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Camara MB, Sobeh AM, Eichhorn CD. Progress in 7SK ribonucleoprotein structural biology. Front Mol Biosci 2023; 10:1154622. [PMID: 37051324 PMCID: PMC10083321 DOI: 10.3389/fmolb.2023.1154622] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 03/16/2023] [Indexed: 03/29/2023] Open
Abstract
The 7SK ribonucleoprotein (RNP) is a dynamic and multifunctional regulator of RNA Polymerase II (RNAPII) transcription in metazoa. Comprised of the non-coding 7SK RNA, core proteins, and numerous accessory proteins, the most well-known 7SK RNP function is the sequestration and inactivation of the positive transcription elongation factor b (P-TEFb). More recently, 7SK RNP has been shown to regulate RNAPII transcription through P-TEFb-independent pathways. Due to its fundamental role in cellular function, dysregulation has been linked with human diseases including cancers, heart disease, developmental disorders, and viral infection. Significant advances in 7SK RNP structural biology have improved our understanding of 7SK RNP assembly and function. Here, we review progress in understanding the structural basis of 7SK RNA folding, biogenesis, and RNP assembly.
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Affiliation(s)
- Momodou B. Camara
- Department of Chemistry, University of Nebraska, Lincoln, NE, United States
| | - Amr M. Sobeh
- Department of Chemistry, University of Nebraska, Lincoln, NE, United States
| | - Catherine D. Eichhorn
- Department of Chemistry, University of Nebraska, Lincoln, NE, United States
- Nebraska Center for Integrated Biomolecular Communication, Lincoln, NE, United States
- *Correspondence: Catherine D. Eichhorn,
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2
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Fang Y, Wang Y, Spector BM, Xiao X, Yang C, Li P, Yuan Y, Ding P, Xiao ZX, Zhang P, Qiu T, Zhu X, Price DH, Li Q. Dynamic regulation of P-TEFb by 7SK snRNP is integral to the DNA damage response to regulate chemotherapy sensitivity. iScience 2022; 25:104844. [PMID: 36034227 PMCID: PMC9399290 DOI: 10.1016/j.isci.2022.104844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 07/15/2022] [Accepted: 07/21/2022] [Indexed: 11/28/2022] Open
Abstract
Testicular germ cell tumors and closely related embryonal stem cells are exquisitely sensitive to cisplatin, a feature thought to be linked to their pluripotent state and p53 status. It remains unclear whether and how cellular state is coordinated with p53 to confer cisplatin sensitivity. Here, we report that positive transcription elongation factor b (P-TEFb) determines cell fate upon DNA damage. We find that cisplatin rapidly activates P-TEFb by releasing it from inhibitory 7SK small nuclear ribonucleoprotein complex. P-TEFb directly phosphorylates pluripotency factor estrogen-related receptor beta (ESRRB), and induces its proteasomal degradation to enhance pro-survival glycolysis. On the other hand, P-TEFb is required for the transcription of a substantial portion of p53 target genes, triggering cell death during prolonged cisplatin treatment. These results reveal previously underappreciated roles of P-TEFb to coordinate the DNA damage response. We discuss the implications for using P-TEFb inhibitors to treat cancer and ameliorate cisplatin-induced ototoxicity. P-TEFb regulates pro-survival and pro-death pathways during DNA damage response P-TEFb promotes ESRRB proteasomal degradation to enhance pro-survival glycolysis P-TEFb induces a substantial portion of p53 target genes to trigger cell death Chemical inhibitors of P-TEFb blocks cisplatin- or UV-induced cell death
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Affiliation(s)
- Yin Fang
- Departments of Pediatrics and Obstetrics & Gynecology, West China Second University Hospital, Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, Development and Related Diseases of Women and Children Key Laboratory of Sichuan Province, Center of Growth, Metabolism and Aging, College of Life Sciences, State Key Laboratory of Biotherapy and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu 610041, China
| | - Yan Wang
- Departments of Pediatrics and Obstetrics & Gynecology, West China Second University Hospital, Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, Development and Related Diseases of Women and Children Key Laboratory of Sichuan Province, Center of Growth, Metabolism and Aging, College of Life Sciences, State Key Laboratory of Biotherapy and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu 610041, China
| | | | - Xue Xiao
- Departments of Pediatrics and Obstetrics & Gynecology, West China Second University Hospital, Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, Development and Related Diseases of Women and Children Key Laboratory of Sichuan Province, Center of Growth, Metabolism and Aging, College of Life Sciences, State Key Laboratory of Biotherapy and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu 610041, China
| | - Chao Yang
- Division of Bioinformatics, Sichuan Cunde Therapeutics, Chengdu 610093, China
- Non-coding RNA and Drug Discovery Key Laboratory of Sichuan Province, Chengdu Medical College, Chengdu 610500, China
| | - Ping Li
- Departments of Pediatrics and Obstetrics & Gynecology, West China Second University Hospital, Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, Development and Related Diseases of Women and Children Key Laboratory of Sichuan Province, Center of Growth, Metabolism and Aging, College of Life Sciences, State Key Laboratory of Biotherapy and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu 610041, China
| | - Yuan Yuan
- Division of Bioinformatics, Sichuan Cunde Therapeutics, Chengdu 610093, China
- Non-coding RNA and Drug Discovery Key Laboratory of Sichuan Province, Chengdu Medical College, Chengdu 610500, China
| | - Ping Ding
- Division of Bioinformatics, Sichuan Cunde Therapeutics, Chengdu 610093, China
- Non-coding RNA and Drug Discovery Key Laboratory of Sichuan Province, Chengdu Medical College, Chengdu 610500, China
| | - Zhi-Xiong Xiao
- Center of Growth, Metabolism and Aging, Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610064, China
| | - Peixuan Zhang
- Departments of Pediatrics and Obstetrics & Gynecology, West China Second University Hospital, Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, Development and Related Diseases of Women and Children Key Laboratory of Sichuan Province, Center of Growth, Metabolism and Aging, College of Life Sciences, State Key Laboratory of Biotherapy and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu 610041, China
| | - Tong Qiu
- Departments of Pediatrics and Obstetrics & Gynecology, West China Second University Hospital, Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, Development and Related Diseases of Women and Children Key Laboratory of Sichuan Province, Center of Growth, Metabolism and Aging, College of Life Sciences, State Key Laboratory of Biotherapy and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu 610041, China
| | - Xiaofeng Zhu
- Center of Growth, Metabolism and Aging, Key Laboratory of Bio-Resource and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu 610064, China
- Corresponding author
| | - David H. Price
- Department of Biochemistry, University of Iowa, Iowa City, IA 52242, USA
- Corresponding author
| | - Qintong Li
- Departments of Pediatrics and Obstetrics & Gynecology, West China Second University Hospital, Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, Development and Related Diseases of Women and Children Key Laboratory of Sichuan Province, Center of Growth, Metabolism and Aging, College of Life Sciences, State Key Laboratory of Biotherapy and Collaborative Innovation Center of Biotherapy, Sichuan University, Chengdu 610041, China
- Corresponding author
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3
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Shadrina OA, Kikhay TF, Agapkina YY, Gottikh MB. SFPQ and NONO Proteins and Long Non-Coding NEAT1 RNA: Cellular Functions and Role in the HIV-1 Life Cycle. Mol Biol 2022. [DOI: 10.1134/s0026893322020133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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4
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Chen Z, Wu H, Yang H, Fan Y, Zhao S, Zhang M. Identification and validation of RNA-binding protein-related gene signature revealed potential associations with immunosuppression and drug sensitivity in glioma. Cancer Med 2021; 10:7418-7439. [PMID: 34482648 PMCID: PMC8525098 DOI: 10.1002/cam4.4248] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Revised: 07/31/2021] [Accepted: 08/22/2021] [Indexed: 12/11/2022] Open
Abstract
Background Glioma is the most common central nervous system tumor in adults, and a considerable part of them are high‐degree ones with high malignancy and poor prognosis. At present, the classification and treatment of glioma are mainly based on its histological characteristics, so studies at the molecular level are needed. Methods RNA‐seq data from The Cancer Genome Atlas (TCGA) datasets (n = 703) and Chinese Glioma Genome Atlas (CGGA) were utilized to find out the differentially expressed RNA‐binding proteins (RBPs) between normal cerebral tissue and glioma. A prediction system for the prognosis of glioma patients based on 11 RBPs was established and validated using uni‐ and multi‐variate Cox regression analyses. STITCH and CMap databases were exploited to identify putative drugs and their targets. Single sample gene set enrichment analysis (ssGSEA) was used to calculate scores of specific immune‐related gene sets. IC50 of over 20,000 compounds in 60 cancer cell lines was collected from the CellMiner database to test the drug sensitivity prediction value of the RBP‐based signature. Results We established a reliable prediction system for the prognosis of glioma patients based on 11 RBPs including THOC3, LSM11, SARNP, PABPC1L2B, SMN1, BRCA1, ZC3H8, DZIP1L, HEXIM2, LARP4B, and ZC3H12B. These RBPs were primarily associated with ribosome and post‐transcriptional regulation. RBP‐based risk scores were closely related to immune cells and immune function. We also confirmed the potential of the signature to predict the drug sensitivity of currently approved or evaluated drugs. Conclusions Differentially expressed RBPs in glioma can be used as a basis for prognosis prediction, new drugs screening and drug sensitivity prediction. As RBP‐based glioma risk scores were associated with immunity, immunotherapy may become an important treatment for glioma in the future.
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Affiliation(s)
- Zhuohui Chen
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Haiyue Wu
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Haojun Yang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Yishu Fan
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Songfeng Zhao
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
| | - Mengqi Zhang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, China
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Shadrina O, Garanina I, Korolev S, Zatsepin T, Van Assche J, Daouad F, Wallet C, Rohr O, Gottikh M. Analysis of RNA binding properties of human Ku protein reveals its interactions with 7SK snRNA and protein components of 7SK snRNP complex. Biochimie 2020; 171-172:110-123. [PMID: 32105815 DOI: 10.1016/j.biochi.2020.02.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 02/21/2020] [Indexed: 12/21/2022]
Abstract
Human Ku heterodimeric protein composed of Ku70 and Ku80 subunits plays an important role in the non-homologous end-joining DNA repair pathway as a sensor of double strand DNA breaks. Ku is also involved in numerous cellular processes, and in some of them it acts in an RNA-dependent manner. However, RNA binding properties of the human Ku have not been well studied. Here we have analyzed interactions of a recombinant Ku heterodimer with a set of RNAs of various structure as well as eCLIP (enhanced crosslinking and immunoprecipitation) data for human Ku70. As a result, we have proposed a consensus RNA structure preferable for the Ku binding that is a hairpin possessing a bulge just near GpG sequence-containing terminal loop. 7SK snRNA is a scaffold for a ribonucleoprotein complex (7SK snRNP), which is known to participate in transcription regulation. We have shown that the recombinant Ku specifically binds a G-rich loop of hairpin 1 within 7SK snRNA. Moreover, Ku protein has been co-precipitated from HEK 293T cells with endogenous 7SK snRNA and such proteins included in 7SK snRNP as HEXIM1, Cdk9 and CTIP2. Ku and Cdk9 binding is found to be RNA-independent, meanwhile HEXIM1 and Ku co-precipitation depended on the presence of intact 7SK snRNA. The latter result has been confirmed using recombinant HEXIM1 and Ku proteins. Colocalization of Ku and CTIP2 was additionally confirmed by confocal microscopy. These results allow us to propose human Ku as a new component of the 7SK snRNP complex.
