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Walker RL, Hornicek FJ, Duan Z. Transcriptional regulation and therapeutic potential of cyclin-dependent kinase 9 (CDK9) in sarcoma. Biochem Pharmacol 2024; 226:116342. [PMID: 38848777 DOI: 10.1016/j.bcp.2024.116342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2024] [Revised: 05/17/2024] [Accepted: 06/04/2024] [Indexed: 06/09/2024]
Abstract
Sarcomas include various subtypes comprising two significant groups - soft tissue and bone sarcomas. Although the survival rate for some sarcoma subtypes has improved over time, the current methods of treatment remain efficaciously limited, as recurrent, and metastatic diseases remain a major obstacle. There is a need for better options and therapeutic strategies in treating sarcoma. Cyclin dependent kinase 9 (CDK9) is a transcriptional kinase and has emerged as a promising target for treating various cancers. The aberrant expression and activation of CDK9 have been observed in several sarcoma subtypes, including rhabdomyosarcoma, synovial sarcoma, osteosarcoma, Ewing sarcoma, and chordoma. Enhanced CDK9 expression has also been correlated with poorer prognosis in sarcoma patients. As a master regulator of transcription, CDK9 promotes transcription elongation by phosphorylation and releasing RNA polymerase II (RNAPII) from its promoter proximal pause. Release of RNAPII from this pause induces transcription of critical genes in the tumor cell. Overexpression and activation of CDK9 have been observed to lead to the expression of oncogenes, including MYC and MCL-1, that aid sarcoma development and progression. Inhibition of CDK9 in sarcoma has been proven to reduce these oncogenes' expression and decrease proliferation and growth in different sarcoma cells. Currently, there are several CDK9 inhibitors in preclinical and clinical investigations. This review aims to highlight the recent discovery and results on the transcriptional role and therapeutic potential of CDK9 in sarcoma.
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Affiliation(s)
- Robert L Walker
- Department of Orthopedic Surgery, Sarcoma Biology Laboratory, Sylvester Comprehensive Cancer Center, and the University of Miami Miller School of Medicine, Papanicolaou Cancer Research Building, 1550 N.W. 10(th) Avenue, Miami, FL 33136. USA
| | - Francis J Hornicek
- Department of Orthopedic Surgery, Sarcoma Biology Laboratory, Sylvester Comprehensive Cancer Center, and the University of Miami Miller School of Medicine, Papanicolaou Cancer Research Building, 1550 N.W. 10(th) Avenue, Miami, FL 33136. USA
| | - Zhenfeng Duan
- Department of Orthopedic Surgery, Sarcoma Biology Laboratory, Sylvester Comprehensive Cancer Center, and the University of Miami Miller School of Medicine, Papanicolaou Cancer Research Building, 1550 N.W. 10(th) Avenue, Miami, FL 33136. USA.
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2
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Boytsov A, Abramov S, Aiusheeva AZ, Kasianova A, Baulin E, Kuznetsov I, Aulchenko Y, Kolmykov S, Yevshin I, Kolpakov F, Vorontsov I, Makeev V, Kulakovskiy I. ANANASTRA: annotation and enrichment analysis of allele-specific transcription factor binding at SNPs. Nucleic Acids Res 2022; 50:W51-W56. [PMID: 35446421 PMCID: PMC9252736 DOI: 10.1093/nar/gkac262] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 03/15/2022] [Accepted: 04/04/2022] [Indexed: 11/12/2022] Open
Abstract
We present ANANASTRA, https://ananastra.autosome.org, a web server for the identification and annotation of regulatory single-nucleotide polymorphisms (SNPs) with allele-specific binding events. ANANASTRA accepts a list of dbSNP IDs or a VCF file and reports allele-specific binding (ASB) sites of particular transcription factors or in specific cell types, highlighting those with ASBs significantly enriched at SNPs in the query list. ANANASTRA is built on top of a systematic analysis of allelic imbalance in ChIP-Seq experiments and performs the ASB enrichment test against background sets of SNPs found in the same source experiments as ASB sites but not displaying significant allelic imbalance. We illustrate ANANASTRA usage with selected case studies and expect that ANANASTRA will help to conduct the follow-up of GWAS in terms of establishing functional hypotheses and designing experimental verification.
