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Sun Y, Liu Z, Cao X, Lu Y, Mi Z, He C, Liu J, Zheng Z, Li MJ, Li T, Xu D, Wu M, Cao Y, Li Y, Yang B, Mei C, Zhang L, Chen Y. Activation of P-TEFb by cAMP-PKA signaling in autosomal dominant polycystic kidney disease. Sci Adv 2019; 5:eaaw3593. [PMID: 31183407 PMCID: PMC6551191 DOI: 10.1126/sciadv.aaw3593] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2018] [Accepted: 05/02/2019] [Indexed: 05/06/2023]
Abstract
Positive transcription elongation factor b (P-TEFb) functions as a central regulator of transcription elongation. Activation of P-TEFb occurs through its dissociation from the transcriptionally inactive P-TEFb/HEXIM1/7SK snRNP complex. However, the mechanisms of signal-regulated P-TEFb activation and its roles in human diseases remain largely unknown. Here, we demonstrate that cAMP-PKA signaling disrupts the inactive P-TEFb/HEXIM1/7SK snRNP complex by PKA-mediated phosphorylation of HEXIM1 at serine-158. The cAMP pathway plays central roles in the development of autosomal dominant polycystic kidney disease (ADPKD), and we show that P-TEFb is hyperactivated in mouse and human ADPKD kidneys. Genetic activation of P-TEFb promotes cyst formation in a zebrafish ADPKD model, while pharmacological inhibition of P-TEFb attenuates cyst development by suppressing the pathological gene expression program in ADPKD mice. Our study therefore elucidates a mechanism by which P-TEFb activation by cAMP-PKA signaling promotes cystogenesis in ADPKD.
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Affiliation(s)
- Yongzhan Sun
- 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Tianjin Key Laboratory of Medical Epigenetics, Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China
| | - Zhiheng Liu
- 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Tianjin Key Laboratory of Medical Epigenetics, Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China
| | - Xinyi Cao
- 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Tianjin Key Laboratory of Medical Epigenetics, Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China
| | - Yi Lu
- 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Tianjin Key Laboratory of Medical Epigenetics, Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China
| | - Zeyun Mi
- 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Tianjin Key Laboratory of Medical Epigenetics, Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China
| | - Chaoran He
- 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Tianjin Key Laboratory of Medical Epigenetics, Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China
| | - Jing Liu
- 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Tianjin Key Laboratory of Medical Epigenetics, Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China
| | - Zhanye Zheng
- 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Tianjin Key Laboratory of Medical Epigenetics, Department of Pharmacology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China
| | - Mulin Jun Li
- 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Tianjin Key Laboratory of Medical Epigenetics, Department of Pharmacology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China
| | - Tiegang Li
- Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100050, China
| | - Dechao Xu
- Kidney Institute, Department of Nephrology, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai 200003, China
| | - Ming Wu
- Department of Nephrology, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine, TCM Institute of Kidney Disease of Shanghai University of Traditional Chinese Medicine, Shanghai Key Laboratory of Traditional Chinese Clinical Medicine, Shanghai 201203, China
| | - Ying Cao
- Clinical and Translational Research Center of Shanghai First Maternity and Infant Hospital, School of Life Sciences and Technology, Tongji University, Shanghai 200092, China
| | - Yuhao Li
- Department of Pathology, Nankai University School of Medicine, 94 Weijin Road, Tianjin 300071, China
| | - Baoxue Yang
- Department of Pharmacology, School of Basic Medical Sciences, Peking University, Beijing 100038, China
| | - Changlin Mei
- Kidney Institute, Department of Nephrology, Shanghai Changzheng Hospital, Second Military Medical University, Shanghai 200003, China
- Corresponding author. (C.M.); (L.Z.); (Y.C.)
| | - Lirong Zhang
- 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Tianjin Key Laboratory of Medical Epigenetics, Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China
- Corresponding author. (C.M.); (L.Z.); (Y.C.)
| | - Yupeng Chen
- 2011 Collaborative Innovation Center of Tianjin for Medical Epigenetics, Tianjin Key Laboratory of Medical Epigenetics, Key Laboratory of Immune Microenvironment and Disease (Ministry of Education), Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tianjin Medical University, Tianjin 300070, China
- Department of Thyroid and Neck Tumor, Tianjin Medical University Cancer Institute and Hospital, Oncology Key Laboratory of Cancer Prevention and Therapy, National Clinical Research Center of Cancer, Tianjin 300060, China
- Corresponding author. (C.M.); (L.Z.); (Y.C.)
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Robert VJ, Garvis S, Palladino F. Repression of somatic cell fate in the germline. Cell Mol Life Sci 2015; 72:3599-620. [PMID: 26043973 DOI: 10.1007/s00018-015-1942-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2015] [Revised: 05/26/2015] [Accepted: 05/27/2015] [Indexed: 01/13/2023]
Abstract
Germ cells must transmit genetic information across generations, and produce gametes while also maintaining the potential to form all cell types after fertilization. Preventing the activation of somatic programs is, therefore, crucial to the maintenance of germ cell identity. Studies in Caenorhabditis elegans, Drosophila melanogaster, and mouse have revealed both similarities and differences in how somatic gene expression is repressed in germ cells, thereby preventing their conversion into somatic tissues. This review will focus on recent developments in our understanding of how global or gene-specific transcriptional repression, chromatin regulation, and translational repression operate in the germline to maintain germ cell identity and repress somatic differentiation programs.
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Affiliation(s)
- Valérie J Robert
- Ecole Normale Supérieure de Lyon, Université de Lyon, 46 allée d'Italie, 69007, Lyon, France
| | - Steve Garvis
- Ecole Normale Supérieure de Lyon, Université de Lyon, 46 allée d'Italie, 69007, Lyon, France
| | - Francesca Palladino
- Ecole Normale Supérieure de Lyon, Université de Lyon, 46 allée d'Italie, 69007, Lyon, France.