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Affiliation(s)
- Olga Shadrina
- Chemistry Department, Lomonosov Moscow State University, Moscow, 199991, Russia; Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119992, Moscow, Russia.
| | - Irina Garanina
- Federal Research and Clinical Center of Physical-Chemical Medicine of Federal Medical Biological Agency, Moscow, 119435, Russia
| | - Sergey Korolev
- Chemistry Department, Lomonosov Moscow State University, Moscow, 199991, Russia; Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119992, Moscow, Russia
| | - Timofei Zatsepin
- Chemistry Department, Lomonosov Moscow State University, Moscow, 199991, Russia; Skolkovo Institute of Science and Technology, Skolkovo, 121205, Russia
| | - Jeanne Van Assche
- Université de Strasbourg, EA7292, FMTS, IUT Louis Pasteur, Schiltigheim, France
| | - Fadoua Daouad
- Université de Strasbourg, EA7292, FMTS, IUT Louis Pasteur, Schiltigheim, France
| | - Clementine Wallet
- Université de Strasbourg, EA7292, FMTS, IUT Louis Pasteur, Schiltigheim, France
| | - Olivier Rohr
- Université de Strasbourg, EA7292, FMTS, IUT Louis Pasteur, Schiltigheim, France
| | - Marina Gottikh
- Chemistry Department, Lomonosov Moscow State University, Moscow, 199991, Russia; Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119992, Moscow, Russia
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6
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Wang Y, Qiu T. Positive transcription elongation factor b and its regulators in development. ALL LIFE 2020. [DOI: 10.1080/21553769.2019.1663277] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Affiliation(s)
- Yan Wang
- Department of Pediatrics, West China Second University Hospital, Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, Sichuan University, Chengdu, People’s Republic of China
| | - Tong Qiu
- Department of Pediatrics, West China Second University Hospital, Key Laboratory of Birth Defects and Related Diseases of Women and Children, Ministry of Education, Sichuan University, Chengdu, People’s Republic of China
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7
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Abstract
Hexim1 acts as a tumor suppressor and is involved in the regulation of innate immunity. It was initially described as a non-coding RNA-dependent regulator of transcription. Here, we detail how 7SK RNA binds to Hexim1 and turns it into an inhibitor of the positive transcription elongation factor (P-TEFb). In addition to its action on P-TEFb, it plays a role in a variety of different mechanisms: it controls the stability of transcription factor components and assists binding of transcription factors to their targets.
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Affiliation(s)
- Annemieke A Michels
- a IBENS , Ecole Normale Supérieure UMR CNRS 8107, UA INSERM 1024 , 46 rue d'Ulm Paris Cedex France
| | - Olivier Bensaude
- a IBENS , Ecole Normale Supérieure UMR CNRS 8107, UA INSERM 1024 , 46 rue d'Ulm Paris Cedex France
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8
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Brogie JE, Price DH. Reconstitution of a functional 7SK snRNP. Nucleic Acids Res 2017; 45:6864-6880. [PMID: 28431135 PMCID: PMC5499737 DOI: 10.1093/nar/gkx262] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 04/11/2017] [Indexed: 01/29/2023] Open
Abstract
The 7SK small nuclear ribonucleoprotein (snRNP) plays a central role in RNA polymerase II elongation control by regulating the availability of active P-TEFb. We optimized conditions for analyzing 7SK RNA by SHAPE and demonstrated a hysteretic effect of magnesium on 7SK folding dynamics including a 7SK GAUC motif switch. We also found evidence that the 5΄ end pairs alternatively with two different regions of 7SK giving rise to open and closed forms that dictate the state of the 7SK motif. We then used recombinant P-TEFb, HEXIM1, LARP7 and MEPCE to reconstruct a functional 7SK snRNP in vitro. Stably associated P-TEFb was highly inhibited, but could still be released and activated by HIV-1 Tat. Notably, P-TEFb association with both in vitro-reconstituted and cellular snRNPs led to similar changes in SHAPE reactivities, confirming that 7SK undergoes a P-TEFb-dependent structural change. We determined that the xRRM of LARP7 binds to the 3΄ stem loop of 7SK and inhibits the methyltransferase activity of MEPCE through a C-terminal MEPCE interaction domain (MID). Inhibition of MEPCE is dependent on the structure of the 3΄ stem loop and the closed form of 7SK RNA. This study provides important insights into intramolecular interactions within the 7SK snRNP.
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Affiliation(s)
- John E Brogie
- Biochemistry Department, University of Iowa, Iowa City, IA 52242, USA
| | - David H Price
- Biochemistry Department, University of Iowa, Iowa City, IA 52242, USA
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9
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Morchikh M, Cribier A, Raffel R, Amraoui S, Cau J, Severac D, Dubois E, Schwartz O, Bennasser Y, Benkirane M. HEXIM1 and NEAT1 Long Non-coding RNA Form a Multi-subunit Complex that Regulates DNA-Mediated Innate Immune Response. Mol Cell 2017; 67:387-399.e5. [PMID: 28712728 DOI: 10.1016/j.molcel.2017.06.020] [Citation(s) in RCA: 166] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Revised: 05/15/2017] [Accepted: 06/16/2017] [Indexed: 12/23/2022]
Abstract
The DNA-mediated innate immune response underpins anti-microbial defenses and certain autoimmune diseases. Here we used immunoprecipitation, mass spectrometry, and RNA sequencing to identify a ribonuclear complex built around HEXIM1 and the long non-coding RNA NEAT1 that we dubbed the HEXIM1-DNA-PK-paraspeckle components-ribonucleoprotein complex (HDP-RNP). The HDP-RNP contains DNA-PK subunits (DNAPKc, Ku70, and Ku80) and paraspeckle proteins (SFPQ, NONO, PSPC1, RBM14, and MATRIN3). We show that binding of HEXIM1 to NEAT1 is required for its assembly. We further demonstrate that the HDP-RNP is required for the innate immune response to foreign DNA, through the cGAS-STING-IRF3 pathway. The HDP-RNP interacts with cGAS and its partner PQBP1, and their interaction is remodeled by foreign DNA. Remodeling leads to the release of paraspeckle proteins, recruitment of STING, and activation of DNAPKc and IRF3. Our study establishes the HDP-RNP as a key nuclear regulator of DNA-mediated activation of innate immune response through the cGAS-STING pathway.
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Affiliation(s)
- Mehdi Morchikh
- Institut de Génétique Humaine, Laboratoire de Virologie Moléculaire, Université de Montpellier, CNRS UMR9002, 34000 Montpellier, France.
| | - Alexandra Cribier
- Institut de Génétique Humaine, Laboratoire de Virologie Moléculaire, Université de Montpellier, CNRS UMR9002, 34000 Montpellier, France.
| | - Raoul Raffel
- Institut de Génétique Humaine, Laboratoire de Virologie Moléculaire, Université de Montpellier, CNRS UMR9002, 34000 Montpellier, France
| | - Sonia Amraoui
- Institut Pasteur, Virus and Immunity Unit, URA CNRS 3015, 75015 Paris, France
| | - Julien Cau
- MRI-Montpellier, Biocampus, Montpellier, 34095 France; IGH CNRS- Université de Montpellier, UMR9002, 34396 Montpellier, France
| | - Dany Severac
- MGX-Montpellier GenomiX, 34094 Montpellier, France
| | | | - Olivier Schwartz
- Institut Pasteur, Virus and Immunity Unit, URA CNRS 3015, 75015 Paris, France
| | - Yamina Bennasser
- Institut de Génétique Humaine, Laboratoire de Virologie Moléculaire, Université de Montpellier, CNRS UMR9002, 34000 Montpellier, France
| | - Monsef Benkirane
- Institut de Génétique Humaine, Laboratoire de Virologie Moléculaire, Université de Montpellier, CNRS UMR9002, 34000 Montpellier, France.
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Martinez-Zapien D, Saliou JM, Han X, Atmanene C, Proux F, Cianférani S, Dock-Bregeon AC. Intermolecular recognition of the non-coding RNA 7SK and HEXIM protein in perspective. Biochimie 2015; 117:63-71. [PMID: 25863285 DOI: 10.1016/j.biochi.2015.03.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Accepted: 03/25/2015] [Indexed: 11/18/2022]
Abstract
A 7SKsnRNP complex, comprising the non-coding RNA 7SK and proteins MePCE and LARP7, participates in the regulation of the transcription elongation by RNA-polymerase II in higher eukaryotes. Binding of a HEXIM protein triggers the inhibition of the kinase complex P-TEFb, a key actor of the switch from paused transcription to elongation. The present paper reviews what is known about the specific recognition of the 7SK RNA by the HEXIM protein. HEXIM uses an arginine-rich motif (ARM) peptide to bind one specific site in the 5'-hairpin of the 7SK RNA. Since HEXIM forms a dimer, what happens with the second ARM impacts the assembly symmetry. In order to help sort through possible models, a combination of native mass spectrometry and electrophoretic mobility shift assays was used. It provides evidence that only one ARM of the HEXIM dimer is directly binding to the RNA hairpin and that another sequence downstream of the ARM participates in a second binding event allowing the other monomer of HEXIM to bind the RNA.
