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Dylgjeri E, Knudsen KE. DNA-PKcs: A Targetable Protumorigenic Protein Kinase. Cancer Res 2022; 82:523-533. [PMID: 34893509 PMCID: PMC9306356 DOI: 10.1158/0008-5472.can-21-1756] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 08/17/2021] [Accepted: 11/10/2021] [Indexed: 01/07/2023]
Abstract
DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is a pleiotropic protein kinase that plays critical roles in cellular processes fundamental to cancer. DNA-PKcs expression and activity are frequently deregulated in multiple hematologic and solid tumors and have been tightly linked to poor outcome. Given the potentially influential role of DNA-PKcs in cancer development and progression, therapeutic targeting of this kinase is being tested in preclinical and clinical settings. This review summarizes the latest advances in the field, providing a comprehensive discussion of DNA-PKcs functions in cancer and an update on the clinical assessment of DNA-PK inhibitors in cancer therapy.
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Affiliation(s)
- Emanuela Dylgjeri
- Department of Cancer Biology, Thomas Jefferson University, Philadelphia, Pennsylvania.,Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Karen E. Knudsen
- Department of Cancer Biology, Thomas Jefferson University, Philadelphia, Pennsylvania.,Sidney Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, Pennsylvania.,Department of Medical Oncology, Thomas Jefferson University, Philadelphia, Pennsylvania.,Department of Urology, Thomas Jefferson University, Philadelphia, Pennsylvania.,Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, Pennsylvania.,Corresponding Author: Karen E. Knudsen, Thomas Jefferson University, 233 South 10th Street, BLSB 1050, Philadelphia, PA 19107. Phone: 215-503-5692; E-mail:
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2
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Nieto Moreno N, Villafañez F, Giono LE, Cuenca C, Soria G, Muñoz MJ, Kornblihtt AR. GSK-3 is an RNA polymerase II phospho-CTD kinase. Nucleic Acids Res 2020; 48:6068-6080. [PMID: 32374842 PMCID: PMC7293024 DOI: 10.1093/nar/gkaa322] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 04/17/2020] [Accepted: 04/23/2020] [Indexed: 12/28/2022] Open
Abstract
We have previously found that UV-induced DNA damage causes hyperphosphorylation of the carboxy terminal domain (CTD) of RNA polymerase II (RNAPII), inhibition of transcriptional elongation and changes in alternative splicing (AS) due to kinetic coupling between transcription and splicing. In an unbiased search for protein kinases involved in the AS response to DNA damage, we have identified glycogen synthase kinase 3 (GSK-3) as an unforeseen participant. Unlike Cdk9 inhibition, GSK-3 inhibition only prevents CTD hyperphosphorylation triggered by UV but not basal phosphorylation. This effect is not due to differential degradation of the phospho-CTD isoforms and can be reproduced, at the AS level, by overexpression of a kinase-dead GSK-3 dominant negative mutant. GSK-3 inhibition abrogates both the reduction in RNAPII elongation and changes in AS elicited by UV. We show that GSK-3 phosphorylates the CTD in vitro, but preferentially when the substrate is previously phosphorylated, consistently with the requirement of a priming phosphorylation reported for GSK-3 efficacy. In line with a role for GSK-3 in the response to DNA damage, GSK-3 inhibition prevents UV-induced apoptosis. In summary, we uncover a novel role for a widely studied kinase in key steps of eukaryotic transcription and pre-mRNA processing.
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Affiliation(s)
- Nicolás Nieto Moreno
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales (FCEN), Universidad de Buenos Aires (UBA) and Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE-UBA-CONICET), Ciudad Universitaria, Pabellón IFIBYNE (C1428EHA), Buenos Aires, Argentina
| | - Florencia Villafañez
- Centro de Investigación en Bioquímica Clínica e Inmunología (CIBICI-CONICET) and Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Luciana E Giono
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales (FCEN), Universidad de Buenos Aires (UBA) and Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE-UBA-CONICET), Ciudad Universitaria, Pabellón IFIBYNE (C1428EHA), Buenos Aires, Argentina
| | - Carmen Cuenca
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales (FCEN), Universidad de Buenos Aires (UBA) and Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE-UBA-CONICET), Ciudad Universitaria, Pabellón IFIBYNE (C1428EHA), Buenos Aires, Argentina
| | - Gastón Soria
- Centro de Investigación en Bioquímica Clínica e Inmunología (CIBICI-CONICET) and Departamento de Bioquímica Clínica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Córdoba, Argentina
| | - Manuel J Muñoz
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales (FCEN), Universidad de Buenos Aires (UBA) and Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE-UBA-CONICET), Ciudad Universitaria, Pabellón IFIBYNE (C1428EHA), Buenos Aires, Argentina.,Fondazione Istituto FIRC di Oncologia Molecolare (IFOM), Via Adamello 16, 20139 Milan, Italy.,Departamento de Biodiversidad y Biología Experimental, FCEN, UBA
| | - Alberto R Kornblihtt
- Departamento de Fisiología, Biología Molecular y Celular, Facultad de Ciencias Exactas y Naturales (FCEN), Universidad de Buenos Aires (UBA) and Instituto de Fisiología, Biología Molecular y Neurociencias (IFIBYNE-UBA-CONICET), Ciudad Universitaria, Pabellón IFIBYNE (C1428EHA), Buenos Aires, Argentina
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3
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Anisenko A, Kan M, Shadrina O, Brattseva A, Gottikh M. Phosphorylation Targets of DNA-PK and Their Role in HIV-1 Replication. Cells 2020; 9:E1907. [PMID: 32824372 PMCID: PMC7464883 DOI: 10.3390/cells9081907] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2020] [Revised: 08/13/2020] [Accepted: 08/14/2020] [Indexed: 02/07/2023] Open
Abstract
The DNA dependent protein kinase (DNA-PK) is a trimeric nuclear complex consisting of a large protein kinase and the Ku heterodimer. The kinase activity of DNA-PK is required for efficient repair of DNA double-strand breaks (DSB) by non-homologous end joining (NHEJ). We also showed that the kinase activity of DNA-PK is essential for post-integrational DNA repair in the case of HIV-1 infection. Besides, DNA-PK is known to participate in such cellular processes as protection of mammalian telomeres, transcription, and some others where the need for its phosphorylating activity is not clearly elucidated. We carried out a systematic search and analysis of DNA-PK targets described in the literature and identified 67 unique DNA-PK targets phosphorylated in response to various in vitro and/or in vivo stimuli. A functional enrichment analysis of DNA-PK targets and determination of protein-protein associations among them were performed. For 27 proteins from these 67 DNA-PK targets, their participation in the HIV-1 life cycle was demonstrated. This information may be useful for studying the functioning of DNA-PK in various cellular processes, as well as in various stages of HIV-1 replication.
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Affiliation(s)
- Andrey Anisenko
- Chemistry Department and Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119234, Russia; (O.S.); (M.G.)
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow 119234, Russia;; (M.K.); (A.B.)
| | - Marina Kan
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow 119234, Russia;; (M.K.); (A.B.)
| | - Olga Shadrina
- Chemistry Department and Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119234, Russia; (O.S.); (M.G.)
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow 119234, Russia;; (M.K.); (A.B.)
| | - Anna Brattseva
- Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow 119234, Russia;; (M.K.); (A.B.)
| | - Marina Gottikh
- Chemistry Department and Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119234, Russia; (O.S.); (M.G.)
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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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Knyazhanskaya ES, Shadrina OA, Anisenko AN, Gottikh MB. Role of DNA-dependent protein kinase in the HIV-1 replication cycle. Mol Biol 2016. [DOI: 10.1134/s0026893316040075] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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6
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Ammosova T, Platonov M, Ivanov A, Kont YS, Kumari N, Kehn-Hall K, Jerebtsova M, Kulkarni AA, Uren A, Kovalskyy D, Nekhai S. 1E7-03, a low MW compound targeting host protein phosphatase-1, inhibits HIV-1 transcription. Br J Pharmacol 2015; 171:5059-75. [PMID: 25073485 DOI: 10.1111/bph.12863] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2014] [Revised: 06/07/2014] [Accepted: 06/14/2014] [Indexed: 01/20/2023] Open
Abstract
BACKGROUND AND PURPOSE HIV-1 transcription is activated by the Tat protein which recruits the cyclin-dependent kinase CDK9/cyclin T1 to TAR RNA. Tat binds to protein phosphatase-1 (PP1) through the Q(35) VCF(38) sequence and translocates PP1 to the nucleus. PP1 dephosphorylates CDK9 and activates HIV-1 transcription. We have synthesized a low MW compound 1H4, that targets PP1 and prevents HIV-1 Tat interaction with PP1 and inhibits HIV-1 gene transcription. Here, we report our further work with the 1H4-derived compounds and analysis of their mechanism of action. EXPERIMENTAL APPROACH Using the 1H4-PP1 complex as a model, we iteratively designed and synthesized follow-up libraries that were analysed for the inhibition of HIV-1 transcription and toxicity. We also confirmed the mechanism of action of the PP1-targeting molecules by determining the affinity of binding of these molecules to PP1, by analysing their effects on PP1 activity, disruption of PP1 binding to Tat and shuttling of PP1 to the nucleus. KEY RESULTS We identified a tetrahydroquinoline derivative, compound 7, which disrupted the interaction of Tat with PP1. We further optimized compound 7 and obtained compound 7c, renamed 1E7-03, which inhibited HIV-1 with low IC50 (fivefold lower than the previously reported compound, 1H4), showed no cytotoxicity and displayed a plasma half-life greater than 8 h in mice. 1E7-03 bound to PP1 in vitro and prevented shuttling of PP1 into the nucleus. CONCLUSIONS AND IMPLICATIONS Our study shows that low MW compounds that functionally mimic the PP1-binding RVxF peptide can inhibit HIV-1 transcription by deregulating PP1.
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Affiliation(s)
- Tatyana Ammosova
- Center for Sickle Cell Disease, Department of Medicine, Howard University, Washington, DC, USA
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Jaramillo-Tatis S, Bamm VV, Vassall KA, Harauz G. Over-expression in E. coli and purification of functional full-length murine small C-terminal domain phosphatase (SCP1, or Golli-interacting protein). Protein Expr Purif 2014; 101:106-14. [PMID: 24925644 DOI: 10.1016/j.pep.2014.05.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Revised: 05/26/2014] [Accepted: 05/31/2014] [Indexed: 01/13/2023]
Abstract
During myelination in the central nervous system, proteins arising from the gene in the oligodendrocyte lineage (golli) participate in diverse events in signal transduction and gene regulation. One of the interacting partners of the Golli-isoform BG21 was discovered by yeast-2-hybrid means and was denoted the Golli-interacting-protein (GIP). In subsequent in vitro studies of recombinant murine GIP, it was not possible to produce a full-length version of recombinant murine rmGIP in functional form under native conditions, primarily because of solubility issues, necessitating the study of a hexahistidine-tagged, truncated form ΔN-rmGIP. This protein is an acidic phosphatase belonging to the family of RNA-polymerase-2, small-subunit, C-terminal phosphatases (SCP1), and studies of the human ortholog hSCP1 have also been performed on truncated forms. Here, a new SUMO-expression and purification protocol has been developed for the preparation of a functional, full-length mSCP1/GIP (our nomenclature henceforth), with no additional purification tags. Both full-length mSCP1/GIP and the truncated murine form (now denoted ΔN-rmSCP1/GIP) had similar melting temperatures, indicating that the integrity of the catalytic core per se was minimally affected by the N-terminus. Characterization of mSCP1/GIP activity with the artificial substrate p-NPP (p-nitrophenylphosphate) yielded kinetic parameters comparable to those of ΔN-rmSCP1/GIP and the truncated human ortholog ΔN-hSCP1. Similarly, mSCP1/GIP dephosphorylated a more natural CTD-peptide substrate (but not protein kinase C-phosphorylated BG21) with comparable kinetics to ΔN-hSCP1. The successful production of an active, full-length mSCP1/GIP will enable future evaluation of the functional role of its N-terminus in protein-protein interactions (e.g., BG21) that regulate its phosphatase activity.
