1
|
Bracken RC, Davison LM, Buehler DP, Fulton ME, Carson EE, Sheng Q, Stolze LK, Guillermier C, Steinhauser ML, Brown JD. Transcriptional synergy in human aortic endothelial cells is vulnerable to combination p300/CBP and BET bromodomain inhibition. iScience 2024; 27:110011. [PMID: 38868181 PMCID: PMC11167439 DOI: 10.1016/j.isci.2024.110011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 03/14/2024] [Accepted: 05/14/2024] [Indexed: 06/14/2024] Open
Abstract
Combinatorial signaling by proinflammatory cytokines synergizes to exacerbate toxicity to cells and tissue injury during acute infections. To explore synergism at the gene-regulatory level, we investigated the dynamics of transcription and chromatin signaling in response to dual cytokines by integrating nascent RNA imaging mass spectrometry, RNA sequencing, amplification-independent mRNA quantification, assay for transposase-accessible chromatin using sequencing (ATAC-seq), and transcription factor profiling. Costimulation with interferon-gamma (IFNγ) and tumor necrosis factor alpha (TNFα) synergistically induced a small subset of genes, including the chemokines CXCL9, -10, and -11. Gene induction coincided with increased chromatin accessibility at non-coding regions enriched for p65 and STAT1 binding sites. To discover coactivator dependencies, we conducted a targeted chemogenomic screen of transcriptional inhibitors followed by modeling of inhibitor dose-response curves. These results identified high efficacy of either p300/CREB-binding protein (CBP) or bromodomain and extra-terminal (BET) bromodomain inhibitors to disrupt induction of synergy genes. Combination p300/CBP and BET bromodomain inhibition at half-maximal inhibitory concentrations (subIC50) synergistically abrogated IFNγ/TNFα-induced chemokine gene and protein levels.
Collapse
Affiliation(s)
- Ronan C. Bracken
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
| | - Lindsay M. Davison
- Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Dennis P. Buehler
- Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Maci E. Fulton
- Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Emily E. Carson
- Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Quanhu Sheng
- Department of Biostatistics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
- Center for Quantitative Sciences, Vanderbilt University Medical Center, Nashville, TN 3723, USA
| | - Lindsey K. Stolze
- Department of Biostatistics, Vanderbilt University School of Medicine, Nashville, TN 37232, USA
- Center for Quantitative Sciences, Vanderbilt University Medical Center, Nashville, TN 3723, USA
| | - Christelle Guillermier
- Harvard Medical School, Boston, MA 02115, USA
- Center for NanoImaging, Cambridge MA 02115, USA
- Department of Medicine, Division of Genetics, Brigham and Women’s Hospital, Boston, MA 02115, USA
| | | | - Jonathan D. Brown
- Division of Cardiovascular Medicine, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| |
Collapse
|
2
|
Bell CC, Balic JJ, Talarmain L, Gillespie A, Scolamiero L, Lam EYN, Ang CS, Faulkner GJ, Gilan O, Dawson MA. Comparative cofactor screens show the influence of transactivation domains and core promoters on the mechanisms of transcription. Nat Genet 2024; 56:1181-1192. [PMID: 38769457 DOI: 10.1038/s41588-024-01749-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2023] [Accepted: 04/09/2024] [Indexed: 05/22/2024]
Abstract
Eukaryotic transcription factors (TFs) activate gene expression by recruiting cofactors to promoters. However, the relationships between TFs, promoters and their associated cofactors remain poorly understood. Here we combine GAL4-transactivation assays with comparative CRISPR-Cas9 screens to identify the cofactors used by nine different TFs and core promoters in human cells. Using this dataset, we associate TFs with cofactors, classify cofactors as ubiquitous or specific and discover transcriptional co-dependencies. Through a reductionistic, comparative approach, we demonstrate that TFs do not display discrete mechanisms of activation. Instead, each TF depends on a unique combination of cofactors, which influences distinct steps in transcription. By contrast, the influence of core promoters appears relatively discrete. Different promoter classes are constrained by either initiation or pause-release, which influences their dynamic range and compatibility with cofactors. Overall, our comparative cofactor screens characterize the interplay between TFs, cofactors and core promoters, identifying general principles by which they influence transcription.
Collapse
Affiliation(s)
- Charles C Bell
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia.
- Mater Research Institute, University of Queensland, TRI Building, Woolloongabba, Queensland, Australia.
| | - Jesse J Balic
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia
| | - Laure Talarmain
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia
| | - Andrea Gillespie
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Laura Scolamiero
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia
| | - Enid Y N Lam
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
| | - Ching-Seng Ang
- Bio21 Mass Spectrometry and Proteomics Facility, The University of Melbourne, Parkville, Victoria, Australia
| | - Geoffrey J Faulkner
- Mater Research Institute, University of Queensland, TRI Building, Woolloongabba, Queensland, Australia
- Queensland Brain Institute, University of Queensland, Brisbane, Queensland, Australia
| | - Omer Gilan
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia
- Australian Centre for Blood Diseases, Monash University, Melbourne, Victoria, Australia
| | - Mark A Dawson
- Cancer Research Division, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.
- Sir Peter MacCallum Department of Oncology, University of Melbourne, Melbourne, Victoria, Australia.
- Department of Haematology, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.
- Centre for Cancer Research, University of Melbourne, Melbourne, Victoria, Australia.
| |
Collapse
|
3
|
Doughty BR, Hinks MM, Schaepe JM, Marinov GK, Thurm AR, Rios-Martinez C, Parks BE, Tan Y, Marklund E, Dubocanin D, Bintu L, Greenleaf WJ. Single-molecule chromatin configurations link transcription factor binding to expression in human cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.02.578660. [PMID: 38352517 PMCID: PMC10862896 DOI: 10.1101/2024.02.02.578660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
The binding of multiple transcription factors (TFs) to genomic enhancers activates gene expression in mammalian cells. However, the molecular details that link enhancer sequence to TF binding, promoter state, and gene expression levels remain opaque. We applied single-molecule footprinting (SMF) to measure the simultaneous occupancy of TFs, nucleosomes, and components of the transcription machinery on engineered enhancer/promoter constructs with variable numbers of TF binding sites for both a synthetic and an endogenous TF. We find that activation domains enhance a TF's capacity to compete with nucleosomes for binding to DNA in a BAF-dependent manner, TF binding on nucleosome-free DNA is consistent with independent binding between TFs, and average TF occupancy linearly contributes to promoter activation rates. We also decompose TF strength into separable binding and activation terms, which can be tuned and perturbed independently. Finally, we develop thermodynamic and kinetic models that quantitatively predict both the binding microstates observed at the enhancer and subsequent time-dependent gene expression. This work provides a template for quantitative dissection of distinct contributors to gene activation, including the activity of chromatin remodelers, TF activation domains, chromatin acetylation, TF concentration, TF binding affinity, and TF binding site configuration.
Collapse
Affiliation(s)
| | - Michaela M Hinks
- Bioengineering Department, Stanford University, Stanford, CA 94305, USA
| | - Julia M Schaepe
- Bioengineering Department, Stanford University, Stanford, CA 94305, USA
| | - Georgi K Marinov
- Genetics Department, Stanford University, Stanford, CA 94305, USA
| | - Abby R Thurm
- Biophysics Graduate Program, Stanford University, Stanford, CA 94305, USA
| | | | - Benjamin E Parks
- Computer Science Department, Stanford University, Stanford, CA 94305, USA
| | - Yingxuan Tan
- Computer Science Department, Stanford University, Stanford, CA 94305, USA
| | - Emil Marklund
- Science for Life Laboratory, Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden
| | - Danilo Dubocanin
- Genetics Department, Stanford University, Stanford, CA 94305, USA
| | - Lacramioara Bintu
- Bioengineering Department, Stanford University, Stanford, CA 94305, USA
| | - William J Greenleaf
- Genetics Department, Stanford University, Stanford, CA 94305, USA
- Department of Applied Physics, Stanford University, Stanford, CA 94205, USA
| |
Collapse
|
4
|
Santos MM, Costa TC, Silva W, Pistillo LZ, Junior DTV, Verardo LL, Paulino PVR, Sampaio CB, Gionbelli MP, Du M, Duarte MS. Nutrient supplementation of beef female calves at pre-weaning enhances the commitment of fibro-adipogenic progenitor cells to preadipocytes. Meat Sci 2023; 204:109286. [PMID: 37494740 DOI: 10.1016/j.meatsci.2023.109286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 07/13/2023] [Accepted: 07/18/2023] [Indexed: 07/28/2023]
Abstract
We aimed to evaluate the impact of nutrient supplementation of beef female calves at pre-weaning on adipogenic determination. Thirty-four female calves were assigned to two experimental treatments: Control (CON, n = 17), where animals were supplemented only with mineral mixture; Supplemented (SUP, n = 17), where animals received energy-protein supplement containing minerals (5 g/kg of BW per day) of their body weight. Animals were supplemented from 100 to 250 days of age, and muscle samples were biopsied at the end of the supplementation period. Regarding the performance variables, there were no differences between treatments for initial body weight (P = 0.75). The final body weight (P = 0.07), average daily gain (P = 0.07), rib eye area (P = 0.03), and rib fat thickness (P = 0.08) were greater in SUP female calves compared with CON treatment. The number of fibro-adipogenic progenitor cells (P = 0.69) did not differ between treatments, while a greater number of intramuscular pre-adipocytes were observed in SUP than CON female calves (P = 0.01). The expression of miRNA-4429 (P = 0.20) did not differ between treatments, while the expression of miRNA-129-5p (P = 0.09) and miRNA-129-2-3p (P = 0.05) was greater in CON than SUP female calves. Our results suggest that nutrient supplementation at early postnatal stages of development enhances the commitment of fibro-adipogenic progenitor cells into the adipogenic lineages allowing to an increase in intramuscular fat deposition potential of the animals later in life.
Collapse
Affiliation(s)
- M M Santos
- Department of Animal Science, Universidade Federal de Viçosa, Viçosa, Brazil; Muscle Biology and Nutrigenomics Laboratory, Universidade Federal de Viçosa, Viçosa, Brazil
| | - T C Costa
- Muscle Biology and Nutrigenomics Laboratory, Universidade Federal de Viçosa, Viçosa, Brazil; Department of Animal Science, Universidade Federal de Lavras, Lavras, MG, Brazil
| | - W Silva
- Department of Animal Science, Universidade Federal de Viçosa, Viçosa, Brazil; Department of Animal Biosciences, University of Guelph, Guelph, ON, Canada
| | - L Z Pistillo
- Department of Animal Science, Universidade Federal de Viçosa, Viçosa, Brazil
| | - D T Valente Junior
- Department of Animal Science, Universidade Federal de Viçosa, Viçosa, Brazil; Muscle Biology and Nutrigenomics Laboratory, Universidade Federal de Viçosa, Viçosa, Brazil; Department of Animal Biosciences, University of Guelph, Guelph, ON, Canada
| | - L L Verardo
- Department of Animal Science, Universidade Federal dos Vales do Jequitinhonha e Mucuri, Diamantina, Brazil
| | | | - C B Sampaio
- Department of Animal Science, Universidade Federal de Viçosa, Viçosa, Brazil
| | - M P Gionbelli
- Department of Animal Science, Universidade Federal de Lavras, Lavras, MG, Brazil
| | - M Du
- Department of Animal Sciences, Washington State University, Pullman, WA, USA
| | - M S Duarte
- Department of Animal Biosciences, University of Guelph, Guelph, ON, Canada.
| |
Collapse
|
5
|
Harden TT, Vincent BJ, DePace AH. Transcriptional activators in the early Drosophila embryo perform different kinetic roles. Cell Syst 2023; 14:258-272.e4. [PMID: 37080162 PMCID: PMC10473017 DOI: 10.1016/j.cels.2023.03.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2021] [Revised: 06/26/2022] [Accepted: 03/21/2023] [Indexed: 04/22/2023]
Abstract
Combinatorial regulation of gene expression by transcription factors (TFs) may in part arise from kinetic synergy-wherein TFs regulate different steps in the transcription cycle. Kinetic synergy requires that TFs play distinguishable kinetic roles. Here, we used live imaging to determine the kinetic roles of three TFs that activate transcription in the Drosophila embryo-Zelda, Bicoid, and Stat92E-by introducing their binding sites into the even-skipped stripe 2 enhancer. These TFs influence different sets of kinetic parameters, and their influence can change over time. All three TFs increased the fraction of transcriptionally active nuclei; Zelda also shortened the first-passage time into transcription and regulated the interval between transcription events. Stat92E also increased the lifetimes of active transcription. Different TFs can therefore play distinct kinetic roles in activating the transcription. This has consequences for understanding the composition and flexibility of regulatory DNA sequences and the biochemical function of TFs. A record of this paper's transparent peer review process is included in the supplemental information.