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Affiliation(s)
- Denise Martinez-Zapien
- Department of Integrated Structural Biology, Centre for Integrative Biology (CBI), Institute of Genetics and of Molecular and Cellular Biology (IGBMC) 67404 Illkirch, France; Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France; Institut National de la Santé et de la Recherche Médicale (INSERM) U964, Illkirch, France; Université de Strasbourg, Strasbourg, France; Biotechnologie et Signalisation Cellulaire UMR 7242, Ecole Supérieure de Biotechnologie de Strasbourg, Boulevard Sébastien Brant, BP 10413, F-67412 Illkirch, France.
| | - Jean-Michel Saliou
- BioOrganic Mass Spectrometry Laboratory (LSMBO), Université de Strasbourg, IPHC, 25 rue Becquerel, 67087 Strasbourg, France; CNRS, UMR7178, 67087 Strasbourg, France; Center for Infection and Immunity of Lille (CIIL), Institut Pasteur de Lille, CNRS UMR 8204, INSERM U1019, Université Lille Nord de France, 1 rue du Pr. Calmette, 59000 Lille, France.
| | - Xiao Han
- Department of Functional Genomics, Institut de Biologie de l''Ecole Normale Supérieure (IBENS), 75005 Paris, France; CNRS UMR 8197, 75005 Paris, France; INSERM U1024, 75005 Paris, France; Key Laboratory of Brain Functional Genomics, East China Normal University (ECNU), Shanghai, PR China.
| | - Cedric Atmanene
- BioOrganic Mass Spectrometry Laboratory (LSMBO), Université de Strasbourg, IPHC, 25 rue Becquerel, 67087 Strasbourg, France; CNRS, UMR7178, 67087 Strasbourg, France.
| | - Florence Proux
- Department of Functional Genomics, Institut de Biologie de l''Ecole Normale Supérieure (IBENS), 75005 Paris, France; CNRS UMR 8197, 75005 Paris, France; INSERM U1024, 75005 Paris, France.
| | - Sarah Cianférani
- BioOrganic Mass Spectrometry Laboratory (LSMBO), Université de Strasbourg, IPHC, 25 rue Becquerel, 67087 Strasbourg, France; CNRS, UMR7178, 67087 Strasbourg, France.
| | - Anne-Catherine Dock-Bregeon
- Department of Functional Genomics, Institut de Biologie de l''Ecole Normale Supérieure (IBENS), 75005 Paris, France; CNRS UMR 8197, 75005 Paris, France; INSERM U1024, 75005 Paris, France.
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11
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Uchikawa E, Natchiar KS, Han X, Proux F, Roblin P, Zhang E, Durand A, Klaholz BP, Dock-Bregeon AC. Structural insight into the mechanism of stabilization of the 7SK small nuclear RNA by LARP7. Nucleic Acids Res 2015; 43:3373-88. [PMID: 25753663 PMCID: PMC4381077 DOI: 10.1093/nar/gkv173] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 02/20/2015] [Indexed: 12/17/2022] Open
Abstract
The non-coding RNA 7SK is the scaffold for a small nuclear ribonucleoprotein (7SKsnRNP) which regulates the function of the positive transcription elongation factor P-TEFb in the control of RNA polymerase II elongation in metazoans. The La-related protein LARP7 is a component of the 7SKsnRNP required for stability and function of the RNA. To address the function of LARP7 we determined the crystal structure of its La module, which binds a stretch of uridines at the 3′-end of 7SK. The structure shows that the penultimate uridine is tethered by the two domains, the La-motif and the RNA-recognition motif (RRM1), and reveals that the RRM1 is significantly smaller and more exposed than in the La protein. Sequence analysis suggests that this impacts interaction with 7SK. Binding assays, footprinting and small-angle scattering experiments show that a second RRM domain located at the C-terminus binds the apical loop of the 3′ hairpin of 7SK, while the N-terminal domains bind at its foot. Our results suggest that LARP7 uses both its N- and C-terminal domains to stabilize 7SK in a closed structure, which forms by joining conserved sequences at the 5′-end with the foot of the 3′ hairpin and has thus functional implications.
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Affiliation(s)
- Emiko Uchikawa
- Department of Integrated Structural Biology, Centre for Integrative Biology (CBI), IGBMC (Institute of Genetics and of Molecular and Cellular Biology, 67404 Illkirch, France Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France Institut National de la Santé et de la Recherche Médicale (INSERM) U964, Illkirch, France Université de Strasbourg, 67000 Strasbourg, France
| | - Kundhavai S Natchiar
- Department of Integrated Structural Biology, Centre for Integrative Biology (CBI), IGBMC (Institute of Genetics and of Molecular and Cellular Biology, 67404 Illkirch, France Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France Institut National de la Santé et de la Recherche Médicale (INSERM) U964, Illkirch, France Université de Strasbourg, 67000 Strasbourg, France
| | - Xiao Han
- Department of functional genomics, Institut de Biologie de l'Ecole Normale Supérieure (IBENS), 75005 Paris, France CNRS UMR 8197, 75005 Paris, France INSERM U1024, 75005 Paris, France Key Laboratory of Brain Functional Genomics, East China Normal University (ECNU), 200241 Shanghai, PR China
| | - Florence Proux
- Department of functional genomics, Institut de Biologie de l'Ecole Normale Supérieure (IBENS), 75005 Paris, France CNRS UMR 8197, 75005 Paris, France INSERM U1024, 75005 Paris, France
| | - Pierre Roblin
- SOLEIL Synchrotron, 91192 Gif-sur-Yvette, France INRA-URBIA, 44316 Nantes, France
| | - Elodie Zhang
- Department of functional genomics, Institut de Biologie de l'Ecole Normale Supérieure (IBENS), 75005 Paris, France CNRS UMR 8197, 75005 Paris, France INSERM U1024, 75005 Paris, France
| | - Alexandre Durand
- Department of Integrated Structural Biology, Centre for Integrative Biology (CBI), IGBMC (Institute of Genetics and of Molecular and Cellular Biology, 67404 Illkirch, France Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France Institut National de la Santé et de la Recherche Médicale (INSERM) U964, Illkirch, France Université de Strasbourg, 67000 Strasbourg, France
| | - Bruno P Klaholz
- Department of Integrated Structural Biology, Centre for Integrative Biology (CBI), IGBMC (Institute of Genetics and of Molecular and Cellular Biology, 67404 Illkirch, France Centre National de la Recherche Scientifique (CNRS) UMR 7104, Illkirch, France Institut National de la Santé et de la Recherche Médicale (INSERM) U964, Illkirch, France Université de Strasbourg, 67000 Strasbourg, France
| | - Anne-Catherine Dock-Bregeon
- Department of functional genomics, Institut de Biologie de l'Ecole Normale Supérieure (IBENS), 75005 Paris, France CNRS UMR 8197, 75005 Paris, France INSERM U1024, 75005 Paris, France
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12
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Fujinaga K, Luo Z, Peterlin BM. Genetic analysis of the structure and function of 7SK small nuclear ribonucleoprotein (snRNP) in cells. J Biol Chem 2015; 289:21181-90. [PMID: 24917669 DOI: 10.1074/jbc.m114.557751] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The positive transcription elongation factor b (P-TEFb), comprised of cyclin-dependent kinase 9 (CDK9) and cyclins T1 (CycT1) or T2 (CycT2), activates eukaryotic transcription elongation. In growing cells, P-TEFb exists in active and inactive forms. In the latter, it is incorporated into the 7SK small nuclear ribonucleoprotein, which contains hexamethylene bisacetamide-induced proteins (HEXIM) 1 or 2, La-related protein 7 (LaRP7), methyl phosphate capping enzyme, and 7SK small nuclear RNA (7SK). HEXIM1 inhibits the kinase activity of CDK9 via interactions between 7SK, HEXIM1, and CycT1. LaRP7 and methyl phosphate capping enzyme interact with 7SK independently of HEXIM1 and P-TEFb. To analyze genetic interactions between HEXIM1 and/or LaRP7 and 7SK using a cell-based system, we established artificial heterologous RNA tethering assays in which reporter gene expression depended on interactions between selected regions of 7SK and its cognate binding partners fused to a strong activator. This system enabled us to map the HEXIM1- and LaRP7- binding regions of 7SK. Assays with various mutant 7SK plasmid targets revealed that the 5'U-Ubulge and central loop of stem-loop I or RNA motif 3 of 7SK are required for transactivation, suggesting that HEXIM1 and CycT1 form a combinatorial binding surface for 7SK. Moreover, a region in HEXIM1 C-terminal to its previously mapped RNA-binding motif was also required for interactions between HEXIM1 and 7SK. Finally, a tyrosine-to-alanine mutation in HEXIM1, which is critical for its inhibitory effect on CDK9, changed HEXIM1 into an activator. These cell-based assays elucidate this important aspect of transcription elongation in vivo.
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Dai Q, Luan G, Deng L, Lei T, Kang H, Song X, Zhang Y, Xiao ZX, Li Q. Primordial dwarfism gene maintains Lin28 expression to safeguard embryonic stem cells from premature differentiation. Cell Rep 2014; 7:735-46. [PMID: 24768001 DOI: 10.1016/j.celrep.2014.03.053] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2013] [Revised: 01/15/2014] [Accepted: 03/20/2014] [Indexed: 01/09/2023] Open
Abstract
Primordial dwarfism (PD) is characterized by global growth failure, both during embryogenesis and postnatally. Loss-of-function germline mutations in La ribonucleoprotein domain family, member 7 (LAPR7) have recently been linked to PD. Paradoxically, LARP7 deficiency was previously assumed to be associated with increased cell growth and proliferation via activation of positive transcription elongation factor b (P-TEFb). Here, we show that Larp7 deficiency likely does not significantly increase P-TEFb activity. We further discover that Larp7 knockdown does not affect pluripotency but instead primes embryonic stem cells (ESCs) for differentiation via downregulation of Lin28, a positive regulator of organismal growth. Mechanistically, we show that Larp7 interacts with a poly(A) polymerase Star-PAP to maintain Lin28 mRNA stability. We propose that proper regulation of Lin28 and PTEFb is essential for embryonic cells to achieve a sufficient number of cell divisions prior to differentiation and ultimately to maintain proper organismal size.
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Affiliation(s)
- Qian Dai
- Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu 610064, Sichuan, China
| | - Guangxin Luan
- Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu 610064, Sichuan, China
| | - Li Deng
- Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu 610064, Sichuan, China
| | - Tingjun Lei
- Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu 610064, Sichuan, China
| | - Han Kang
- Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu 610064, Sichuan, China
| | - Xu Song
- Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu 610064, Sichuan, China
| | - Yujun Zhang
- Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu 610064, Sichuan, China
| | - Zhi-Xiong Xiao
- Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu 610064, Sichuan, China
| | - Qintong Li
- Center of Growth, Metabolism, and Aging, Key Laboratory of Bio-Resources and Eco-Environment, and State Key Laboratory of Biotherapy, College of Life Sciences, Sichuan University, Chengdu 610064, Sichuan, China.