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Affiliation(s)
- Sergio Jaramillo-Tatis
- Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada
| | - Vladimir V Bamm
- Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada
| | - Kenrick A Vassall
- Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada
| | - George Harauz
- Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada.
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Jaramillo-Tatis S, Vassall KA, Bamm VV, Harauz G. Regulatory effect of the glial Golli-BG21 protein on the full-length murine small C-terminal domain phosphatase (SCP1, or Golli-interacting protein). Biochem Biophys Res Commun 2014; 447:633-7. [PMID: 24751520 DOI: 10.1016/j.bbrc.2014.04.050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Accepted: 04/10/2014] [Indexed: 12/12/2022]
Abstract
The gene in the oligodendrocyte lineage (golli) encodes a number of proteins essential for myelination, comprising Golli and classic isoforms that are expressed in a developmentally-regulated manner. The Golli-interacting-protein (GIP) was previously discovered in a search for potential interacting partners of the Golli-isoform BG21, and was realised to be an acidic phosphatase belonging to the family of RNA-polymerase-2, small-subunit, C-terminal phosphatases (viz., SCP1). Here, we refer to this protein as mSCP1/GIP. In subsequent in vitro studies of recombinant murine SCP1/GIP, the inability to produce an active full-length version of the protein under native conditions necessitated the study of a truncated form ΔN-rmSCP1/GIP, but with inconclusive results regarding its interaction with BG21 [13]. We have since developed a new SUMO-expression and purification protocol for the preparation of a functional, full-length mGIP/SCP1, with no additional purification tags. Here, the interaction between mSCP1/GIP (with intact N-terminus) and BG21 is shown to be different than for the truncation mutant studied previously. Specifically, this interaction shows a dual effect on the enzymatic activity of mSCP1/GIP by BG21: BG21 enhanced mSCP1/GIP phosphatase activity (Ka = 30 μM), whereas PKCα-phosphorylated BG21 inhibited its activity (Ki = 2.9 μM), suggesting a potential role of BG21 as a molecular switch ("quick-brake mechanism") on mSCP1/GIP. The successful production of an active, full-length mSCP1/GIP thus demonstrates a role for its N-terminus in regulation of phosphatase activity, in events such as the regulation of transcription in oligodendrocytes.
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Affiliation(s)
- Sergio Jaramillo-Tatis
- Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada
| | - Kenrick A Vassall
- Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada
| | - Vladimir V Bamm
- Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada
| | - George Harauz
- Department of Molecular and Cellular Biology, University of Guelph, 50 Stone Road East, Guelph, Ontario N1G 2W1, Canada.
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Schröder S, Herker E, Itzen F, He D, Thomas S, Gilchrist DA, Kaehlcke K, Cho S, Pollard KS, Capra JA, Schnölzer M, Cole PA, Geyer M, Bruneau BG, Adelman K, Ott M. Acetylation of RNA polymerase II regulates growth-factor-induced gene transcription in mammalian cells. Mol Cell 2013; 52:314-24. [PMID: 24207025 PMCID: PMC3936344 DOI: 10.1016/j.molcel.2013.10.009] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 08/26/2013] [Accepted: 09/27/2013] [Indexed: 11/17/2022]
Abstract
Lysine acetylation regulates transcription by targeting histones and nonhistone proteins. Here we report that the central regulator of transcription, RNA polymerase II, is subject to acetylation in mammalian cells. Acetylation occurs at eight lysines within the C-terminal domain (CTD) of the largest polymerase subunit and is mediated by p300/KAT3B. CTD acetylation is specifically enriched downstream of the transcription start sites of polymerase-occupied genes genome-wide, indicating a role in early stages of transcription initiation or elongation. Mutation of lysines or p300 inhibitor treatment causes the loss of epidermal growth-factor-induced expression of c-Fos and Egr2, immediate-early genes with promoter-proximally paused polymerases, but does not affect expression or polymerase occupancy at housekeeping genes. Our studies identify acetylation as a new modification of the mammalian RNA polymerase II required for the induction of growth factor response genes.
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Affiliation(s)
- Sebastian Schröder
- Gladstone Institutes, San Francisco, CA 94158, USA
- University of California, San Francisco, San Francisco, CA 94143, USA
| | - Eva Herker
- Gladstone Institutes, San Francisco, CA 94158, USA
- Heinrich-Pette-Institute, Leibniz Institute for Experimental Virology, 20251 Hamburg, Germany
| | - Friederike Itzen
- Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
| | - Daniel He
- Gladstone Institutes, San Francisco, CA 94158, USA
- University of California, San Francisco, San Francisco, CA 94143, USA
| | - Sean Thomas
- Gladstone Institutes, San Francisco, CA 94158, USA
- University of California, San Francisco, San Francisco, CA 94143, USA
| | - Daniel A. Gilchrist
- National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Katrin Kaehlcke
- Gladstone Institutes, San Francisco, CA 94158, USA
- University of California, San Francisco, San Francisco, CA 94143, USA
| | - Sungyoo Cho
- Gladstone Institutes, San Francisco, CA 94158, USA
- University of California, San Francisco, San Francisco, CA 94143, USA
| | - Katherine S. Pollard
- Gladstone Institutes, San Francisco, CA 94158, USA
- University of California, San Francisco, San Francisco, CA 94143, USA
| | - John A. Capra
- Gladstone Institutes, San Francisco, CA 94158, USA
- University of California, San Francisco, San Francisco, CA 94143, USA
| | | | | | - Matthias Geyer
- Max Planck Institute of Molecular Physiology, 44227 Dortmund, Germany
- Research Center Caesar, 53175 Bonn, Germany
| | - Benoit G. Bruneau
- Gladstone Institutes, San Francisco, CA 94158, USA
- University of California, San Francisco, San Francisco, CA 94143, USA
| | - Karen Adelman
- National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA
| | - Melanie Ott
- Gladstone Institutes, San Francisco, CA 94158, USA
- University of California, San Francisco, San Francisco, CA 94143, USA
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Two cellular protein kinases, DNA-PK and PKA, phosphorylate the adenoviral L4-33K protein and have opposite effects on L1 alternative RNA splicing. PLoS One 2012; 7:e31871. [PMID: 22363758 PMCID: PMC3283702 DOI: 10.1371/journal.pone.0031871] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Accepted: 01/13/2012] [Indexed: 01/21/2023] Open
Abstract
Accumulation of the complex set of alternatively processed mRNA from the adenovirus major late transcription unit (MLTU) is subjected to a temporal regulation involving both changes in poly (A) site choice and alternative 3′ splice site usage. We have previously shown that the adenovirus L4-33K protein functions as an alternative splicing factor involved in activating the shift from L1-52,55K to L1-IIIa mRNA. Here we show that L4-33K specifically associates with the catalytic subunit of the DNA-dependent protein kinase (DNA-PK) in uninfected and adenovirus-infected nuclear extracts. Further, we show that L4-33K is highly phosphorylated by DNA-PK in vitro in a double stranded DNA-independent manner. Importantly, DNA-PK deficient cells show an enhanced production of the L1-IIIa mRNA suggesting an inhibitory role of DNA-PK on the temporal switch in L1 alternative RNA splicing. Moreover, we show that L4-33K also is phosphorylated by protein kinase A (PKA), and that PKA has an enhancer effect on L4-33K-stimulated L1-IIIa splicing. Hence, we demonstrate that these kinases have opposite effects on L4-33K function; DNA-PK as an inhibitor and PKA as an activator of L1-IIIa mRNA splicing. Taken together, this is the first report identifying protein kinases that phosphorylate L4-33K and to suggest novel regulatory roles for DNA-PK and PKA in adenovirus alternative RNA splicing.
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Ammosova T, Obukhov Y, Kotelkin A, Breuer D, Beullens M, Gordeuk VR, Bollen M, Nekhai S. Protein phosphatase-1 activates CDK9 by dephosphorylating Ser175. PLoS One 2011; 6:e18985. [PMID: 21533037 PMCID: PMC3080879 DOI: 10.1371/journal.pone.0018985] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Accepted: 03/24/2011] [Indexed: 11/19/2022] Open
Abstract
The cyclin-dependent kinase CDK9/cyclin T1 induces HIV-1 transcription by phosphorylating the carboxyterminal domain (CTD) of RNA polymerase II (RNAPII). CDK9 activity is regulated by protein phosphatase-1 (PP1) which was previously shown to dephosphorylate CDK9 Thr186. Here, we analyzed the effect of PP1 on RNAPII phosphorylation and CDK9 activity. The selective inhibition of PP1 by okadaic acid and by NIPP1 inhibited phosphorylation of RNAPII CTD in vitro and in vivo. Expression of the central domain of NIPP1 in cultured cells inhibited the enzymatic activity of CDK9 suggesting its activation by PP1. Comparison of dephosphorylation of CDK9 phosphorylated by (32P) in vivo and dephosphorylation of CDK9's Thr186 analyzed by Thr186 phospho-specific antibodies, indicated that a residue other than Thr186 might be dephosphorylated by PP1. Analysis of dephosphorylation of phosphorylated peptides derived from CDK9's T-loop suggested that PP1 dephosphorylates CDK9 Ser175. In cultured cells, CDK9 was found to be phosphorylated on Ser175 as determined by combination of Hunter 2D peptide mapping and LC-MS analysis. CDK9 S175A mutant was active and S175D – inactive, and dephosphorylation of CDK9's Ser175 upregulated HIV-1 transcription in PP1-dependent manner. Collectively, our results point to CDK9 Ser175 as novel PP1-regulatory site which dephosphorylation upregulates CDK9 activity and contribute to the activation of HIV-1 transcription.