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Affiliation(s)
- Alexandr Boytsov
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 119991, Russia
- Moscow Institute of Physics and Technology, Dolgoprudny, 141701, Russia
- Laboratory of Regulatory Genomics, Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, 420008, Russia
| | - Sergey Abramov
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 119991, Russia
- Moscow Institute of Physics and Technology, Dolgoprudny, 141701, Russia
- Laboratory of Regulatory Genomics, Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, 420008, Russia
| | - Ariuna Z Aiusheeva
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, 142290, Russia
| | - Alexandra M Kasianova
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, 142290, Russia
- Southern Federal University, Rostov-on-Don, 344006, Russia
| | - Eugene Baulin
- Moscow Institute of Physics and Technology, Dolgoprudny, 141701, Russia
- Institute of Mathematical Problems of Biology RAS - the Branch of Keldysh Institute of Applied Mathematics of Russian Academy of Sciences, Pushchino, 142290, Russia
| | - Ivan A Kuznetsov
- Skolkovo Institute of Science and Technology, Moscow, 121205, Russia
| | - Yurii S Aulchenko
- Institute of Cytology and Genetics SB RAS, Novosibirsk, 630090, Russia
- PolyKnomics BV, ’s-Hertogenbosch, 5237 PA, Netherlands
| | - Semyon Kolmykov
- Sirius University of Science and Technology, Sochi, 354340, Russia
- Biosoft.Ru LLC, Novosibirsk, 630090, Russia
| | - Ivan Yevshin
- Sirius University of Science and Technology, Sochi, 354340, Russia
- Biosoft.Ru LLC, Novosibirsk, 630090, Russia
| | - Fedor Kolpakov
- Sirius University of Science and Technology, Sochi, 354340, Russia
- Federal Research Center for Information and Computational Technologies, Novosibirsk, 630090, Russia
| | - Ilya E Vorontsov
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 119991, Russia
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, 142290, Russia
| | - Vsevolod J Makeev
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 119991, Russia
- Moscow Institute of Physics and Technology, Dolgoprudny, 141701, Russia
- Laboratory of Regulatory Genomics, Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, 420008, Russia
- Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 119991, Russia
| | - Ivan V Kulakovskiy
- Vavilov Institute of General Genetics, Russian Academy of Sciences, Moscow, 119991, Russia
- Laboratory of Regulatory Genomics, Institute of Fundamental Medicine and Biology, Kazan Federal University, Kazan, 420008, Russia
- Institute of Protein Research, Russian Academy of Sciences, Pushchino, 142290, Russia
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3
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CDK9 keeps RNA polymerase II on track. Cell Mol Life Sci 2021; 78:5543-5567. [PMID: 34146121 PMCID: PMC8257543 DOI: 10.1007/s00018-021-03878-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Revised: 05/26/2021] [Accepted: 06/08/2021] [Indexed: 12/30/2022]
Abstract
Cyclin-dependent kinase 9 (CDK9), the kinase component of positive transcription elongation factor b (P-TEFb), is essential for transcription of most protein-coding genes by RNA polymerase II (RNAPII). By releasing promoter-proximally paused RNAPII into gene bodies, CDK9 controls the entry of RNAPII into productive elongation and is, therefore, critical for efficient synthesis of full-length messenger (m)RNAs. In recent years, new players involved in P-TEFb-dependent processes have been identified and an important function of CDK9 in coordinating elongation with transcription initiation and termination has been unveiled. As the regulatory functions of CDK9 in gene expression continue to expand, a number of human pathologies, including cancers, have been associated with aberrant CDK9 activity, underscoring the need to properly regulate CDK9. Here, I provide an overview of CDK9 function and regulation, with an emphasis on CDK9 dysregulation in human diseases.
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Anshabo AT, Milne R, Wang S, Albrecht H. CDK9: A Comprehensive Review of Its Biology, and Its Role as a Potential Target for Anti-Cancer Agents. Front Oncol 2021; 11:678559. [PMID: 34041038 PMCID: PMC8143439 DOI: 10.3389/fonc.2021.678559] [Citation(s) in RCA: 66] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 04/16/2021] [Indexed: 12/25/2022] Open
Abstract
Cyclin-dependent kinases (CDKs) are proteins pivotal to a wide range of cellular functions, most importantly cell division and transcription, and their dysregulations have been implicated as prominent drivers of tumorigenesis. Besides the well-established role of cell cycle CDKs in cancer, the involvement of transcriptional CDKs has been confirmed more recently. Most cancers overtly employ CDKs that serve as key regulators of transcription (e.g., CDK9) for a continuous production of short-lived gene products that maintain their survival. As such, dysregulation of the CDK9 pathway has been observed in various hematological and solid malignancies, making it a valuable anticancer target. This therapeutic potential has been utilized for the discovery of CDK9 inhibitors, some of which have entered human clinical trials. This review provides a comprehensive discussion on the structure and biology of CDK9, its role in solid and hematological cancers, and an updated review of the available inhibitors currently being investigated in preclinical and clinical settings.
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Affiliation(s)
- Abel Tesfaye Anshabo
- Drug Discovery and Development, Centre for Cancer Diagnostics and Therapeutics, Clinical and Health Sciences, University of South Australia, Adelaide, SA, Australia
| | - Robert Milne
- Drug Discovery and Development, Centre for Cancer Diagnostics and Therapeutics, Clinical and Health Sciences, University of South Australia, Adelaide, SA, Australia
| | - Shudong Wang
- Drug Discovery and Development, Centre for Cancer Diagnostics and Therapeutics, Clinical and Health Sciences, University of South Australia, Adelaide, SA, Australia
| | - Hugo Albrecht
- Drug Discovery and Development, Centre for Cancer Diagnostics and Therapeutics, Clinical and Health Sciences, University of South Australia, Adelaide, SA, Australia
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P-TEFb as A Promising Therapeutic Target. Molecules 2020; 25:molecules25040838. [PMID: 32075058 PMCID: PMC7070488 DOI: 10.3390/molecules25040838] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2020] [Revised: 02/06/2020] [Accepted: 02/07/2020] [Indexed: 01/19/2023] Open
Abstract
The positive transcription elongation factor b (P-TEFb) was first identified as a general factor that stimulates transcription elongation by RNA polymerase II (RNAPII), but soon afterwards it turned out to be an essential cellular co-factor of human immunodeficiency virus (HIV) transcription mediated by viral Tat proteins. Studies on the mechanisms of Tat-dependent HIV transcription have led to radical advances in our knowledge regarding the mechanism of eukaryotic transcription, including the discoveries that P-TEFb-mediated elongation control of cellular transcription is a main regulatory step of gene expression in eukaryotes, and deregulation of P-TEFb activity plays critical roles in many human diseases and conditions in addition to HIV/AIDS. P-TEFb is now recognized as an attractive and promising therapeutic target for inflammation/autoimmune diseases, cardiac hypertrophy, cancer, infectious diseases, etc. In this review article, I will summarize our knowledge about basic P-TEFb functions, the regulatory mechanism of P-TEFb-dependent transcription, P-TEFb’s involvement in biological processes and diseases, and current approaches to manipulating P-TEFb functions for the treatment of these diseases.