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14
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Mizutani T, Ishizaka A, Suzuki Y, Iba H. 7SK small nuclear ribonucleoprotein complex is recruited to the HIV-1 promoter via short viral transcripts. FEBS Lett 2014; 588:1630-6. [PMID: 24607481 DOI: 10.1016/j.febslet.2014.01.067] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 01/13/2014] [Accepted: 01/14/2014] [Indexed: 10/25/2022]
Abstract
In this study, we demonstrate that the 7SK small nuclear ribonucleoprotein (snRNP) complex is recruited to the HIV-1 promoter via newly-synthesized HIV-1 nascent transcripts (short transcripts) in an hnRNP A1-dependent manner and negatively regulates viral transcript elongation. Our deep-sequence analysis showed these short transcripts were mainly arrested at approximately +50 to +70 nucleotides from the transcriptional start site in the U1 cells, an HIV-1 latent model. TNF-α treatment promptly disrupted the 7SK snRNP complex on the nascent transcripts and viral elongated transcripts were increased. This report provides insight into how 7SK snRNP complex is recruited to HIV-1 promoter in the absence of Tat.
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Affiliation(s)
- Taketoshi Mizutani
- Division of Host-Parasite Interaction, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan; Laboratory of Basic Science, Institute of Microbial Chemistry;BIKAKEN, 3-14-23 Kamiosaki, Shinagawa-ku, Tokyo 141-0021, Japan; RNA and Biofunctions, Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
| | - Aya Ishizaka
- Division of Host-Parasite Interaction, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan; Laboratory of Basic Science, Institute of Microbial Chemistry;BIKAKEN, 3-14-23 Kamiosaki, Shinagawa-ku, Tokyo 141-0021, Japan
| | - Yutaka Suzuki
- Department of Medical Genome Sciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8568, Japan
| | - Hideo Iba
- Division of Host-Parasite Interaction, Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108-8639, Japan
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15
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Liu P, Xiang Y, Fujinaga K, Bartholomeeusen K, Nilson KA, Price DH, Peterlin BM. Release of positive transcription elongation factor b (P-TEFb) from 7SK small nuclear ribonucleoprotein (snRNP) activates hexamethylene bisacetamide-inducible protein (HEXIM1) transcription. J Biol Chem 2014; 289:9918-25. [PMID: 24515107 DOI: 10.1074/jbc.m113.539015] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
By phosphorylating negative elongation factors and the C-terminal domain of RNA polymerase II (RNAPII), positive transcription elongation factor b (P-TEFb), which is composed of CycT1 or CycT2 and CDK9, activates eukaryotic transcription elongation. In growing cells, it is found in active and inactive forms. In the former, free P-TEFb is a potent transcriptional coactivator. In the latter, it is inhibited by HEXIM1 or HEXIM2 in the 7SK small nuclear ribonucleoprotein (snRNP), which contains, additionally, 7SK snRNA, methyl phosphate-capping enzyme (MePCE), and La-related protein 7 (LARP7). This P-TEFb equilibrium determines the state of growth and proliferation of the cell. In this study, the release of P-TEFb from the 7SK snRNP led to increased synthesis of HEXIM1 but not HEXIM2 in HeLa cells, and this occurred only from an unannotated, proximal promoter. ChIP with sequencing revealed P-TEFb-sensitive poised RNA polymerase II at this proximal but not the previously annotated distal HEXIM1 promoter. Its immediate upstream sequences were fused to luciferase reporters and were found to be responsive to many P-TEFb-releasing compounds. The superelongation complex subunits AF4/FMR2 family member 4 (AFF4) and elongation factor RNA polymerase II 2 (ELL2) were recruited to this proximal promoter after P-TEFb release and were required for its transcriptional effects. Thus, P-TEFb regulates its own equilibrium in cells, most likely to maintain optimal cellular homeostasis.
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Affiliation(s)
- Pingyang Liu
- From the Departments of Medicine, Microbiology, and Immunology, Rosalind Russell Medical Research Center, University of California, San Francisco, California 94143-0703, and
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16
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Affiliation(s)
- Jiannan Guo
- Biochemistry Department, University of Iowa , Iowa City, Iowa 52242, United States
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17
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Zhao W, Liu Y, Timani KA, He JJ. Tip110 protein binds to unphosphorylated RNA polymerase II and promotes its phosphorylation and HIV-1 long terminal repeat transcription. J Biol Chem 2013; 289:190-202. [PMID: 24217245 DOI: 10.1074/jbc.m113.529784] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transcription plays an important role in both HIV-1 gene expression and replication and mandates complicated but coordinated interactions between the host and virus. Our previous studies have shown that an HIV-1 Tat-interacting protein of 110 kDa, Tip110, binds to and enhances Tat function in Tat-mediated HIV-1 gene transcription and replication (Liu, Y., Li, J., Kim, B. O., Pace, B. S., and He, J. J. (2002) HIV-1 Tat protein-mediated transactivation of the HIV-1 long terminal repeat promoter is potentiated by a novel nuclear Tat-interacting protein of 110 kDa, Tip110. J. Biol. Chem. 277, 23854-23863). However, the underlying molecular mechanisms by which this takes place were not understood. In this study, we demonstrated that Tip110 bound to unphosphorylated RNA polymerase II (RNAPII) in a direct and specific manner. In addition, we detected Tip110 at the HIV-1 long terminal repeat (LTR) promoter and found that Tip110 expression was associated with increased phosphorylation of serine 2 of the heptapeptide repeats within the RNAPII C-terminal domain and increased recruitment of positive transcription elongation factor b to the LTR promoter. Consistent with these findings, we showed that Tip110 interaction with Tat directly enhanced transcription elongation of the LTR promoter. Taken together, these findings have provided additional and mechanistic evidence to support Tip110 function in HIV-1 transcription.
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Affiliation(s)
- Weina Zhao
- From the Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana 46202 and
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18
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Fujinaga K, Barboric M, Li Q, Luo Z, Price DH, Peterlin BM. PKC phosphorylates HEXIM1 and regulates P-TEFb activity. Nucleic Acids Res 2012; 40:9160-70. [PMID: 22821562 PMCID: PMC3467075 DOI: 10.1093/nar/gks682] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The positive transcription elongation factor b (P-TEFb) regulates RNA polymerase II elongation. In cells, P-TEFb partitions between small active and larger inactive states. In the latter, HEXIM1 binds to 7SK snRNA and recruits as well as inactivates P-TEFb in the 7SK snRNP. Several stimuli can affect this P-TEFb equilibrium. In this study, we demonstrate that protein kinase C (PKC) phosphorylates the serine at position158 (S158) in HEXIM1. This phosphorylated HEXIM1 protein neither binds to 7SK snRNA nor inhibits P-TEFb. Phorbol esters or the engagement of the T cell antigen receptor, which activate PKC and the expression of the constitutively active (CA) PKCθ protein, which is found in T cells, inhibit the formation of the 7SK snRNP. All these stimuli increase P-TEFb-dependent transcription. In contrast, the kinase-negative PKCθ and the mutant HEXIM1 (S158A) proteins block effects of these PKC-activating stimuli. These results indicate that the phosphorylation of HEXIM1 by PKC represents a major regulatory step of P-TEFb activity in cells.
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Affiliation(s)
- Koh Fujinaga
- Departments of Medicine, Microbiology and Immunology, Rosalind Russell Research Center, University of California, San Francisco, San Francisco, CA 94143-0703, USA
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19
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Ramakrishnan R, Chiang K, Liu H, Budhiraja S, Donahue H, Rice AP. Making a Short Story Long: Regulation of P-TEFb and HIV-1 Transcriptional Elongation in CD4+ T Lymphocytes and Macrophages. BIOLOGY 2012; 1:94-115. [PMID: 24832049 PMCID: PMC4011037 DOI: 10.3390/biology1010094] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/15/2012] [Revised: 06/07/2012] [Accepted: 06/11/2012] [Indexed: 12/22/2022]
Abstract
Productive transcription of the integrated HIV-1 provirus is restricted by cellular factors that inhibit RNA polymerase II elongation. The viral Tat protein overcomes this by recruiting a general elongation factor, P-TEFb, to the TAR RNA element that forms at the 5' end of nascent viral transcripts. P-TEFb exists in multiple complexes in cells, and its core consists of a kinase, Cdk9, and a regulatory subunit, either Cyclin T1 or Cyclin T2. Tat binds directly to Cyclin T1 and thereby targets the Cyclin T1/P-TEFb complex that phosphorylates the CTD of RNA polymerase II and the negative factors that inhibit elongation, resulting in efficient transcriptional elongation. P-TEFb is tightly regulated in cells infected by HIV-1-CD4+ T lymphocytes and monocytes/macrophages. A number of mechanisms have been identified that inhibit P-TEFb in resting CD4+ T lymphocytes and monocytes, including miRNAs that repress Cyclin T1 protein expression and dephosphorylation of residue Thr186 in the Cdk9 T-loop. These repressive mechanisms are overcome upon T cell activation and macrophage differentiation when the permissivity for HIV-1 replication is greatly increased. This review will summarize what is currently known about mechanisms that regulate P-TEFb and how this regulation impacts HIV-1 replication and latency.
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Affiliation(s)
- Rajesh Ramakrishnan
- Department of Molecular Virology & Microbiology, Baylor College of Medicine, Houston, TX 77030, USA.
| | - Karen Chiang
- Department of Molecular Virology & Microbiology, Baylor College of Medicine, Houston, TX 77030, USA.
| | - Hongbing Liu
- Department of Molecular Virology & Microbiology, Baylor College of Medicine, Houston, TX 77030, USA.
| | - Sona Budhiraja
- Department of Molecular Virology & Microbiology, Baylor College of Medicine, Houston, TX 77030, USA.
| | - Hart Donahue
- Department of Molecular Virology & Microbiology, Baylor College of Medicine, Houston, TX 77030, USA.
| | - Andrew P Rice
- Department of Molecular Virology & Microbiology, Baylor College of Medicine, Houston, TX 77030, USA.