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Affiliation(s)
- Tatiana Ammosova
- Center for Sickle Cell Disease, Howard University, Washington, D.C., United States of America
- RCMI Proteomics Core Facility, Howard University, Washington, D.C., United States of America
| | - Yuri Obukhov
- Center for Sickle Cell Disease, Howard University, Washington, D.C., United States of America
- RCMI Proteomics Core Facility, Howard University, Washington, D.C., United States of America
| | - Alexander Kotelkin
- Center for Sickle Cell Disease, Howard University, Washington, D.C., United States of America
| | - Denitra Breuer
- Center for Sickle Cell Disease, Howard University, Washington, D.C., United States of America
- Department of Microbiology, Howard University, Washington, D.C., United States of America
| | - Monique Beullens
- Department of Molecular Cell Biology, Catholic University of Leuven, Leuven, Belgium
| | - Victor R. Gordeuk
- Center for Sickle Cell Disease, Howard University, Washington, D.C., United States of America
| | - Mathieu Bollen
- Department of Molecular Cell Biology, Catholic University of Leuven, Leuven, Belgium
| | - Sergei Nekhai
- Center for Sickle Cell Disease, Howard University, Washington, D.C., United States of America
- RCMI Proteomics Core Facility, Howard University, Washington, D.C., United States of America
- Department of Microbiology, Howard University, Washington, D.C., United States of America
- * E-mail:
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12
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Jouvet N, Poschmann J, Douville J, Bulet L, Ramotar D. Rrd1 isomerizes RNA polymerase II in response to rapamycin. BMC Mol Biol 2010; 11:92. [PMID: 21129186 PMCID: PMC3019149 DOI: 10.1186/1471-2199-11-92] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2010] [Accepted: 12/03/2010] [Indexed: 01/11/2023] Open
Abstract
Background In Saccharomyces cerevisiae, the immunosuppressant rapamycin engenders a profound modification in the transcriptional profile leading to growth arrest. Mutants devoid of Rrd1, a protein possessing in vitro peptidyl prolyl cis/trans isomerase activity, display striking resistance to the drug, although how Rrd1 activity is linked to the biological responses has not been elucidated. Results We now provide evidence that Rrd1 is associated with the chromatin and it interacts with RNA polymerase II. Circular dichroism revealed that Rrd1 mediates structural changes onto the C-terminal domain (CTD) of the large subunit of RNA polymerase II (Rpb1) in response to rapamycin, although this appears to be independent of the overall phosphorylation status of the CTD. In vitro experiments, showed that recombinant Rrd1 directly isomerizes purified GST-CTD and that it releases RNA polymerase II from the chromatin. Consistent with this, we demonstrated that Rrd1 is required to alter RNA polymerase II occupancy on rapamycin responsive genes. Conclusion We propose as a mechanism, that upon rapamycin exposure Rrd1 isomerizes Rpb1 to promote its dissociation from the chromatin in order to modulate transcription.
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Affiliation(s)
- Nathalie Jouvet
- Maisonneuve-Rosemont Hospital, Research Center, Department of Immunology and Oncology, University of Montreal, 5415 de l'Assomption, Montreal, Quebec, Canada
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13
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Verbruggen P, Ruf M, Blakqori G, Överby AK, Heidemann M, Eick D, Weber F. Interferon antagonist NSs of La Crosse virus triggers a DNA damage response-like degradation of transcribing RNA polymerase II. J Biol Chem 2010; 286:3681-92. [PMID: 21118815 DOI: 10.1074/jbc.m110.154799] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
La Crosse encephalitis virus (LACV) is a mosquito-borne member of the negative-strand RNA virus family Bunyaviridae. We have previously shown that the virulence factor NSs of LACV is an efficient inhibitor of the antiviral type I interferon system. A recombinant virus unable to express NSs (rLACVdelNSs) strongly induced interferon transcription, whereas the corresponding wt virus (rLACV) suppressed it. Here, we show that interferon induction by rLACVdelNSs mainly occurs through the signaling pathway leading from the pattern recognition receptor RIG-I to the transcription factor IRF-3. NSs expressed by rLACV, however, acts downstream of IRF-3 by specifically blocking RNA polymerase II-dependent transcription. Further investigations revealed that NSs induces proteasomal degradation of the mammalian RNA polymerase II subunit RPB1. NSs thereby selectively targets RPB1 molecules of elongating RNA polymerase II complexes, the so-called IIo form. This phenotype has similarities to the cellular DNA damage response, and NSs was indeed found to transactivate the DNA damage response gene pak6. Moreover, NSs expressed by rLACV boosted serine 139 phosphorylation of histone H2A.X, one of the earliest cellular reactions to damaged DNA. However, other DNA damage response markers such as up-regulation and serine 15 phosphorylation of p53 or serine 1524 phosphorylation of BRCA1 were not triggered by LACV infection. Collectively, our data indicate that the strong suppression of interferon induction by LACV NSs is based on a shutdown of RNA polymerase II transcription and that NSs achieves this by exploiting parts of the cellular DNA damage response pathway to degrade IIo-borne RPB1 subunits.
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Affiliation(s)
- Paul Verbruggen
- Department of Virology, Institute for Medical Microbiology and Hygiene, University of Freiburg, D-79008 Freiburg, Germany
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14
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Manceau V, Kielkopf CL, Sobel A, Maucuer A. Different requirements of the kinase and UHM domains of KIS for its nuclear localization and binding to splicing factors. J Mol Biol 2008; 381:748-62. [PMID: 18588901 DOI: 10.1016/j.jmb.2008.06.026] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2008] [Revised: 06/07/2008] [Accepted: 06/10/2008] [Indexed: 11/29/2022]
Abstract
The protein kinase KIS is made by the juxtaposition of a unique kinase domain and a C-terminal domain with a U2AF homology motif (UHM), a sequence motif for protein interaction initially identified in the heterodimeric pre-mRNA splicing factor U2AF. This domain of KIS is closely related to the C-terminal UHM domain of the U2AF large subunit, U2AF(65). KIS phosphorylates the splicing factor SF1, which in turn enhances SF1 binding to U2AF(65) and the 3' splice site, an event known to take place at an early step of spliceosome assembly. Here, the analysis of the subcellular localization of mutated forms of KIS indicates that the kinase domain of KIS is the necessary domain for its nuclear localization. As in the case of U2AF(65), the UHM-containing C-terminal domain of KIS is required for binding to the splicing factors SF1 and SF3b155. The efficiency of KIS binding to SF1 and SF3b155 is similar to that of U2AF(65) in pull-down assays. These results further support the functional link of KIS with splicing factors. Interestingly, when compared to other UHM-containing proteins, KIS presents a different specificity for the UHM docking sites that are present in the N-terminal region of SF3b155, thus providing a new insight into the variety of interactions mediated by UHM domains.
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Affiliation(s)
- Valérie Manceau
- Institut National de la Santé et de la Recherche Médicale, UMR839, 17, rue du Fer à Moulin, F-75005 Paris, France
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15
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Qian H, Ji C, Zhao S, Chen J, Jiang M, Zhang Y, Yan M, Zheng D, Sun Y, Xie Y, Mao Y. Expression and characterization of HSPC129, a RNA polymerase II C-terminal domain phosphatase. Mol Cell Biochem 2007; 303:183-8. [PMID: 17487459 DOI: 10.1007/s11010-007-9472-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2006] [Accepted: 04/03/2007] [Indexed: 11/25/2022]
Abstract
Phosphorylation status of RNA polymerase (RNAP) II's largest subunit C-terminal domain (CTD) plays an important role during transcription cycles. The reversible phosphorylation mainly occurs at serine 2 and serine 5 of CTD heptapeptide repeats and regulates RNAP II's activity during transcription initiation, elongation and RNA processing. Here we expressed and characterized HSPC129, a putative human protein bearing a CTD phosphatase domain (CPD). PCR analysis showed that it was ubiquitously expressed. HSPC129DeltaTM, the truncate HSPC129 with first 156 N terminal amino acids deleted, exhibited Mg(2+) dependent phosphatase activity at pH 5.0. Its specific CTD phosphatase activity was verified in vitro. Our research suggests that HSPC129 may regulate the dynamic phosphorylation of RNAP II CTD.
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Affiliation(s)
- Hui Qian
- State Key Laboratory of Genetic Engineering, Institute of Genetics, School of Life Sciences, Fudan University, Room 602, Science Building, Shanghai, PR China
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16
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Tamrakar S, Kapasi AJ, Spector DH. Human cytomegalovirus infection induces specific hyperphosphorylation of the carboxyl-terminal domain of the large subunit of RNA polymerase II that is associated with changes in the abundance, activity, and localization of cdk9 and cdk7. J Virol 2006; 79:15477-93. [PMID: 16306619 PMCID: PMC1316045 DOI: 10.1128/jvi.79.24.15477-15493.2005] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human cytomegalovirus infection in the presence of the cyclin-dependent kinase (cdk) inhibitor roscovitine leads to changes in differential splicing and the polyadenylation of immediate early IE1/IE2 and UL37 transcripts (V. Sanchez, A. K. McElroy, J. Yen, S. Tamrakar, C. L. Clark, R. A. Schwartz, and D. H. Spector, J. Virol. 78:11219-11232, 2004). To determine if this was associated with specific phosphorylation of the C-terminal domain (CTD) of the RNA polymerase II (RNAP II) large subunit by cdk7/cyclin H and cdk9/cyclin T1, we examined the expression and localization of these kinases and the various phosphorylated forms of RNAP II. Infection resulted in increased RNAP II CTD phosphorylated on serines 2 and 5 and increased levels of activity of cdk7 and cdk9. At early times, cdk9 localizes with input viral DNA, and aggregates of cdk9 and cdk7 and a subset of Ser2-phosphorylated RNAP II colocalize with IE1/IE2 proteins adjacent to promyelocytic leukemia protein oncogenic domains. Later, cdk9 and Ser2-phosphorylated RNAP II form a nuclear punctate pattern; cdk7 resides in replication centers, and Ser5-phosphorylated RNAP II clusters at the peripheries of replication centers. Roscovitine treatment leads to decreased levels of hyperphosphorylated RNAP II (RNAP IIo) in infected cells and of hypophosphorylated RNAP II in mock-infected and infected cells. The RNAP IIo decrease does not occur if roscovitine is added 8 h postinfection, as was previously observed for processing of IE transcripts. These results suggest that accurate IE gene expression requires specific phosphorylation of the RNAP II CTD early in infection.
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Affiliation(s)
- Sama Tamrakar
- Cellular and Molecular Medicine East, Room 2059, Mail Code 0712, 9500 Gilman Drive, University of California, San Diego, La Jolla, California 92093-0712, USA
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17
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Jovanovic M, Dynan WS. Terminal DNA structure and ATP influence binding parameters of the DNA-dependent protein kinase at an early step prior to DNA synapsis. Nucleic Acids Res 2006; 34:1112-20. [PMID: 16488883 PMCID: PMC1373693 DOI: 10.1093/nar/gkj504] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The DNA-dependent protein kinase catalytic subunit (DNA-PKcs) regulates the non-homologous end-joining pathway of DNA double-strand break repair in mammalian cells. The ability of DNA-PKcs to sense and respond to different terminal DNA structures is postulated to be important for its regulatory function. It is unclear whether discrimination occurs at the time of formation of the initial protein–DNA complex or later, at the time of formation of a paired, or synaptic complex between opposing DNA ends. To gain further insight into the mechanism of regulation, we characterized the binding of DNA-PKcs to immobilized DNA fragments that cannot undergo synapsis. Results showed that DNA-PKcs strongly discriminates between different terminal structures at the time of initial complex formation. Although Ku protein stabilizes DNA-PKcs binding overall, it is not required for discrimination between terminal structures. Base mispairing, temperature and the presence of an interstrand linkage influence the stability of the initial complex in a manner that suggests a requirement for DNA unwinding, reminiscent of the ‘open complex’ model of RNA polymerase–promoter DNA interaction. ATP and a nonhydrolyzable ATP analog also influence the stability of the DNA-PKcs•DNA complex, apparently by an allosteric mechanism that does not require DNA-PKcs autophosphorylation.