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6
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Pon JR, Marra MA. MEF2 transcription factors: developmental regulators and emerging cancer genes. Oncotarget 2016; 7:2297-312. [PMID: 26506234 PMCID: PMC4823036 DOI: 10.18632/oncotarget.6223] [Citation(s) in RCA: 115] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Accepted: 10/14/2015] [Indexed: 12/22/2022] Open
Abstract
The MEF2 transcription factors have roles in muscle, cardiac, skeletal, vascular, neural, blood and immune system cell development through their effects on cell differentiation, proliferation, apoptosis, migration, shape and metabolism. Altered MEF2 activity plays a role in human diseases and has recently been implicated in the development of several cancer types. In particular, MEF2B, the most divergent and least studied protein of the MEF2 family, has a role unique from its paralogs in non-Hodgkin lymphomas. The use of genome-scale technologies has enabled comprehensive MEF2 target gene sets to be identified, contributing to our understanding of MEF2 proteins as nodes in complex regulatory networks. This review surveys the molecular interactions of MEF2 proteins and their effects on cellular and organismal phenotypes. We include a discussion of the emerging roles of MEF2 proteins as oncogenes and tumor suppressors of cancer. Throughout this article we highlight similarities and differences between the MEF2 family proteins, including a focus on functions of MEF2B.
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Affiliation(s)
- Julia R Pon
- Canada's Michael Smith Genome Sciences Centre, BC Cancer Agency, Vancouver, Canada
| | - Marco A Marra
- Canada's Michael Smith Genome Sciences Centre, BC Cancer Agency, Vancouver, Canada.,Department of Medical Genetics, University of British Columbia, Vancouver, Canada
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Pak V, Eifler TT, Jäger S, Krogan NJ, Fujinaga K, Peterlin BM. CDK11 in TREX/THOC Regulates HIV mRNA 3' End Processing. Cell Host Microbe 2016; 18:560-70. [PMID: 26567509 DOI: 10.1016/j.chom.2015.10.012] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2015] [Revised: 09/23/2015] [Accepted: 10/16/2015] [Indexed: 10/22/2022]
Abstract
Transcriptional cyclin-dependent kinases play important roles in eukaryotic gene expression. CDK7, CDK9 (P-TEFb), and CDK13 are also critical for HIV replication. However, the function of CDK11 remained enigmatic. In this report, we determined that CDK11 regulates the cleavage and polyadenylation (CPA) of all viral transcripts. CDK11 was found associated with the TREX/THOC, which recruited this kinase to DNA. Once at the viral genome, CDK11 phosphorylated serines at position 2 in the CTD of RNAPII, which increased levels of CPA factors at the HIV 3' end. In its absence, cleavage of viral transcripts was greatly attenuated. In contrast, higher levels of CDK11 increased the length of HIV poly(A) tails and the stability of mature viral transcripts. We conclude that CDK11 plays a critical role for the cotranscriptional processing of all HIV mRNA species.
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Affiliation(s)
- Vladimir Pak
- Departments of Medicine, Microbiology, and Immunology, University of California at San Francisco, San Francisco, CA 94143, USA
| | - Tristan T Eifler
- Departments of Medicine, Microbiology, and Immunology, University of California at San Francisco, San Francisco, CA 94143, USA
| | - Stefanie Jäger
- Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, CA 94143, USA; Gladstone Institutes, San Francisco, CA, 94143, USA
| | - Nevan J Krogan
- Department of Cellular and Molecular Pharmacology, University of California at San Francisco, San Francisco, CA 94143, USA; Gladstone Institutes, San Francisco, CA, 94143, USA
| | - Koh Fujinaga
- Departments of Medicine, Microbiology, and Immunology, University of California at San Francisco, San Francisco, CA 94143, USA
| | - B Matija Peterlin
- Departments of Medicine, Microbiology, and Immunology, University of California at San Francisco, San Francisco, CA 94143, USA.