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20
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HEXIM1-binding elements on mRNAs identified through transcriptomic SELEX and computational screening. Biochimie 2012; 94:1900-9. [PMID: 22609015 DOI: 10.1016/j.biochi.2012.05.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2012] [Accepted: 05/04/2012] [Indexed: 11/20/2022]
Abstract
The positive transcription elongation factor b (P-TEFb) is one of the main regulatory factors of the transcription mediated by RNA polymerase II (RNAPII). P-TEFb promotes transcriptional elongation by phosphorylating its targets, which include the C-terminal domain of RNAPII. The activity of P-TEFb is negatively regulated by an RNA-binding protein HEXIM1 in association with 7SK snRNA. To search for other cellular RNAs that bind to HEXIM1, we used systematic evolution of ligands by exponential enrichment (SELEX) with the HeLa cDNA library as the initial pool source. We identified cad mRNA as a HEXIM1-binding RNA and confirmed their association in HeLa cells. In vitro mutational analysis showed that cad mRNA binds to HEXIM1 through its bulged stem structure located in exon 11. In addition, a computational search revealed other RNAs with similar stem structures, including brd4 and tcf3 mRNAs, both of which were shown to be coimmunoprecipitable with anti-HEXIM1 antibody in HeLa cells. Our findings suggest a possible role for HEXIM1 in the regulation of specific gene expressions.
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21
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Nguyen D, Krueger BJ, Sedore SC, Brogie JE, Rogers JT, Rajendra TK, Saunders A, Matera AG, Lis JT, Uguen P, Price DH. The Drosophila 7SK snRNP and the essential role of dHEXIM in development. Nucleic Acids Res 2012; 40:5283-97. [PMID: 22379134 PMCID: PMC3384314 DOI: 10.1093/nar/gks191] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Regulation of the positive transcription elongation factor, P-TEFb, plays a major role in controlling mammalian transcription and this is accomplished in part by controlled release of P-TEFb from the 7SK snRNP that sequesters the kinase in an inactive state. We demonstrate here that a similar P-TEFb control system exists in Drosophila. We show that an RNA previously suggested to be a 7SK homolog is, in fact, associated with P-TEFb, through the action of a homolog of the human HEXIM1/2 proteins (dHEXIM). In addition, a Drosophila La related protein (now called dLARP7) is shown to be the functional homolog of human LARP7. The Drosophila 7SK snRNP (d7SK snRNP) responded to treatment of cells with P-TEFb inhibitors and to nuclease treatment of cell lysates by releasing P-TEFb. Supporting a critical role for the d7SK snRNP in Drosophila development, dLARP7 and dHEXIM were found to be ubiquitously expressed throughout embryos and tissues at all stages. Importantly, knockdown of dHEXIM was embryonic lethal, and reduction of dHEXIM in specific tissues led to serious developmental defects. Our results suggest that regulation of P-TEFb by the d7SK snRNP is essential for the growth and differentiation of tissues required during Drosophila development.
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Affiliation(s)
- Duy Nguyen
- Université Paris-Sud 11, UMR-S757, Bât. 443, Orsay, F-91405, INSERM, Orsay, F-91405, France
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22
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Mbonye U, Karn J. Control of HIV latency by epigenetic and non-epigenetic mechanisms. Curr HIV Res 2011; 9:554-67. [PMID: 22211660 PMCID: PMC3319922 DOI: 10.2174/157016211798998736] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Revised: 10/10/2011] [Accepted: 10/21/2011] [Indexed: 12/17/2022]
Abstract
Intensive antiretroviral therapy successfully suppresses viral replication but is unable to eradicate the virus. HIV persists in a small number of resting memory T cells where HIV has been transcriptionally silenced. This review will focus on recent insights into the HIV transcriptional control mechanisms that provide the biochemical basis for understanding latency. There are no specific repressors of HIV transcription encoded by the virus, instead latency arises when the regulatory feedback mechanism driven by HIV Tat expression is disrupted. Small changes in transcriptional initiation, induced by epigenetic silencing, lead to profound restrictions in Tat levels and force the entry of proviruses into latency. In resting memory T cells, which carry the bulk of the latent viral pool, additional restrictions, especially the limiting cellular levels of the essential Tat cofactor P-TEFb and the transcription initiation factors NF-κB and NFAT ensure that the provirus remains silenced unless the host cell is activated. The detailed understanding of HIV transcription is providing a framework for devising new therapeutic strategies designed to purge the latent viral pool. Importantly, the recognition that there are multiple restrictions imposed on latent proviruses suggest that proviral reactivation will not be achieved when only a single reactivation step is targeted and that any optimal activation strategy will require both removal of epigenetic blocks and the activation of P-TEFb.
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Affiliation(s)
| | - Jonathan Karn
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, OH 44106, USA
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Nilson KA, Price DH. The Role of RNA Polymerase II Elongation Control in HIV-1 Gene Expression, Replication, and Latency. GENETICS RESEARCH INTERNATIONAL 2011; 2011:726901. [PMID: 22567366 PMCID: PMC3335632 DOI: 10.4061/2011/726901] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 07/22/2011] [Indexed: 11/20/2022]
Abstract
HIV-1 usurps the RNA polymerase II elongation control machinery to regulate the expression of its genome during lytic and latent viral stages. After integration into the host genome, the HIV promoter within the long terminal repeat (LTR) is subject to potent downregulation in a postinitiation step of transcription. Once produced, the viral protein Tat commandeers the positive transcription elongation factor, P-TEFb, and brings it to the engaged RNA polymerase II (Pol II), leading to the production of viral proteins and genomic RNA. HIV can also enter a latent phase during which factors that regulate Pol II elongation may play a role in keeping the virus silent. HIV, the causative agent of AIDS, is a worldwide health concern. It is hoped that knowledge of the mechanisms regulating the expression of the HIV genome will lead to treatments and ultimately a cure.
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Affiliation(s)
- Kyle A Nilson
- Molecular and Cellular Biology Program, The University of Iowa, Iowa City, IA 52242, USA
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24
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Peterlin BM, Brogie JE, Price DH. 7SK snRNA: a noncoding RNA that plays a major role in regulating eukaryotic transcription. WILEY INTERDISCIPLINARY REVIEWS-RNA 2011; 3:92-103. [PMID: 21853533 DOI: 10.1002/wrna.106] [Citation(s) in RCA: 137] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The human 7SK small nuclear RNA (snRNA) is an abundant noncoding RNA whose function has been conserved in evolution from invertebrates to humans. It is transcribed by RNA polymerase III (RNAPIII) and is located in the nucleus. Together with associated cellular proteins, 7SK snRNA regulates the activity of the positive transcription elongation factor b (P-TEFb). In humans, this regulation is accomplished by the recruitment of P-TEFb by the 7SK snRNA-binding proteins, hexamethylene bisacetamide (HMBA)-induced mRNA 1/2 (HEXIM1 or HEXIM2), which inhibit the kinase activity of P-TEFb. P-TEFb regulates the transition of promoter proximally paused RNA polymerase II (RNAPII) into productive elongation, thereby, allowing efficient mRNA production. The protein composition of the 7SK small nuclear ribonucleoprotein (snRNP) is regulated dynamically. While the Lupus antigen (La)-related protein 7 (LARP7) is a constitutive component, the methylphosphate capping enzyme (MePCE) associates secondarily to phosphorylate the 5' end of 7SK snRNA. The release of active P-TEFb is closely followed by release of HEXIM proteins and both are replaced by heterogeneous nuclear ribonucleoproteins (hnRNPs). The released P-TEFb activates the expression of most cellular and viral genes. Regulated release of P-TEFb determines the expression pattern of many of the genes that respond to environmental stimuli and regulate growth, proliferation, and differentiation of cells.
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Affiliation(s)
- B Matija Peterlin
- Department of Medicine, Rosalind Russel Medical Research Center, University of California, San Francisco, CA, USA.
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Choudhary SK, Margolis DM. Curing HIV: Pharmacologic approaches to target HIV-1 latency. Annu Rev Pharmacol Toxicol 2011; 51:397-418. [PMID: 21210747 DOI: 10.1146/annurev-pharmtox-010510-100237] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
HIV-1 infection persists even after years of antiretroviral therapy (ART). Although ART can halt viral replication and thereby reduce viremia to clinically undetectable levels, proviral latency established within the host genome remains largely unaffected by ART and can replenish systemic infection following interruption of therapy. Pharmacologic strategies, which not only target viral replication but also deplete proviral infection, are required for successful clearance of HIV-1 infection. This review highlights the current understanding of molecular mechanisms that establish and maintain HIV-1 latency in its major reservoir, the resting memory CD4(+) T cell. We also identify the molecular targets that might be exploited to induce HIV-1 expression, remove epigenetic restrictions, or enhance effective transcription. Finally, we discuss the potential pharmacologic approaches toward targeting viral persistence in different cellular and anatomical reservoirs to achieve a cure of HIV-1 infection.
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Affiliation(s)
- Shailesh K Choudhary
- Departments of Medicine, University of North Carolina at Chapel Hill, 27599, USA
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Muniz L, Egloff S, Ughy B, Jády BE, Kiss T. Controlling cellular P-TEFb activity by the HIV-1 transcriptional transactivator Tat. PLoS Pathog 2010; 6:e1001152. [PMID: 20976203 PMCID: PMC2954905 DOI: 10.1371/journal.ppat.1001152] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Accepted: 09/13/2010] [Indexed: 11/18/2022] Open
Abstract
The human immunodeficiency virus 1 (HIV-1) transcriptional transactivator (Tat) is essential for synthesis of full-length transcripts from the integrated viral genome by RNA polymerase II (Pol II). Tat recruits the host positive transcription elongation factor b (P-TEFb) to the HIV-1 promoter through binding to the transactivator RNA (TAR) at the 5′-end of the nascent HIV transcript. P-TEFb is a general Pol II transcription factor; its cellular activity is controlled by the 7SK small nuclear RNA (snRNA) and the HEXIM1 protein, which sequester P-TEFb into transcriptionally inactive 7SK/HEXIM/P-TEFb snRNP. Besides targeting P-TEFb to HIV transcription, Tat also increases the nuclear level of active P-TEFb through promoting its dissociation from the 7SK/HEXIM/P-TEFb RNP by an unclear mechanism. In this study, by using in vitro and in vivo RNA-protein binding assays, we demonstrate that HIV-1 Tat binds with high specificity and efficiency to an evolutionarily highly conserved stem-bulge-stem motif of the 5′-hairpin of human 7SK snRNA. The newly discovered Tat-binding motif of 7SK is structurally and functionally indistinguishable from the extensively characterized Tat-binding site of HIV TAR and importantly, it is imbedded in the HEXIM-binding elements of 7SK snRNA. We show that Tat efficiently replaces HEXIM1 on the 7SK snRNA in vivo and therefore, it promotes the disassembly of the 7SK/HEXIM/P-TEFb negative transcriptional regulatory snRNP to augment the nuclear level of active P-TEFb. This is the first demonstration that HIV-1 specifically targets an important cellular regulatory RNA, most probably to promote viral transcription and replication. Demonstration that the human 7SK snRNA carries a TAR RNA-like Tat-binding element that is essential for the normal transcriptional regulatory function of 7SK questions the viability of HIV therapeutic approaches based on small drugs blocking the Tat-binding site of HIV TAR. Expression and replication of the human immunodeficiency virus (HIV) is supported by the viral transcriptional transactivator (Tat) that recruits the host positive transcription elongation factor b (P-TEFb) to the promoter of the integrated viral genome. Here, we demonstrate that HIV Tat specifically and efficiently binds to the host 7SK small nuclear RNA (snRNA) that is a negative regulator of P-TEFb. Although HIV Tat has been reported to interact with a plethora of host factors, our results indicate that the 7SK transcriptional regulatory snRNA is a major and important cellular target of HIV Tat. We demonstrate that binding of Tat to the 7SK snRNA disrupts the 7SK-P-TEFb negative transcriptional regulatory complex and releases active P-TEFb. Thus, we propose that Tat not only targets P-TEFb for HIV transcription, but also modulates the nuclear level of active P-TEFb in HIV-infected cells.