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Affiliation(s)
| | - William S. Dynan
- To whom correspondence should be addressed. Tel: +1 706 721 8756; Fax: +1 706 721 8752;
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18
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Even Y, Durieux S, Escande ML, Lozano JC, Peaucellier G, Weil D, Genevière AM. CDC2L5, a Cdk-like kinase with RS domain, interacts with the ASF/SF2-associated protein p32 and affects splicing in vivo. J Cell Biochem 2006; 99:890-904. [PMID: 16721827 DOI: 10.1002/jcb.20986] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The human CDC2L5 gene encodes a protein of unknown physiological function. This protein is closely related to the cyclin-dependent kinase (Cdks) family and contains an arginine/serine-rich (RS) domain. The Cdks were first identified as crucial regulators of cell-cycle progression, more recently they were found to be involved in transcription and mRNA processing. RS domains are mainly present in proteins regulating pre-mRNA splicing, suggesting CDC2L5 having a possible role in this process. In this study, we demonstrate that CDC2L5 is located in the nucleoplasm, at a higher concentration in speckles, the storage sites for splicing factors. Furthermore, this localization is dependent on the presence of the N-terminal sequence including the RS domain. Then, we report that CDC2L5 directly interacts with the ASF/SF2-associated protein p32, a protein involved in splicing regulation. Overexpression of CDC2L5 constructs disturbs constitutive splicing and switches alternative splice site selection in vivo. These results argue in favor of a functional role of the CDC2L5 kinase in splicing regulation.
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Affiliation(s)
- Yasmine Even
- Laboratoire Arago, CNRS-UMR 7628/Université Pierre et Marie Curie, BP 44, F-66651 Banyuls-sur-Mer cedex, France
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19
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Zheng H, Ji C, Gu S, Shi B, Wang J, Xie Y, Mao Y. Cloning and characterization of a novel RNA polymerase II C-terminal domain phosphatase. Biochem Biophys Res Commun 2005; 331:1401-7. [PMID: 15883030 DOI: 10.1016/j.bbrc.2005.04.065] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2005] [Indexed: 12/12/2022]
Abstract
Reversible phosphorylation of RNA polymerase (RNAP) II's largest subunit C-terminal domain (CTD) is a key event during mRNA metabolism. The CTD phosphatase, FCP1, catalyzes the dephosphorylation of RNAP II and is thought to play a major role in polymerase recycling. In this study, we isolated a novel phosphatase gene by large-scale sequencing analysis of a human fetal brain cDNA library. Its cDNA is 2215 bp in length, encoding a 318-amino acid polypeptide that contains a ubiquitin-like domain and a CTD phosphatase domain. Therefore, it was termed ubiquitin-like domain containing CTD phosphatase 1 (UBLCP1). Reverse transcription PCR (RT-PCR) revealed that UBLCP1 was expressed with relatively lower levels in most adult normal tissues and higher levels in fast growing or tumor tissues. Transient transfection experiment suggested that UBLCP1 was localized in the nucleus of COS-7 cells. Significantly, UBLCP1 could dephosphorylate GST-CTD in vitro. Accordingly, UBLCP1 may play a role in the regulation of phosphorylation state of RNA polymerase II C-terminal domain.
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Affiliation(s)
- Huarui Zheng
- State Key Laboratory of Genetic Engineering, Institute of Genetics, School of Life Sciences, Fudan University, Shanghai 200433, People's Republic of China
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20
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Millhouse S, Manley JL. The C-terminal domain of RNA polymerase II functions as a phosphorylation-dependent splicing activator in a heterologous protein. Mol Cell Biol 2005; 25:533-44. [PMID: 15632056 PMCID: PMC543425 DOI: 10.1128/mcb.25.2.533-544.2005] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2004] [Accepted: 10/18/2004] [Indexed: 11/20/2022] Open
Abstract
RNA polymerase II, and specifically the C-terminal domain (CTD) of its largest subunit, has been demonstrated to play important roles in capping, splicing, and 3' processing of mRNA precursors. But how the CTD functions in these reactions, especially splicing, is not well understood. To address some of the basic questions concerning CTD function in splicing, we constructed and purified two fusion proteins, a protein in which the CTD is positioned at the C terminus of the splicing factor ASF/SF2 (ASF-CTD) and an RS domain deletion mutant protein (ASFDeltaRS-CTD). Significantly, compared to ASF/SF2, ASF-CTD increased the reaction rate during the early stages of splicing, detected as a 20- to 60-min decrease in splicing lag time depending on the pre-mRNA substrate. The increased splicing rate correlated with enhanced production of prespliceosomal complex A and the early spliceosomal complex B but, interestingly, not the very early ATP-independent complex E. Additional assays indicate that the RS domain and CTD perform distinct functions, as exemplified by our identification of an activity that cooperates only with the CTD. Dephosphorylated ASFDeltaRS-CTD and a glutathione S-transferase-CTD fusion protein were both inactive, suggesting that an RNA-targeting domain and CTD phosphorylation were necessary. Our results provide new insights into the mechanism by which the CTD functions in splicing.
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Affiliation(s)
- Scott Millhouse
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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21
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Ohkawa K, Ishida H, Nakanishi F, Hosui A, Ueda K, Takehara T, Hori M, Hayashi N. Hepatitis C virus core functions as a suppressor of cyclin-dependent kinase-activating kinase and impairs cell cycle progression. J Biol Chem 2004; 279:11719-26. [PMID: 14711830 DOI: 10.1074/jbc.m308560200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
We investigated how the hepatitis C virus (HCV) core protein affects the cell cycle profile and cell cycle-related molecules by using the HCV core-expressing stable transfectant. Analysis of the cell cycle profile showed that HCV core impaired G(1) to S transition. The E2F-mediated transcription, phosphorylation of the retinoblastoma protein, and cyclin-dependent kinase (CDK) 4 and CDK2 activities were suppressed in HCV core-expressing cells. The expression levels of G(1) phase-related CDKs/cyclins and various CDK inhibitors were not substantially affected by expression of HCV core. When influences of HCV core on CDK-activating kinase (CAK) were examined, the expression levels of the CAK components, CDK7, cyclin H, and MAT1, were not affected. However, formation of the ternary CAK complex, CAK activity, and the CDK2 level with activating phosphorylation were inhibited by expression of the HCV core. The direct effect of HCV core on CAK was further assessed in the cell-free system by adding the in vitro translated HCV core protein to the anti-CDK7 immunoprecipitate from the cell. The results showed that HCV core led to dissociation of MAT1 from the CAK complex and suppressed the CAK activity. Furthermore, the binding assay revealed that the HCV core was directed against CDK7. Their interaction occurred mainly in the nucleus by the immunostaining. In conclusion, the HCV core protein interacts with CAK and functions as an extrinsic suppressor of CAK. This may be the molecular basis of HCV core-mediated suppression of cell cycle progression. Our findings suggest a novel mechanism concerning HCV core-mediated alteration in the cell cycle machinery.
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Affiliation(s)
- Kazuyoshi Ohkawa
- Department of Molecular Therapeutics, Osaka University Graduate School of Medicine, Suita, Osaka 565-0871, Japan
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22
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Chapman RD, Palancade B, Lang A, Bensaude O, Eick D. The last CTD repeat of the mammalian RNA polymerase II large subunit is important for its stability. Nucleic Acids Res 2004; 32:35-44. [PMID: 14704341 PMCID: PMC373282 DOI: 10.1093/nar/gkh172] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
The phosphorylation of the RNA polymerase II (Pol II) C-terminal domain (CTD) has been shown to affect the initiation, and transition to elongation of the Pol II complex. The differential phosphorylation of serines within this domain coincides with the recruitment of factors important for pre-mRNA processing and transcriptional elongation. A role for tyrosine and threonine phosphorylation has yet to be described. The discovery of kinases that express a preference for specific residues within this sequence suggests a mechanism for the controlled recruitment and displacement of CTD-interacting partners during the transcription cycle. The last CTD repeat (CTD52) contains unique interaction sites for the only known CTD tyrosine kinases, Abl1/c-Abl and Abl2/Arg, and the serine/threonine kinase casein kinase II (CKII). Here, we show that removal or severe disruption of the last CTD repeat, but not point mutation of its CKII sites, results in its proteolytic degradation to the Pol IIb form in vivo, but does not appear to affect the specific transcription of genes. These results suggest a possible mechanism of transcription control through the proteolytic removal of the Pol II CTD.
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Affiliation(s)
- Rob D Chapman
- Institute of Clinical Molecular Biology and Tumour Genetics, GSF Research Center for Environment and Health, Marchioninistr. 25, D-81377 Munich, Germany
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23
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Fan H, Sakuraba K, Komuro A, Kato S, Harada F, Hirose Y. PCIF1, a novel human WW domain-containing protein, interacts with the phosphorylated RNA polymerase II. Biochem Biophys Res Commun 2003; 301:378-85. [PMID: 12565871 DOI: 10.1016/s0006-291x(02)03015-2] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Phosphorylation of the carboxy-terminal domain (CTD) of RNA polymerase II (RNAP II) largest subunit has an important role in transcription elongation and in coupling transcription to pre-mRNA processing. To identify proteins that can directly bind to the phosphorylated CTD, we screened a human cDNA expression library using 32P-labeled CTD as a probe. Here we report the cloning and characterization of a novel human WW domain-containing protein, PCIF1 (phosphorylated CTD interacting factor 1). PCIF1 is composed of 704 amino acids. The WW domain of PCIF1 can directly and preferentially bind to the phosphorylated CTD compared to the unphosphorylated CTD. PCIF1 binds to the hyperphosphorylated RNAP II (RNAP IIO) in vitro and in vivo. Double immunofluorescence labeling in HeLa cells demonstrated that PCIF1 and endogenous RNAP IIO are co-localized in the cell nucleus. Thus, PCIF1 may play a role in mRNA synthesis by modulating RNAP IIO activity.
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Affiliation(s)
- Hong Fan
- Division of Cell Biology, Cancer Research Institute, Kanazawa University, 13-1, Takara-machi, Kanazawa, Ishikawa 920-0934, Japan
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24
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Mo X, Dynan WS. Subnuclear localization of Ku protein: functional association with RNA polymerase II elongation sites. Mol Cell Biol 2002; 22:8088-99. [PMID: 12391174 PMCID: PMC134733 DOI: 10.1128/mcb.22.22.8088-8099.2002] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ku is an abundant nuclear protein with an essential function in the repair of DNA double-strand breaks. Various observations suggest that Ku also interacts with the cellular transcription machinery, although the mechanism and significance of this interaction are not well understood. In the present study, we investigated the subnuclear distribution of Ku in normally growing human cells by using confocal microscopy, chromatin immunoprecipitation, and protein immunoprecipitation. All three approaches indicated association of Ku with RNA polymerase II (RNAP II) elongation sites. This association occurred independently of the DNA-dependent protein kinase catalytic subunit and was highly selective. There was no detectable association with the initiating isoform of RNAP II or with the general transcription initiation factors. In vitro protein-protein interaction assays demonstrated that the association of Ku with elongation proteins is mediated, in part, by a discrete C-terminal domain in the Ku80 subunit. Functional disruption of this interaction with a dominant-negative mutant inhibited transcription in vitro and in vivo and suppressed cell growth. These results suggest that association of Ku with transcription sites is important for maintenance of global transcription levels. Tethering of double-strand break repair proteins to defined subnuclear structures may also be advantageous in maintenance of genome stability.