Collapse
Affiliation(s)
- Timothy T Harden
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Ben J Vincent
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Angela H DePace
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.
| |
Collapse
|
6
|
Martinez-Corral R, Park M, Biette KM, Friedrich D, Scholes C, Khalil AS, Gunawardena J, DePace AH. Transcriptional kinetic synergy: A complex landscape revealed by integrating modeling and synthetic biology. Cell Syst 2023; 14:324-339.e7. [PMID: 37080164 PMCID: PMC10472254 DOI: 10.1016/j.cels.2023.02.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2021] [Revised: 08/22/2022] [Accepted: 02/10/2023] [Indexed: 04/22/2023]
Abstract
Transcription factors (TFs) control gene expression, often acting synergistically. Classical thermodynamic models offer a biophysical explanation for synergy based on binding cooperativity and regulated recruitment of RNA polymerase. Because transcription requires polymerase to transition through multiple states, recent work suggests that "kinetic synergy" can arise through TFs acting on distinct steps of the transcription cycle. These types of synergy are not mutually exclusive and are difficult to disentangle conceptually and experimentally. Here, we model and build a synthetic circuit in which TFs bind to a single shared site on DNA, such that TFs cannot synergize by simultaneous binding. We model mRNA production as a function of both TF binding and regulation of the transcription cycle, revealing a complex landscape dependent on TF concentration, DNA binding affinity, and regulatory activity. We use synthetic TFs to confirm that the transcription cycle must be integrated with recruitment for a quantitative understanding of gene regulation.
Collapse
Affiliation(s)
| | - Minhee Park
- Biological Design Center, Boston University, Boston, MA 02215, USA; Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA
| | - Kelly M Biette
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Dhana Friedrich
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Clarissa Scholes
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Ahmad S Khalil
- Biological Design Center, Boston University, Boston, MA 02215, USA; Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA; Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA 02115, USA
| | - Jeremy Gunawardena
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Angela H DePace
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.
| |
Collapse
|
7
|
Cheng L, De C, Li J, Pertsinidis A. Mechanisms of transcription control by distal enhancers from high-resolution single-gene imaging. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.19.533190. [PMID: 36993179 PMCID: PMC10055225 DOI: 10.1101/2023.03.19.533190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
Abstract
How distal enhancers physically control promoters over large genomic distances, to enable cell-type specific gene expression, remains obscure. Using single-gene super-resolution imaging and acute targeted perturbations, we define physical parameters of enhancer-promoter communication and elucidate processes that underlie target gene activation. Productive enhancer-promoter encounters happen at 3D distances δ200 nm - a spatial scale corresponding to unexpected enhancer-associated clusters of general transcription factor (GTF) components of the Pol II machinery. Distal activation is achieved by increasing transcriptional bursting frequency, a process facilitated by embedding a promoter into such GTF clusters and by accelerating an underlying multi-step cascade comprising early phases in the Pol II transcription cycle. These findings help clarify molecular/biochemical signals involved in long-range activation and their means of transmission from enhancer to promoter.
Collapse
Affiliation(s)
- Lingling Cheng
- Structural Biology Program, Memorial Sloan Kettering Cancer Center; New York, NY 10065, USA
| | - Chayan De
- Structural Biology Program, Memorial Sloan Kettering Cancer Center; New York, NY 10065, USA
| | - Jieru Li
- Structural Biology Program, Memorial Sloan Kettering Cancer Center; New York, NY 10065, USA
| | - Alexandros Pertsinidis
- Structural Biology Program, Memorial Sloan Kettering Cancer Center; New York, NY 10065, USA
| |
Collapse
|
8
|
Das SK, Lewis BA, Levens D. MYC: a complex problem. Trends Cell Biol 2023; 33:235-246. [PMID: 35963793 PMCID: PMC9911561 DOI: 10.1016/j.tcb.2022.07.006] [Citation(s) in RCA: 30] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 07/11/2022] [Accepted: 07/13/2022] [Indexed: 12/22/2022]
Abstract
The MYC protooncogene functions as a universal amplifier of transcription through interaction with numerous factors and complexes that regulate almost every cellular process. However, a comprehensive model that explains MYC's actions and the interplay governing the complicated dynamics of components of the transcription and replication machinery is still lacking. Here, we review the potency of MYC as an oncogenic driver and how it regulates the broad spectrum of complexes (effectors and regulators). We propose a 'hand-over model' for differential partitioning and trafficking of unstructured MYC via a loose interaction network between various gene-regulatory complexes and factors. Additionally, the article discusses how unstructured-MYC energetically favors efficient modulation of the energy landscape of the transcription cycle.
Collapse
Affiliation(s)
- Subhendu K Das
- Gene Regulation Section, Laboratory of Pathology, Center for Cancer Research, National Cancer Institute (NCI), Bethesda, MD 20892-1500, USA
| | - Brian A Lewis
- Gene Regulation Section, Laboratory of Pathology, Center for Cancer Research, National Cancer Institute (NCI), Bethesda, MD 20892-1500, USA
| | - David Levens
- Gene Regulation Section, Laboratory of Pathology, Center for Cancer Research, National Cancer Institute (NCI), Bethesda, MD 20892-1500, USA.
| |
Collapse
|
9
|
Panigrahi A, O'Malley BW. Mechanisms of enhancer action: the known and the unknown. Genome Biol 2021; 22:108. [PMID: 33858480 PMCID: PMC8051032 DOI: 10.1186/s13059-021-02322-1] [Citation(s) in RCA: 125] [Impact Index Per Article: 41.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 03/23/2021] [Indexed: 12/13/2022] Open
Abstract
Differential gene expression mechanisms ensure cellular differentiation and plasticity to shape ontogenetic and phylogenetic diversity of cell types. A key regulator of differential gene expression programs are the enhancers, the gene-distal cis-regulatory sequences that govern spatiotemporal and quantitative expression dynamics of target genes. Enhancers are widely believed to physically contact the target promoters to effect transcriptional activation. However, our understanding of the full complement of regulatory proteins and the definitive mechanics of enhancer action is incomplete. Here, we review recent findings to present some emerging concepts on enhancer action and also outline a set of outstanding questions.
Collapse
Affiliation(s)
- Anil Panigrahi
- Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA
| | - Bert W O'Malley
- Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX, 77030, USA.
| |
Collapse
|
10
|
Moldavski O, Zushin PJH, Berdan CA, Van Eijkeren RJ, Jiang X, Qian M, Ory DS, Covey DF, Nomura DK, Stahl A, Weiss EJ, Zoncu R. 4β-Hydroxycholesterol is a prolipogenic factor that promotes SREBP1c expression and activity through the liver X receptor. J Lipid Res 2021; 62:100051. [PMID: 33631213 PMCID: PMC8042401 DOI: 10.1016/j.jlr.2021.100051] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 01/06/2021] [Accepted: 02/12/2021] [Indexed: 12/16/2022] Open
Abstract
Oxysterols are oxidized derivatives of cholesterol that play regulatory roles in lipid biosynthesis and homeostasis. How oxysterol signaling coordinates different lipid classes such as sterols and triglycerides remains incompletely understood. Here, we show that 4β-hydroxycholesterol (HC) (4β-HC), a liver and serum abundant oxysterol of poorly defined functions, is a potent and selective inducer of the master lipogenic transcription factor, SREBP1c, but not the related steroidogenic transcription factor SREBP2. By correlating tracing of lipid synthesis with lipogenic gene expression profiling, we found that 4β-HC acts as a putative agonist for the liver X receptor (LXR), a sterol sensor and transcriptional regulator previously linked to SREBP1c activation. Unique among the oxysterol agonists of the LXR, 4β-HC induced expression of the lipogenic program downstream of SREBP1c and triggered de novo lipogenesis both in primary hepatocytes and in the mouse liver. In addition, 4β-HC acted in parallel to insulin-PI3K-dependent signaling to stimulate triglyceride synthesis and lipid-droplet accumulation. Thus, 4β-HC is an endogenous regulator of de novo lipogenesis through the LXR-SREBP1c axis.
Collapse
Affiliation(s)
- Ofer Moldavski
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA; The Paul F. Glenn Center for Aging Research, University of California, Berkeley, Berkeley, CA, USA; Cardiovascular Research Institute, UCSF, San Francisco, CA, USA
| | - Peter-James H Zushin
- Department of Nutritional Sciences and Toxicology, University of California at Berkeley, Berkeley, CA, USA
| | - Charles A Berdan
- Department of Nutritional Sciences and Toxicology, University of California at Berkeley, Berkeley, CA, USA
| | - Robert J Van Eijkeren
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA; The Paul F. Glenn Center for Aging Research, University of California, Berkeley, Berkeley, CA, USA
| | - Xuntian Jiang
- Diabetic Cardiovascular Disease Center, Washington University School of Medicine, St Louis, MO, USA
| | - Mingxing Qian
- Department of Developmental Biology, Washington University School of Medicine, St Louis, MO, USA
| | - Daniel S Ory
- Diabetic Cardiovascular Disease Center, Washington University School of Medicine, St Louis, MO, USA
| | - Douglas F Covey
- Department of Developmental Biology, Washington University School of Medicine, St Louis, MO, USA
| | - Daniel K Nomura
- Department of Nutritional Sciences and Toxicology, University of California at Berkeley, Berkeley, CA, USA
| | - Andreas Stahl
- Department of Nutritional Sciences and Toxicology, University of California at Berkeley, Berkeley, CA, USA
| | - Ethan J Weiss
- Cardiovascular Research Institute, UCSF, San Francisco, CA, USA
| | - Roberto Zoncu
- Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA; The Paul F. Glenn Center for Aging Research, University of California, Berkeley, Berkeley, CA, USA.
| |
Collapse
|
11
|
Abstract
Determining whether and how a gene is transcribed are two of the central processes of life. The conceptual basis for understanding such gene regulation arose from pioneering biophysical studies in eubacteria. However, eukaryotic genomes exhibit vastly greater complexity, which raises questions not addressed by this bacterial paradigm. First, how is information integrated from many widely separated binding sites to determine how a gene is transcribed? Second, does the presence of multiple energy-expending mechanisms, which are absent from eubacterial genomes, indicate that eukaryotes are capable of improved forms of genetic information processing? An updated biophysical foundation is needed to answer such questions. We describe the linear framework, a graph-based approach to Markov processes, and show that it can accommodate many previous studies in the field. Under the assumption of thermodynamic equilibrium, we introduce a language of higher-order cooperativities and show how it can rigorously quantify gene regulatory properties suggested by experiment. We point out that fundamental limits to information processing arise at thermodynamic equilibrium and can only be bypassed through energy expenditure. Finally, we outline some of the mathematical challenges that must be overcome to construct an improved biophysical understanding of gene regulation.