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Affiliation(s)
- Lisa Muniz
- Laboratoire de Biologie Moléculaire Eucaryote du CNRS, UMR5099, IFR109 CNRS, Université Paul Sabatier, Toulouse, France
| | - Sylvain Egloff
- Laboratoire de Biologie Moléculaire Eucaryote du CNRS, UMR5099, IFR109 CNRS, Université Paul Sabatier, Toulouse, France
| | - Bettina Ughy
- Laboratoire de Biologie Moléculaire Eucaryote du CNRS, UMR5099, IFR109 CNRS, Université Paul Sabatier, Toulouse, France
- Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Beáta E. Jády
- Laboratoire de Biologie Moléculaire Eucaryote du CNRS, UMR5099, IFR109 CNRS, Université Paul Sabatier, Toulouse, France
| | - Tamás Kiss
- Laboratoire de Biologie Moléculaire Eucaryote du CNRS, UMR5099, IFR109 CNRS, Université Paul Sabatier, Toulouse, France
- Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
- * E-mail:
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The mechanism of release of P-TEFb and HEXIM1 from the 7SK snRNP by viral and cellular activators includes a conformational change in 7SK. PLoS One 2010; 5:e12335. [PMID: 20808803 PMCID: PMC2925947 DOI: 10.1371/journal.pone.0012335] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Accepted: 08/01/2010] [Indexed: 12/30/2022] Open
Abstract
Background The positive transcription elongation factor, P-TEFb, is required for the production of mRNAs, however the majority of the factor is present in the 7SK snRNP where it is inactivated by HEXIM1. Expression of HIV-1 Tat leads to release of P-TEFb and HEXIM1 from the 7SK snRNP in vivo, but the release mechanisms are unclear. Methodology/Principal Findings We developed an in vitro P-TEFb release assay in which the 7SK snRNP immunoprecipitated from HeLa cell lysates using antibodies to LARP7 was incubated with potential release factors. We found that P-TEFb was directly released from the 7SK snRNP by HIV-1 Tat or the P-TEFb binding region of the cellular activator Brd4. Glycerol gradient sedimentation analysis was used to demonstrate that the same Brd4 protein transfected into HeLa cells caused the release of P-TEFb and HEXIM1 from the 7SK snRNP in vivo. Although HEXIM1 binds tightly to 7SK RNA in vitro, release of P-TEFb from the 7SK snRNP is accompanied by the loss of HEXIM1. Using a chemical modification method, we determined that concomitant with the release of HEXIM1, 7SK underwent a major conformational change that blocks re-association of HEXIM1. Conclusions/Significance Given that promoter proximally paused polymerases are present on most human genes, understanding how activators recruit P-TEFb to those genes is critical. Our findings reveal that the two tested activators can extract P-TEFb from the 7SK snRNP. Importantly, we found that after P-TEFb is extracted a dramatic conformational change occurred in 7SK concomitant with the ejection of HEXIM1. Based on our findings, we hypothesize that reincorporation of HEXIM1 into the 7SK snRNP is likely the regulated step of reassembly of the 7SK snRNP containing P-TEFb.
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Lebars I, Martinez-Zapien D, Durand A, Coutant J, Kieffer B, Dock-Bregeon AC. HEXIM1 targets a repeated GAUC motif in the riboregulator of transcription 7SK and promotes base pair rearrangements. Nucleic Acids Res 2010; 38:7749-63. [PMID: 20675720 PMCID: PMC2995076 DOI: 10.1093/nar/gkq660] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
7SK snRNA, an abundant RNA discovered in human nucleus, regulates transcription by RNA polymerase II (RNAPII). It sequesters and inhibits the transcription elongation factor P-TEFb which, by phosphorylation of RNAPII, switches transcription from initiation to processive elongation and relieves pauses of transcription. This regulation process depends on the association between 7SK and a HEXIM protein, neither isolated partner being able to inhibit P-TEFb alone. In this work, we used a combined NMR and biochemical approach to determine 7SK and HEXIM1 elements that define their binding properties. Our results demonstrate that a repeated GAUC motif located in the upper part of a hairpin on the 5'-end of 7SK is essential for specific HEXIM1 recognition. Binding of a peptide comprising the HEXIM Arginine Rich Motif (ARM) induces an opening of the GAUC motif and stabilization of an internal loop. A conserved proline-serine sequence in the middle of the ARM is shown to be essential for the binding specificity and the conformational change of the RNA. This work provides evidences for a recognition mechanism involving a first event of induced fit, suggesting that 7SK plasticity is involved in the transcription regulation.
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Affiliation(s)
- Isabelle Lebars
- IGBMC, BP10142, 1 rue Laurent Fries, 67404 Illkirch Cedex, France.
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29
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Schönichen A, Bigalke JM, Urbanke C, Grzesiek S, Dames SA, Geyer M. A flexible bipartite coiled coil structure is required for the interaction of Hexim1 with the P-TEFB subunit cyclin T1. Biochemistry 2010; 49:3083-91. [PMID: 20210365 DOI: 10.1021/bi902072f] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Transcription elongation is regulated by the cellular protein Hexim1, which inhibits phosphorylation of RNA polymerase II by interacting with the positive transcription elongation factor P-TEFb. Hexim1 binds directly to Cyclin T1 of P-TEFb with its coiled coil domain that is subdivided into a highly polar N-terminal segment containing nonconservative residues in the dimer interface and a C-terminal segment with an evolutionarily conserved sequence composition. Here we show that the noncanonical sequence composition of the first coiled coil segment is required for the interaction with Cyclin T1 while the second segment keeps the Cyclin T-binding domain dimeric upon binding. Both coiled coil segments exhibit distinct melting points as shown by heat denaturation experiments using circular dichroism spectroscopy. Deletion of the central stammer motif (Delta316-318) leads to a single denaturation reaction, suggesting formation of a continuous coiled coil. Mutation of noncanonical coiled coil residues K284 and Y291 to valines in the dimer interface of the first segment only slightly increases its stability. Concomitantly, deletion of the stammer but not the double point mutation led to a reduced affinity for Cyclin T1 as shown by isothermal titration calorimetry. Moreover, Cyclin T1 bound Hexim1 with a 1:2 stoichiometry, whereas truncation of the C-terminal coiled coil led to formation of an equimolar complex. These observations suggest that binding to Cyclin T1 induces an asymmetry or sterical hindrance in the first coiled coil segment of dimeric Hexim1 that disallows formation of a 2:2 complex as further supported by analytical ultracentrifugation and cross-linking experiments.
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Affiliation(s)
- André Schönichen
- Max-Planck-Institut für molekulare Physiologie, Abteilung Physikalische Biochemie, Otto-Hahn-Strasse 11, 44227 Dortmund, Germany
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Liu TY, Wu SJ, Huang MH, Lo FY, Tsai MH, Tsai CH, Hsu SM, Lin CW. EBV-positive Hodgkin lymphoma is associated with suppression of p21cip1/waf1 and a worse prognosis. Mol Cancer 2010; 9:32. [PMID: 20144199 PMCID: PMC2834611 DOI: 10.1186/1476-4598-9-32] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2009] [Accepted: 02/09/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND About 30-50% of Hodgkin lymphomas (HLs) harbor the Epstein-Barr virus (EBV), but the impact of EBV infection on clinical outcomes has been unclear. EBV-encoded small RNAs (EBERs) are presented in all EBV-infected cells, but their functions are still less understood. RESULTS EBER1 was transfected into two HL cell lines, KMH2 and L428, and microarrays were used to screen for EBER1-induced changes. We found that EBER1 suppressed p21cip1/waf1 transcription in HL cell lines. In addition, positive regulators of p21cip1/waf1 transcription, such as p53, EGR1, and STAT1, were decreased. Suppression of p21cip1/waf1 in the EBER1+ HL cell lines was associated with increased resistance to histone deacetylase inhibitors or proteasome inhibitors, drugs known to cause apoptosis by increasing p21cip1/waf1 levels. On biopsy specimens, EBV+ HLs had weaker expression of both p21cip1/waf1 and active caspase 3. Clinically, suppression of p21cip1/waf1 in EBV+ HLs was associated with a worse 2-year disease-free survival rate (45% for EBV+ HLs vs. 77% for EBV- HLs, p = 0.002). CONCLUSION Although the underlying mechanisms are still relatively unclear, EBER1 inhibits p21cip1/waf1 transcription and prevents apoptosis through down-regulation of p53, EGR1, and STAT1. The anti-apoptotic activity of EBER1 may be important in the rescue of Reed-Sternberg cells from drug-induced apoptosis and in the clinical behaviors of EBV+ HLs.