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Affiliation(s)
- Xianming Mo
- Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Georgia 30912, USA
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25
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Washington K, Ammosova T, Beullens M, Jerebtsova M, Kumar A, Bollen M, Nekhai S. Protein phosphatase-1 dephosphorylates the C-terminal domain of RNA polymerase-II. J Biol Chem 2002; 277:40442-8. [PMID: 12185079 DOI: 10.1074/jbc.m205687200] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Transcription by RNA polymerase-II (RNAPII) is controlled by multisite phosphorylation of the heptapeptide repeats in the C-terminal domain (CTD) of the largest subunit. Phosphorylation of CTD is mediated by the cyclin-dependent protein kinases Cdk7 and Cdk9, whereas protein serine/threonine phosphatase FCP1 dephosphorylates CTD. We have recently reported that human immunodeficiency virus-1 (HIV-1) transcription is positively regulated by protein phosphatase-1 (PP1) and that PP1 dephosphorylates recombinant CTD. Here, we provide further evidence that PP1 can dephosphorylate RNAPII CTD. In vitro, PP1 dephosphorylated recombinant CTD as well as purified RNAPII CTD. HeLa nuclear extracts were found to contain a species of PP1 that dephosphorylates both serine 2 and serine 5 of the heptapeptide repeats. In nuclear extracts, PP1 and FCP1 contributed roughly equally to the dephosphorylation of serine 2. PP1 co-purified with RNAPII by gel filtration and associated with RNAPII on immunoaffinity columns prepared with anti-CTD antibodies. In cultured cells treated with CTD kinase inhibitors, the dephosphorylation of RNAPII on serine 2 was inhibited by 45% by preincubation with okadaic acid, which inhibits phosphatases of PPP family, including PP1 but not FCP1. Our data demonstrate that RNAPII CTD is dephosphorylated by PP1 in vitro and by PPP-type phosphatase, distinct from FCP1, in vivo.
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Affiliation(s)
- Kareem Washington
- Center for Sickle Cell Disease, Department of Biochemistry and Molecular Biology, Howard University, 2121 Georgia Avenue, Washington, D. C. 20059, USA
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26
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Lee KJ, Dong X, Wang J, Takeda Y, Dynan WS. Identification of human autoantibodies to the DNA ligase IV/XRCC4 complex and mapping of an autoimmune epitope to a potential regulatory region. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 169:3413-21. [PMID: 12218164 DOI: 10.4049/jimmunol.169.6.3413] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The nonhomologous end-joining pathway is the principal mechanism for repair of ionizing radiation-induced, double-strand breaks in mammalian cells. Three polypeptides in this pathway, including the two subunits of Ku protein and the catalytic subunit of the DNA-dependent protein kinase, are known targets of autoantibodies in systemic rheumatic diseases. Here we show that two additional polypeptides in the pathway, DNA ligase IV and XRCC4, are also targets of autoantibodies. These Abs were present in 20% of patients with systemic lupus erythematosus and overlap syndrome. Previous work has shown that XRCC4 is subject to radiation-induced post-translational modification, including phosphorylation by DNA-dependent protein kinase and cleavage by caspase 3. We mapped a major autoimmune epitope in XRCC4 and found that it encompassed a DNA-dependent protein kinase phosphorylation site, which is located at serine 260; that it was adjacent to a site for caspase 3, which cleaves after residue 265; and that it also spanned a site for the inflammatory protease, granzyme B, which cleaves after residue 254. The finding that five different polypeptides in the nonhomologous end-joining pathway are potential targets of autoantibodies together with the observation that one of the autoimmune epitopes in XRCC4 coincides with a sequence that is a nexus for radiation-induced regulatory events suggest that exposure to agents that introduce DNA double-strand breaks may be one of the factors that influences the development of an autoimmune response in susceptible individuals.
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Affiliation(s)
- Kyung-Jong Lee
- Program in Gene Regulation, Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA 30912, USA
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27
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Deng L, Ammosova T, Pumfery A, Kashanchi F, Nekhai S. HIV-1 Tat interaction with RNA polymerase II C-terminal domain (CTD) and a dynamic association with CDK2 induce CTD phosphorylation and transcription from HIV-1 promoter. J Biol Chem 2002; 277:33922-9. [PMID: 12114499 DOI: 10.1074/jbc.m111349200] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Human immunodeficiency virus, type 1 (HIV-1), Tat protein activates viral gene expression through promoting transcriptional elongation by RNA polymerase II (RNAPII). In this process Tat enhances phosphorylation of the C-terminal domain (CTD) of RNAPII by activating cell cycle-dependent kinases (CDKs) associated with general transcription factors of the promoter complex, specifically CDK7 and CDK9. We reported a Tat-associated T-cell-derived kinase, which contained CDK2. Here, we provide further evidence that CDK2 is involved in Tat-mediated CTD phosphorylation and in HIV-1 transcription in vitro. Tat-mediated CTD phosphorylation by CDK2 required cysteine 22 in the activation domain of Tat and amino acids 42-72 of Tat. CDK2 phosphorylated Tat itself, apparently by forming dynamic contacts with amino acids 15-24 and 36-49 of Tat. Also, amino acids 24-36 and 45-72 of Tat interacted with CTD. CDK2 associated with RNAPII and was found in elongation complexes assembled on HIV-1 long-terminal repeat template. Recombinant CDK2/cyclin E stimulated Tat-dependent HIV-1 transcription in reconstituted transcription assay. Immunodepletion of CDK2/cyclin E in HeLa nuclear extract blocked Tat-dependent transcription. We suggest that CDK2 is part of a transcription complex that is required for Tat-dependent transcription and that interaction of Tat with CTD and a dynamic association of Tat with CDK2/cyclin E stimulated CTD phosphorylation by CDK2.
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Affiliation(s)
- Longwen Deng
- Department of Biochemistry & Molecular Biology, George Washington University Medical Center, Washington, D.C. 20037, USA
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Nekhai S, Zhou M, Fernandez A, Lane WS, Lamb NJC, Brady J, Kumar A. HIV-1 Tat-associated RNA polymerase C-terminal domain kinase, CDK2, phosphorylates CDK7 and stimulates Tat-mediated transcription. Biochem J 2002; 364:649-57. [PMID: 12049628 PMCID: PMC1222613 DOI: 10.1042/bj20011191] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
HIV-1 gene expression is regulated by a viral transactivator protein (Tat) which induces transcriptional elongation of HIV-1 long tandem repeat (LTR). This induction requires hyperphosphorylation of the C-terminal domain (CTD) repeats of RNA polymerase II (Pol II). To achieve CTD hyperphosphorylation, Tat stimulates CTD kinases associated with general transcription factors of the promoter complex, specifically TFIIH-associated CDK7 and positive transcription factor b-associated CDK9 (cyclin-dependent kinase 9). Other studies indicate that Tat may bind an additional CTD kinase that regulates the target-specific phosphorylation of RNA Pol II CTD. We previously reported that Tat-associated T-cell-derived kinase (TTK), purified from human primary T-cells, stimulates Tat-dependent transcription of HIV-1 LTR in vivo [Nekhai, Shukla, Fernandez, Kumar and Lamb (2000) Virology 266, 246-256]. In the work presented here, we characterized the components of TTK by biochemical fractionation and the function of TTK in transcription assays in vitro. TTK uniquely co-purified with CDK2 and not with either CDK9 or CDK7. Tat induced the TTK-associated CDK2 kinase to phosphorylate CTD, specifically at Ser-2 residues. The TTK fraction restored Tat-mediated transcription activation of HIV-1 LTR in a HeLa nuclear extract immunodepleted of CDK9, but not in the HeLa nuclear extract double-depleted of CDK9 and CDK7. Direct microinjection of the TTK fraction augmented Tat transactivation of HIV-1 LTR in human primary HS68 fibroblasts. The results argue that TTK-associated CDK2 may function to maintain target-specific phosphorylation of RNA Pol II that is essential for Tat transactivation of HIV-1 promoter. They are also consistent with the observed cell-cycle-specific induction of viral gene transactivation.
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Affiliation(s)
- Sergei Nekhai
- Department of Biochemistry and Molecular Biology, The George Washington University, School of Medicine, 2300 Eye Street N.W., Washington, DC 20037, USA
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29
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Näär AM, Taatjes DJ, Zhai W, Nogales E, Tjian R. Human CRSP interacts with RNA polymerase II CTD and adopts a specific CTD-bound conformation. Genes Dev 2002; 16:1339-44. [PMID: 12050112 PMCID: PMC186316 DOI: 10.1101/gad.987602] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Activation of gene transcription in mammalian cells requires several classes of coactivators that participate in different steps of the activation cascade. Using conventional and affinity chromatography, we have isolated a human coactivator complex that interacts directly with the C-terminal domain (CTD) of RNA polymerase II (Pol II). The CTD-binding complex is structurally and functionally indistinguishable from our previously isolated CRSP coactivator complex. The closely related, but transcriptionally inactive, ARC-L complex failed to interact with the CTD, indicating a significant biochemical difference between CRSP and ARC-L that may, in part, explain their functional divergence. Electron microscopy and three-dimensional single-particle reconstruction reveals a conformation for CTD-CRSP that is structurally distinct from unliganded CRSP or CRSP bound to SREBP-1a, but highly similar to CRSP bound to the VP16 activator. Together, our findings suggest that the human CRSP coactivator functions, at least in part, by mediating activator-dependent recruitment of RNA Pol II via the CTD.
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Affiliation(s)
- Anders M Näär
- Department of Cell Biology, Harvard Medical School, Massachusetts General Hospital Cancer Center, Charlestown 02129, USA
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30
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Bharucha DC, Zhou M, Nekhai S, Brady JN, Shukla RR, Kumar A. A protein phosphatase from human T cells augments tat transactivation of the human immunodeficiency virus type 1 long-terminal repeat. Virology 2002; 296:6-16. [PMID: 12036313 DOI: 10.1006/viro.2002.1438] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
HIV-1 Tat protein regulates viral gene expression by modulating the activity and association of cellular transcription factors with RNA polymerase II (RNAPII). Possible mechanisms include Tat-associated protein kinase(s) and phosphatase(s) that regulate phosphorylation of the C-terminal domain (CTD) of the large subunit of RNAPII. Hypophosphorylated RNAPII (RNAPIIa) is recruited to promoters during formation of a preinitiation complex, whereas hyperphosphorylated RNAPII (RNAPIIo) is associated with the elongation complex. The role of phosphatases in maintaining the equilibrium between the two phosphorylated states of RNAPII, which is required for sustained transcriptional activation from the HIV-1 LTR, is not clear. In this study, we discuss the properties of a Tat-associated CTD phosphatase fractionated from Jurkat T cells. The Tat-associated protein phosphatase (TAPP) is related to the serine/threonine, type 1, protein phosphatase (PP1) family. TAPP dephosphorylates the hyperphosphorylated form of recombinant CTD specifically on serine 2, and augments Tat-mediated transcriptional transactivation of HIV-1 LTR in an in vitro transcription reaction. TAPP is associated with the transcription complex during the early initiation steps, and its release from the HIV-1 promoter coincides with the Tat-specific activation of CDK9. The results suggest a unique role of the Tat-associated phosphatase which regulates viral transcription by target-specific dephosphorylation of RNAPII during the early stages of elongation.