Collapse
Affiliation(s)
- Felix Wong
- Institute for Medical Engineering & Science, Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.,Infectious Disease and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02142, USA
| | - Jeremy Gunawardena
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts 02115, USA;
| |
Collapse
|
12
|
Nie Z, Guo C, Das SK, Chow CC, Batchelor E, Simons SS, Levens D. Dissecting transcriptional amplification by MYC. eLife 2020; 9:52483. [PMID: 32715994 PMCID: PMC7384857 DOI: 10.7554/elife.52483] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2019] [Accepted: 07/08/2020] [Indexed: 12/13/2022] Open
Abstract
Supraphysiological MYC levels are oncogenic. Originally considered a typical transcription factor recruited to E-boxes (CACGTG), another theory posits MYC a global amplifier increasing output at all active promoters. Both models rest on large-scale genome-wide "-omics'. Because the assumptions, statistical parameter and model choice dictates the '-omic' results, whether MYC is a general or specific transcription factor remains controversial. Therefore, an orthogonal series of experiments interrogated MYC's effect on the expression of synthetic reporters. Dose-dependently, MYC increased output at minimal promoters with or without an E-box. Driving minimal promoters with exogenous (glucocorticoid receptor) or synthetic transcription factors made expression more MYC-responsive, effectively increasing MYC-amplifier gain. Mutations of conserved MYC-Box regions I and II impaired amplification, whereas MYC-box III mutations delivered higher reporter output indicating that MBIII limits over-amplification. Kinetic theory and experiments indicate that MYC activates at least two steps in the transcription-cycle to explain the non-linear amplification of transcription that is essential for global, supraphysiological transcription in cancer.
Collapse
Affiliation(s)
- Zuqin Nie
- Laboratory of Pathology, CCR, NCI, NIH, Bethesda, United States
| | - Chunhua Guo
- Steroid Hormones Section, NIDDK/LERB, NIH, Bethesda, United States
| | - Subhendu K Das
- Laboratory of Pathology, CCR, NCI, NIH, Bethesda, United States
| | - Carson C Chow
- Mathematical Biology Section, NIDDK/LBM, NIH, Bethesda, United States
| | - Eric Batchelor
- Laboratory of Pathology, CCR, NCI, NIH, Bethesda, United States.,Laboratory of Cell Biology, CCR, NCI, NIH, Bethesda, United States.,Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, United States
| | - S Stoney Simons
- Steroid Hormones Section, NIDDK/LERB, NIH, Bethesda, United States
| | - David Levens
- Laboratory of Pathology, CCR, NCI, NIH, Bethesda, United States
| |
Collapse
|
13
|
Kullmann MK, Podmirseg SR, Roilo M, Hengst L. The CDK inhibitor p57 Kip2 enhances the activity of the transcriptional coactivator FHL2. Sci Rep 2020; 10:7140. [PMID: 32346031 PMCID: PMC7188849 DOI: 10.1038/s41598-020-62641-4] [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: 09/25/2019] [Accepted: 12/19/2019] [Indexed: 01/29/2023] Open
Abstract
The eukaryotic cell cycle is negatively regulated by cyclin-dependent kinase inhibitors (CKIs). p57Kip2 is a member of the Cip/Kip family of CKIs and frequently inactivated by genomic mutations associated with human overgrowth disorders. There is increasing evidence for p57 to control cellular processes in addition to cell cycle and CDK regulation including transcription, apoptosis, migration or development. In order to obtain molecular insights to unknown functions of p57, we performed a protein interaction screen. We identified the transcription regulator four-and-a-half LIM-only protein 2 (FHL2) as a novel p57-binding protein. Co-immunoprecipitation and reporter gene assays were used to elucidate the physiological and functional relevance of p57/FHL2 interaction. We found in cancer cells that endogenous p57 and FHL2 are in a complex. We observed a substantial induction of established FHL2-regulated gene promoters by p57 in reporter gene experiments and detected strong induction of the intrinsic transactivation activity of FHL2. Treatment of cells with histone deacetylase (HDAC) inhibitors and binding of exogenous FHL2 to HDACs indicated repression of FHL2 transcription activity by HDACs. In the presence of the HDAC inhibitor sodium butyrate activation of FHL2 by p57 is abrogated suggesting that p57 shares a common pathway with HDAC inhibitors. p57 competes with HDACs for FHL2 binding which might partly explain the mechanism of FHL2 activation by p57. These results suggest a novel function of p57 in transcription regulation.
Collapse
Affiliation(s)
- Michael Keith Kullmann
- Institute of Medical Biochemistry, Biocenter, Medical University of Innsbruck, Innrain 80-82, A-6020, Innsbruck, Austria.
| | - Silvio Roland Podmirseg
- Institute of Medical Biochemistry, Biocenter, Medical University of Innsbruck, Innrain 80-82, A-6020, Innsbruck, Austria
| | - Martina Roilo
- Institute of Medical Biochemistry, Biocenter, Medical University of Innsbruck, Innrain 80-82, A-6020, Innsbruck, Austria
| | - Ludger Hengst
- Institute of Medical Biochemistry, Biocenter, Medical University of Innsbruck, Innrain 80-82, A-6020, Innsbruck, Austria
| |
Collapse
|
14
|
Jayaprakash C, Das J. Stochastic Sequestration Promotes Specificity in Decision Making in Single Cells. J Phys Chem B 2019; 123:10323-10330. [PMID: 31577902 DOI: 10.1021/acs.jpcb.9b05722] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cellular functions are mediated by specific molecular interactions; however, often competing nonspecific interactions can occur instead, for example, in noncoding regions of genes during transcription or in the response of cell receptors to external signals. Various functional roles have been proposed for such interactions. Motivated by these considerations, we study the time-dependent behavior of a class of discrete, stochastic models in which decoy molecules mediate nonspecific reactions that sequester activated molecules. It is shown that such nonspecific interactions can lead to a time delay in the completion of the specific reaction by the activated molecule, thus permitting discrimination between signals of different duration. We study the effect of stochastic fluctuations in a simple model of gene transcription by numerical solution of the Master Equation and find that the distribution of first passage times for the specific reaction shows surprising nonexponential (non-Debye) behavior over a range of time scales. The mathematical mechanism underlying this behavior is explained in terms of the behavior of the eigensystem of the linear operator associated with the time evolution. Our results demonstrate that stochastic sequestration can be used to enhance the specificity achieved by the well-known kinetic proofreading mechanism.
Collapse
Affiliation(s)
- Ciriyam Jayaprakash
- Department of Physics , The Ohio State University , Columbus , Ohio 43210 , United States
| | - Jayajit Das
- Battelle Center for Mathematical Medicine , The Research Institute at the Nationwide Children's Hospital , Columbus , Ohio 43205 , United States.,Department of Pediatrics, The Wexner College of Medicine , The Ohio State University , Columbus , Ohio 43210 , United States
| |
Collapse
|
15
|
Park J, Estrada J, Johnson G, Vincent BJ, Ricci-Tam C, Bragdon MDJ, Shulgina Y, Cha A, Wunderlich Z, Gunawardena J, DePace AH. Dissecting the sharp response of a canonical developmental enhancer reveals multiple sources of cooperativity. eLife 2019; 8:e41266. [PMID: 31223115 PMCID: PMC6588347 DOI: 10.7554/elife.41266] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 03/04/2019] [Indexed: 12/19/2022] Open
Abstract
Developmental enhancers integrate graded concentrations of transcription factors (TFs) to create sharp gene expression boundaries. Here we examine the hunchback P2 (HbP2) enhancer which drives a sharp expression pattern in the Drosophila blastoderm embryo in response to the transcriptional activator Bicoid (Bcd). We systematically interrogate cis and trans factors that influence the shape and position of expression driven by HbP2, and find that the prevailing model, based on pairwise cooperative binding of Bcd to HbP2 is not adequate. We demonstrate that other proteins, such as pioneer factors, Mediator and histone modifiers influence the shape and position of the HbP2 expression pattern. Comparing our results to theory reveals how higher-order cooperativity and energy expenditure impact boundary location and sharpness. Our results emphasize that the bacterial view of transcription regulation, where pairwise interactions between regulatory proteins dominate, must be reexamined in animals, where multiple molecular mechanisms collaborate to shape the gene regulatory function.
Collapse
Affiliation(s)
- Jeehae Park
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | - Javier Estrada
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | - Gemma Johnson
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | - Ben J Vincent
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | - Chiara Ricci-Tam
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | - Meghan DJ Bragdon
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | | | - Anna Cha
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | - Zeba Wunderlich
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| | | | - Angela H DePace
- Department of Systems BiologyHarvard Medical SchoolBostonUnited States
| |
Collapse
|
16
|
Haberle V, Arnold CD, Pagani M, Rath M, Schernhuber K, Stark A. Transcriptional cofactors display specificity for distinct types of core promoters. Nature 2019; 570:122-126. [PMID: 31092928 PMCID: PMC7613045 DOI: 10.1038/s41586-019-1210-7] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 04/15/2019] [Indexed: 12/24/2022]
Abstract
Transcriptional cofactors (COFs) communicate regulatory cues from enhancers to promoters and are central effectors of transcription activation and gene expression1. Although some COFs have been shown to prefer certain promoter types2-5 over others (for example, see refs 6,7), the extent to which different COFs display intrinsic specificities for distinct promoters is unclear. Here we use a high-throughput promoter-activity assay in Drosophila melanogaster S2 cells to screen 23 COFs for their ability to activate 72,000 candidate core promoters (CPs). We observe differential activation of CPs, indicating distinct regulatory preferences or 'compatibilities'8,9 between COFs and specific types of CPs. These functionally distinct CP types are differentially enriched for known sequence elements2,4, such as the TATA box, downstream promoter element (DPE) or TCT motif, and display distinct chromatin properties at endogenous loci. Notably, the CP types differ in their relative abundance of H3K4me3 and H3K4me1 marks (see also refs 10-12), suggesting that these histone modifications might distinguish trans-regulatory factors rather than promoter- versus enhancer-type cis-regulatory elements. We confirm the existence of distinct COF-CP compatibilities in two additional Drosophila cell lines and in human cells, for which we find COFs that prefer TATA-box or CpG-island promoters, respectively. Distinct compatibilities between COFs and promoters can explain how different enhancers specifically activate distinct sets of genes9, alternative promoters within the same genes, and distinct transcription start sites within the same promoter13. Thus, COF-promoter compatibilities may underlie distinct transcriptional programs in species as divergent as flies and humans.
Collapse
Affiliation(s)
- Vanja Haberle
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Cosmas D. Arnold
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Michaela Pagani
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Martina Rath
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Katharina Schernhuber
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Campus-Vienna-Biocenter 1, 1030 Vienna, Austria
| | - Alexander Stark
- Research Institute of Molecular Pathology (IMP), Vienna Biocenter (VBC), Campus-Vienna-Biocenter 1, 1030 Vienna, Austria,Medical University of Vienna, Vienna Biocenter (VBC), 1030 Vienna, Austria,Correspondence and requests for materials should be addressed to A.S. ()
| |
Collapse
|
17
|
Braun JE, Friedman LJ, Gelles J, Moore MJ. Synergistic assembly of human pre-spliceosomes across introns and exons. eLife 2018; 7:37751. [PMID: 29932423 PMCID: PMC6035042 DOI: 10.7554/elife.37751] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2018] [Accepted: 06/12/2018] [Indexed: 01/05/2023] Open
Abstract
Most human genes contain multiple introns, necessitating mechanisms to effectively define exons and ensure their proper connection by spliceosomes. Human spliceosome assembly involves both cross-intron and cross-exon interactions, but how these work together is unclear. We examined in human nuclear extracts dynamic interactions of single pre-mRNA molecules with individual fluorescently tagged spliceosomal subcomplexes to investigate how cross-intron and cross-exon processes jointly promote pre-spliceosome assembly. U1 subcomplex bound to the 5' splice site of an intron acts jointly with U1 bound to the 5' splice site of the next intron to dramatically increase the rate and efficiency by which U2 subcomplex is recruited to the branch site/3' splice site of the upstream intron. The flanking 5' splice sites have greater than additive effects implying distinct mechanisms facilitating U2 recruitment. This synergy of 5' splice sites across introns and exons is likely important in promoting correct and efficient splicing of multi-intron pre-mRNAs. A gene is a segment of DNA that usually carries the information required to build a protein, the molecules responsible for most of life’s processes. This DNA segment is organized in modules, with coding sections separated by portions of non-coding DNA known as introns. When a gene is ‘turned on’, it gets faithfully copied into a molecule of pre-messenger RNA (pre-mRNA), which contains the alternating coding and non-coding modules. Before it can serve as a template to create a protein, this pre-mRNA must be processed and all the introns removed by a structure called the spliceosome. If this delicate process goes wrong, inaccurate protein templates are produced that may be damaging for the cell. Spliceosomes are precise molecular ‘scissors’ that can recognize where a coding module stops and an intron starts, and then make a snip in the pre-mRNA to remove the non-coding sequence. The spliceosome is a complex molecular machine formed of numerous parts – including one known as U1 snRNP – that must come together. When a pre-mRNA has several introns, a spliceosome assembles anew for each of them. Braun et al. designed a new method that allows them to ‘tag’ spliceosomes extracted from a human cell and follow them as they come together. The experiments show that spliceosomes working on different introns in the same pre-mRNA actually help each other out. As one assembles, this helps the spliceosome that processes the neighboring intron to get built. In particular, the U1 snRNPs processing nearby introns collaborate to promote the assembly and activity of the spliceosomes. This teamwork is likely important to guarantee that multiple introns are cut out quickly and accurately.