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Wang ZQ, Johnson CL, Kumar A, Molkentine DP, Molkentine JM, Rabin T, Mason KA, Milas L, Raju U. Inhibition of P-TEFb by DRB suppresses SIRT1/CK2α pathway and enhances radiosensitivity of human cancer cells. Anticancer Res 2014; 34:6981-6989. [PMID: 25503124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
BACKGROUND Positive transcription elongation factor-b (P-TEFb) is a complex containing CDK9 and a cyclin (T1, T2 or K). The effect of inhibition of P-TEFb by 5,6-dichloro-l-β-D-ribofuranosyl benzimidazole (DRB) on cell radiosensitivity and the underlying mechanisms were investigated. MATERIALS AND METHODS Six human cancer cell lines were subjected to (3)H-uridine incorporation, cell viability and clonogenic cell survival assays; cell-cycle redistribution and apoptosis assay; western blots and nuclear 53BP1 foci analysis after exposing the cells to DRB with/without γ-radiation. RESULTS DRB suppressed colony formation and enhanced radiosensitivity of all cell lines. DRB caused a further increase in radiation-induced apoptosis and cell-cycle redistribution depending on p53 status. DRB prolonged the presence of radiation-induced nuclear p53 binding protein-1 (53BP1) foci and suppressed the expression of sirtuin-1 (SIRT1) and casein kinase 2-alpha (CK2α), suggesting an inhibition of DNA repair processes. CONCLUSION Our findings indicate that DRB has the potential to increase the efficacy of radiotherapy and warrants further investigation using in vivo tumor models.
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Affiliation(s)
- Zhi-Qiang Wang
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, U.S.A
| | - Casey L Johnson
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, U.S.A
| | - Amit Kumar
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, U.S.A
| | - David P Molkentine
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, U.S.A
| | - Jessica M Molkentine
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, U.S.A
| | - Tatiana Rabin
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, U.S.A
| | - Kathryn A Mason
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, U.S.A
| | - Luka Milas
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, U.S.A
| | - Uma Raju
- Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, U.S.A.
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Zaborowska J, Baumli S, Laitem C, O'Reilly D, Thomas PH, O'Hare P, Murphy S. Herpes Simplex Virus 1 (HSV-1) ICP22 protein directly interacts with cyclin-dependent kinase (CDK)9 to inhibit RNA polymerase II transcription elongation. PLoS One 2014; 9:e107654. [PMID: 25233083 PMCID: PMC4169428 DOI: 10.1371/journal.pone.0107654] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2014] [Accepted: 08/13/2014] [Indexed: 11/18/2022] Open
Abstract
The Herpes Simplex Virus 1 (HSV-1)-encoded ICP22 protein plays an important role in viral infection and affects expression of host cell genes. ICP22 is known to reduce the global level of serine (Ser)2 phosphorylation of the Tyr1Ser2Pro3Thr4Ser5Pro6Ser7 heptapeptide repeats comprising the carboxy-terminal domain (CTD) of the large subunit of RNA polymerase (pol) II. Accordingly, ICP22 is thought to associate with and inhibit the activity of the positive-transcription elongation factor b (P-TEFb) pol II CTD Ser2 kinase. We show here that ICP22 causes loss of CTD Ser2 phosphorylation from pol II engaged in transcription of protein-coding genes following ectopic expression in HeLa cells and that recombinant ICP22 interacts with the CDK9 subunit of recombinant P-TEFb. ICP22 also interacts with pol II in vitro. Residues 193 to 256 of ICP22 are sufficient for interaction with CDK9 and inhibition of pol II CTD Ser2 phosphorylation but do not interact with pol II. These results indicate that discrete regions of ICP22 interact with either CDK9 or pol II and that ICP22 interacts directly with CDK9 to inhibit expression of host cell genes.
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Affiliation(s)
- Justyna Zaborowska
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Sonja Baumli
- Northern Institute for Cancer Research, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Clelia Laitem
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Dawn O'Reilly
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
| | - Peter H. Thomas
- Department of Oncology, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Peter O'Hare
- Section of Virology, Faculty of Medicine, Imperial College, St Mary's Medical School, London, United Kingdom
| | - Shona Murphy
- Sir William Dunn School of Pathology, University of Oxford, Oxford, United Kingdom
- * E-mail:
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Miyazaki H, Higashimoto K, Yada Y, Endo TA, Sharif J, Komori T, Matsuda M, Koseki Y, Nakayama M, Soejima H, Handa H, Koseki H, Hirose S, Nishioka K. Ash1l methylates Lys36 of histone H3 independently of transcriptional elongation to counteract polycomb silencing. PLoS Genet 2013; 9:e1003897. [PMID: 24244179 PMCID: PMC3820749 DOI: 10.1371/journal.pgen.1003897] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Accepted: 09/03/2013] [Indexed: 12/27/2022] Open
Abstract
Molecular mechanisms for the establishment of transcriptional memory are poorly understood. 5,6-dichloro-1-D-ribofuranosyl-benzimidazole (DRB) is a P-TEFb kinase inhibitor that artificially induces the poised RNA polymerase II (RNAPII), thereby manifesting intermediate steps for the establishment of transcriptional activation. Here, using genetics and DRB, we show that mammalian Absent, small, or homeotic discs 1-like (Ash1l), a member of the trithorax group proteins, methylates Lys36 of histone H3 to promote the establishment of Hox gene expression by counteracting Polycomb silencing. Importantly, we found that Ash1l-dependent Lys36 di-, tri-methylation of histone H3 in a coding region and exclusion of Polycomb group proteins occur independently of transcriptional elongation in embryonic stem (ES) cells, although both were previously thought to be consequences of transcription. Genome-wide analyses of histone H3 Lys36 methylation under DRB treatment have suggested that binding of the retinoic acid receptor (RAR) to a certain genomic region promotes trimethylation in the RAR-associated gene independent of its ongoing transcription. Moreover, DRB treatment unveils a parallel response between Lys36 methylation of histone H3 and occupancy of either Tip60 or Mof in a region-dependent manner. We also found that Brg1 is another key player involved in the response. Our results uncover a novel regulatory cascade orchestrated by Ash1l with RAR and provide insights into mechanisms underlying the establishment of the transcriptional activation that counteracts Polycomb silencing.