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Affiliation(s)
- Diana C Bharucha
- Department of Biochemistry and Molecular Biology, The George Washington University Medical Center, Washington, DC 20037, USA
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31
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Ryan K, Murthy KGK, Kaneko S, Manley JL. Requirements of the RNA polymerase II C-terminal domain for reconstituting pre-mRNA 3' cleavage. Mol Cell Biol 2002; 22:1684-92. [PMID: 11865048 PMCID: PMC135617 DOI: 10.1128/mcb.22.6.1684-1692.2002] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2001] [Revised: 12/12/2001] [Accepted: 12/18/2001] [Indexed: 12/29/2022] Open
Abstract
RNA polymerase II (RNAP II) has previously been shown to be required for the pre-mRNA polyadenylation cleavage reaction in vitro. This activity was found to reside solely in the C-terminal domain (CTD) of the enzyme's largest subunit. Using a deletion analysis of glutathione S-transferase-CTD fusion proteins, we searched among the CTD's 52 imperfectly repetitive heptapeptides for the minimal subset that possesses this property. We found that heptads in the vicinity of 30 to 37 contribute modestly more than other sections, but that no specific subsection of the CTD is necessary or sufficient for cleavage. To investigate further the heptad requirements for cleavage, we constructed a series of all-consensus CTDs having 13, 26, 39, and 52 YSPTSPS repeats. We found that the nonconsensus CTD heptads are together responsible for only 20% of the wild-type cleavage activity. Analysis of the all-consensus CTD series revealed that the remaining 80% of the CTD-dependent cleavage activity directly correlates with CTD length, with significant activity requiring approximately 26 or more repeats. These results are consistent with a scaffolding role for the RNAP II CTD in the pre-mRNA cleavage reaction.
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Affiliation(s)
- Kevin Ryan
- Department of Biological Sciences, Columbia University, 117A Fairchild Building, New York, NY 10027, USA
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Kops O, Zhou XZ, Lu KP. Pin1 modulates the dephosphorylation of the RNA polymerase II C-terminal domain by yeast Fcp1. FEBS Lett 2002; 513:305-11. [PMID: 11904169 DOI: 10.1016/s0014-5793(02)02288-3] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The reversible phosphorylation of serine and threonine residues N-terminal to proline (pSer/Thr-Pro) is an important signaling mechanism in the cell. The pSer/Thr-Pro moiety exists in the two distinct cis and trans conformations, whose conversion is catalyzed by the peptidyl-prolyl isomerase (PPIase) Pin1. Among others, Pin1 binds to the phosphorylated C-terminal domain (CTD) of the largest subunit of the RNA polymerase II, but the biochemical and functional relevance of this interaction is unknown. Here we confirm that the CTD phosphatase Fcp1 can suppress a Pin1 mutation in yeast. Furthermore, this genetic interaction requires the phosphatase domain as well as the BRCT domain of Fcp1, suggesting a critical role of the Fcp1 localization. Based on these observations, we developed a new in vitro assay to analyze the CTD dephosphorylation by Fcp1 that uses only recombinant proteins and mimics the in vivo situation. This assay allows us to present strong evidence that Pin1 is able to stimulate CTD dephosphorylation by Fcp1 in vitro, and that this stimulation depends on Pin1's PPIase activity. Finally, Pin1 significantly increased the dephosphorylation of the CTD on the Ser(5)-Pro motif, but not on Ser(2)-Pro in yeast, which can be explained with Pin1's substrate specificity. Together, our results indicate a new role for Pin1 in the regulation of CTD phosphorylation and present a further example for prolyl isomerization-dependent protein dephosphorylation.
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Affiliation(s)
- Oliver Kops
- Cancer Biology Program, Division of Hematology/Oncology, Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, HIM 1047, 330 Brookline Avenue, Boston, MA 02215, USA
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33
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Kumar NV, Bernstein LR. Ten ERK-related proteins in three distinct classes associate with AP-1 proteins and/or AP-1 DNA. J Biol Chem 2001; 276:32362-72. [PMID: 11431474 DOI: 10.1074/jbc.m103677200] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have identified seven ERK-related proteins ("ERPs"), including ERK2, that are stably associated in vivo with AP-1 dimers composed of diverse Jun and Fos family proteins. These complexes have kinase activity. We designate them as "class I ERPs." We originally hypothesized that these ERPs associate with DNA along with AP-1 proteins. We devised a DNA affinity chromatography-based analytical assay for DNA binding, the "nucleotide affinity preincubation specificity test recognition" (NAPSTER) assay. In this assay, class I ERPs do not associate with AP-1 DNA. However, several new "class II" ERPs do associate with DNA. p41 and p44 are ERK1/2-related ERPs that lack kinase activity and associate along with AP-1 proteins with AP-1 DNA. Class I ERPs and their associated kinase activity thus appear to bind AP-1 dimers when they are not bound to DNA and then disengage and are replaced by class II ERPs to form higher order complexes when AP-1 dimers bind DNA. p97 is a class III ERP, related to ERK3, that associates with AP-1 DNA without AP-1 proteins. With the exception of ERK2, none of the 10 ERPs appear to be known mitogen-activated protein kinase superfamily members.
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Affiliation(s)
- N V Kumar
- Department of Pathology and Laboratory Medicine, Texas A & M University System Health Science Center, College Station, Texas 77843-1114, USA
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34
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Abstract
The DNA-dependent protein kinase (DNA-PK), comprised of the Ku70/Ku80 (now known as G22p1/Xrcc5) heterodimer and the catalytic subunit DNA-PKcs (now known as Prkdc), is required for the nonhomologous end joining (NHEJ) pathway of DNA double-strand break repair. The mechanism of action of DNA-PK remains unclear. We have investigated whether DNA-PK regulates gene transcription in vivo after DNA damage using the subtractive hybridization technique of cDNA representational difference analysis (cDNA RDA). Differential transcription, both radiation-dependent and independent, was detected and confirmed in primary mouse embryo fibroblasts from DNA-PKcs(-/-) and DNA-PKcs(+/+) mice. We present evidence that transcription of the extracellular matrix gene laminin alpha 4 (Lama4) is regulated by DNA-PK in a radiation-independent manner. However, screening of both primary and immortalized DNA-PKcs-deficient cell lines demonstrates that the majority of differences were not consistently dependent on DNA-PK status. Similar results were obtained in experiments using KU mutant hamster cell lines, indicating heterogeneity of transcription between closely related cell lines. Our results suggest that while DNA-PK may be involved in limited gene-specific transcription, it does not play a major role in the transcriptional response to DNA damage.
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Affiliation(s)
- F Bryntesson
- Department of Molecular Haematology and Cancer Biology, Institute of Child Health, University College, London, 30 Guildford Street, London WC1N 1EH, United Kingdom
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Fukuda A, Yamauchi J, Wu SY, Chiang CM, Muramatsu M, Hisatake K. Reconstitution of recombinant TFIIH that can mediate activator-dependent transcription. Genes Cells 2001; 6:707-19. [PMID: 11532030 DOI: 10.1046/j.1365-2443.2001.00456.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND TFIIH is one of the general transcription factors required for accurate transcription of protein-coding genes by RNA polymerase II. TFIIH has helicase and kinase activities, plays a role in promoter opening and promoter escape, and is also implicated in efficient activator-dependent transcription. RESULTS We have established a reconstitution system of recombinant TFIIH using a three-virus baculovirus expression system. The recombinant TFIIH was active in CTD kinase and DNA helicase assays, and showed both basal and activator-dependent transcriptional activities that were indistinguishable from those of HeLa cell-derived TFIIH. Further analyses using recombinant TFIIH confirmed a critical role of TFIIH in activator-dependent transcription. The dose response of TFIIH in activator-dependent transcription suggested that mere recruitment of TFIIH is not sufficient for transcriptional activation. The sensitivity of activator-dependent transcription to nonhydrolysable ATP analogues indicated the importance of the enzymatic activities of TFIIH in transcriptional activation. CONCLUSIONS Our results raise a possibility that transcriptional activation by GAL4-VP16 requires enzymatic activities. Recombinant TFIIH reconstituted from this baculovirus system should be useful for analysis of the mechanisms of activation by GAL4-VP16.
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Affiliation(s)
- A Fukuda
- Department of Biochemistry, Saitama Medical School, 38 Morohongo, Moroyama, Iruma-gun, Saitama 350-0495, Japan
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Ramanathan Y, Rajpara SM, Reza SM, Lees E, Shuman S, Mathews MB, Pe'ery T. Three RNA polymerase II carboxyl-terminal domain kinases display distinct substrate preferences. J Biol Chem 2001; 276:10913-20. [PMID: 11278802 DOI: 10.1074/jbc.m010975200] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
CDK7, CDK8, and CDK9 are cyclin-dependent kinases (CDKs) that phosphorylate the C-terminal domain (CTD) of RNA polymerase II. They have distinct functions in transcription. Because the three CDKs target only serine 5 in the heptad repeat of model CTD substrates containing various numbers of repeats, we tested the hypothesis that the kinases differ in their ability to phosphorylate CTD heptad arrays. Our data show that the kinases display different preferences for phosphorylating individual heptads in a synthetic CTD substrate containing three heptamer repeats and specific regions of the CTD in glutathione S-transferase fusion proteins. They also exhibit differences in their ability to phosphorylate a synthetic CTD peptide that contains Ser-2-PO(4). This phosphorylated peptide is a poor substrate for CDK9 complexes. CDK8 and CDK9 complexes, bound to viral activators E1A and Tat, respectively, target only serine 5 for phosphorylation in the CTD peptides, and binding to the viral activators does not change the substrate preference of these kinases. These results imply that the display of different CTD heptads during transcription, as well as their phosphorylation state, can affect their phosphorylation by the different transcription-associated CDKs.
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Affiliation(s)
- Y Ramanathan
- Department of Biochemistry and Molecular Biology, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, New Jersey 07103, USA
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Barillà D, Lee BA, Proudfoot NJ. Cleavage/polyadenylation factor IA associates with the carboxyl-terminal domain of RNA polymerase II in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2001; 98:445-50. [PMID: 11149954 PMCID: PMC14606 DOI: 10.1073/pnas.98.2.445] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The carboxyl-terminal domain (CTD) of the largest subunit of RNA polymerase II plays an important role in transcription and processing of the nascent transcript by interacting with both transcription and RNA processing factors. We show here that the cleavage/polyadenylation factor IA of Saccharomyces cerevisiae directly contacts CTD. First by affinity chromatography experiments with yeast extracts we demonstrate that the Rna15p, Rna14p, and Pcf11p subunits of this complex are associated with phosphorylated CTD. This interaction is confirmed for Rna15p by yeast two-hybrid analysis. Second, Pcf11p, but not Rna15p, is shown to directly contact phosphorylated CTD based on in vitro binding studies with recombinant proteins. These findings establish a direct interaction of cleavage/polyadenylation factor IA with the CTD. Furthermore, a quantitative analysis of transcription run-on performed on temperature-sensitive mutant strains reveals that the lack of either functional Rna14p or Pcf11p affects transcription termination more severely than the absence of a functional Rna15p. Moreover, these data reinforce the concept that CTD phosphorylation acts as a regulatory mechanism in the maturation of the primary transcript.