Collapse
Affiliation(s)
- Joerg E Braun
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, United States.,Department of Biochemistry, Brandeis University, Waltham, United States
| | - Larry J Friedman
- Department of Biochemistry, Brandeis University, Waltham, United States
| | - Jeff Gelles
- Department of Biochemistry, Brandeis University, Waltham, United States
| | - Melissa J Moore
- RNA Therapeutics Institute, University of Massachusetts Medical School, Worcester, United States
| |
Collapse
|
18
|
Lipid engineering reveals regulatory roles for membrane fluidity in yeast flocculation and oxygen-limited growth. Metab Eng 2017; 41:46-56. [DOI: 10.1016/j.ymben.2017.03.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Revised: 02/10/2017] [Accepted: 03/08/2017] [Indexed: 12/20/2022]
|
19
|
Cheng CS, Behar MS, Suryawanshi GW, Feldman KE, Spreafico R, Hoffmann A. Iterative Modeling Reveals Evidence of Sequential Transcriptional Control Mechanisms. Cell Syst 2017; 4:330-343.e5. [PMID: 28237795 PMCID: PMC5434763 DOI: 10.1016/j.cels.2017.01.012] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2016] [Revised: 11/30/2016] [Accepted: 01/13/2017] [Indexed: 02/03/2023]
Abstract
Combinatorial control of gene expression is presumed to be mediated by molecular interactions between coincident transcription factors (TFs). While information on the genome-wide locations of TFs is available, the genes they regulate and whether they function combinatorially often remain open questions. Here, we developed a mechanistic, rather than statistical, modeling approach to elucidate TF control logic from gene expression data. Applying this approach to hundreds of genes in 85 datasets measuring the transcriptional responses of murine fibroblasts and macrophages to cytokines and pathogens, we found that stimulus-responsive TFs generally function sequentially in logical OR gates or singly. Logical AND gates were found between NF-κB-responsive mRNA synthesis and MAPKp38-responsive control of mRNA half-life, but not between temporally coincident TFs. Our analyses identified the functional target genes of each of the pathogen-responsive TFs and prompt a revision of the conceptual underpinnings of combinatorial control of gene expression to include sequentially acting molecular mechanisms that govern mRNA synthesis and decay.
Collapse
Affiliation(s)
- Christine S Cheng
- Signaling Systems Laboratory, San Diego Center for Systems Biology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Marcelo S Behar
- Signaling Systems Laboratory, San Diego Center for Systems Biology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA; Department of Microbiology, Immunology, and Molecular Genetics, Institute for Quantitative and Computational Biosciences (QCBio) and Molecular Biology Institute (MBI), University of California, Los Angeles, Los Angeles, CA 90025, USA
| | - Gajendra W Suryawanshi
- Department of Microbiology, Immunology, and Molecular Genetics, Institute for Quantitative and Computational Biosciences (QCBio) and Molecular Biology Institute (MBI), University of California, Los Angeles, Los Angeles, CA 90025, USA
| | - Kristyn E Feldman
- Signaling Systems Laboratory, San Diego Center for Systems Biology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Roberto Spreafico
- Department of Microbiology, Immunology, and Molecular Genetics, Institute for Quantitative and Computational Biosciences (QCBio) and Molecular Biology Institute (MBI), University of California, Los Angeles, Los Angeles, CA 90025, USA
| | - Alexander Hoffmann
- Signaling Systems Laboratory, San Diego Center for Systems Biology, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA; Department of Microbiology, Immunology, and Molecular Genetics, Institute for Quantitative and Computational Biosciences (QCBio) and Molecular Biology Institute (MBI), University of California, Los Angeles, Los Angeles, CA 90025, USA.
| |
Collapse
|
20
|
Scholes C, DePace AH, Sánchez Á. Combinatorial Gene Regulation through Kinetic Control of the Transcription Cycle. Cell Syst 2016; 4:97-108.e9. [PMID: 28041762 DOI: 10.1016/j.cels.2016.11.012] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2016] [Revised: 08/09/2016] [Accepted: 11/23/2016] [Indexed: 11/20/2022]
Abstract
Cells decide when, where, and to what level to express their genes by "computing" information from transcription factors (TFs) binding to regulatory DNA. How is the information contained in multiple TF-binding sites integrated to dictate the rate of transcription? The dominant conceptual and quantitative model is that TFs combinatorially recruit one another and RNA polymerase to the promoter by direct physical interactions. Here, we develop a quantitative framework to explore kinetic control, an alternative model in which combinatorial gene regulation can result from TFs working on different kinetic steps of the transcription cycle. Kinetic control can generate a wide range of analog and Boolean computations without requiring the input TFs to be simultaneously bound to regulatory DNA. We propose experiments that will illuminate the role of kinetic control in transcription and discuss implications for deciphering the cis-regulatory "code."
Collapse
Affiliation(s)
- Clarissa Scholes
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA; Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA
| | - Angela H DePace
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115, USA.
| | - Álvaro Sánchez
- The Rowland Institute at Harvard, Harvard University, Cambridge, MA 02142, USA.
| |
Collapse
|
21
|
Bouchat S, Delacourt N, Kula A, Darcis G, Van Driessche B, Corazza F, Gatot JS, Melard A, Vanhulle C, Kabeya K, Pardons M, Avettand-Fenoel V, Clumeck N, De Wit S, Rohr O, Rouzioux C, Van Lint C. Sequential treatment with 5-aza-2'-deoxycytidine and deacetylase inhibitors reactivates HIV-1. EMBO Mol Med 2016; 8:117-38. [PMID: 26681773 PMCID: PMC4734845 DOI: 10.15252/emmm.201505557] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Reactivation of HIV gene expression in latently infected cells together with an efficient cART has been proposed as an adjuvant therapy aimed at eliminating/decreasing the reservoir size. Results from HIV clinical trials using deacetylase inhibitors (HDACIs) question the efficiency of these latency‐reversing agents (LRAs) used alone and underline the need to evaluate other LRAs in combination with HDACIs. Here, we evaluated the therapeutic potential of a demethylating agent (5‐AzadC) in combination with clinically tolerable HDACIs in reactivating HIV‐1 from latency first in vitro and next ex vivo. We showed that a sequential treatment with 5‐AzadC and HDACIs was more effective than the corresponding simultaneous treatment both in vitro and ex vivo. Interestingly, only two of the sequential LRA combinatory treatments tested induced HIV‐1 particle recovery in a higher manner than the drugs alone ex vivo and at concentrations lower than the human tolerable plasmatic concentrations. Taken together, our data reveal the benefit of using combinations of 5‐AzadC with an HDACI and, for the first time, the importance of treatment time schedule for LRA combinations in order to reactivate HIV.
Collapse
Affiliation(s)
- Sophie Bouchat
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies, Belgium
| | - Nadège Delacourt
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies, Belgium
| | - Anna Kula
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies, Belgium
| | - Gilles Darcis
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies, Belgium Service des Maladies Infectieuses, Centre Hospitalier Universitaire (CHU) de Liège, Domaine Universitaire du Sart-Tilman, Université de Liège, Liège, Belgium
| | - Benoit Van Driessche
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies, Belgium
| | - Francis Corazza
- Laboratory of Immunology, IRISLab, CHU-Brugmann, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Jean-Stéphane Gatot
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies, Belgium
| | - Adeline Melard
- Service de Virologie, EA7327, AP-HP, Hôpital Necker-Enfants-Malades, Université Paris-Descartes, Paris, France
| | - Caroline Vanhulle
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies, Belgium
| | - Kabamba Kabeya
- Service des Maladies Infectieuses, CHU St-Pierre, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Marion Pardons
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies, Belgium
| | - Véronique Avettand-Fenoel
- Service de Virologie, EA7327, AP-HP, Hôpital Necker-Enfants-Malades, Université Paris-Descartes, Paris, France
| | - Nathan Clumeck
- Service des Maladies Infectieuses, CHU St-Pierre, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Stéphane De Wit
- Service des Maladies Infectieuses, CHU St-Pierre, Université Libre de Bruxelles (ULB), Brussels, Belgium
| | - Olivier Rohr
- IUT Louis Pasteur de Schiltigheim, University of Strasbourg, Schiltigheim, France Institut Universitaire de France (IUF), Paris, France
| | - Christine Rouzioux
- Service de Virologie, EA7327, AP-HP, Hôpital Necker-Enfants-Malades, Université Paris-Descartes, Paris, France
| | - Carine Van Lint
- Service of Molecular Virology, Department of Molecular Biology (DBM), Université Libre de Bruxelles (ULB), Gosselies, Belgium
| |
Collapse
|
22
|
Bagamasbad PD, Bonett RM, Sachs L, Buisine N, Raj S, Knoedler JR, Kyono Y, Ruan Y, Ruan X, Denver RJ. Deciphering the regulatory logic of an ancient, ultraconserved nuclear receptor enhancer module. Mol Endocrinol 2015; 29:856-72. [PMID: 25866873 DOI: 10.1210/me.2014-1349] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Cooperative, synergistic gene regulation by nuclear hormone receptors can increase sensitivity and amplify cellular responses to hormones. We investigated thyroid hormone (TH) and glucocorticoid (GC) synergy on the Krüppel-like factor 9 (Klf9) gene, which codes for a zinc finger transcription factor involved in development and homeostasis of diverse tissues. We identified regions of the Xenopus and mouse Klf9 genes 5-6 kb upstream of the transcription start sites that supported synergistic transactivation by TH plus GC. Within these regions, we found an orthologous sequence of approximately 180 bp that is highly conserved among tetrapods, but absent in other chordates, and possesses chromatin marks characteristic of an enhancer element. The Xenopus and mouse approximately 180-bp DNA element conferred synergistic transactivation by hormones in transient transfection assays, so we designate this the Klf9 synergy module (KSM). We identified binding sites within the mouse KSM for TH receptor, GC receptor, and nuclear factor κB. TH strongly increased recruitment of liganded GC receptor and serine 5 phosphorylated (initiating) RNA polymerase II to chromatin at the KSM, suggesting a mechanism for transcriptional synergy. The KSM is transcribed to generate long noncoding RNAs, which are also synergistically induced by combined hormone treatment, and the KSM interacts with the Klf9 promoter and a far upstream region through chromosomal looping. Our findings support that the KSM plays a central role in hormone regulation of vertebrate Klf9 genes, it evolved in the tetrapod lineage, and has been maintained by strong stabilizing selection.