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8
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Dadson K, Turdi S, Hashemi S, Zhao J, Polidovitch N, Beca S, Backx PH, McDermott JC, Sweeney G. Adiponectin is required for cardiac MEF2 activation during pressure overload induced hypertrophy. J Mol Cell Cardiol 2015. [PMID: 26196305 DOI: 10.1016/j.yjmcc.2015.06.020] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cardiomyocyte (CM) hypertrophy and increased heart mass in response to pressure overload are associated with hyper-activation of the myocyte enhancer factor-2 (MEF2) family of transcriptional regulators, and concomitant initiation of the fetal gene program. Adiponectin, an adipokine that is reduced in individuals with obesity and diabetes, has been characterized both as a negative regulator or permissive factor in cardiac hypertrophy. We therefore sought to analyze temporal regulation of MEF2 activity in response to pressure overload (PO) and changes in adiponectin status. To address this we crossed a well characterized transgenic MEF2 "sensor" mouse (MEF2-lacZ) with adiponectin null mice (Ad-KO) to create compound MEF2 lacZ/Ad-KO mice. Initially, we established that transverse aortic banding induced PO in wild-type (WT) mice increased heart mass and CM hypertrophy from 1 to 4weeks following surgery, indicated by increased CM diameter and heart weight/tibia length ratio. This was associated with cardiac dysfunction determined by echocardiography. Hypertrophic changes and dysfunction were observed in Ad-KO mice 4weeks following surgery. MEF2 lacZ activity and endogenous ANF mRNA levels, used as indicators of hypertrophic gene activation, were both robustly increased in WT mice after MTAB but attenuated in the Ad-KO background. Furthermore, activation of the pro-hypertrophic molecule p38 was increased following MTAB surgery in WT mice, but not in Ad-KO animals, and treatment of primary isolated CM with recombinant adiponectin induced p38 phosphorylation in a time dependent manner. Adiponectin also increased MEF2 activation in primary cardiomyocytes, an effect attenuated by p38 MAPK inhibition. In conclusion, our data indicate that robust hypertrophic MEF2 activation in the heart in vivo requires a background of adiponectin signaling and that adiponectin signaling in primary isolated CM directly enhances MEF2 activity through activation of p38 MAPK. We conclude that adiponectin is required for full induction of cardiomyocyte MEF2 activation, thus contributing to the myocardial hypertrophic gene expression program in response to PO.
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Affiliation(s)
- Keith Dadson
- Department of Biology, York University, Toronto, Canada
| | - Subat Turdi
- Department of Biology, York University, Toronto, Canada
| | - Sarah Hashemi
- Department of Biology, York University, Toronto, Canada
| | | | - Nazar Polidovitch
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada; Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Sanja Beca
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada; Department of Medicine, University of Toronto, Toronto, Ontario, Canada
| | - Peter H Backx
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada; Department of Medicine, University of Toronto, Toronto, Ontario, Canada; Peter Munk Cardiac Centre and the Division of Cardiology, University Health Network,Toronto, Ontario, Canada
| | | | - Gary Sweeney
- Department of Biology, York University, Toronto, Canada.
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9
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Role of noncoding RNAs in the regulation of P-TEFb availability and enzymatic activity. BIOMED RESEARCH INTERNATIONAL 2014; 2014:643805. [PMID: 24701579 PMCID: PMC3950470 DOI: 10.1155/2014/643805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 01/13/2014] [Indexed: 11/23/2022]
Abstract
P-TEFb is a transcriptional factor that specifically regulates the elongation step of RNA polymerase II-dependent transcription and its activity strictly required for Human Immunodeficiency Virus (HIV) infection and during cardiac differentiation. P-TEFb role has emerged as a crucial regulator of transcription elongation and its activity found finely tuned in vivo at transcriptional level as well as posttranscriptionally by dynamic association with different multisubunit molecular particles. Both physiological and pathological cellular signals rapidly converge on P-TEFb regulation by modifying expression and activity of the complex to allow cells to properly respond to different stimuli. In this review we will give a panoramic view on P-TEFb regulation by noncoding RNAs in both physiological and pathological conditions.
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Sivachenko A, Li Y, Abruzzi KC, Rosbash M. The transcription factor Mef2 links the Drosophila core clock to Fas2, neuronal morphology, and circadian behavior. Neuron 2013; 79:281-92. [PMID: 23889933 PMCID: PMC3859024 DOI: 10.1016/j.neuron.2013.05.015] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/03/2013] [Indexed: 12/01/2022]
Abstract
The transcription factor Mef2 regulates activity-dependent neuronal plasticity and morphology in mammals, and clock neurons are reported to experience activity-dependent circadian remodeling in Drosophila. We show here that Mef2 is required for this daily fasciculation-defasciculation cycle. Moreover, the master circadian transcription complex CLK/CYC directly regulates Mef2 transcription. ChIP-Chip analysis identified numerous Mef2 target genes implicated in neuronal plasticity, including the cell-adhesion gene Fas2. Genetic epistasis experiments support this transcriptional regulatory hierarchy, CLK/CYC- > Mef2- > Fas2, indicate that it influences the circadian fasciculation cycle within pacemaker neurons, and suggest that this cycle also contributes to circadian behavior. Mef2 therefore transmits clock information to machinery involved in neuronal remodeling, which contributes to locomotor activity rhythms.