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Affiliation(s)
- D Barillà
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom
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38
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Garber ME, Mayall TP, Suess EM, Meisenhelder J, Thompson NE, Jones KA. CDK9 autophosphorylation regulates high-affinity binding of the human immunodeficiency virus type 1 tat-P-TEFb complex to TAR RNA. Mol Cell Biol 2000; 20:6958-69. [PMID: 10958691 PMCID: PMC88771 DOI: 10.1128/mcb.20.18.6958-6969.2000] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human immunodeficiency virus type 1 (HIV-1) Tat interacts with cyclin T1 (CycT1), a regulatory partner of CDK9 in the positive transcription elongation factor (P-TEFb) complex, and binds cooperatively with CycT1 to TAR RNA to recruit P-TEFb and promote transcription elongation. We show here that Tat also stimulates phosphorylation of affinity-purified core RNA polymerase II and glutathione S-transferase-C-terminal-domain substrates by CycT1-CDK9, but not CycH-CDK7, in vitro. Interestingly, incubation of recombinant Tat-P-TEFb complexes with ATP enhanced binding to TAR RNA dramatically, and the C-terminal half of CycT1 masked binding of Tat to TAR RNA in the absence of ATP. ATP incubation lead to autophosphorylation of CDK9 at multiple C-terminal Ser and Thr residues, and full-length CycT1 (amino acids 728) [CycT1(1-728)], but not truncated CycT1(1-303), was also phosphorylated by CDK9. P-TEFb complexes containing a catalytically inactive CDK9 mutant (D167N) bound TAR RNA weakly and independently of ATP, as did a C-terminal truncated CDK9 mutant that was catalytically active but unable to undergo autophosphorylation. Analysis of different Tat proteins revealed that the 101-amino-acid SF2 HIV-1 Tat was unable to bind TAR with CycT1(1-303) in the absence of phosphorylated CDK9, whereas unphosphorylated CDK9 strongly blocked binding of HIV-2 Tat to TAR RNA in a manner that was reversed upon autophosphorylation. Replacement of CDK9 phosphorylation sites with negatively charged residues restored binding of CycT1(1-303)-D167N-Tat, and rendered D167N a more potent inhibitor of transcription in vitro. Taken together, these results demonstrate that CDK9 phosphorylation is required for high-affinity binding of Tat-P-TEFb to TAR RNA and that the state of P-TEFb phosphorylation may regulate Tat transactivation in vivo.
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Affiliation(s)
- M E Garber
- Regulatory Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
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Zhu W, Downey JS, Gu J, Di Padova F, Gram H, Han J. Regulation of TNF expression by multiple mitogen-activated protein kinase pathways. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 164:6349-58. [PMID: 10843689 DOI: 10.4049/jimmunol.164.12.6349] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Stimulating macrophages with bacterial endotoxin (LPS) activates numerous intracellular signaling pathways that lead to the production of TNF. In this study, we show that four mitogen-activated protein (MAP) kinase pathways are activated in LPS-stimulated macrophages: the extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase/stress-activated protein kinase, p38, and Big MAP kinase (BMK)/ERK5 pathways. Although specific activation of a single MAP kinase pathway produces only a modest effect on TNF promoter activation, activation of each MAP kinase pathway is important for full induction of the TNF gene. Interestingly, a dramatic induction of TNF promoter-driven gene expression was observed when all of the four MAP kinase pathways were activated simultaneously, suggesting a cooperative effect among these kinases. Unexpectedly, cis elements known to be targeted by MAP kinases do not play a major role in multiple MAP kinase-induced TNF gene expression. Rather, a 40-bp sequence harboring the TATA box, is responsible for the gene up-regulation induced by MAP kinases. The proximity of the MAP kinase-responsive element to the transcriptional initiation site suggested that MAP kinases regulate the transcriptional initiation complex. Utilizing alpha-amanitin-resistant RNA polymerase II mutants with or without a C-terminal domain (CTD) deletion, we found that deleting the CTD to 31 tandem repeats (Delta31) led to >90% reduction in MAP kinase-mediated TNF production. Thus, our data demonstrate coordination of multiple MAP kinase pathways in TNF production and suggest that the CTD of RNA polymerase II is required to execute MAP kinase signaling in TNF expression.
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Affiliation(s)
- W Zhu
- Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA
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40
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Watanabe Y, Fujimoto H, Watanabe T, Maekawa T, Masutani C, Hanaoka F, Ohkuma Y. Modulation of TFIIH-associated kinase activity by complex formation and its relationship with CTD phosphorylation of RNA polymerase II. Genes Cells 2000; 5:407-23. [PMID: 10886368 DOI: 10.1046/j.1365-2443.2000.00336.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND The general transcription factor TFIIH plays important roles in initiation and the transition to elongation steps of transcription by RNA polymerase II (PolII). Both roles are dependent on the protein kinase, DNA-dependent ATPase and DNA helicase activities of TFIIH. However, how these enzyme activities of TFIIH contribute to transcription has remained elusive. TFIIH consists of nine subunits, and one of them, Cdk7, possesses kinase activity. Here the substrate specificities of TFIIH and two forms of the Cdk7-containing kinase complex are compared, and the relationship between transcription activity and the TFIIH-dependent phosphorylation of the carboxy terminal domain of the largest subunit of PolII (CTD) is studied. RESULTS We prepared TFIIH and two Cdk7-containing kinase complexes, Cdk7/Cyclin H and CAK (Cdk7/Cyclin H/MAT1). Consistent with previous reports, CAK strongly phosphorylated Cdk2, Cdk4, CTD and intact PolII. In contrast, Cdk7/Cyclin H, which lacks MAT1, did not phosphorylate these substrates, except for weak phosphorylation of Cdk2. The kinase activity of TFIIH displayed stronger substrate preference for Cdk4 than did CAK. In addition, TFIIH phosphorylation of PolII was stimulated by TFIIE both in solution and during preinitiation complex formation, whereas Cdk7/Cyclin H and CAK phosphorylation of PolII was not. In combination with other general transcription factors, TFIIH, but not Cdk7/CycH or CAK, promoted transcription on a linear DNA template. This transcription was well correlated with TFIIE stimulated TFIIH phosphorylation of serine at position 5 (Ser-5) within the heptapeptide repeat of the PolII CTD. CONCLUSION These results provide clues about the roles of CTD phosphorylation at Ser-5 in transcription.
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Affiliation(s)
- Y Watanabe
- Institute for Molecular and Cellular Biology and; The Graduate School of Pharmaceutical Sciences, Osaka University, Suita, Osaka 565-0871, Japan
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Bienkiewicz EA, Moon Woody A, Woody RW. Conformation of the RNA polymerase II C-terminal domain: circular dichroism of long and short fragments. J Mol Biol 2000; 297:119-33. [PMID: 10704311 DOI: 10.1006/jmbi.2000.3545] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The C-terminal domain (CTD) of the largest subunit of RNA polymerase II consists of tandemly repeated copies of a heptapeptide with the Y(1)S(2)P(3)T(4)S(5)P(6)S(7) consensus sequence. This repeat contains two overlapping SPXX motifs that can adopt a beta-turn conformation. In addition, each CTD repeat contains the PXXP sequence characteristic of the left-handed helix of polyproline II (P(II)) found in SH3 domain ligands and the PXY sequence that is the target for WW domains. We have studied CTD fragments using circular dichroism (CD) to characterize the conformation of the CTD in water and in the hydrogen bond-promoting solvent trifluoroethanol (TFE). In water, an eight-repeat fragment is predominantly unordered, but at 32 degrees C has P(II) and beta-turn contents estimated to be about 15 % and less than 10 %, respectively. In 90 % TFE, the beta-turn fraction is estimated to be about 75 %, the remainder being unordered and P(II) conformations. The Tyr side-chains are ordered to a significant extent in 90 % TFE. Replacement of the fully conserved Pro residues by alpha-aminoisobutyric acid leads to a large increase in beta-turn. Replacement of Ser2 by Ala does not substantially alter the CTD conformation in water or TFE. Ser5 replacement by Ala increases the P(II) content in water and affects the conformation in TFE-rich solutions. Phosphorylation of Ser2 and Ser5 has little effect in water, but Ser2 affects the conformation in TFE-rich solution in much the same way as Ser5-->Ala substitution. The CD of the full-length murine CTD in water is similar to that of the eight-repeat fragment, indicating little difference in conformation with increasing chain length beyond eight repeats. The roles of P(II) and beta-turn in the interaction of CTD with its target proteins (mediator and RNA-processing components) are discussed. The most likely interactions are between P(II) and WW or SH3 domains, or with some unknown P(II)-binding motif.
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Affiliation(s)
- E A Bienkiewicz
- Department of Biochemistry and Molecular Biology, Colorado State University, Fort Collins, CO 80523, USA
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Xiao H, Palhan V, Yang Y, Roeder RG. TIP30 has an intrinsic kinase activity required for up-regulation of a subset of apoptotic genes. EMBO J 2000; 19:956-63. [PMID: 10698937 PMCID: PMC305635 DOI: 10.1093/emboj/19.5.956] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
CC3 is a metastasis suppressor that inhibits metastasis of the variant small cell lung carcinoma (v-SCLC) by predisposing cells to apoptosis. The same protein was also reported as a cellular cofactor, TIP30, which stimulates HIV-1 Tat-activated transcription by interacting with both Tat and RNA polymerase II. We report here that TIP30/CC3 is a novel serine/threonine kinase. It phosphorylates the heptapeptide repeats of the C-terminal domain (CTD) of the largest RNA polymerase II subunit in a Tat-dependent manner. Amino acid substitutions in the putative ATP binding motif that abolish the TIP30 kinase activity also inhibit the ability of TIP30 to enhance Tat-activated transcription or to sensitize NIH 3T3 and v-SCLC cells to apoptosis. Furthermore, ectopic expression of TIP30/CC3 in v-SCLC cells induces expression of a number of genes that include the apoptosis-related genes Bad and Siva, as well as metastasis suppressor NM23-H2. These data demonstrate a molecular mechanism for TIP30/CC3 function and suggest a novel pathway for regulating apoptosis.
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Affiliation(s)
- H Xiao
- Laboratory of Biochemistry, The Rockefeller University, New York, NY 10021, USA
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43
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Kim MK, Nikodem VM. hnRNP U inhibits carboxy-terminal domain phosphorylation by TFIIH and represses RNA polymerase II elongation. Mol Cell Biol 1999; 19:6833-44. [PMID: 10490622 PMCID: PMC84680 DOI: 10.1128/mcb.19.10.6833] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This study describes a potential new function of hnRNP U as an RNA polymerase (Pol II) elongation inhibitor. We demonstrated that a subfraction of human hnRNP U is associated with the Pol II holoenzyme in vivo and as such recruited to the promoter as part of the preinitiation complex. hnRNP U, however, appears to dissociate from the Pol II complex at the early stage of transcription and is therefore absent from the elongating Pol II complex. When tested in the human immunodeficiency virus type 1 transcription system, hnRNP U inhibits elongation rather than initiation of transcription by Pol II. This inhibition requires the carboxy-terminal domain (CTD) of Pol II. We showed that hnRNP U can bind TFIIH in vivo under certain conditions and inhibit TFIIH-mediated CTD phosphorylation in vitro. We find that the middle domain of hnRNP U is sufficient to mediate its Pol II association and its inhibition of TFIIH-mediated phosphorylation and Pol II elongation. The abilities of hnRNP U to inhibit TFIIH-mediated CTD phosphorylation and its Pol II association are necessary for hnRNP U to mediate the repression of Pol II elongation. Based on these observations, we suggest that a subfraction of hnRNP U, as a component of the Pol II holoenzyme, may downregulate TFIIH-mediated CTD phosphorylation in the basal transcription machinery and repress Pol II elongation. With such functions, hnRNP U might provide one of the mechanisms by which the CTD is maintained in an unphosphorylated state in the Pol II holoenzyme.