Collapse
Affiliation(s)
- Pia D Bagamasbad
- Department of Molecular, Cellular and Developmental Biology (P.D.B., S.R., R.J.D.), University of Michigan, Ann Arbor, Michigan 48109; Department of Biological Science (R.M.B.), The University of Tulsa, Tulsa, Oklahoma 74104; Unité Mixte de Recherche 7221 (L.S., N.B.), Muséum National d'Histoire Naturelle, Centre Nationale de Recherche Scientifique, CP32 Paris, France; Neuroscience Graduate Program (J.R.K., Y.K., R.J.D.), The University of Michigan, Ann Arbor, Michigan 48109; Genome Institute of Singapore (Y.R., X.R.), 138672 Singapore; The Jackson Laboratory of Genomic Medicine (Y.R., X.R.), Farmington, Connecticut 06030; and Department of Genetics and Developmental Biology (Y.R., X.R.), University of Connecticut, Storrs, Connecticut 06269
| | - Ronald M Bonett
- Department of Molecular, Cellular and Developmental Biology (P.D.B., S.R., R.J.D.), University of Michigan, Ann Arbor, Michigan 48109; Department of Biological Science (R.M.B.), The University of Tulsa, Tulsa, Oklahoma 74104; Unité Mixte de Recherche 7221 (L.S., N.B.), Muséum National d'Histoire Naturelle, Centre Nationale de Recherche Scientifique, CP32 Paris, France; Neuroscience Graduate Program (J.R.K., Y.K., R.J.D.), The University of Michigan, Ann Arbor, Michigan 48109; Genome Institute of Singapore (Y.R., X.R.), 138672 Singapore; The Jackson Laboratory of Genomic Medicine (Y.R., X.R.), Farmington, Connecticut 06030; and Department of Genetics and Developmental Biology (Y.R., X.R.), University of Connecticut, Storrs, Connecticut 06269
| | - Laurent Sachs
- Department of Molecular, Cellular and Developmental Biology (P.D.B., S.R., R.J.D.), University of Michigan, Ann Arbor, Michigan 48109; Department of Biological Science (R.M.B.), The University of Tulsa, Tulsa, Oklahoma 74104; Unité Mixte de Recherche 7221 (L.S., N.B.), Muséum National d'Histoire Naturelle, Centre Nationale de Recherche Scientifique, CP32 Paris, France; Neuroscience Graduate Program (J.R.K., Y.K., R.J.D.), The University of Michigan, Ann Arbor, Michigan 48109; Genome Institute of Singapore (Y.R., X.R.), 138672 Singapore; The Jackson Laboratory of Genomic Medicine (Y.R., X.R.), Farmington, Connecticut 06030; and Department of Genetics and Developmental Biology (Y.R., X.R.), University of Connecticut, Storrs, Connecticut 06269
| | - Nicolas Buisine
- Department of Molecular, Cellular and Developmental Biology (P.D.B., S.R., R.J.D.), University of Michigan, Ann Arbor, Michigan 48109; Department of Biological Science (R.M.B.), The University of Tulsa, Tulsa, Oklahoma 74104; Unité Mixte de Recherche 7221 (L.S., N.B.), Muséum National d'Histoire Naturelle, Centre Nationale de Recherche Scientifique, CP32 Paris, France; Neuroscience Graduate Program (J.R.K., Y.K., R.J.D.), The University of Michigan, Ann Arbor, Michigan 48109; Genome Institute of Singapore (Y.R., X.R.), 138672 Singapore; The Jackson Laboratory of Genomic Medicine (Y.R., X.R.), Farmington, Connecticut 06030; and Department of Genetics and Developmental Biology (Y.R., X.R.), University of Connecticut, Storrs, Connecticut 06269
| | - Samhitha Raj
- Department of Molecular, Cellular and Developmental Biology (P.D.B., S.R., R.J.D.), University of Michigan, Ann Arbor, Michigan 48109; Department of Biological Science (R.M.B.), The University of Tulsa, Tulsa, Oklahoma 74104; Unité Mixte de Recherche 7221 (L.S., N.B.), Muséum National d'Histoire Naturelle, Centre Nationale de Recherche Scientifique, CP32 Paris, France; Neuroscience Graduate Program (J.R.K., Y.K., R.J.D.), The University of Michigan, Ann Arbor, Michigan 48109; Genome Institute of Singapore (Y.R., X.R.), 138672 Singapore; The Jackson Laboratory of Genomic Medicine (Y.R., X.R.), Farmington, Connecticut 06030; and Department of Genetics and Developmental Biology (Y.R., X.R.), University of Connecticut, Storrs, Connecticut 06269
| | - Joseph R Knoedler
- Department of Molecular, Cellular and Developmental Biology (P.D.B., S.R., R.J.D.), University of Michigan, Ann Arbor, Michigan 48109; Department of Biological Science (R.M.B.), The University of Tulsa, Tulsa, Oklahoma 74104; Unité Mixte de Recherche 7221 (L.S., N.B.), Muséum National d'Histoire Naturelle, Centre Nationale de Recherche Scientifique, CP32 Paris, France; Neuroscience Graduate Program (J.R.K., Y.K., R.J.D.), The University of Michigan, Ann Arbor, Michigan 48109; Genome Institute of Singapore (Y.R., X.R.), 138672 Singapore; The Jackson Laboratory of Genomic Medicine (Y.R., X.R.), Farmington, Connecticut 06030; and Department of Genetics and Developmental Biology (Y.R., X.R.), University of Connecticut, Storrs, Connecticut 06269
| | - Yasuhiro Kyono
- Department of Molecular, Cellular and Developmental Biology (P.D.B., S.R., R.J.D.), University of Michigan, Ann Arbor, Michigan 48109; Department of Biological Science (R.M.B.), The University of Tulsa, Tulsa, Oklahoma 74104; Unité Mixte de Recherche 7221 (L.S., N.B.), Muséum National d'Histoire Naturelle, Centre Nationale de Recherche Scientifique, CP32 Paris, France; Neuroscience Graduate Program (J.R.K., Y.K., R.J.D.), The University of Michigan, Ann Arbor, Michigan 48109; Genome Institute of Singapore (Y.R., X.R.), 138672 Singapore; The Jackson Laboratory of Genomic Medicine (Y.R., X.R.), Farmington, Connecticut 06030; and Department of Genetics and Developmental Biology (Y.R., X.R.), University of Connecticut, Storrs, Connecticut 06269
| | - Yijun Ruan
- Department of Molecular, Cellular and Developmental Biology (P.D.B., S.R., R.J.D.), University of Michigan, Ann Arbor, Michigan 48109; Department of Biological Science (R.M.B.), The University of Tulsa, Tulsa, Oklahoma 74104; Unité Mixte de Recherche 7221 (L.S., N.B.), Muséum National d'Histoire Naturelle, Centre Nationale de Recherche Scientifique, CP32 Paris, France; Neuroscience Graduate Program (J.R.K., Y.K., R.J.D.), The University of Michigan, Ann Arbor, Michigan 48109; Genome Institute of Singapore (Y.R., X.R.), 138672 Singapore; The Jackson Laboratory of Genomic Medicine (Y.R., X.R.), Farmington, Connecticut 06030; and Department of Genetics and Developmental Biology (Y.R., X.R.), University of Connecticut, Storrs, Connecticut 06269
| | - Xiaoan Ruan
- Department of Molecular, Cellular and Developmental Biology (P.D.B., S.R., R.J.D.), University of Michigan, Ann Arbor, Michigan 48109; Department of Biological Science (R.M.B.), The University of Tulsa, Tulsa, Oklahoma 74104; Unité Mixte de Recherche 7221 (L.S., N.B.), Muséum National d'Histoire Naturelle, Centre Nationale de Recherche Scientifique, CP32 Paris, France; Neuroscience Graduate Program (J.R.K., Y.K., R.J.D.), The University of Michigan, Ann Arbor, Michigan 48109; Genome Institute of Singapore (Y.R., X.R.), 138672 Singapore; The Jackson Laboratory of Genomic Medicine (Y.R., X.R.), Farmington, Connecticut 06030; and Department of Genetics and Developmental Biology (Y.R., X.R.), University of Connecticut, Storrs, Connecticut 06269
| | - Robert J Denver
- Department of Molecular, Cellular and Developmental Biology (P.D.B., S.R., R.J.D.), University of Michigan, Ann Arbor, Michigan 48109; Department of Biological Science (R.M.B.), The University of Tulsa, Tulsa, Oklahoma 74104; Unité Mixte de Recherche 7221 (L.S., N.B.), Muséum National d'Histoire Naturelle, Centre Nationale de Recherche Scientifique, CP32 Paris, France; Neuroscience Graduate Program (J.R.K., Y.K., R.J.D.), The University of Michigan, Ann Arbor, Michigan 48109; Genome Institute of Singapore (Y.R., X.R.), 138672 Singapore; The Jackson Laboratory of Genomic Medicine (Y.R., X.R.), Farmington, Connecticut 06030; and Department of Genetics and Developmental Biology (Y.R., X.R.), University of Connecticut, Storrs, Connecticut 06269
| |
Collapse
|
23
|
P Singh R, Brysbaert G, F Lensink M, Cleri F, Blossey R. Kinetic proofreading of chromatin remodeling: from gene activation to gene repression and back. AIMS BIOPHYSICS 2015. [DOI: 10.3934/biophy.2015.4.398] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
|
24
|
Cloutier SC, Wang S, Ma WK, Petell CJ, Tran EJ. Long noncoding RNAs promote transcriptional poising of inducible genes. PLoS Biol 2013; 11:e1001715. [PMID: 24260025 PMCID: PMC3833879 DOI: 10.1371/journal.pbio.1001715] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Accepted: 10/09/2013] [Indexed: 11/19/2022] Open
Abstract
The GAL cluster-associated long non-coding RNAs (lncRNAs) promote rapid induction of GAL genes in budding yeast, thereby promoting a faster switch in transcriptional programs when needed. Long noncoding RNAs (lncRNAs) are a class of molecules that impinge on the expression of protein-coding genes. Previous studies have suggested that the GAL cluster-associated lncRNAs of Saccharomyces cerevisiae repress expression of the protein-coding GAL genes. Herein, we demonstrate a previously unrecognized role for the GAL lncRNAs in activating gene expression. In yeast strains lacking the RNA helicase, DBP2, or the RNA decay enzyme, XRN1, we find that the GAL lncRNAs specifically accelerate gene expression from a prior repressive state. Furthermore, we provide evidence that the previously suggested repressive role is a result of specific mutant phenotypes, rather than a reflection of the normal, wild-type function of these noncoding RNAs. To shed light on the mechanism for lncRNA-dependent gene activation, we show that rapid induction of the protein-coding GAL genes is associated with faster recruitment of RNA polymerase II and reduced association of transcriptional repressors with GAL gene promoters. This suggests that the GAL lncRNAs enhance expression by derepressing the GAL genes. Consistently, the GAL lncRNAs enhance the kinetics of transcriptional induction, promoting faster expression of the protein-coding GAL genes upon the switch in carbon source. We suggest that the GAL lncRNAs poise inducible genes for rapid activation, enabling cells to more effectively trigger new transcriptional programs in response to cellular cues. Long noncoding RNAs (lncRNAs) are a recently identified class of molecules that regulate the expression of protein-coding genes through a number of mechanisms, some of them poorly characterized. The GAL gene cluster of the yeast Saccharomyces cerevisiae encodes a series of three inducible genes that are turned on or off by the presence or absence of specific carbon sources in the environment. Previous studies have documented the presence of two lncRNAs—GAL10 and GAL10s—encoded by genes that overlap the GAL cluster. We have now uncovered a role for both these lncRNAs in promoting the activation of the GAL genes when they are released from repressive conditions. This activation occurs at the kinetic level, through more rapid recruitment of RNA polymerase II and decreased association of the co-repressor, Cyc8. Under normal conditions, but also especially when they are stabilized and their levels are up-regulated, these GAL lncRNAs promote faster GAL gene activation. We suggest that these lncRNA molecules poise inducible genes for quick response to extracellular cues, triggering a faster switch in transcriptional programs.