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Affiliation(s)
- Hitomi Miyazaki
- Division of Molecular Genetics and Epigenetics, Department of Biomolecular Sciences, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga City, Saga, Japan
- Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi City, Saitama, Japan
| | - Ken Higashimoto
- Division of Molecular Genetics and Epigenetics, Department of Biomolecular Sciences, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga City, Saga, Japan
| | - Yukari Yada
- Division of Gene Expression, Department of Developmental Genetics, National Institute of Genetics, 1111 Yata, Mishima City, Shizuoka, Japan
| | - Takaho A. Endo
- RIKEN Center for Integrative Medical Sciences, RIKEN Yokohama Institute, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama City, Kanagawa, Japan
| | - Jafar Sharif
- RIKEN Center for Integrative Medical Sciences, RIKEN Yokohama Institute, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama City, Kanagawa, Japan
| | - Toshiharu Komori
- Division of Gene Expression, Department of Developmental Genetics, National Institute of Genetics, 1111 Yata, Mishima City, Shizuoka, Japan
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama City, Kanagawa, Japan
| | - Masashi Matsuda
- RIKEN Center for Integrative Medical Sciences, RIKEN Yokohama Institute, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama City, Kanagawa, Japan
| | - Yoko Koseki
- RIKEN Center for Integrative Medical Sciences, RIKEN Yokohama Institute, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama City, Kanagawa, Japan
| | - Manabu Nakayama
- Laboratory of Medical Genomics, Department of Human Genome Research, Kazusa DNA Research Institute, 2-6-7 Kazusa-kamatari, Kisarazu City, Chiba, Japan
| | - Hidenobu Soejima
- Division of Molecular Genetics and Epigenetics, Department of Biomolecular Sciences, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga City, Saga, Japan
| | - Hiroshi Handa
- Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama City, Kanagawa, Japan
| | - Haruhiko Koseki
- RIKEN Center for Integrative Medical Sciences, RIKEN Yokohama Institute, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama City, Kanagawa, Japan
- Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi City, Saitama, Japan
| | - Susumu Hirose
- Division of Gene Expression, Department of Developmental Genetics, National Institute of Genetics, 1111 Yata, Mishima City, Shizuoka, Japan
| | - Kenichi Nishioka
- Division of Molecular Genetics and Epigenetics, Department of Biomolecular Sciences, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga City, Saga, Japan
- Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi City, Saitama, Japan
- Division of Gene Expression, Department of Developmental Genetics, National Institute of Genetics, 1111 Yata, Mishima City, Shizuoka, Japan
- * E-mail:
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Ding V, Lew QJ, Chu KL, Natarajan S, Rajasegaran V, Gurumurthy M, Choo ABH, Chao SH. HEXIM1 induces differentiation of human pluripotent stem cells. PLoS One 2013; 8:e72823. [PMID: 23977357 PMCID: PMC3748041 DOI: 10.1371/journal.pone.0072823] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2013] [Accepted: 07/19/2013] [Indexed: 02/07/2023] Open
Abstract
Hexamethylene bisacetamide inducible protein 1 (HEXIM1) is best known as the inhibitor of positive transcription elongation factor b (P-TEFb), which is composed of cyclin-dependent kinase 9 (CDK9)/cyclin T1. P-TEFb is an essential regulator for the transcriptional elongation by RNA polymerase II. A genome-wide study using human embryonic stem cells shows that most mRNA synthesis is regulated at the stage of transcription elongation, suggesting a possible role for P-TEFb/HEXIM1 in the gene regulation of stem cells. In this report, we detected a marked increase in HEXIM1 protein levels in the differentiated human pluripotent stem cells (hPSCs) induced by LY294002 treatment. Since no changes in CDK9 and cyclin T1 were observed in the LY294002-treated cells, increased levels of HEXIM1 might lead to inhibition of P-TEFb activity. However, treatment with a potent P-TEFb inhibiting compound, flavopiridol, failed to induce hPSC differentiation, ruling out the possible requirement for P-TEFb kinase activity in hPSC differentiation. Conversely, differentiation was observed when hPSCs were incubated with hexamethylene bisacetamide, a HEXIM1 inducing reagent. The involvement of HEXIM1 in the regulation of hPSCs was further supported when overexpression of HEXIM1 concomitantly induced hPSC differentiation. Collectively, our study demonstrates a novel role of HEXIM1 in regulating hPSC fate through a P-TEFb-independent pathway.
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Affiliation(s)
- Vanessa Ding
- Stem Cell Group, Bioprocessing Technology Institute, A*STAR (Agency for Science, Technology and Research), Singapore, Singapore
| | - Qiao Jing Lew
- Expression Engineering Group, Bioprocessing Technology Institute, A*STAR (Agency for Science, Technology and Research), Singapore, Singapore
| | - Kai Ling Chu
- Expression Engineering Group, Bioprocessing Technology Institute, A*STAR (Agency for Science, Technology and Research), Singapore, Singapore
| | - Subaashini Natarajan
- Stem Cell Group, Bioprocessing Technology Institute, A*STAR (Agency for Science, Technology and Research), Singapore, Singapore
| | - Vikneswari Rajasegaran
- Expression Engineering Group, Bioprocessing Technology Institute, A*STAR (Agency for Science, Technology and Research), Singapore, Singapore
| | - Meera Gurumurthy
- Expression Engineering Group, Bioprocessing Technology Institute, A*STAR (Agency for Science, Technology and Research), Singapore, Singapore
| | - Andre B. H. Choo
- Stem Cell Group, Bioprocessing Technology Institute, A*STAR (Agency for Science, Technology and Research), Singapore, Singapore
- Department of Bioengineering, Faculty of Engineering, National University of Singapore, Singapore, Singapore
| | - Sheng-Hao Chao
- Expression Engineering Group, Bioprocessing Technology Institute, A*STAR (Agency for Science, Technology and Research), Singapore, Singapore
- Department of Microbiology, National University of Singapore, Singapore, Singapore
- * E-mail:
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Mitra P, Pereira LA, Drabsch Y, Ramsay RG, Gonda TJ. Estrogen receptor-α recruits P-TEFb to overcome transcriptional pausing in intron 1 of the MYB gene. Nucleic Acids Res 2012; 40:5988-6000. [PMID: 22492511 PMCID: PMC3401469 DOI: 10.1093/nar/gks286] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
The MYB proto-oncogene is expressed in most estrogen receptor-positive (ERα+) breast tumors and cell lines. Expression of MYB is controlled, in breast cancer and other cell types, by a transcriptional pausing mechanism involving an attenuation site located ∼1.7 kb downstream from the transcription start site. In breast cancer cells, ligand-bound ERα binds close to, and drives transcription beyond this attenuation site, allowing synthesis of complete transcripts. However, little is known, in general, about the factors involved in relieving transcriptional attenuation, or specifically how ERα coordinates such factors to promote transcriptional elongation. Using cyclin dependent kinase 9 (CDK9) inhibitors, reporter gene assays and measurements of total and intronic MYB transcription, we show that functionally active CDK9 is required for estrogen-dependent transcriptional elongation. We further show by ChIP and co-immunoprecipitation studies that the P-TEFb complex (CDK9/CyclinT1) is recruited to the attenuation region by ligand-bound ERα, resulting in increased RNA polymerase II Ser-2 phosphorylation. These data provide new insights into MYB regulation, and given the critical roles of MYB in tumorigenesis, suggest targeting MYB elongation as potential therapeutic strategy.