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Affiliation(s)
- M K Kim
- Genetics and Biochemistry Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
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44
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Sapir T, Cahana A, Seger R, Nekhai S, Reiner O. LIS1 is a microtubule-associated phosphoprotein. EUROPEAN JOURNAL OF BIOCHEMISTRY 1999; 265:181-8. [PMID: 10491172 DOI: 10.1046/j.1432-1327.1999.00711.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Lissencephaly, a severe brain malformation, may be caused by mutations in the LIS1 gene. LIS1 encodes a microtubule-associated protein (MAP) that is also part of the enzyme complex, platelet-activating factor acetylhydrolase. LIS1 is also found in a complex with two protein kinases; a T-cell Tat-associated kinase, which contains casein-dependent kinase (CDK) activating kinase (CAK), as well as CAK-inducing activity, and with a spleen protein-tyrosine kinase similar to the catalytic domain of p72syk. As phosphorylation is one of the ways to control cellular localization and protein-protein interactions, we investigated whether LIS1 undergoes this post-translational modification. Our results demonstrate that LIS1 is a developmentally regulated phosphoprotein. Phosphorylated LIS1 is mainly found in the MAP fraction. Phosphoamino acid analysis revealed that LIS1 is phosphorylated on serine residues. Alkaline phosphatase treatment reduced the number of visible LIS1 isoforms. In-gel assays demonstrate a 50-kDa LIS1 kinase that is enriched in microtubule-associated fractions. In vitro, LIS1 was phosphorylated by protein kinase CKII (casein kinase II), but not many other kinases that were tested. We suggest that LIS1 activity may be regulated by phosphorylation.
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Affiliation(s)
- T Sapir
- Department of Molecular Genetics, The Weizmann Institute of Science, Rehovot, Israel
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45
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Li Z, Childs G. Temporal activation of the sea urchin late H1 gene requires stage-specific phosphorylation of the embryonic transcription factor SSAP. Mol Cell Biol 1999; 19:3684-95. [PMID: 10207092 PMCID: PMC84181 DOI: 10.1128/mcb.19.5.3684] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Stage-specific activator protein (SSAP) is a 41-kDa polypeptide that binds to embryonic enhancer elements of the sea urchin late H1 gene. These enhancer elements mediate the transcriptional activation of the late H1 gene in a temporally specific manner at the mid-blastula stage of embryogenesis. Although SSAP can transactivate the late H1 gene only at late stages of the development, it resides in the sea urchin nucleus and maintains DNA binding activity throughout early embryogenesis. In addition, it has been shown that SSAP undergoes a conversion from a 41-kDa monomer to a approximately 80- to 100-kDa dimer when the late H1 gene is activated. We have demonstrated that SSAP is differentially phosphorylated during embryogenesis. Serine 87, a cyclic AMP-dependent protein kinase consensus site located in the N-terminal DNA binding domain, is constitutively phosphorylated. At the mid-blastula stage of embryogenesis, temporally correlated with SSAP dimer formation and late H1 gene activation, a threonine residue in the C-terminal transactivation domain is phosphorylated. This phosphorylation can be catalyzed by a break-ended double-stranded DNA-activated protein kinase activity from the sea urchin nucleus in vitro. Microinjection of synthetic SSAP mRNAs encoding either serine or threonine phosphorylation mutants results in the failure to transactivate reporter genes that contain the enhancer element, suggesting that both serine and threonine phosphorylation of SSAP are required for the activation of the late H1 gene. Furthermore, SSAP can undergo blastula-stage-specific homodimerization through its GQ-rich transactivation domain. The late-specific threonine phosphorylation in this domain is essential for the dimer assembly. These observations indicate that temporally regulated SSAP activation is promoted by threonine phosphorylation on its transactivation domain, which triggers the formation of a transcriptionally active SSAP homodimer.
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Affiliation(s)
- Z Li
- Department of Molecular Genetics, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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46
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Chen D, Fong Y, Zhou Q. Specific interaction of Tat with the human but not rodent P-TEFb complex mediates the species-specific Tat activation of HIV-1 transcription. Proc Natl Acad Sci U S A 1999; 96:2728-33. [PMID: 10077579 PMCID: PMC15837 DOI: 10.1073/pnas.96.6.2728] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Tat stimulation of HIV-1 transcriptional elongation is species-specific and is believed to require a specific cellular cofactor present in many human and primate cells but not in nonpermissive rodent cells. Human P-TEFb, composed of Cdk9 and cyclin T1, is a general transcription elongation factor that phosphorylates the C-terminal domain of RNA polymerase II. Previous studies have also implicated P-TEFb as a Tat-specific cellular cofactor and, in particular, human cyclin T1 as responsible for the species-specific Tat activation. To obtain functional evidence in support of these hypotheses, we generated and examined the activities of human-rodent "hybrid" P-TEFb complexes. We found that P-TEFb complexes containing human cyclin T1 complexed with either human or rodent Cdk9 supported Tat transactivation and interacted with the Tat activation domain and the HIV-1 TAR RNA element to form TAR loop-dependent ribonucleoprotein complexes. Although a stable complex containing rodent cyclin T1 and human Cdk9 was capable of phosphorylating CTD and mediating basal HIV-1 elongation, it failed to interact with Tat and to mediate Tat transactivation, indicating that the abilities of P-TEFb to support basal elongation and Tat activation can be separated. Together, our data indicated that the specific interaction of human P-TEFb with Tat/TAR, mostly through cyclin T1, is crucial for P-TEFb to mediate a Tat-specific and species-restricted activation of HIV-1 transcription. Amino acid residues unique to human Cdk9 also contributed partially to the formation of the P-TEFb-Tat-TAR complex. Moreover, the cyclin box of cyclin T1 and its immediate flanking region are largely responsible for the specific P-TEFb-Tat interaction.
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Affiliation(s)
- D Chen
- Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720-3206, USA
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47
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Woodard RL, Anderson MG, Dynan WS. Nuclear extracts lacking DNA-dependent protein kinase are deficient in multiple round transcription. J Biol Chem 1999; 274:478-85. [PMID: 9867868 DOI: 10.1074/jbc.274.1.478] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We have compared levels of in vitro transcription in nuclear extracts from DNA-dependent protein kinase (DNA-PK)-deficient and DNA-PK-containing Chinese hamster ovary cell lines. DNA-PK-deficient cell lines are radiosensitive mutants lacking either the catalytic subunit or the 80-kDa subunit of the Ku protein regulatory component. Extracts from DNA-PK-deficient cell lines had a 2-7-fold decrease in the level of in vitro transcription when compared with matched controls. This decrease was observed with several promoters. Transcription could be restored to either of the deficient extracts by addition of small amounts of extract from the DNA-PK-containing cell lines. Transcription was not restored by addition of purified DNA-PK catalytic subunit, Ku protein, or individually purified general transcription factors. We conclude that extracts from DNA-PK-deficient cells lack a positively acting regulatory factor or a complex of factors not readily reconstituted with individual proteins. We have also investigated the mechanistic defect in the deficient extracts and have found that the observed differences in transcription levels between Ku-positive and Ku-negative cell lines can be attributed solely to a greater ability of the Ku-positive nuclear extracts to carry out secondary initiation events subsequent to the first round of transcription.
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Affiliation(s)
- R L Woodard
- Institute of Molecular Medicine and Genetics, Program in Gene Regulation, Medical College of Georgia, Augusta, Georgia 30912, USA
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48
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Garber ME, Wei P, KewalRamani VN, Mayall TP, Herrmann CH, Rice AP, Littman DR, Jones KA. The interaction between HIV-1 Tat and human cyclin T1 requires zinc and a critical cysteine residue that is not conserved in the murine CycT1 protein. Genes Dev 1998; 12:3512-27. [PMID: 9832504 PMCID: PMC317238 DOI: 10.1101/gad.12.22.3512] [Citation(s) in RCA: 356] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/1998] [Accepted: 09/30/1998] [Indexed: 11/24/2022]
Abstract
HIV-1 Tat activates transcription through binding to human cyclin T1, a regulatory subunit of the TAK/P-TEFb CTD kinase complex. Here we show that the cyclin domain of hCycT1 is necessary and sufficient to interact with Tat and promote cooperative binding to TAR RNA in vitro, as well as mediate Tat transactivation in vivo. A Tat:TAR recognition motif (TRM) was identified at the carboxy-terminal edge of the cyclin domain, and we show that hCycT1 can interact simultaneously with Tat and CDK9 on TAR RNA in vitro. Alanine-scanning mutagenesis of the hCycT1 TRM identified residues that are critical for the interaction with Tat and others that are required specifically for binding of the complex to TAR RNA. Interestingly, we find that the interaction between Tat and hCycT1 requires zinc as well as essential cysteine residues in both proteins. Cloning and characterization of the murine CycT1 protein revealed that it lacks a critical cysteine residue (C261) and forms a weak, zinc-independent complex with HIV-1 Tat that greatly reduces binding to TAR RNA. A point mutation in mCycT1 (Y261C) restores high-affinity, zinc-dependent binding to Tat and TAR in vitro, and rescues Tat transactivation in vivo. Although overexpression of hCycT1 in NIH3T3 cells strongly enhances transcription from an integrated proviral promoter, we find that this fails to overcome all blocks to productive HIV-1 infection in murine cells.
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Affiliation(s)
- M E Garber
- Regulatory Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037-1099, USA
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49
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Abstract
Production of messenger RNA in eukaryotic cells is a complex, multistep process. mRNA polyadenylation, or 3' processing, requires several protein factors, including cleavage/polyadenylation-specificity factor (CPSF), cleavage-stimulation factor, two cleavage factors and poly(A) polymerase. These proteins seem to be unnecessary for other steps in mRNA synthesis such as transcription and splicing, and factors required for these processes were not considered to be essential for polyadenylation. Nonetheless, these reactions may be linked so that they are effectively coordinated in vivo. For example, the CTD carboxy-terminal domain of the largest subunit of RNA polymerase II (RNAP II) is required for efficient splicing and polyadenylation in vivo, and CPSF is brought to a promoter by the transcription factor TFIID and transferred to RNAP II at the time of transcription initiation. These findings suggest that polyadenylation factors can be recruited to an RNA 3'-processing signal by RNAP II, where they dissociate from the polymerase and initiate polyadenylation. Here we present results that extend this model by showing that RNAP II is actually required, in the absence of transcription, for 3' processing in vitro.
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Affiliation(s)
- Y Hirose
- Department of Biological Sciences, Columbia University, New York, New York 10027, USA
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50
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Fischer KM. Expanded (CAG)n, (CGG)n and (GAA)n trinucleotide repeat microsatellites, and mutant purine synthesis and pigmentation genes cause schizophrenia and autism. Med Hypotheses 1998; 51:223-33. [PMID: 9792200 DOI: 10.1016/s0306-9877(98)90080-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Unstable (CAG)n trinucleotide repeat microsatellites are hypothesized to cause schizophrenia. The (CAG)n microsatellite of dominant spinal cerebellar ataxia type 1 (SCA1) is a candidate schizophrenia gene. Autism results from expansions of (CGG)n and (GAA)n trinucleotide repeat stretches at fragile X syndrome (FRAXA), and the recessive Friedreich's ataxia (FA). Dominant ataxia genes may cause schizophrenia and recessive ataxia genes may cause autism. Syndromes with autism show purine synthesis defects (PSDs) and/or pigmentation defects (PDs). Autism is caused by very lengthy expansions of (CAG)n, (CGG)n and (GAA)n repeats, while schizophrenia results from much smaller (CAG)n and (CGG)n repeat expansions.
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