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Affiliation(s)
- Ting-Yun Liu
- Department of Pathology, National Taiwan University Hospital, National Taiwan University College of Medicine, Taipei, Taiwan
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31
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Czudnochowski N, Vollmuth F, Baumann S, Vogel-Bachmayr K, Geyer M. Specificity of Hexim1 and Hexim2 complex formation with cyclin T1/T2, importin alpha and 7SK snRNA. J Mol Biol 2009; 395:28-41. [PMID: 19883659 DOI: 10.1016/j.jmb.2009.10.055] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2009] [Revised: 10/26/2009] [Accepted: 10/27/2009] [Indexed: 10/20/2022]
Abstract
Positive transcription elongation factor b (P-TEFb) stimulates the transition from transcription initiation to productive elongation by phosphorylation of the C-terminal domain of RNA polymerase II. P-TEFb consists of the cyclin-dependent kinase Cdk9 and a T-type cyclin and is regulated by the small nuclear RNA 7SK and the coupling protein Hexim1 or Hexim2. In this study, we analyzed the tripartite protein-RNA complex formation between Hexim, Cyclin T and 7SK snRNA. Using isothermal titration calorimetry, we observed higher affinities for Cyclin T1-Hexim1 and Cyclin T2-Hexim2 complex formations compared with the interactions in reverse. Importin alpha, which is part of the Ran-mediated nuclear import pathway, bound Hexim1 and Hexim2 with dissociation constants of 2.0 and 0.5 muM, respectively. Furthermore, tripartite complex formations between Cyclin T, Hexim and Importin alpha showed the suitability of a collaborative nuclear import pathway for Cyclin T. Electrophoretic mobility shift assays using radioactively labelled full-length 7SK snRNA revealed a tight association of the RNA to Cyclin T1-Hexim1 with dissociation constants lower than 0.3 muM. Similar binding affinities were recorded for both Hexim orthologues to a 66-mer double-stranded 5' hairpin loop encompassing nucleotides 23-88 of 7SK, while a 39-mer fragment, resulting from different RNA folding predictions, did not bind as tightly. These results provide the molecular basis for the generation of a core complex for the inhibition of P-TEFb.
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Affiliation(s)
- Nadine Czudnochowski
- Abteilung Physikalische Biochemie, Max-Planck-Institut für molekulare Physiologie, Otto-Hahn-Strasse 11, D-44227 Dortmund, Germany
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32
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Bélanger F, Baigude H, Rana TM. U30 of 7SK RNA forms a specific photo-cross-link with Hexim1 in the context of both a minimal RNA-binding site and a fully reconstituted 7SK/Hexim1/P-TEFb ribonucleoprotein complex. J Mol Biol 2009; 386:1094-107. [PMID: 19244621 DOI: 10.1016/j.jmb.2009.01.015] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Eukaryotic transcription by RNA polymerase II is a highly regulated process and divided into three major steps: initiation, elongation, and termination. Each step of transcription is controlled by a number of cellular factors. Positive transcription factor b, P-TEFb, is composed of cyclin-dependent kinase 9 and a regulatory cyclin (T1/T2). P-TEFb promotes transcriptional elongation of RNA polymerase II by using the catalytic function of CDK9 to phosphorylate various substrates during transcription. P-TEFb is inactivated by sequestration in a complex with the Hexim1 protein and 7SK RNA. The structure of this inactive P-TEFb complex and the mechanisms controlling its equilibrium with the active complex are poorly understood. Here, we used a photoactive nucleotide, 4-thioU, to study the interactions between 7SK RNA and Hexim1. We identified a specific cross-link between nucleotide U30 of 7SK RNA and amino acids 210-220 of Hexim1, in the context of both a minimal RNA-binding site and a fully reconstituted 7SK/Hexim1/P-TEFb ribonucleoprotein complex. We show also that a minimal 7SK RNA hairpin comprising nucleotides 24-87 can bind specifically to Hexim1 in vivo. Our results demonstrate directly that the Hexim1 binding site is located in the 24-87 region of 7SK RNA and that the protein residues outside the basic domain of Hexim1 are involved in specific RNA interactions.
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Affiliation(s)
- François Bélanger
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605-2324, USA
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33
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Shimizu N, Yoshikawa N, Wada T, Handa H, Sano M, Fukuda K, Suematsu M, Sawai T, Morimoto C, Tanaka H. Tissue- and context-dependent modulation of hormonal sensitivity of glucocorticoid-responsive genes by hexamethylene bisacetamide-inducible protein 1. Mol Endocrinol 2008; 22:2609-23. [PMID: 18801933 DOI: 10.1210/me.2008-0101] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Physiological and pharmacological processes mediated by glucocorticoids involve tissue- and context-specific regulation of glucocorticoid-responsive gene expression via glucocorticoid receptor (GR). However, the molecular mechanisms underlying such highly coordinated regulation of glucocorticoid actions remain to be studied. We here addressed this issue using atp1a1 and scnn1a, both of which are up-regulated in response to corticosteroids in human embryonic kidney-derived 293 cells, but resistant in liver-derived HepG2 cells. Hexamethylene bisacetamide-inducible protein 1 (HEXIM1) represses gene expression via, at least, two distinct mechanisms, i.e. positive transcription elongation factor b sequestration and direct interaction with GR, and is relatively high in HepG2 cells compared with 293 cells. Given this, we focused on the role of HEXIM1 in transcriptional regulation of these GR target genes. In HepG2 cells, hormone resistance of atp1a1 and scnn1a was diminished by either knockdown of HEXIM1 or overexpression of GR. Such a positive effect of exogenous expression of GR was counteracted by concomitant overexpression of HEXIM1, indicating the balance between GR and HEXIM1 modulates hormonal sensitivity of these genes. In support of this, the hormone-dependent recruitment of RNA polymerase II onto atp1a1 promoter was in parallel with that of GR. Moreover, we revealed that not positive transcription elongation factor b-suppressing activity but direct interaction with GR of HEXIM1 plays a major role in suppression of promoter recruitment of the receptor and subsequent atp1a1 and scnn1a gene activation. Collectively, we may conclude that HEXIM1 may participate in tissue-selective determination of glucocorticoid sensitivity via direct interaction with GR at least in certain gene sets including atp1a1 and scnn1a.
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Affiliation(s)
- Noriaki Shimizu
- Division of Clinical Immunology, Advanced Clinical Research Center, Research Hospital, Institute of Medical Science, University of Tokyo, Tokyo, Japan
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Michels AA, Bensaude O. RNA-driven cyclin-dependent kinase regulation: When CDK9/cyclin T subunits of P-TEFb meet their ribonucleoprotein partners. Biotechnol J 2008; 3:1022-32. [DOI: 10.1002/biot.200800104] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
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35
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Abstract
Recent global analyses have determined that many Drosophila and human genes have engaged polymerase molecules trapped immediately downstream of promoters. These results strongly implicate RNA polymerase II elongation control as a major regulator of differentiation and development.
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Affiliation(s)
- David H Price
- Biochemistry Department, University of Iowa, Iowa City, IA 52240, USA.
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36
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Gurumurthy M, Tan CH, Ng R, Zeiger L, Lau J, Lee J, Dey A, Philp R, Li Q, Lim TM, Price DH, Lane DP, Chao SH. Nucleophosmin interacts with HEXIM1 and regulates RNA polymerase II transcription. J Mol Biol 2008; 378:302-17. [PMID: 18371977 DOI: 10.1016/j.jmb.2008.02.055] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2007] [Revised: 02/18/2008] [Accepted: 02/25/2008] [Indexed: 11/17/2022]
Abstract
Hexamethylene bis-acetamide-inducible protein 1 (HEXIM1) was identified earlier as an inhibitor of positive transcription elongation factor b (P-TEFb), which is a key transcriptional regulator of RNA polymerase II (Pol II). Studies show that more than half of P-TEFb in cells is associated with HEXIM1, which results in the inactivation of P-TEFb. Here, we identify a nucleolar protein, nucleophosmin (NPM), as a HEXIM1-binding protein. NPM binds to HEXIM1 in vitro and in vivo, and functions as a negative regulator of HEXIM1. Over-expression of NPM leads to proteasome-mediated degradation of HEXIM1, resulting in activation of P-TEFb-dependent transcription. In contrast, an increase in HEXIM1 protein levels and a decrease in transcription are detected when NPM is knocked down. We show that a cytoplasmic mutant of NPM, NPMc+, associates with and sequesters HEXIM1 in the cytoplasm resulting in higher RNA Pol II transcription. Correspondingly, cytoplasmic localization of endogenous HEXIM1 is detected in an acute myeloid leukemia (AML) cell line containing the NPMc+ mutation, suggesting the physiological importance of HEXIM1-NPMc+ interaction. Over-expression of NPM has been detected in tumors of various histological origins and our results may provide a possible molecular mechanism for the proto-oncogenic function of NPM. Furthermore, considering that 35% of AML patients are diagnosed with NPMc+ mutation, our findings suggest that in some cases of AML, RNA Pol II transcription may be disregulated by the malfunction of NPM and the mislocation of HEXIM1.
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Affiliation(s)
- Meera Gurumurthy
- Expression Engineering Group, Bioprocessing Technology Institute, 20 Biopolis Way, #06-01 Centros, Singapore 138668, Singapore
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Krueger BJ, Jeronimo C, Roy BB, Bouchard A, Barrandon C, Byers SA, Searcey CE, Cooper JJ, Bensaude O, Cohen EA, Coulombe B, Price DH. LARP7 is a stable component of the 7SK snRNP while P-TEFb, HEXIM1 and hnRNP A1 are reversibly associated. Nucleic Acids Res 2008; 36:2219-29. [PMID: 18281698 PMCID: PMC2367717 DOI: 10.1093/nar/gkn061] [Citation(s) in RCA: 189] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
Regulation of the elongation phase of RNA polymerase II transcription by P-TEFb is a critical control point for gene expression. The activity of P-TEFb is regulated, in part, by reversible association with one of two HEXIMs and the 7SK snRNP. A recent proteomics survey revealed that P-TEFb and the HEXIMs are tightly connected to two previously-uncharacterized proteins, the methyphosphate capping enzyme, MEPCE, and a La-related protein, LARP7. Glycerol gradient sedimentation analysis of lysates from cells treated with P-TEFb inhibitors, suggested that the 7SK snRNP reorganized such that LARP7 and 7SK remained associated after P-TEFb and HEXIM1 were released. Immunodepletion of LARP7 also depleted most of the 7SK regardless of the presence of P-TEFb, HEXIM or hnRNP A1 in the complex. Small interfering RNA knockdown of LARP7 in human cells decreased the steady-state level of 7SK, led to an initial increase in free P-TEFb and increased Tat transactivation of the HIV-1 LTR. Knockdown of LARP7 or 7SK ultimately caused a decrease in total P-TEFb protein levels. Our studies have identified LARP7 as a 7SK-binding protein and suggest that free P-TEFb levels are determined by a balance between release from the large form and reduction of total P-TEFb.