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Affiliation(s)
- Anna Sivachenko
- Howard Hughes Medical Institute, National Center for Behavioral Genomics, Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02454 USA
| | - Yue Li
- Howard Hughes Medical Institute, National Center for Behavioral Genomics, Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02454 USA
| | - Katharine C. Abruzzi
- Howard Hughes Medical Institute, National Center for Behavioral Genomics, Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02454 USA
| | - Michael Rosbash
- Howard Hughes Medical Institute, National Center for Behavioral Genomics, Department of Biology, Brandeis University, 415 South Street, Waltham, MA 02454 USA
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Hong P, Chen K, Huang B, Liu M, Cui M, Rozenberg I, Chaqour B, Pan X, Barton ER, Jiang XC, Siddiqui MAQ. HEXIM1 controls satellite cell expansion after injury to regulate skeletal muscle regeneration. J Clin Invest 2013; 122:3873-87. [PMID: 23023707 DOI: 10.1172/jci62818] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2012] [Accepted: 08/02/2012] [Indexed: 01/07/2023] Open
Abstract
The native capacity of adult skeletal muscles to regenerate is vital to the recovery from physical injuries and dystrophic diseases. Currently, the development of therapeutic interventions has been hindered by the complex regulatory network underlying the process of muscle regeneration. Using a mouse model of skeletal muscle regeneration after injury, we identified hexamethylene bisacetamide inducible 1 (HEXIM1, also referred to as CLP-1), the inhibitory component of the positive transcription elongation factor b (P-TEFb) complex, as a pivotal regulator of skeletal muscle regeneration. Hexim1-haplodeficient muscles exhibited greater mass and preserved function compared with those of WT muscles after injury, as a result of enhanced expansion of satellite cells. Transplanted Hexim1-haplodeficient satellite cells expanded and improved muscle regeneration more effectively than WT satellite cells. Conversely, HEXIM1 overexpression restrained satellite cell proliferation and impeded muscle regeneration. Mechanistically, dissociation of HEXIM1 from P-TEFb and subsequent activation of P-TEFb are required for satellite cell proliferation and the prevention of early myogenic differentiation. These findings suggest a crucial role for the HEXIM1/P-TEFb pathway in the regulation of satellite cell–mediated muscle regeneration and identify HEXIM1 as a potential therapeutic target for degenerative muscular diseases.
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Affiliation(s)
- Peng Hong
- Department of Cell Biology, State University of New York Downstate Medical Center,New York, New York, USA
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12
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Ramakrishnan R, Liu H, Donahue H, Malovannaya A, Qin J, Rice AP. Identification of novel CDK9 and Cyclin T1-associated protein complexes (CCAPs) whose siRNA depletion enhances HIV-1 Tat function. Retrovirology 2012; 9:90. [PMID: 23110726 PMCID: PMC3494656 DOI: 10.1186/1742-4690-9-90] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 10/05/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND HIV-1 Tat activates RNA Polymerase II (RNAP II) elongation of the integrated provirus by recruiting a protein kinase known as P-TEFb to TAR RNA at the 5' end of nascent viral transcripts. The catalytic core of P-TEFb contains CDK9 and Cyclin T1 (CCNT1). A human endogenous complexome has recently been described - the set of multi-protein complexes in HeLa cell nuclei. We mined this complexome data set and identified 12 distinct multi-protein complexes that contain both CDK9 and CCNT1. We have termed these complexes CCAPs for CDK9/CCNT1-associated protein complexes. Nine CCAPs are novel, while three were previously identified as Core P-TEFb, the 7SK snRNP, and the Super-Elongation Complex. We have investigated the role of five newly identified CCAPs in Tat function and viral gene expression. RESULTS We examined five CCAPs that contain: 1) PPP1R10/TOX3/WDR82; 2) TTF2; 3) TPR; 4) WRNIP1; 5) FBXO11/CUL1/SKP1. SiRNA depletions of protein subunits of the five CCAPs enhanced Tat activation of an integrated HIV-1 LTR-Luciferase reporter in TZM-bl cells. Using plasmid transfection assays in HeLa cells, we also found that siRNA depletions of TTF2, FBXO11, PPP1R10, WDR82, and TOX3 enhanced Tat activation of an HIV-1 LTR-luciferase reporter, but the depletions did not enhance expression of an NF-κB reporter plasmid with the exception of PPP1R10. We found no evidence that depletion of CCAPs perturbed the level of CDK9/CCNT1 in the 7SK snRNP. We also found that the combination of siRNA depletions of both TTF2 and FBXO11 sensitized a latent provirus in Jurkat cells to reactivation by sub-optimal amounts of αCD3/CD28 antibodies. CONCLUSIONS Our results identified five novel CDK9/CCNT1 complexes that are capable of negative regulation of HIV-1 Tat function and viral gene expression. Because siRNA depletions of CCAPs enhance Tat function, it is possible that these complexes reduce the level of CDK9 and CCNT1 available for Tat, similar to the negative regulation of Tat by the 7SK snRNP. Our results highlight the complexity in the biological functions of CDK9 and CCNT1.
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Affiliation(s)
- Rajesh Ramakrishnan
- Department of Molecular Virology & Microbiology, Baylor College of Medicine, Houston, Texas, USA
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13
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Du C, Jin YQ, Qi JJ, Ji ZX, Li SY, An GS, Jia HT, Ni JH. Effects of myogenin on expression of late muscle genes through MyoD-dependent chromatin remodeling ability of myogenin. Mol Cells 2012; 34:133-42. [PMID: 22814845 PMCID: PMC3887822 DOI: 10.1007/s10059-012-2286-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Revised: 05/26/2012] [Accepted: 06/07/2012] [Indexed: 01/09/2023] Open
Abstract
MyoD and myogenin (Myog) recognize sets of distinct but overlapping target genes and play different roles in skeletal muscle differentiation. MyoD is sufficient for near-full expression of early targets, while Myog can only partially enhance expression of MyoD-initiated late muscle genes. However, the way in which Myog enhances the expression of MyoD-initiated late muscle genes remains unclear. Here, we examine the effects of Myog on chromatin remodeling at late muscle gene promoters and their activation within chromatin environment. Chromatin immunoprecipitation (ChIP) assay showed that Myog selectively bound to the regulatory sequences of late muscle genes. Overexpression of Myog was found to overcome sodium butyrateinhibited chromatin at late muscle genes in differentiating C2C12 myoblasts, shifting the transcriptional activation of these genes to an earlier time period. Furthermore, overexpression of Myog led to increased hyperacetylation of core histone H4 in differentiating C2C12 myoblasts but not NIH3T3 fibroblasts, and hyperacetylated H4 was associated directly with the late muscle genes in differentiating C2C12, indicating that Myog can induce chromatin remodeling in the presence of MyoD. In addition, co-immunoprecipitation (CoIP) revealed that Myog was associated with the nuclear protein Brd4 in differentiating C2C12 myoblasts. Together, these results suggest that Myog enhances the expression of MyoD-initiated late muscle genes through MyoD-dependent ability of Myog to induce chromatin remodeling, in which Myog-Brd4 interaction may be involved.