Collapse
Affiliation(s)
- Sara C. Cloutier
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
| | - Siwen Wang
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
| | - Wai Kit Ma
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
| | - Christopher J. Petell
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
| | - Elizabeth J. Tran
- Department of Biochemistry, Purdue University, West Lafayette, Indiana, United States of America
- Purdue University Center for Cancer Research, Purdue University, West Lafayette, Indiana, United States of America
- * E-mail:
| |
Collapse
|
25
|
Larson DR, Fritzsch C, Sun L, Meng X, Lawrence DS, Singer RH. Direct observation of frequency modulated transcription in single cells using light activation. eLife 2013; 2:e00750. [PMID: 24069527 PMCID: PMC3780543 DOI: 10.7554/elife.00750] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 08/20/2013] [Indexed: 12/21/2022] Open
Abstract
Single-cell analysis has revealed that transcription is dynamic and stochastic, but tools are lacking that can determine the mechanism operating at a single gene. Here we utilize single-molecule observations of RNA in fixed and living cells to develop a single-cell model of steroid-receptor mediated gene activation. We determine that steroids drive mRNA synthesis by frequency modulation of transcription. This digital behavior in single cells gives rise to the well-known analog dose response across the population. To test this model, we developed a light-activation technology to turn on a single steroid-responsive gene and follow dynamic synthesis of RNA from the activated locus. DOI:http://dx.doi.org/10.7554/eLife.00750.001 The process by which a gene is expressed as a protein consists of two stages: transcription, which involves the DNA of the gene being copied into messenger RNA (mRNA); and translation, in which the mRNA is used as a template to assemble amino acids into a protein. Transcription and translation are controlled by many interlinked pathways, which ensures that genes are expressed when and where required. One of these regulatory pathways involves steroid receptors. The binding of a steroid molecule to its receptor causes the receptor to move into the nucleus and interact with a specific gene, triggering transcription of that gene. When measured at the level of the whole organism, this transcriptional response is dose-dependent—the more steroid molecules that are present, the greater the amount of transcription. However, this is not the case in single cells, in which transcription is either activated or not. This ‘on/off’ behaviour is also seen over time: steroid-activated transcription occurs in bursts, separated by periods of inactivity. To unravel the molecular mechanism behind this phenomenon, Larson et al. created a light-activated form of the ligand that activates a specific steroid receptor. Using this molecule, they were able to switch transcription of the gene controlled by that receptor on and off. They then used fluorescent proteins to label the mRNA and protein molecules that were produced as a result. They found that activating the steroid receptor increases the likelihood of transcription occurring inside a cell, but not the duration of individual bursts of transcriptional activity, nor the amount of mRNA produced during each burst. Activation of a steroid receptor seems to control transcription by reducing the length of time each cell spends in the ‘off’ state between bursts. Larson et al. incorporated their findings into a model that also takes into account the natural variability in levels of transcription between cells, and found that this could explain how the digital (on/off) control of transcription at the cellular level leads to analogue, dose-dependent control at the level of a whole organism. These findings should lead to further insights into how transcription is controlled at the molecular level. DOI:http://dx.doi.org/10.7554/eLife.00750.002
Collapse
Affiliation(s)
- Daniel R Larson
- Laboratory of Receptor Biology and Gene Expression , Center for Cancer Research, National Cancer Institute, National Institutes of Health , Bethesda , United States
| | | | | | | | | | | |
Collapse
|
26
|
Nie Z, Hu G, Wei G, Cui K, Yamane A, Resch W, Wang R, Green DR, Tessarollo L, Casellas R, Zhao K, Levens D. c-Myc is a universal amplifier of expressed genes in lymphocytes and embryonic stem cells. Cell 2012; 151:68-79. [PMID: 23021216 PMCID: PMC3471363 DOI: 10.1016/j.cell.2012.08.033] [Citation(s) in RCA: 800] [Impact Index Per Article: 66.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2012] [Revised: 06/17/2012] [Accepted: 08/08/2012] [Indexed: 01/19/2023]
Abstract
The c-Myc HLH-bZIP protein has been implicated in physiological or pathological growth, proliferation, apoptosis, metabolism, and differentiation at the cellular, tissue, or organismal levels via regulation of numerous target genes. No principle yet unifies Myc action due partly to an incomplete inventory and functional accounting of Myc's targets. To observe Myc target expression and function in a system where Myc is temporally and physiologically regulated, the transcriptomes and the genome-wide distributions of Myc, RNA polymerase II, and chromatin modifications were compared during lymphocyte activation and in ES cells as well. A remarkably simple rule emerged from this quantitative analysis: Myc is not an on-off specifier of gene activity, but is a nonlinear amplifier of expression, acting universally at active genes, except for immediate early genes that are strongly induced before Myc. This rule of Myc action explains the vast majority of Myc biology observed in literature.
Collapse
Affiliation(s)
- Zuqin Nie
- Laboratory of Pathology, NCI, Bethesda, MD, 20892
| | - Gangqing Hu
- Systems Biology Center, NHLBI, Bethesda, MD, 20892
| | - Gang Wei
- Systems Biology Center, NHLBI, Bethesda, MD, 20892
| | - Kairong Cui
- Systems Biology Center, NHLBI, Bethesda, MD, 20892
| | - Arito Yamane
- Genomics and Immunity Section, NIAMS, Bethesda, MD, 20892
| | - Wolfgang Resch
- Genomics and Immunity Section, NIAMS, Bethesda, MD, 20892
| | - Ruoning Wang
- Department of Immunology, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105, USA
| | - Douglas R. Green
- Department of Immunology, St. Jude Children’s Research Hospital, Memphis, Tennessee 38105, USA
| | | | | | - Keji Zhao
- Systems Biology Center, NHLBI, Bethesda, MD, 20892
| | - David Levens
- Laboratory of Pathology, NCI, Bethesda, MD, 20892
| |
Collapse
|
27
|
Phosphorylation and activation of the plasma membrane Na+/H+ exchanger (NHE1) during osmotic cell shrinkage. PLoS One 2011; 6:e29210. [PMID: 22216214 PMCID: PMC3247252 DOI: 10.1371/journal.pone.0029210] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Accepted: 11/22/2011] [Indexed: 11/19/2022] Open
Abstract
The Na(+)/H(+)Exchanger isoform 1 (NHE1) is a highly versatile, broadly distributed and precisely controlled transport protein that mediates volume and pH regulation in most cell types. NHE1 phosphorylation contributes to Na(+)/H(+) exchange activity in response to phorbol esters, growth factors or protein phosphatase inhibitors, but has not been observed during activation by osmotic cell shrinkage (OCS). We examined the role of NHE1 phosphorylation during activation by OCS, using an ideal model system, the Amphiuma tridactylum red blood cell (atRBC). Na(+)/H(+) exchange in atRBCs is mediated by an NHE1 homolog (atNHE1) that is 79% identical to human NHE1 at the amino acid level. NHE1 activity in atRBCs is exceptionally robust in that transport activity can increase more than 2 orders of magnitude from rest to full activation. Michaelis-Menten transport kinetics indicates that either OCS or treatment with the phosphatase inhibitor calyculin-A (CLA) increase Na(+) transport capacity without affecting transport affinity (K(m)=44 mM) in atRBCs. CLA and OCS act non-additively to activate atNHE1, indicating convergent, phosphorylation-dependent signaling in atNHE1 activation. In situ(32)P labeling and immunoprecipitation demonstrates that the net phosphorylation of atNHE1 is increased 4-fold during OCS coinciding with a more than 2-order increase in Na(+) transport activity. This is the first reported evidence of increased NHE1 phosphorylation during OCS in any vertebrate cell type. Finally, liquid chromatography and mass spectrometry (LC-MS/MS) analysis of atNHE1 immunoprecipitated from atRBC membranes reveals 9 phosphorylated serine/threonine residues, suggesting that activation of atNHE1 involves multiple phosphorylation and/or dephosphorylation events.
Collapse
|
28
|
Larson DR. What do expression dynamics tell us about the mechanism of transcription? Curr Opin Genet Dev 2011; 21:591-9. [PMID: 21862317 PMCID: PMC3475196 DOI: 10.1016/j.gde.2011.07.010] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2011] [Revised: 07/18/2011] [Accepted: 07/27/2011] [Indexed: 11/16/2022]
Abstract
Single-cell microscopy studies have the potential to provide an unprecedented view of gene expression with exquisite spatial and temporal sensitivity. However, there is a challenge to connect the holistic cellular view with a reductionist biochemical view. In particular, experimental efforts to characterize the in vivo regulation of transcription have focused primarily on measurements of the dynamics of transcription factors and chromatin modifying factors. Such measurements have elucidated the transient nature of many nuclear interactions. In the past few years, experimental approaches have emerged that allow for interrogation of the output of transcription at the single-molecule, single-cell level. Here, I summarize the experimental results and models that aim to provide an integrated view of transcriptional regulation.
Collapse
Affiliation(s)
- Daniel R Larson
- National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, United States.
| |
Collapse
|
29
|
Pierard V, Guiguen A, Colin L, Wijmeersch G, Vanhulle C, Van Driessche B, Dekoninck A, Blazkova J, Cardona C, Merimi M, Vierendeel V, Calomme C, Nguyên TLA, Nuttinck M, Twizere JC, Kettmann R, Portetelle D, Burny A, Hirsch I, Rohr O, Van Lint C. DNA cytosine methylation in the bovine leukemia virus promoter is associated with latency in a lymphoma-derived B-cell line: potential involvement of direct inhibition of cAMP-responsive element (CRE)-binding protein/CRE modulator/activation transcription factor binding. J Biol Chem 2010; 285:19434-49. [PMID: 20413592 PMCID: PMC2885223 DOI: 10.1074/jbc.m110.107607] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2010] [Revised: 03/31/2010] [Indexed: 02/02/2023] Open
Abstract
Bovine leukemia virus (BLV) proviral latency represents a viral strategy to escape the host immune system and allow tumor development. Besides the previously demonstrated role of histone deacetylation in the epigenetic repression of BLV expression, we showed here that BLV promoter activity was induced by several DNA methylation inhibitors (such as 5-aza-2'-deoxycytidine) and that overexpressed DNMT1 and DNMT3A, but not DNMT3B, down-regulated BLV promoter activity. Importantly, cytosine hypermethylation in the 5'-long terminal repeat (LTR) U3 and R regions was associated with true latency in the lymphoma-derived B-cell line L267 but not with defective latency in YR2 cells. Moreover, the virus-encoded transactivator Tax(BLV) decreased DNA methyltransferase expression levels, which could explain the lower level of cytosine methylation observed in the L267(LTaxSN) 5'-LTR compared with the L267 5'-LTR. Interestingly, DNA methylation inhibitors and Tax(BLV) synergistically activated BLV promoter transcriptional activity in a cAMP-responsive element (CRE)-dependent manner. Mechanistically, methylation at the -154 or -129 CpG position (relative to the transcription start site) impaired in vitro binding of CRE-binding protein (CREB) transcription factors to their respective CRE sites. Methylation at -129 CpG alone was sufficient to decrease BLV promoter-driven reporter gene expression by 2-fold. We demonstrated in vivo the recruitment of CREB/CRE modulator (CREM) and to a lesser extent activating transcription factor-1 (ATF-1) to the hypomethylated CRE region of the YR2 5'-LTR, whereas we detected no CREB/CREM/ATF recruitment to the hypermethylated corresponding region in the L267 cells. Altogether, these findings suggest that site-specific DNA methylation of the BLV promoter represses viral transcription by directly inhibiting transcription factor binding, thereby contributing to true proviral latency.