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Affiliation(s)
- Partha Mitra
- University of Queensland Diamantina Institute, Brisbane, Queensland 4102, Peter MacCallum Cancer Centre, St Andrews Place, East Melbourne 3002 and Department of Pathology, The University of Melbourne, Victoria, 3010 Australia
| | - Lloyd A. Pereira
- University of Queensland Diamantina Institute, Brisbane, Queensland 4102, Peter MacCallum Cancer Centre, St Andrews Place, East Melbourne 3002 and Department of Pathology, The University of Melbourne, Victoria, 3010 Australia
| | - Yvette Drabsch
- University of Queensland Diamantina Institute, Brisbane, Queensland 4102, Peter MacCallum Cancer Centre, St Andrews Place, East Melbourne 3002 and Department of Pathology, The University of Melbourne, Victoria, 3010 Australia
| | - Robert G. Ramsay
- University of Queensland Diamantina Institute, Brisbane, Queensland 4102, Peter MacCallum Cancer Centre, St Andrews Place, East Melbourne 3002 and Department of Pathology, The University of Melbourne, Victoria, 3010 Australia
| | - Thomas J. Gonda
- University of Queensland Diamantina Institute, Brisbane, Queensland 4102, Peter MacCallum Cancer Centre, St Andrews Place, East Melbourne 3002 and Department of Pathology, The University of Melbourne, Victoria, 3010 Australia
- *To whom correspondence should be addressed. Tel: +61 7 3176 2524; Fax: +61 7 3176 5946;
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Abstract
Tumor suppressor p53 is stabilized in response to gamma-irradiation or treatment with DNA-damaging agents, and as a result p53 transcriptionally activates its targets leading to cell-cycle arrest or apoptosis. P-TEFb (positive transcription elongation factor b) inhibitors such as flavopiridol or 4-amino-6-hydrazino-7-b-d-ribofuranosyl-7H-pyrrolo[2,3-d]-pyrimidine-5-carboxamide (ARC) upregulate p53 protein levels, but inhibit the expression of its targets p21 and hdm2. DNA-damaging agents, doxorubicin and cisplatin are being used in combination with P-TEFb inhibitor flavopiridol in clinical trials for the treatment of some cancer patients. In this study, we found that P-TEFb inhibitors block the phosphorylation of p53 induced by doxorubicin. Furthermore, treatment of cells with P-TEFb inhibitors together with doxorubicin inhibits doxorubicin-induced binding of p53 to DNA and p53 transcriptional activity. These data suggest that P-TEFb inhibitors may antagonize the activation of p53 by DNA-damaging agents in tumors with wild-type p53.
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Affiliation(s)
- S K Radhakrishnan
- Department of Medicine, University of Illinois at Chicago, Chicago, IL, USA
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Biglione S, Byers SA, Price JP, Nguyen VT, Bensaude O, Price DH, Maury W. Inhibition of HIV-1 replication by P-TEFb inhibitors DRB, seliciclib and flavopiridol correlates with release of free P-TEFb from the large, inactive form of the complex. Retrovirology 2007; 4:47. [PMID: 17625008 PMCID: PMC1948018 DOI: 10.1186/1742-4690-4-47] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Accepted: 07/11/2007] [Indexed: 01/07/2023] Open
Abstract
Background The positive transcription elongation factor, P-TEFb, comprised of cyclin dependent kinase 9 (Cdk9) and cyclin T1, T2 or K regulates the productive elongation phase of RNA polymerase II (Pol II) dependent transcription of cellular and integrated viral genes. P-TEFb containing cyclin T1 is recruited to the HIV long terminal repeat (LTR) by binding to HIV Tat which in turn binds to the nascent HIV transcript. Within the cell, P-TEFb exists as a kinase-active, free form and a larger, kinase-inactive form that is believed to serve as a reservoir for the smaller form. Results We developed a method to rapidly quantitate the relative amounts of the two forms based on differential nuclear extraction. Using this technique, we found that titration of the P-TEFb inhibitors flavopiridol, DRB and seliciclib onto HeLa cells that support HIV replication led to a dose dependent loss of the large form of P-TEFb. Importantly, the reduction in the large form correlated with a reduction in HIV-1 replication such that when 50% of the large form was gone, HIV-1 replication was reduced by 50%. Some of the compounds were able to effectively block HIV replication without having a significant impact on cell viability. The most effective P-TEFb inhibitor flavopiridol was evaluated against HIV-1 in the physiologically relevant cell types, peripheral blood lymphocytes (PBLs) and monocyte derived macrophages (MDMs). Flavopiridol was found to have a smaller therapeutic index (LD50/IC50) in long term HIV-1 infectivity studies in primary cells due to greater cytotoxicity and reduced efficacy at blocking HIV-1 replication. Conclusion Initial short term studies with P-TEFb inhibitors demonstrated a dose dependent loss of the large form of P-TEFb within the cell and a concomitant reduction in HIV-1 infectivity without significant cytotoxicity. These findings suggested that inhibitors of P-TEFb may serve as effective anti-HIV-1 therapies. However, longer term HIV-1 replication studies indicated that these inhibitors were more cytotoxic and less efficacious against HIV-1 in the primary cell cultures.