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Affiliation(s)
- Chao Du
- Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Beijing 100191,
People’s Republic of China
| | - Ya-Qiong Jin
- Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Beijing 100191,
People’s Republic of China
| | - Jun-Juan Qi
- Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Beijing 100191,
People’s Republic of China
| | - Zhen-Xing Ji
- Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Beijing 100191,
People’s Republic of China
| | - Shu-Yan Li
- Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Beijing 100191,
People’s Republic of China
| | - Guo-Shun An
- Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Beijing 100191,
People’s Republic of China
| | - Hong-Ti Jia
- Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Beijing 100191,
People’s Republic of China
- Department of Biochemistry and Molecular Biology, Capital University of Medical Sciences, Beijing 100069,
People’s Republic of China
| | - Ju-Hua Ni
- Department of Biochemistry and Molecular Biology, Peking University Health Science Center, Beijing 100191,
People’s Republic of China
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14
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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: 39] [Impact Index Per Article: 3.3] [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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15
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Kuzmina A, Hadad U, Fujinaga K, Taube R. Functional characterization of a human cyclin T1 mutant reveals a different binding surface for Tat and HEXIM1. Virology 2012; 426:152-61. [PMID: 22342181 DOI: 10.1016/j.virol.2012.01.033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Revised: 01/17/2012] [Accepted: 01/27/2012] [Indexed: 11/25/2022]
Abstract
HIV transcription is regulated at the step of elongation by the viral Tat protein and the cellular positive transcription elongation factor b (P-TEFb; Cdk9/cyclin T1). Herein, a human cyclin T1 mutant, cyclin T1-U7, which contains four substitutions and one deletion in the N-terminal cyclin box, was stably expressed in HeLa cells. HIV transcription was efficiently inhibited in HeLa-HA-CycT1-U7 stable cells. Cyclin T1-U7 bound Tat but did not modulate its expression levels, which remained high. Importantly cyclin T1-U7 failed to interact with Cdk9 or HEXIM1 and did not interfere with endogenous P-TEFb activity to stimulate MEF2C or NFkB mediated transcription. In a T cell line and primary CD4+ cells, cyclin T1-U7 also inhibited HIV transcription. We conclude that cyclin T1-U7 sequesters Tat from P-TEFb and inhibits HIV transcription. Importantly, N-terminal residues in cyclin T1 are specifically involved in the binding of cyclin T1 to HEXIM1 but not to Tat.
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Affiliation(s)
- Alona Kuzmina
- Department of Virology and Developmental Genetics Faculty of Health Sciences, Ben-Gurion University of the Negev, Israel
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16
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O'Brien SK, Knight KL, Rana TM. Phosphorylation of histone H1 by P-TEFb is a necessary step in skeletal muscle differentiation. J Cell Physiol 2011; 227:383-9. [PMID: 21503884 DOI: 10.1002/jcp.22797] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Positive transcription elongation factor b (P-TEFb), the complex of Cyclin T1 and CDK9, activates the transcription of many viral and eukaryotic genes at the point of mRNA elongation. The activity of P-TEFb has been implicated in the differentiation of a number of cell types, including skeletal muscle. In order to promote transcription, P-TEFb hyperphosphorylates RNA Pol II, thereby increasing its processivity. Our previous work identified histone H1 as a P-TEFb substrate during HIV-1 and immediate-early transcription. Here, we examine the role of P-TEFb phosphorylation of histone H1 during differentiation, using the myoblast cell line C2C12 as a model for skeletal muscle differentiation. We found that H1 phosphorylation is elevated in differentiating C2C12, and this phosphorylation is sensitive to P-TEFb inhibition. H1 phosphorylation was also necessary for the induction of three muscle marker genes that require P-TEFb for expression. Additionally, ChIP experiments demonstrate that H1 dissociates from muscle differentiation marker genes in C2C12 cells under active P-TEFb conditions. We determine that both P-TEFb activity and H1 phosphorylation are necessary for the full differentiation of C2C12 myoblasts into myotubes.