Collapse
Affiliation(s)
- Valérie Pierard
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Allan Guiguen
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Laurence Colin
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Gaëlle Wijmeersch
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Caroline Vanhulle
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Benoît Van Driessche
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Ann Dekoninck
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Jana Blazkova
- the Institut de Cancérologie de Marseille, UMR 599 INSERM, Institut Paoli-Calmettes, Université de la Méditerranée, Boulevard Lei Roure 27, 13009 Marseille, France
| | - Christelle Cardona
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Makram Merimi
- the Laboratory of Experimental Hematology, Institut Jules Bordet, Université Libre de Bruxelles, Boulevard de Waterloo 121, 1000 Bruxelles, Belgium
| | - Valérie Vierendeel
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Claire Calomme
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Thi Liên-Anh Nguyên
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | - Michèle Nuttinck
- the Département de Biologie Moléculaire, Faculté Universitaire des Sciences Agronomiques de Gembloux, Avenue du Maréchal Juin 6, 5030 Gembloux, Belgium, and
| | - Jean-Claude Twizere
- the Département de Biologie Moléculaire, Faculté Universitaire des Sciences Agronomiques de Gembloux, Avenue du Maréchal Juin 6, 5030 Gembloux, Belgium, and
| | - Richard Kettmann
- the Département de Biologie Moléculaire, Faculté Universitaire des Sciences Agronomiques de Gembloux, Avenue du Maréchal Juin 6, 5030 Gembloux, Belgium, and
| | - Daniel Portetelle
- the Département de Biologie Moléculaire, Faculté Universitaire des Sciences Agronomiques de Gembloux, Avenue du Maréchal Juin 6, 5030 Gembloux, Belgium, and
| | - Arsène Burny
- the Département de Biologie Moléculaire, Faculté Universitaire des Sciences Agronomiques de Gembloux, Avenue du Maréchal Juin 6, 5030 Gembloux, Belgium, and
| | - Ivan Hirsch
- the Institut de Cancérologie de Marseille, UMR 599 INSERM, Institut Paoli-Calmettes, Université de la Méditerranée, Boulevard Lei Roure 27, 13009 Marseille, France
| | - Olivier Rohr
- the Institut Universitaire de Technologie Louis Pasteur de Schiltigheim, University of Strasbourg, 1 Allée d'Athènes, 67300 Schiltigheim, France
| | - Carine Van Lint
- From the Laboratoire de Virologie Moléculaire, Institut de Biologie et de Médecine Moléculaires (IBMM), Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| |
Collapse
|
30
|
Abstract
In the eukaryotic genome, the thousands of genes that encode messenger RNA are transcribed by a molecular machine called RNA polymerase II. Analysing the distribution and status of RNA polymerase II across a genome has provided crucial insights into the long-standing mysteries of transcription and its regulation. These studies identify points in the transcription cycle where RNA polymerase II accumulates after encountering a rate-limiting step. When coupled with genome-wide mapping of transcription factors, these approaches identify key regulatory steps and factors and, importantly, provide an understanding of the mechanistic generalities, as well as the rich diversities, of gene regulation.
Collapse
|
31
|
Leon TYY, Ngan ESW, Poon HC, So MT, Lui VCH, Tam PKH, Garcia-Barcelo MM. Transcriptional regulation of RET by Nkx2-1, Phox2b, Sox10, and Pax3. J Pediatr Surg 2009; 44:1904-12. [PMID: 19853745 DOI: 10.1016/j.jpedsurg.2008.11.055] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2008] [Accepted: 11/25/2008] [Indexed: 12/13/2022]
Abstract
BACKGROUND The rearranged during transfection (RET) gene encodes a single-pass receptor whose proper expression and function are essential for the development of enteric nervous system. Mutations in RET regulatory regions are also associated with Hirschsprung disease (HSCR) (aganglionosis of the colon). We previously showed that 2 polymorphisms in RET promoter are associated with the increased risk of HSCR. These single nucleotide polymorphisms overlap with the NK2 homeobox 1 (Nkx2-1) binding motif interrupting the physical interaction of NKX2-1 with the RET promoter and result in reduced RET transcription. In this study, we further delineated Nkx2-1-mediated RET Transcription. METHODS AND RESULTS First, we demonstrated that PHOX2B, like SOX10 and NKX2-1, is expressed in the mature enteric ganglions of human gut by immunohistochemistry. Second, subsequent dual-luciferase-reporter studies indicated that Nkx2-1 indeed works coordinately with Phox2b and Sox10, but not Pax3, to mediate RET transcription. In addition, identification of Phox2b responsive region in RET promoter further provides solid evidence of the potential functional interaction between Phox2b and RET. CONCLUSION In sum, Phox2b and Sox10 act together with Nkx2.1 to modify RET signaling and this interaction may also contribute to HSCR susceptibility.
Collapse
Affiliation(s)
- Thomas Y Y Leon
- Division of Paediatric Surgery, Department of Surgery, The University of Hong Kong, Hong Kong SAR, China
| | | | | | | | | | | | | |
Collapse
|
32
|
Gutierrez PS, Monteoliva D, Diambra L. Role of cooperative binding on noise expression. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:011914. [PMID: 19658736 DOI: 10.1103/physreve.80.011914] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2009] [Indexed: 05/28/2023]
Abstract
The origin of stochastic fluctuations in gene expression has received considerable attention recently. Fluctuations in gene expression are particularly pronounced in cellular systems because of the small copy number of species undergoing transitions between discrete chemical states and the small size of biological compartments. In this paper, we propose a stochastic model for gene expression regulation including several binding sites, considering elementary reactions only. The model is used to investigate the role of cooperativity on the intrinsic fluctuations of gene expression by means of master-equation formalism. We found that the Hill coefficient and the level of noise increase as the interaction energy between activators increases. Additionally, we show that the model allows one to distinguish between two cooperative binding mechanisms.
Collapse
Affiliation(s)
- P S Gutierrez
- Laboratorio de Biología de Sistemas, CREG-UNLP, Av. Calchaqui Km 23.5, CP 1888, Florencio Varela, Argentina
| | | | | |
Collapse
|
33
|
Gupta P, Gurudutta GU, Saluja D, Tripathi RP. PU.1 and partners: regulation of haematopoietic stem cell fate in normal and malignant haematopoiesis. J Cell Mol Med 2009; 13:4349-63. [PMID: 19382896 PMCID: PMC4515051 DOI: 10.1111/j.1582-4934.2009.00757.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
During normal haematopoiesis, cell development and differentiation programs are accomplished by switching ‘on’ and ‘off’ specific set of genes. Specificity of gene expression is primarily achieved by combinatorial control, i.e. through physical and functional interactions among several transcription factors that form sequence-specific multiprotein complexes on regulatory regions (gene promoters and enhancers). Such combinatorial gene switches permit flexibility of regulation and allow numerous developmental decisions to be taken with a limited number of regulators. The haematopoietic-specific Ets family transcription factor PU.1 regulates many lymphoid- and myeloid-specific gene promoters and enhancers by interacting with multiple proteins during haematopoietic development. Such protein–protein interactions regulate DNA binding, subcellular localization, target gene selection and transcriptional activity of PU.1 itself in response to diverse signals including cytokines, growth factors, antigen and cellular stresses. Specific domains of PU.1 interact with many protein motifs such as bHLH, bZipper, zinc fingers and paired domain for regulating its activity. This review focuses on important protein–protein interactions of PU.1 that play a crucial role in regulation of normal as well as malignant haematopoiesis. Precise delineation of PU.1 protein-partner interacting interface may provide an improved insight of the molecular mechanisms underlying haematopoietic stem cell fate regulation. Its interactions with some proteins could be targeted to modulate the aberrant signalling pathways for reversing the malignant phenotype and to control the generation of specific haematopoietic progeny for treatment of haematopoietic disorders.
Collapse
Affiliation(s)
- Pallavi Gupta
- Stem Cell & Gene Therapy Research Group, Institute of Nuclear Medicine & Allied Sciences, DRDO, Delhi, India
| | | | | | | |
Collapse
|
34
|
|
35
|
Ivanova O, Braas D, Klempnauer KH. Oncogenic point mutations in the Myb DNA-binding domain alter the DNA-binding properties of Myb at a physiological target gene. Nucleic Acids Res 2007; 35:7237-47. [PMID: 17959653 PMCID: PMC2175353 DOI: 10.1093/nar/gkm675] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
The oncoprotein v-Myb of avian myeloblastosis virus (AMV) transforms myelomonocytic cells by deregulating specific target genes. Previous work has shown that the oncogenic potential of v-Myb was activated by truncation of N- and C-terminal sequences of c-Myb and was further increased by amino acid substitutions in the DNA-binding domain and other parts of the protein. We have analyzed the activation of the chicken lysozyme gene which is strongly activated by c-Myb but not by its oncogenic counterpart v-Myb. We report that Myb acts on two different cis-regulatory elements, the promoter and an enhancer located upstream of the gene. Interestingly, the activation of the enhancer was abolished by the oncogenic amino acid substitutions. We demonstrated that a single Myb-binding site is responsible for the activation of the lysozyme enhancer by Myb and showed that the v-Myb protein of AMV was unable to bind to this site. Our data demonstrate for the first time that oncogenic activation of Myb alters its DNA-binding specificity at a physiological Myb target gene.
Collapse
Affiliation(s)
- Olga Ivanova
- Institut für Biochemie, Westfälische-Wilhelms-Universität Münster, Wilhelm-Klemm-Strasse 2, D-48149 Münster, Germany
| | | | | |
Collapse
|
36
|
Xiao X, Yu P, Lim HS, Sikder D, Kodadek T. Design and synthesis of a cell-permeable synthetic transcription factor mimic. ACTA ACUST UNITED AC 2007; 9:592-600. [PMID: 17530904 PMCID: PMC2518654 DOI: 10.1021/cc070023a] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Synthetic molecules capable of activating the expression of specific genes are of great interest as tools for biological research and, potentially, as a novel class of pharmaceutical agents. It has been demonstrated previously that such synthetic transcription factor mimics (STFMs) can be constructed by connecting a sequence-specific DNA-binding module to a molecule capable of binding to the transcriptional machinery via a suitable linker. These chimeras mimic the two basic properties of native transcription factors, which are able to recognize a promoter sequence specifically and to recruit the transcriptional machinery to that promoter. However, none of the compounds of this type reported to date have been shown to function in living cells. We report here the first example of a cell-permeable STFM that activates the transcription of a reporter gene in mammalian cells. The compound is composed of a cell-permeable coactivator-binding peptoid fused to a DNA-binding hairpin polyamide. The peptoid was identified by screening a combinatorial library of approximately 50,000 compounds for binding to the KIX domain of the CREB-binding protein (CBP), a mammalian transcription coactivator. When incubated with cultured HeLa cells carrying a luciferase reporter plasmid bearing several hairpin polyamide-binding sites, a 5-fold increase in luciferase expression was observed. These experiments set the stage for the identification of hairpin polyamide-peptoid conjugates that are targeted to native genes.
Collapse
Affiliation(s)
| | | | | | | | - Thomas Kodadek
- To whom correspondence should be addressed. Phone: 214-648-1239. FAX: 214-648-4156. E-mail:
| |
Collapse
|
37
|
Nguyên TLA, de Walque S, Veithen E, Dekoninck A, Martinelli V, de Launoit Y, Burny A, Harrod R, Van Lint C. Transcriptional regulation of the bovine leukemia virus promoter by the cyclic AMP-response element modulator tau isoform. J Biol Chem 2007; 282:20854-67. [PMID: 17526487 DOI: 10.1074/jbc.m703060200] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bovine leukemia virus (BLV) expression is controlled at the transcriptional level through three Tax(BLV)-responsive elements (TxREs) responsive to the viral transactivator Tax(BLV). The cAMP-responsive element (CRE)-binding protein (CREB) has been shown to interact with CRE-like sequences present in the middle of each of these TxREs and to play critical transcriptional roles in both basal and Tax(BLV)-transactivated BLV promoter activity. In this study, we have investigated the potential involvement of the cAMP-response element modulator (CREM) in BLV transcriptional regulation, and we have demonstrated that CREM proteins were expressed in BLV-infected cells and bound to the three BLV TxREs in vitro. Chromatin immunoprecipitation assays using BLV-infected cell lines demonstrated in the context of chromatin that CREM proteins were recruited to the BLV promoter TxRE region in vivo. Functional studies, in the absence of Tax(BLV), indicated that ectopic CREMtau protein had a CRE-dependent stimulatory effect on BLV promoter transcriptional activity. Cross-link of the B-cell receptor potentiated CREMtau transactivation of the viral promoter. Further experiments supported the notion that this potentiation involved CREMtau Ser-117 phosphorylation and recruitment of CBP/p300 to the BLV promoter. Although CREB and Tax(BLV) synergistically transactivated the BLV promoter, CREMtau repressed this Tax(BLV)/CREB synergism, suggesting that a modulation of the level of Tax(BLV) transactivation through opposite actions of CREB and CREMtau could facilitate immune escape and allow tumor development.