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Affiliation(s)
- Sebastian Biglione
- Interdisciplinary Molecular and Cellular Biology Program, University of Iowa, Iowa City, IA, USA
- CBR Institute for Biomedical Research, Harvard Medical School, Boston, MA, 02115, USA
| | - Sarah A Byers
- Interdisciplinary Molecular and Cellular Biology Program, University of Iowa, Iowa City, IA, USA
- Oregon Health & Science University, Department of Molecular and Medical Genetics, Portland, OR 97239, USA
| | - Jason P Price
- Department of Microbiology, University of Iowa, Iowa City, IA, USA
| | - Van Trung Nguyen
- Laboratoire de Regulation de l'Expression Genetique, Ecole Normale Superieure, Paris, France
| | - Olivier Bensaude
- Laboratoire de Regulation de l'Expression Genetique, Ecole Normale Superieure, Paris, France
| | - David H Price
- Interdisciplinary Molecular and Cellular Biology Program, University of Iowa, Iowa City, IA, USA
- Department of Biochemistry, University of Iowa, Iowa City, IA, USA
| | - Wendy Maury
- Interdisciplinary Molecular and Cellular Biology Program, University of Iowa, Iowa City, IA, USA
- Department of Microbiology, University of Iowa, Iowa City, IA, USA
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10
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Abstract
Myc forms an heterodimer with Max and operates as a transcription factor upon binding to specific DNA sites in cellular chromatin. In addition to recruit histone acetylation activity, Myc binds to the positive transcription elongation factor b (P-TEFb) which consists of the cyclin-dependent kinase CKD9 and its regulatory subunit cyclin T. P-TEFb phosphorylates the carboxyl-terminal-domain (CTD) of the larger subunit of RNA polymerase II as well as negative elongation factors allowing efficient transcription elongation. Here, we report that Myc binds, as heterodimer with Max, exclusively the core active P-TEFb complex, and it recruits P-TEFb at Myc targets in vivo. Pharmacological inhibition of P-TEFb by 5.6-di-chloro-1-b-D-ribofuranosyl-bensimidazole (DRB) specifically inhibits expression of Myc-responsive CAD and NUC genes, and impairs the Myc-induced S-phase and apoptosis of quiescent cells grown in low serum. Chromatin immunoprecipitation assays (ChIP) demonstrated co-occupancy of Myc and P-TEFb to CAD and NUC E-boxes, and DRB treatment diminished the density of Pol II phosphorylated on Ser-2 of its CTD. These results indicate that P-TEFb is recruited in vivo to Myc-target promoters and CDK9 activity is an important step for Myc-dependent stimulation of responsive genes.
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Affiliation(s)
- Barbara Gargano
- Department of Structural and Functional Biology, University of Naples Federico II, Naples, Italy
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11
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Abstract
The transactivation responsive (TAR) RNA is the 5'-leader sequence of the HIV-1 mRNA genome and interacts with the Tat protein during transcription. Tat and the positive transcription elongation factor (P-TEFb) complex bind to TAR to promote efficient transcription of the full-length HIV genome. In the absence of the TAR.Tat.P-TEFb interaction, viral transcription is inefficient, which makes this RNA-protein complex an important target for therapeutic intervention of HIV replication. Inhibitors of HIV-1 transactivation mainly target: 1) TAR RNA, 2) Tat protein and 3) Tat.P-TEFb complex. 1) Compounds against TAR RNA are the most numerous: besides cationic peptides, which were initially developed, recent advances in TAR binding inhibitors include oligonucleotide based-agents and small molecules. Specific research efforts are currently underway to increase cellular uptake. 2) By targeting the Tat protein, both transactivation and other Tat-mediated intra/extracellular functions are affected. Various biopolymeric drugs are reported to effectively inhibit Tat activity. In addition, Tat-targeted antibodies have recently been developed. 3) Intracellular proteins have been discovered to disrupt Tat.P-TEFb interaction, raising the chance of inhibiting HIV-1 transcription via novel mechanisms.
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Affiliation(s)
- S N Richter
- Department of Histology, Microbiology and Medical Biotechnologies, University of Padua, via Gabelli 63, 35123 Padua, Italy.
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12
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Gomes NP, Bjerke G, Llorente B, Szostek SA, Emerson BM, Espinosa JM. Gene-specific requirement for P-TEFb activity and RNA polymerase II phosphorylation within the p53 transcriptional program. Genes Dev 2006; 20:601-12. [PMID: 16510875 PMCID: PMC1410802 DOI: 10.1101/gad.1398206] [Citation(s) in RCA: 214] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Activation of the p53 pathway mediates cellular responses to diverse forms of stress. Here we report that the p53 target gene p21(CIP1) is regulated by stress at post-initiation steps through conversion of paused RNA polymerase II (RNAP II) into an elongating form. High-resolution chromatin immunoprecipitation assays (ChIP) demonstrate that p53-dependent activation of p21(CIP1) transcription after DNA damage occurs concomitantly with changes in RNAP II phosphorylation status and recruitment of the elongation factors DSIF (DRB Sensitivity-Inducing Factor), P-TEFb (Positive Transcription Elongation Factor b), TFIIH, TFIIF, and FACT (Facilitates Chromatin Transcription) to distinct regions of the p21(CIP1) locus. Paradoxically, pharmacological inhibition of P-TEFb leads to global inhibition of mRNA synthesis but activation of the p53 pathway through p53 accumulation, expression of specific p53 target genes, and p53-dependent apoptosis. ChIP analyses of p21(CIP1) activation in the absence of functional P-TEFb reveals the existence of two distinct kinases that phosphorylate Ser5 of the RNAP II C-terminal domain (CTD). Importantly, CTD phosphorylation at Ser2 is not required for p21(CIP1) transcription, mRNA cleavage, or polyadenylation. Furthermore, recruitment of FACT requires CTD kinases, yet FACT is dispensable for p21(CIP1) expression. Thus, select genes within the p53 pathway bypass the requirement for P-TEFb and RNAP II phosphorylation to trigger a cellular response to inhibition of global mRNA synthesis.