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Affiliation(s)
- Siobhan K O'Brien
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School Worcester, Worcester, Massachusetts, USA
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17
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Taneda T, Zhu W, Cao Q, Watanabe H, Yamaguchi Y, Handa H, Wada T. Erythropoiesis is regulated by the transcription elongation factor Foggy/Spt5 through gata1 gene regulation. Genes Cells 2011; 16:231-42. [DOI: 10.1111/j.1365-2443.2010.01481.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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18
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Kaichi S, Takaya T, Morimoto T, Sunagawa Y, Kawamura T, Ono K, Shimatsu A, Baba S, Heike T, Nakahata T, Hasegawa K. Cyclin-dependent kinase 9 forms a complex with GATA4 and is involved in the differentiation of mouse ES cells into cardiomyocytes. J Cell Physiol 2010; 226:248-54. [PMID: 20665673 DOI: 10.1002/jcp.22336] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The treatment of ES cells with trichostatin A (TSA), an HDAC inhibitor, induces the acetylation of GATA4 as well as histones, and facilitates their differentiation into cardiomyocytes. Recently, we demonstrated that cyclin-dependent kinase 9 (Cdk9), a core component of positive elongation factor-b, is a novel GATA4-binding partner. The present study examined whether Cdk9 forms a complex with GATA4 in mouse ES cells and is involved in their differentiation into cardiomyocytes. Mouse ES cells and Nkx2.5/GFP ES cells, in which green fluorescent protein (GFP) is expressed under the control of the cardiac-specific Nkx2.5 promoter, were induced to differentiate on feeder-free gelatin-coated plates. Immunoprecipitation/Western blotting in nuclear extracts from mouse ES cells demonstrated that Cdk9 as well as cyclin T1 interact with GATA4 during myocardial differentiation. TSA treatment increased Nkx2.5/GFP-positive cells and endogenous mRNA levels of Nkx2.5 and atrial natriuretic factor. To determine the role of Cdk9 in myocardial cell differentiation, we examined the effects of a dominant-negative form of Cdk9 (DN-Cdk9), which loses its kinase activity, and a Cdk9 kinase inhibitor, 5,6-dichloro-1-β-ribofuranosyl-benzimidazole (DRB) on TSA-induced myocardial cell differentiation. The introduction of the DN-Cdk9 inhibited TSA-induced increase in GFP expression in Nkx2.5/GFP ES cells. The administration of DRB into ES cells significantly inhibited TSA-induced increase of endogenous Nkx2.5 mRNA levels in ES cells as well as GFP expression in Nkx2.5/GFP ES cells. These findings demonstrate that Cdk9 is involved in the differentiation of mouse ES cells into cardiomyocytes by interacting with GATA4.
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Affiliation(s)
- Shinji Kaichi
- Division of Translational Research, Kyoto Medical Center, National Hospital Organization, Fushimi-ku, Kyoto, Japan
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19
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Eilebrecht S, Brysbaert G, Wegert T, Urlaub H, Benecke BJ, Benecke A. 7SK small nuclear RNA directly affects HMGA1 function in transcription regulation. Nucleic Acids Res 2010; 39:2057-72. [PMID: 21087998 PMCID: PMC3064786 DOI: 10.1093/nar/gkq1153] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Non-coding (nc) RNAs are increasingly recognized to play important regulatory roles in eukaryotic gene expression. The highly abundant and essential 7SK ncRNA has been shown to negatively regulate RNA Polymerase II transcription by inactivating the positive transcription elongation factor b (P-TEFb) in cellular and Tat-dependent HIV transcription. Here, we identify a more general, P-TEFb-independent role of 7SK RNA in directly affecting the function of the architectural transcription factor and chromatin regulator HMGA1. An important regulatory role of 7SK RNA in HMGA1-dependent cell differentiation and proliferation regulation is uncovered with the identification of over 1500 7SK-responsive HMGA1 target genes. Elevated HMGA1 expression is observed in nearly every type of cancer making the use of a 7SK substructure in the inhibition of HMGA1 activity, as pioneered here, potentially useful in therapy. The 7SK-HMGA1 interaction not only adds an essential facet to the comprehension of transcriptional plasticity at the coupling of initiation and elongation, but also might provide a molecular link between HIV reprogramming of cellular gene expression-associated oncogenesis.
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Affiliation(s)
- Sebastian Eilebrecht
- Institut des Hautes Études Scientifiques & Centre National de la Recherche Scientifique USR3078, 35 route de Chartres, 91440 Bures sur Yvette, France
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20
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Galatioto J, Mascareno E, Siddiqui MAQ. CLP-1 associates with MyoD and HDAC to restore skeletal muscle cell regeneration. J Cell Sci 2010; 123:3789-95. [PMID: 20940258 DOI: 10.1242/jcs.073387] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Emerging evidence suggests that eukaryotic gene transcription is regulated primarily at the elongation stage by association and dissociation of the inhibitory protein cardiac lineage protein 1 (CLP-1/HEXIM1) from the positive transcription elongation factor b (P-TEFb) complex. It was reported recently that P-TEFb interacts with skeletal muscle-specific regulatory factor, MyoD, suggesting a linkage between CLP-1-mediated control of transcription and skeletal myogenesis. To examine this, we produced CLP-1 knockdown skeletal muscle C2C12 cells by homologous recombination, and demonstrated that the C2C12 CLP-1 +/- cells failed to differentiate when challenged by low serum in the medium. We also showed that CLP-1 interacts with both MyoD and histone deacetylases (HDACs) maximally at the early stage of differentiation of C2C12 cells. This led us to hypothesize that the association might be crucial to inhibition of MyoD-target proliferative genes. Chromatin immunoprecipitation analysis revealed that the CLP-1/MyoD/HDAC complex binds to the promoter of the cyclin D1 gene, which is downregulated in differentiated muscle cells. These findings suggest a novel transcriptional paradigm whereby CLP-1, in conjunction with MyoD and HDAC, acts to inhibit growth-related gene expression, a requirement for myoblasts to exit the cell cycle and transit to myotubes.
