mll3/4 complexes are distinguished by bearing a unique subunit, the H3K27 demethylase UTX, we propose a model in which the H3K4 monomethyltransferases Trr/Mll3/Mll4 and the H3K27 demethylase UTX cooperate to regulate the transition from inactive/poised to active enhancers.
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Affiliation(s)
- Hans-Martin Herz
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA
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449
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Li Z, Guo J, Wu Y, Zhou Q. The BET bromodomain inhibitor JQ1 activates HIV latency through antagonizing Brd4 inhibition of Tat-transactivation. Nucleic Acids Res 2012; 41:277-87. [PMID: 23087374 PMCID: PMC3592394 DOI: 10.1093/nar/gks976] [Citation(s) in RCA: 221] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Latent HIV reservoirs are the primary hurdle to eradication of infection. Identification of agents, pathways and molecular mechanisms that activate latent provirus may, in the presence of highly active antiretroviral therapy, permit clearance of infected cells by the immune system. Promoter-proximal pausing of RNA polymerase (Pol) II is a major rate-limiting step in HIV gene expression. The viral Tat protein recruits human Super Elongation Complex (SEC) to paused Pol II to overcome this limitation. Here, we identify the bromodomain protein Brd4 and its inhibition of Tat-transactivation as a major impediment to latency reactivation. Brd4 competitively blocks the Tat-SEC interaction on HIV promoter. The BET bromodomain inhibitor JQ1 dissociates Brd4 from the HIV promoter to allow Tat recruitment of SEC to stimulate HIV elongation. JQ1 synergizes with another latency activator prostratin, which promotes Pol II loading onto the viral promoter. Because JQ1 activates viral latency without inducing global T cell activation, this and other closely related compounds and their antagonization of Brd4 to promote Tat-SEC interaction merit further investigations as effective agents/strategies for eliminating latent HIV.
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Affiliation(s)
- Zichong Li
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
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450
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Conaway RC, Conaway JW. The Mediator complex and transcription elongation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1829:69-75. [PMID: 22983086 DOI: 10.1016/j.bbagrm.2012.08.017] [Citation(s) in RCA: 104] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Revised: 08/14/2012] [Accepted: 08/29/2012] [Indexed: 11/25/2022]
Abstract
BACKGROUND Mediator is an evolutionarily conserved multisubunit RNA polymerase II (Pol II) coregulatory complex. Although Mediator was initially found to play a critical role in the regulation of the initiation of Pol II transcription, recent studies have brought to light an expanded role for Mediator at post-initiation stages of transcription. SCOPE OF REVIEW We provide a brief description of the structure of Mediator and its function in the regulation of Pol II transcription initiation, and we summarize recent findings implicating Mediator in the regulation of various stages of Pol II transcription elongation. MAJOR CONCLUSIONS Emerging evidence is revealing new roles for Mediator in nearly all stages of Pol II transcription, including initiation, promoter escape, elongation, pre-mRNA processing, and termination. GENERAL SIGNIFICANCE Mediator plays a central role in the regulation of gene expression by impacting nearly all stages of mRNA synthesis. This article is part of a Special Issue entitled: RNA polymerase II Transcript Elongation.
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Affiliation(s)
- Ronald C Conaway
- Stowers Institute for Medical Research, Kansas City, MO 64110, USA.
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