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Affiliation(s)
- Nathan P Gomes
- Regulatory Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
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13
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Jiang H, Zhang F, Kurosu T, Peterlin BM. Runx1 binds positive transcription elongation factor b and represses transcriptional elongation by RNA polymerase II: possible mechanism of CD4 silencing. Mol Cell Biol 2006; 25:10675-83. [PMID: 16314494 PMCID: PMC1316947 DOI: 10.1128/mcb.25.24.10675-10683.2005] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Runx1 binds the silencer and represses CD4 transcription in immature thymocytes. In this study, we found that Runx1 inhibits P-TEFb, which contains CycT1, CycT2, or CycK and Cdk9 and stimulates transcriptional elongation by RNA polymerase II (RNAPII) in eukaryotic cells. Indeed, its inhibitory domain, spanning positions 371 to 411, not only bound CycT1 but was required for silencing CD4 transcription in vivo. Our chromatin immunoprecipitation assays revealed that Runx1 inhibits the elongation but not initiation of transcription and that RNAPII is engaged at the CD4 promoter but is unable to elongate in CD4(-) CD8(+) thymoma cells. These results suggest that active repression by Runx1 occurs by blocking the elongation by RNAPII, which may contribute to CD4 silencing during T-cell development.
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Affiliation(s)
- Huimin Jiang
- Department of Medicine, Microbiology and Immunology, Rosalind Russell Medical Research Center, University of California at San Francisco, 94143-0703, USA
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14
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Blazek D, Barboric M, Kohoutek J, Oven I, Peterlin BM. Oligomerization of HEXIM1 via 7SK snRNA and coiled-coil region directs the inhibition of P-TEFb. Nucleic Acids Res 2005; 33:7000-10. [PMID: 16377779 PMCID: PMC1322273 DOI: 10.1093/nar/gki997] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transcriptional elongation of most eukaryotic genes by RNA polymerase II requires the kinase activity of the positive transcription elongation factor b (P-TEFb). The catalytically active P-TEFb complex becomes inactive when sequestered into the large complex by the cooperative actions of 7SK snRNA and HEXIM1. In this study, we report that HEXIM1 forms oligomers in cells. This oligomerization is mediated by its predicted coiled-coil region in the C-terminal domain and 7SK snRNA that binds a basic region within the central part of HEXIM1. Alanine-mutagenesis of evolutionary conserved leucines in the coiled-coil region and the digestion of 7SK snRNA by RNase A treatment prevent this oligomerization. Importantly, mutations of the N-terminal part of the coiled-coil region abrogate the ability of HEXIM1 to bind and inhibit P-TEFb. Finally, the formation of HEXIM1 oligomers via the C-terminal part of the coiled-coil or basic regions is critical for the inhibition of transcription. Our results suggest that two independent regions in HEXIM1 form oligomers to incorporate P-TEFb into the large complex and determine the inhibition of transcriptional elongation.
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Affiliation(s)
- Dalibor Blazek
- Departments of Medicine, Microbiology and Immunology, Rosalind Russell Medical Research Center, University of California at San FranciscoSan Francisco, CA 94143-0703, USA
| | - Matjaz Barboric
- Departments of Medicine, Microbiology and Immunology, Rosalind Russell Medical Research Center, University of California at San FranciscoSan Francisco, CA 94143-0703, USA
| | - Jiri Kohoutek
- Departments of Medicine, Microbiology and Immunology, Rosalind Russell Medical Research Center, University of California at San FranciscoSan Francisco, CA 94143-0703, USA
| | - Irena Oven
- Departments of Medicine, Microbiology and Immunology, Rosalind Russell Medical Research Center, University of California at San FranciscoSan Francisco, CA 94143-0703, USA
- Biochemical Faculty, Department of Animal Science, University of LjubljanaGroblje 3, SI-1230 Domzale, Slovenia
| | - B. Matija Peterlin
- Departments of Medicine, Microbiology and Immunology, Rosalind Russell Medical Research Center, University of California at San FranciscoSan Francisco, CA 94143-0703, USA
- To whom correspondence should be addressed. Tel: +1 415 502 1902; Fax: +1 415 502 1901;
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15
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Heredia A, Davis C, Bamba D, Le N, Gwarzo MY, Sadowska M, Gallo RC, Redfield RR. Indirubin-3'-monoxime, a derivative of a Chinese antileukemia medicine, inhibits P-TEFb function and HIV-1 replication. AIDS 2005; 19:2087-95. [PMID: 16284457 DOI: 10.1097/01.aids.0000194805.74293.11] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To evaluate the effects of the cyclin dependent kinase (CDK) inhibitor Indirubin-3'-monoxime (IM) on Tat-mediated transactivation function, a step of the HIV-1 cycle that is not currently targeted in antiviral therapy. METHODS The effects of IM on CDK implicated in HIV-1 Tat transactivation function were evaluated by kinase assays, transfection experiments, RNase protection assay and RT-PCR analysis of viral transcripts. The antiviral effect of IM was investigated in cells from HIV-1 infected individuals as well as in cell lines, primary lymphocytes and monocyte-derived macrophages. The antiviral activity of IM was also tested against drug-resistant HIV-1. RESULTS IM inhibits the kinase activity of CDK9 [50% inhibitory concentration (IC50) of 0.05 microM], the catalytic subunit of Positive transcription elongation factor b (P-TEFb). Inhibition of CDK9 activity by IM results in abrogation of Tat-induced expression of HIV-1 RNA in cell lines. In addition, IM inhibits the replication of HIV-1 in both peripheral blood mononuclear cells (IC50 of 1 microM) and macrophages (IC50 of 0.5 microM). IM is effective against primary and drug-resistant strains of HIV-1. Importantly, the antiviral effects of the drug were seen at concentrations that did not affect cell proliferation. CONCLUSIONS Non-toxic concentrations of IM inhibit HIV-1 by blocking viral gene expression mediated by the cellular factor P-TEFb. The drug is effective against wild-type and drug-resistant strains of HIV-1. IM may help control replication of HIV-1 in patients by disrupting a step of the HIV-1 cycle that is not being targeted in current antiretroviral treatments.