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Affiliation(s)
- Josephine Galatioto
- Department of Cell Biology, Center for Cardiovascular and Muscle Research, State University of New York Downstate Medical Center, Brooklyn, New York, NY 11203, USA
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21
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Sánchez-Álvarez M, Montes M, Sánchez-Hernández N, Hernández-Munain C, Suñé C. Differential effects of sumoylation on transcription and alternative splicing by transcription elongation regulator 1 (TCERG1). J Biol Chem 2010; 285:15220-15233. [PMID: 20215116 DOI: 10.1074/jbc.m109.063750] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Modification of proteins by small ubiquitin-like modifier (SUMO) is emerging as an important control of transcription and RNA processing. The human factor TCERG1 (also known as CA150) participates in transcriptional elongation and alternative splicing of pre-mRNAs. Here, we report that SUMO family proteins modify TCERG1. Furthermore, TCERG1 binds to the E2 SUMO-conjugating enzyme Ubc9. Two lysines (Lys-503 and Lys-608) of TCERG1 are the major sumoylation sites. Sumoylation does not affect localization of TCERG1 to the splicing factor-rich nuclear speckles or the alternative splicing function of TCERG1. However, mutation of the SUMO acceptor lysine residues enhanced TCERG1 transcriptional activity, indicating that SUMO modification negatively regulates TCERG1 transcriptional activity. These results reveal a regulatory role for sumoylation in controlling the activity of a transcription factor that modulates RNA polymerase II elongation and mRNA alternative processing, which are discriminated differently by this post-translational modification.
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Affiliation(s)
- Miguel Sánchez-Álvarez
- Departments of Molecular Biology, Consejo Superior de Investigaciones Científicas, Armilla, 18100 Granada, Spain; Departments of Cell Biology and Immunology, Instituto de Parasitología y Biomedicina "López Neyra," Consejo Superior de Investigaciones Científicas, Armilla, 18100 Granada, Spain
| | - Marta Montes
- Departments of Molecular Biology, Consejo Superior de Investigaciones Científicas, Armilla, 18100 Granada, Spain
| | - Noemí Sánchez-Hernández
- Departments of Molecular Biology, Consejo Superior de Investigaciones Científicas, Armilla, 18100 Granada, Spain
| | - Cristina Hernández-Munain
- Departments of Cell Biology and Immunology, Instituto de Parasitología y Biomedicina "López Neyra," Consejo Superior de Investigaciones Científicas, Armilla, 18100 Granada, Spain
| | - Carlos Suñé
- Departments of Molecular Biology, Consejo Superior de Investigaciones Científicas, Armilla, 18100 Granada, Spain.
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22
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A transcription elongation factor that links signals from the reproductive system to lifespan extension in Caenorhabditis elegans. PLoS Genet 2009; 5:e1000639. [PMID: 19749979 PMCID: PMC2729384 DOI: 10.1371/journal.pgen.1000639] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2009] [Accepted: 08/10/2009] [Indexed: 01/28/2023] Open
Abstract
In Caenorhabditis elegans and Drosophila melanogaster, the aging of the soma is influenced by the germline. When germline-stem cells are removed, aging slows and lifespan is increased. The mechanism by which somatic tissues respond to loss of the germline is not well-understood. Surprisingly, we have found that a predicted transcription elongation factor, TCER-1, plays a key role in this process. TCER-1 is required for loss of the germ cells to increase C. elegans' lifespan, and it acts as a regulatory switch in the pathway. When the germ cells are removed, the levels of TCER-1 rise in somatic tissues. This increase is sufficient to trigger key downstream events, as overexpression of tcer-1 extends the lifespan of normal animals that have an intact reproductive system. Our findings suggest that TCER-1 extends lifespan by promoting the expression of a set of genes regulated by the conserved, life-extending transcription factor DAF-16/FOXO. Interestingly, TCER-1 is not required for DAF-16/FOXO to extend lifespan in animals with reduced insulin/IGF-1 signaling. Thus, TCER-1 specifically links the activity of a broadly deployed transcription factor, DAF-16/FOXO, to longevity signals from reproductive tissues.
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23
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Abstract
Regulation of gene expression is essential to all aspects of physiological processes in single-cell as well as multicellular organisms. It gives ultimately cells the ability to efficiently respond to extra- and intracellular stimuli participating in cell cycle, growth, differentiation and survival. Regulation of gene expression is executed primarily at the level of transcription of specific mRNAs by RNA polymerase II (RNAPII), typically in several distinct phases. Among them, transcription elongation is positively regulated by the positive transcription elongation factor b (P-TEFb), consisting of CDK9 and cyclin T1, T2 or K. P-TEFb enables transition from abortive to productive transcription elongation by phosphorylating carboxyl-terminal domain (CTD) in RNAPII and negative transcription elongation factors. Over the years, we have learned a great deal about molecular composition of P-TEFb complexes, their assembly and their role in transcription of specific genes, but function of P-TEFb in other physiological processes was not apparent until just recently. In light of emerging discoveries connecting P-TEFb to regulation of cell cycle, development and several diseases, I would like to discuss these observations as well as future perspectives.
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Affiliation(s)
- Jiri Kohoutek
- Veterinary Research Institute, Hudcova 70, 621 00 Brno, Czech Republic.
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