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Affiliation(s)
- Brian J Krueger
- Molecular and Cellular Biology Program, University of Iowa, Iowa City, Iowa, USA
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Abstract
During the past decade, numerous ncRNAs (non-coding RNAs) have been identified as regulators of transcription. This review focuses on a few examples of ncRNAs that directly interact with and regulate components of the transcription machinery. Artificial RNA aptamers have been selected against components of the transcriptional machinery. The bacterial 6S RNA and the eukaryotic B2 RNA directly target RNA polymerases. The 7SK RNA, U1 snRNA (small nuclear RNA) and SRA (steroid receptor RNA activator) RNA bind to and regulate the activity of transcription factors. Xist (X-inactive-specific transcript) and roX (RNA on the X) RNAs are involved in epigenetic regulation of transcription through the recruitment of histone-modifying enzymes.
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39
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Young TM, Tsai M, Tian B, Mathews MB, Pe'ery T. Cellular mRNA activates transcription elongation by displacing 7SK RNA. PLoS One 2007; 2:e1010. [PMID: 17925858 PMCID: PMC1995758 DOI: 10.1371/journal.pone.0001010] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2007] [Accepted: 09/11/2007] [Indexed: 11/24/2022] Open
Abstract
The positive transcription elongation factor P-TEFb is a pivotal regulator of gene expression in higher cells. Originally identified in Drosophila, attention was drawn to human P-TEFb by the discovery of its role as an essential cofactor for HIV-1 transcription. It is recruited to HIV transcription complexes by the viral transactivator Tat, and to cellular transcription complexes by a plethora of transcription factors. P-TEFb activity is negatively regulated by sequestration in a complex with the HEXIM proteins and 7SK RNA. The mechanism of P-TEFb release from the inhibitory complex is not known. We report that P-TEFb-dependent transcription from the HIV promoter can be stimulated by the mRNA encoding HIC, the human I-mfa domain-containing protein. The 3′-untranslated region of HIC mRNA is necessary and sufficient for this action. It forms complexes with P-TEFb and displaces 7SK RNA from the inhibitory complex in cells and cell extracts. A 314-nucleotide sequence near the 3′ end of HIC mRNA has full activity and contains a predicted structure resembling the 3′-terminal hairpin of 7SK that is critical for P-TEFb binding. This represents the first example of a cellular mRNA that can regulate transcription via P-TEFb. Our findings offer a rationale for 7SK being an RNA transcriptional regulator and suggest a practical means for enhancing gene expression.
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Affiliation(s)
- Tara M. Young
- Department of Biochemistry and Molecular Biology, New Jersey Medical School, Newark, New Jersey, United States of America
| | - Michael Tsai
- Department of Biochemistry and Molecular Biology, New Jersey Medical School, Newark, New Jersey, United States of America
| | - Bin Tian
- Department of Biochemistry and Molecular Biology, New Jersey Medical School, Newark, New Jersey, United States of America
- Graduate School of Biomedical Sciences, University of Medicine and Dentistry of New Jersey, Newark, New Jersey, United States of America
| | - Michael B. Mathews
- Department of Biochemistry and Molecular Biology, New Jersey Medical School, Newark, New Jersey, United States of America
- Graduate School of Biomedical Sciences, University of Medicine and Dentistry of New Jersey, Newark, New Jersey, United States of America
- * To whom correspondence should be addressed. E-mail: (MM); (TP)
| | - Tsafi Pe'ery
- Department of Biochemistry and Molecular Biology, New Jersey Medical School, Newark, New Jersey, United States of America
- Department of Medicine, New Jersey Medical School, Newark, New Jersey, United States of America
- Graduate School of Biomedical Sciences, University of Medicine and Dentistry of New Jersey, Newark, New Jersey, United States of America
- * To whom correspondence should be addressed. E-mail: (MM); (TP)
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Jeronimo C, Forget D, Bouchard A, Li Q, Chua G, Poitras C, Thérien C, Bergeron D, Bourassa S, Greenblatt J, Chabot B, Poirier GG, Hughes TR, Blanchette M, Price DH, Coulombe B. Systematic analysis of the protein interaction network for the human transcription machinery reveals the identity of the 7SK capping enzyme. Mol Cell 2007; 27:262-274. [PMID: 17643375 PMCID: PMC4498903 DOI: 10.1016/j.molcel.2007.06.027] [Citation(s) in RCA: 341] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2006] [Revised: 05/16/2007] [Accepted: 06/22/2007] [Indexed: 01/20/2023]
Abstract
We have performed a survey of soluble human protein complexes containing components of the transcription and RNA processing machineries using protein affinity purification coupled to mass spectrometry. Thirty-two tagged polypeptides yielded a network of 805 high-confidence interactions. Remarkably, the network is significantly enriched in proteins that regulate the formation of protein complexes, including a number of previously uncharacterized proteins for which we have inferred functions. The RNA polymerase II (RNAP II)-associated proteins (RPAPs) are physically and functionally associated with RNAP II, forming an interface between the enzyme and chaperone/scaffolding proteins. BCDIN3 is the 7SK snRNA methylphosphate capping enzyme (MePCE) present in an snRNP complex containing both RNA processing and transcription factors, including the elongation factor P-TEFb. Our results define a high-density protein interaction network for the mammalian transcription machinery and uncover multiple regulatory factors that target the transcription machinery.
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Affiliation(s)
- Célia Jeronimo
- Laboratory of Gene Transcription and Proteomics Discovery Platform, Institut de recherches cliniques de Montréal, 110 avenue des Pins Ouest, Montréal, QC H2W 1R7, Canada
| | - Diane Forget
- Laboratory of Gene Transcription and Proteomics Discovery Platform, Institut de recherches cliniques de Montréal, 110 avenue des Pins Ouest, Montréal, QC H2W 1R7, Canada
| | - Annie Bouchard
- Laboratory of Gene Transcription and Proteomics Discovery Platform, Institut de recherches cliniques de Montréal, 110 avenue des Pins Ouest, Montréal, QC H2W 1R7, Canada
| | - Qintong Li
- Biochemistry Department, University of Iowa, Iowa City, IA 52242-1109, USA
| | - Gordon Chua
- Banting and Best Department of Medical Research, University of Toronto, Toronto, ON M5G 1L6, Canada
| | - Christian Poitras
- Laboratory of Gene Transcription and Proteomics Discovery Platform, Institut de recherches cliniques de Montréal, 110 avenue des Pins Ouest, Montréal, QC H2W 1R7, Canada
| | - Cynthia Thérien
- Laboratory of Gene Transcription and Proteomics Discovery Platform, Institut de recherches cliniques de Montréal, 110 avenue des Pins Ouest, Montréal, QC H2W 1R7, Canada
| | - Dominique Bergeron
- Laboratory of Gene Transcription and Proteomics Discovery Platform, Institut de recherches cliniques de Montréal, 110 avenue des Pins Ouest, Montréal, QC H2W 1R7, Canada
| | - Sylvie Bourassa
- Centre hospitalier universitaire de Québec, Université Laval, Québec, QC G1V 4G2, Canada
| | - Jack Greenblatt
- Banting and Best Department of Medical Research, University of Toronto, Toronto, ON M5G 1L6, Canada
| | - Benoit Chabot
- Département de microbiologie et infectiologie, Université de Sherbrooke, Sherbrooke, QC J1H 5N4, Canada
| | - Guy G Poirier
- Centre hospitalier universitaire de Québec, Université Laval, Québec, QC G1V 4G2, Canada
| | - Timothy R Hughes
- Banting and Best Department of Medical Research, University of Toronto, Toronto, ON M5G 1L6, Canada
| | - Mathieu Blanchette
- McGill Centre for Bioinformatics, McGill University, Montréal, QC H3A 2B4, Canada
| | - David H Price
- Biochemistry Department, University of Iowa, Iowa City, IA 52242-1109, USA
| | - Benoit Coulombe
- Laboratory of Gene Transcription and Proteomics Discovery Platform, Institut de recherches cliniques de Montréal, 110 avenue des Pins Ouest, Montréal, QC H2W 1R7, Canada.
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41
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Sedore SC, Byers SA, Biglione S, Price JP, Maury WJ, Price DH. Manipulation of P-TEFb control machinery by HIV: recruitment of P-TEFb from the large form by Tat and binding of HEXIM1 to TAR. Nucleic Acids Res 2007; 35:4347-58. [PMID: 17576689 PMCID: PMC1935001 DOI: 10.1093/nar/gkm443] [Citation(s) in RCA: 120] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Basal transcription of the HIV LTR is highly repressed and requires Tat to recruit the positive transcription elongation factor, P-TEFb, which functions to promote the transition of RNA polymerase II from abortive to productive elongation. P-TEFb is found in two forms in cells, a free, active form and a large, inactive complex that also contains 7SK RNA and HEXIM1 or HEXIM2. Here we show that HIV infection of cells led to the release of P-TEFb from the large form. Consistent with Tat being the cause of this effect, transfection of a FLAG-tagged Tat in 293T cells caused a dramatic shift of P-TEFb out of the large form to a smaller form containing Tat. In vitro, Tat competed with HEXIM1 for binding to 7SK, blocked the formation of the P-TEFb–HEXIM1–7SK complex, and caused the release P-TEFb from a pre-formed P-TEFb–HEXIM1–7SK complex. These findings indicate that Tat can acquire P-TEFb from the large form. In addition, we found that HEXIM1 binds tightly to the HIV 5′ UTR containing TAR and recruits and inhibits P-TEFb activity. This suggests that in the absence of Tat, HEXIM1 may bind to TAR and repress transcription elongation of the HIV LTR.
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Affiliation(s)
- Stanley C. Sedore
- Department of Biochemistry, Department of Microbiology, Medical Scientist Training Program and Interdisciplinary Molecular Biology Program, University of Iowa, Iowa City, IA, USA
| | - Sarah A. Byers
- Department of Biochemistry, Department of Microbiology, Medical Scientist Training Program and Interdisciplinary Molecular Biology Program, University of Iowa, Iowa City, IA, USA
| | - Sebastian Biglione
- Department of Biochemistry, Department of Microbiology, Medical Scientist Training Program and Interdisciplinary Molecular Biology Program, University of Iowa, Iowa City, IA, USA
| | - Jason P. Price
- Department of Biochemistry, Department of Microbiology, Medical Scientist Training Program and Interdisciplinary Molecular Biology Program, University of Iowa, Iowa City, IA, USA
| | - Wendy J. Maury
- Department of Biochemistry, Department of Microbiology, Medical Scientist Training Program and Interdisciplinary Molecular Biology Program, University of Iowa, Iowa City, IA, USA
| | - David H. Price
- Department of Biochemistry, Department of Microbiology, Medical Scientist Training Program and Interdisciplinary Molecular Biology Program, University of Iowa, Iowa City, IA, USA
- *To whom correspondence should be addressed. +1 319 335 7910+1 319 384 4770
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