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Affiliation(s)
- Alonso Heredia
- Institute of Human Virology, University of Maryland Biotechnology Institute, Baltimore, Maryland 21201, USA
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16
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Luecke HF, Yamamoto KR. The glucocorticoid receptor blocks P-TEFb recruitment by NFkappaB to effect promoter-specific transcriptional repression. Genes Dev 2005; 19:1116-27. [PMID: 15879558 PMCID: PMC1091745 DOI: 10.1101/gad.1297105] [Citation(s) in RCA: 166] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
To investigate the determinants of promoter-specific gene regulation by the glucocorticoid receptor (GR), we compared the composition and function of regulatory complexes at two NFkappaB-responsive genes that are differentially regulated by GR. Transcription of the IL-8 and IkappaBalpha genes is stimulated by TNFalpha in A549 cells, but GR selectively represses IL-8 mRNA synthesis by inhibiting Ser2 phosphorylation of the RNA polymerase II (pol II) C-terminal domain (CTD). The proximal kappaB elements at these genes differ in sequence by a single base pair, and both recruited RelA and p50. Surprisingly, GR was recruited to both of these elements, despite the fact that GR failed to repress the IkappaBalpha promoter. Rather, the regulatory complexes formed at IL-8 and IkappaBalpha were distinguished by differential recruitment of the Ser2 CTD kinase, P-TEFb. Disruption of P-TEFb function by the Cdk-inhibitor, DRB, or by small interfering RNA selectively blocked TNFalpha stimulation of IL-8 mRNA production. GR competed with P-TEFb recruitment to the IL-8 promoter. Strikingly, IL-8 mRNA synthesis was repressed by GR at a post-initiation step, demonstrating that promoter proximal regulatory sequences assemble complexes that impact early and late stages of mRNA synthesis. Thus, GR accomplishes selective repression by targeting promoter-specific components of NFkappaB regulatory complexes.
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Affiliation(s)
- Hans F Luecke
- Department of Cellular and Molecular Pharmacology, University of California-San Francisco, San Francisco, CA 94107-2280, USA
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17
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Yik JHN, Chen R, Pezda AC, Samford CS, Zhou Q. A human immunodeficiency virus type 1 Tat-like arginine-rich RNA-binding domain is essential for HEXIM1 to inhibit RNA polymerase II transcription through 7SK snRNA-mediated inactivation of P-TEFb. Mol Cell Biol 2004; 24:5094-105. [PMID: 15169877 PMCID: PMC419863 DOI: 10.1128/mcb.24.12.5094-5105.2004] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The HEXIM1 protein inhibits the kinase activity of P-TEFb (CDK9/cyclin T) to suppress RNA polymerase II transcriptional elongation in a process that specifically requires the 7SK snRNA, which mediates the interaction of HEXIM1 with P-TEFb. In an attempt to define the sequence requirements for HEXIM1 to interact with 7SK and inactivate P-TEFb, we have identified the first 18 amino acids within the previously described nuclear localization signal (NLS) of HEXIM1 as both necessary and sufficient for binding to 7SK in vivo and in vitro. This 7SK-binding motif was essential for HEXIM1's inhibitory action, as the HEXIM1 mutants with this motif replaced with a foreign NLS failed to interact with 7SK and P-TEFb and hence were unable to inactivate P-TEFb. The 7SK-binding motif alone, however, was not sufficient to inhibit P-TEFb. A region C-terminal to this motif was also required for HEXIM1 to associate with P-TEFb and suppress P-TEFb's kinase and transcriptional activities. The 7SK-binding motif in HEXIM1 contains clusters of positively charged residues reminiscent of the arginine-rich RNA-binding motif found in a wide variety of proteins. Part of it is highly homologous to the TAR RNA-binding motif in the human immunodeficiency virus type 1 (HIV-1) Tat protein, which was able to restore the 7SK-binding ability of a HEXIM1 NLS substitution mutant. We propose that a similar RNA-protein recognition mechanism may exist to regulate the formation of both the Tat-TAR-P-TEFb and the HEXIM1-7SK-P-TEFb ternary complexes, which may help convert the inactive HEXIM1/7SK-bound P-TEFb into an active one for Tat-activated and TAR-dependent HIV-1 transcription.
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Affiliation(s)
- Jasper H N Yik
- Department of Molecular and Cellular Biology, University of California, Berkeley, 94720, USA
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18
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Michels AA, Fraldi A, Li Q, Adamson TE, Bonnet F, Nguyen VT, Sedore SC, Price JP, Price DH, Lania L, Bensaude O. Binding of the 7SK snRNA turns the HEXIM1 protein into a P-TEFb (CDK9/cyclin T) inhibitor. EMBO J 2004; 23:2608-19. [PMID: 15201869 PMCID: PMC449783 DOI: 10.1038/sj.emboj.7600275] [Citation(s) in RCA: 233] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2003] [Accepted: 05/24/2004] [Indexed: 11/08/2022] Open
Abstract
The positive transcription elongation factor b (P-TEFb) plays a pivotal role in productive elongation of nascent RNA molecules by RNA polymerase II. Core active P-TEFb is composed of CDK9 and cyclin T. In addition, mammalian cell extracts contain an inactive P-TEFb complex composed of four components, CDK9, cyclin T, the 7SK snRNA and the MAQ1/HEXIM1 protein. We now report an in vitro reconstitution of 7SK-dependent HEXIM1 association to purified P-TEFb and subsequent CDK9 inhibition. Yeast three-hybrid tests and gel-shift assays indicated that HEXIM1 binds 7SK snRNA directly and a 7SK snRNA-recognition motif was identified in the central part of HEXIM1 (amino acids (aa) 152-155). Data from yeast two-hybrid and pull-down assay on GST fusion proteins converge to a direct binding of P-TEFb to the HEXIM1 C-terminal domain (aa 181-359). Consistently, point mutations in an evolutionarily conserved motif (aa 202-205) were found to suppress P-TEFb binding and inhibition without affecting 7SK recognition. We propose that the RNA-binding domain of HEXIM1 mediates its association with 7SK and that P-TEFb then enters the complex through association with HEXIM1.
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Affiliation(s)
- Annemieke A Michels
- UMR 8541 CNRS, Ecole Normale Supérieure, Régulation de l'Expression Génétique, Paris, France
| | - Alessandro Fraldi
- Dipartimento di Genetica, Biologia Generale e Molecolare, Università di Napoli ‘Federico II', Napoli, Italy
| | - Qintong Li
- Department of Biochemistry, University of Iowa, Iowa City, IA, USA
| | - Todd E Adamson
- Department of Biochemistry, University of Iowa, Iowa City, IA, USA
| | - François Bonnet
- UMR 8541 CNRS, Ecole Normale Supérieure, Régulation de l'Expression Génétique, Paris, France
| | - Van Trung Nguyen
- UMR 8541 CNRS, Ecole Normale Supérieure, Régulation de l'Expression Génétique, Paris, France
| | - Stanley C Sedore
- Medical Scientist Training Program, University of Iowa, Iowa City, IA, USA
| | - Jason P Price
- Department of Biochemistry, University of Iowa, Iowa City, IA, USA
| | - David H Price
- Department of Biochemistry, University of Iowa, Iowa City, IA, USA
| | - Luigi Lania
- Dipartimento di Genetica, Biologia Generale e Molecolare, Università di Napoli ‘Federico II', Napoli, Italy
| | - Olivier Bensaude
- UMR 8541 CNRS, Ecole Normale Supérieure, Régulation de l'Expression Génétique, Paris, France
- Laboratoire de Régulation de l'Expression Génétique, UMR 8541 CNRS, Ecole Normale Supérieure, 46, rue d Ulm, 75230 Paris Cedex 05, France. Tel.: +33 1 4432 3410; Fax: +33 1 4432 3941; E-mail:
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19
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Chen R, Yang Z, Zhou Q. Phosphorylated Positive Transcription Elongation Factor b (P-TEFb) Is Tagged for Inhibition through Association with 7SK snRNA. J Biol Chem 2004; 279:4153-60. [PMID: 14627702 DOI: 10.1074/jbc.m310044200] [Citation(s) in RCA: 141] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The positive transcription elongation factor b (P-TEFb), comprising CDK9 and cyclin T, stimulates transcription of cellular and viral genes by phosphorylating RNA polymerase II. A major portion of nuclear P-TEFb is sequestered and inactivated by the coordinated actions of the 7SK snRNA and the HEXIM1 protein, whose induced dissociation from P-TEFb is crucial for stress-induced transcription and pathogenesis of cardiac hypertrophy. The 7SK.P-TEFb interaction, which can occur independently of HEXIM1 and does not by itself inhibit P-TEFb, recruits HEXIM1 for P-TEFb inactivation. To study the control of this interaction, we established an in vitro system that reconstituted the specific interaction of P-TEFb with 7SK but not other snRNAs. Using this system, together with an in vivo binding assay, we show that the phosphorylation of CDK9, on possibly the conserved Thr-186 in the T-loop, was crucial for the 7SK.P-TEFb interaction. This phosphorylation was not caused by CDK9 autophosphorylation or the general CDK-activating kinase CAK, but rather by a novel HeLa nuclear kinase. Furthermore, the stress-induced disruption of the 7SK.P-TEFb interaction was not caused by any prohibitive changes in 7SK but by the dephosphorylation of P-TEFb, leading to the loss of the key phosphorylation important for 7SK binding. Thus, the phosphorylated P-TEFb is tagged for inhibition through association with 7SK. We discuss the implications of this mechanism in controlling P-TEFb activity during normal and stress-induced transcription.
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Affiliation(s)
- Ruichuan Chen
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202, USA
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20
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Abstract
OBJECTIVE This study was undertaken to determine whether 7SK small nuclear RNA (snRNA), which has been proposed to function as an inhibitor of Tat cofactor P-TEFb, plays a role in transcriptional latency in T cells. DESIGN AND METHODS The association of 7SK snRNA with P-TEFb was investigated in resting and activated peripheral blood lymphocytes (PBLs). Primary PBLs were isolated by standard methods and activated with phytohemagglutinin (PHA). Levels of 7SK snRNA were determined by Northern blotting and levels of the P-TEFb subunits cyclin-dependent kinase 9 and cyclin T1 were analyzed by immunoblotting. RESULTS The association of 7SK snRNA with P-TEFb complexes was specific. Following activation of PBLs, the levels of 7SK snRNA increased in a manner similar to U1 and U6 snRNA, sn RNAs involved in positive aspects of cellular gene expression. Unexpectedly, the association of 7SK snRNA with P-TEFb increased dramatically following lymphocyte activation. CONCLUSION Increased association of 7SK snRNA with P-TEFb in activated lymphocytes correlates with increased global transcription. This suggests that 7SK snRNA is unlikely to promote transcriptional latency in lymphocytes through an association with P-TEFb; it also suggests that the proposal that the association of 7SK snRNA with P-TEFb acts to inhibit transcriptional elongation needs to be re-evaluated.
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Affiliation(s)
- Richard E Haaland
- Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030, USA
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21
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Yik JHN, Chen R, Nishimura R, Jennings JL, Link AJ, Zhou Q. Inhibition of P-TEFb (CDK9/Cyclin T) Kinase and RNA Polymerase II Transcription by the Coordinated Actions of HEXIM1 and 7SK snRNA. Mol Cell 2003; 12:971-82. [PMID: 14580347 DOI: 10.1016/s1097-2765(03)00388-5] [Citation(s) in RCA: 370] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The positive transcriptional elongation factor b (P-TEFb), consisting of CDK9 and cyclin T, stimulates transcription by phosphorylating RNA polymerase II. It becomes inactivated when associated with the abundant 7SK snRNA. Here, we show that the 7SK binding alone was not sufficient to inhibit P-TEFb. P-TEFb was inhibited by the HEXIM1 protein in a process that specifically required 7SK for mediating the HEXIM1:P-TEFb interaction. This allowed HEXIM1 to inhibit transcription both in vivo and in vitro. P-TEFb dissociated from HEXIM1 and 7SK in cells undergoing stress response, increasing the level of active P-TEFb for stress-induced transcription. P-TEFb was the predominant HEXIM1-associated protein factor, and thus likely to be the principal target of inhibition coordinated by HEXIM1 and 7SK. Since HEXIM1 expression is induced in cells treated with hexamethylene bisacetamide, a potent inducer of cell differentiation, targeting the general transcription factor P-TEFb by HEXIM1/7SK may contribute to the global control of cell growth and differentiation.
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Affiliation(s)
- Jasper H N Yik
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA
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