Collapse
Affiliation(s)
- Thi Lien-Anh Nguyên
- Institut de Biologie et de Médecine Moléculaires, Laboratoire de Virologie Moléculaire, Université Libre de Bruxelles, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | | | | | | | | | | | | | | | | |
Collapse
|
38
|
Tirard M, Almeida OFX, Hutzler P, Melchior F, Michaelidis TM. Sumoylation and proteasomal activity determine the transactivation properties of the mineralocorticoid receptor. Mol Cell Endocrinol 2007; 268:20-9. [PMID: 17314004 DOI: 10.1016/j.mce.2007.01.010] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2006] [Revised: 01/16/2007] [Accepted: 01/17/2007] [Indexed: 12/31/2022]
Abstract
MR is a hormone-activated transcription factor that carries a strong synergy inhibitory function at its N-terminus. Using this region as bait in a yeast two-hybrid screening, we isolated major components of the sumoylation pathway, including the SUMO-1-conjugating enzyme Ubc9, and SUMO-1 itself. We found that MR interacts with both, Ubc9 and SUMO-1 in mammalian cells, and that the receptor is sumoylated at four acceptor sites which are clustered within its AF-1 domain. We observed that MR can be poly-ubiquitinated and that proteasome activity is essential for MR-activated transcription. Disruption of the SUMO-1 attachment sites abolished MR sumoylation but interfered with neither the poly-ubiquitination of the receptor nor its transactivation potential on MMTV. However, the hormone-activated mutant displayed enhanced synergistic potential on a compound promoter and delayed mobility in the nucleus. FRAP analysis further showed that proteasome inhibition immobilizes a subpopulation of unliganded MR receptors in the nucleus, a phenomenon that is significantly attenuated in the presence of aldosterone. Interestingly, the ability of the hormone to counteract the immobilizing effect of MG132 requires the sumoylation-competent form of MR. Moreover, increasing exogenously SUMO-1 cellular levels resulted in a selective, dose-dependent inhibition of the activity of the sumoylation-deficient MR. This effect was observed only on a synergy-competent promoter, revealing a mode for negative regulation of synergy that might involve sumoylation of factors different from MR. The data suggest that the overall transcriptional activity of MR can be modulated by its sumoylation potential as well as the sumoylation level of MR-interacting proteins, and requires the continuous function of the proteasome.
Collapse
Affiliation(s)
- M Tirard
- Max Planck Institute of Psychiatry, 80804 Munich, Germany.
| | | | | | | | | |
Collapse
|
39
|
Wierstra I, Alves J. FOXM1c and Sp1 transactivate the P1 and P2 promoters of human c-myc synergistically. Biochem Biophys Res Commun 2007; 352:61-8. [PMID: 17141659 DOI: 10.1016/j.bbrc.2006.10.151] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2006] [Accepted: 10/26/2006] [Indexed: 12/31/2022]
Abstract
We have previously shown that FOXM1c transactivates the c-myc P1 and P2 promoters via their TATA-boxes by a new transactivation mechanism, namely by directly binding to the P1 and P2 TATA-boxes and to TBP, TFIIA, and TFIIB. We now confirm this surprising mechanism by demonstrating that FOXM1c transactivates the human c-myc P1 and P2 promoters synergistically with Sp1, a transcription factor known to bind and transactivate these two promoters. This synergism requires the P1 or P2 TATA-boxes as well as the respective Sp1-binding sites. Moreover FOXM1c binds directly to Sp1. Cooperative DNA binding, if it should occur, is not sufficient for synergism of Sp1 and FOXM1c at P1, but their contacts to multiple components of the basal transcription complex (TFIID, TFIIA, TFIIB) seem to be essential. However, FOXM1c does not synergize with Sp1 if it transactivates via its conventional binding site.
Collapse
Affiliation(s)
- Inken Wierstra
- Institute of Molecular Biology, Medical School Hannover, Carl-Neuberg-Str. 1, D-30625 Hannover, Germany.
| | | |
Collapse
|
40
|
Abstract
The genome supplies information on both the quality and quantity of the transcriptome. However, as it remains unknown how a cell determines transcript levels from the genome sequences, despite comprehensive knowledge of the cellular components involved, the quantity information held by the genome cannot as yet be derived from nucleotide sequences. The model presented here explains on a thermodynamic basis how the components decode the genome to form and maintain the transcriptome. The model describes the level of a transcript as a pseudo-equilibrium between velocities of synthesis and degradation, both of which are controlled by sequence-specific interactions between protein factors and nucleic acids. Each of the transcript levels can be described by a single equation expressing a function of the activity concentrations of the protein factors. Quantitative information in the genome can thus be transformed into constants determined from the nucleotide sequences. Using this model, the transcriptome can be traced back to the protein factors and the state of chromosome packaging. The total description of transcript levels allows the model to be verified through comparison of derived hypotheses with comprehensive measurements of the transcriptome. The hypotheses thus derived in the present study are well supported by experimental microarray data, confirming the appropriateness of the model.
Collapse
Affiliation(s)
- Tomokazu Konishi
- Faculty of Bioresource Sciences, Akita Prefectural University, Shimoshinjyo, Nakano, Akita 010-0195, Japan.
| |
Collapse
|
41
|
Kasper LH, Boussouar F, Boyd K, Xu W, Biesen M, Rehg J, Baudino TA, Cleveland JL, Brindle PK. Two transactivation mechanisms cooperate for the bulk of HIF-1-responsive gene expression. EMBO J 2005; 24:3846-58. [PMID: 16237459 PMCID: PMC1283945 DOI: 10.1038/sj.emboj.7600846] [Citation(s) in RCA: 121] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2005] [Accepted: 09/28/2005] [Indexed: 01/10/2023] Open
Abstract
The C-terminal activation domain (C-TAD) of the hypoxia-inducible transcription factors HIF-1alpha and HIF-2alpha binds the CH1 domains of the related transcriptional coactivators CREB-binding protein (CBP) and p300, an oxygen-regulated interaction thought to be highly essential for hypoxia-responsive transcription. The role of the CH1 domain in vivo is unknown, however. We created mutant mice bearing deletions in the CH1 domains (DeltaCH1) of CBP and p300 that abrogate their interactions with the C-TAD, revealing that the CH1 domains of CBP and p300 are genetically non-redundant and indispensable for C-TAD transactivation function. Surprisingly, the CH1 domain was only required for an average of approximately 35-50% of global HIF-1-responsive gene expression, whereas another HIF transactivation mechanism that is sensitive to the histone deacetylase inhibitor trichostatin A (TSA(S)) accounts for approximately 70%. Both pathways are required for greater than 90% of the response for some target genes. Our findings suggest that a novel functional interaction between the protein acetylases CBP and p300, and deacetylases, is essential for nearly all HIF-responsive transcription.
Collapse
Affiliation(s)
- Lawryn H Kasper
- Department of Biochemistry, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Fayçal Boussouar
- Department of Biochemistry, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Kelli Boyd
- Department of Pathology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Wu Xu
- Department of Biochemistry, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Michelle Biesen
- Department of Biochemistry, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Jerold Rehg
- Department of Pathology, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Troy A Baudino
- Department of Biochemistry, St Jude Children's Research Hospital, Memphis, TN, USA
| | - John L Cleveland
- Department of Biochemistry, St Jude Children's Research Hospital, Memphis, TN, USA
| | - Paul K Brindle
- Department of Biochemistry, St Jude Children's Research Hospital, Memphis, TN, USA
- Department of Biochemistry, St Jude Children's Research Hospital, 332 N Lauderdale, Memphis, TN 38105, USA. Tel.: +1 901 495 2522; Fax: +1 901 525 8025; E-mail:
| |
Collapse
|
42
|
Majmudar CY, Lum JK, Prasov L, Mapp AK. Functional specificity of artificial transcriptional activators. ACTA ACUST UNITED AC 2005; 12:313-21. [PMID: 15797215 DOI: 10.1016/j.chembiol.2005.01.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2004] [Revised: 01/19/2005] [Accepted: 01/20/2005] [Indexed: 12/01/2022]
Abstract
Misregulated transcription is linked to many human diseases, and thus artificial transcriptional activators are highly desirable as mechanistic tools and as replacements for their malfunctioning natural counterparts. We previously reported two artificial transcriptional activation domains obtained from synthetic peptide libraries screened for binding to the yeast transcription protein Med15(Gal11). Here we demonstrate that the transcriptional potency of the Med15 ligands is increased through straightforward structural alterations. These artificial activation domains upregulate transcription via specific Med15 binding interactions and do not function in mammalian cells, which lack Med15. This functional specificity stands in contrast to most natural or artificial activation domains that function across all eukaryotic cell types. The results indicate that the screening strategy holds excellent promise for identifying peptide and small molecule transcriptional activators that function by unique mechanisms with advantageous specificity properties.
Collapse
Affiliation(s)
- Chinmay Y Majmudar
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | | | | | | |
Collapse
|
43
|
Zang MX, Li Y, Xue LX, Jia HT, Jing H. Cooperative activation of atrial naturetic peptide promoter by dHAND and MEF2C. J Cell Biochem 2005; 93:1255-66. [PMID: 15486975 DOI: 10.1002/jcb.20225] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
An intricate array of cell-specific multiprotein complexes participate in programs of cell-specific gene expression through combinatorial interaction with different transcription factors and cofactors. The dHAND basic helix-loop-helix (bHLH) transcription factor, which is essential for heart development and extra embryonic structures, is thought to regulate cardiomyocyte-specific gene expression through combinatorial interactions with other cardiac-restricted transcription factors such as GATA4 and NKX2.5. Here, we determine that dHAND also interacts with the myocyte enhancer binding factor-2c (MEF2C) protein, which belongs to MADS-box transcription factors and is essential for heart development. dHAND and MEF2C synergistically activated expression of the atrial naturetic peptide gene (ANP) in transfected HeLa cells. GST-pulldown and immunoprecipitation assay demonstrate that full-length MEF2C protein is able to interact with dHAND in vitro and in vivo, just like MEF2A and bHLH transcription factors MyoD in skeletal muscle cells. In addition, electrophoretic mobility shift assays (EMSAs) demonstrate that MEF2C and dHAND do not influence each other's DNA binding activity. Using chromatin immunoprecipitation (ChIP) analysis in H9c2 cells we show that dHAND interact with MEF2C to form protein complex and bind A/T sequence in promoter of ANP. Taken together with previous observations, these results suggest the existence of large multiprotein transcriptional complex with core DNA binding proteins that physically interact with other transcriptional factors to form favorable conformation to potentiate transcription.
Collapse
Affiliation(s)
- Ming-Xi Zang
- Department of Nutrition & Food Hygiene, School of Public Health, Laboratory of Development Molecular Biology, Peking University Health Science Center, Beijing, China
| | | | | | | | | |
Collapse
|
44
|
Alex D, Lee KAW. RGG-boxes of the EWS oncoprotein repress a range of transcriptional activation domains. Nucleic Acids Res 2005; 33:1323-31. [PMID: 15743974 PMCID: PMC552958 DOI: 10.1093/nar/gki270] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The Ewings Sarcoma Oncoprotein (EWS) interacts with several components of the mammalian transcriptional and pre-mRNA splicing machinery and is also found in the cytoplasm and even on the cell surface. The apparently diverse cellular functions of EWS are, however, not well characterized. EWS harbours a potent N-terminal transcriptional activation domain (the EAD) that is revealed in the context of oncogenic EWS-fusion proteins (EFPs) and a C-terminal RNA-binding domain (RBD) that recruits pre-mRNA splicing factors and may couple transcription and splicing. In contrast to EFPs, the presumed transcriptional role of normal EWS remains enigmatic. Here, we report that multiple RGG-boxes within the RBD are necessary and sufficient for cis-repression of the EAD and that RGG-boxes can also repress in-trans, within dimeric partners. Lys can functionally substitute for Arg, indicating that the basic nature of the Arg side chain is the critical determinant of RGG-box-mediated repression. In addition to the EAD, RGG-boxes can repress a broad range of activation domains (including those of VP16, E1a and CREB), but repression can be alleviated by the simultaneous presence of more than one activation domain. We therefore propose that a key function of RGG boxes within native EWS is to restrict promiscuous activation by the EAD while still allowing EWS to enter functional transcription complexes and participate in other transactions involving pre-mRNAs.
Collapse
Affiliation(s)
| | - Kevin A. W. Lee
- To whom correspondence should be addressed. Tel: +852 2358 8636; Fax: +852 2358 1559;
| |
Collapse
|
45
|
Zang MX, Li Y, Wang H, Wang JB, Jia HT. Cooperative interaction between the basic helix-loop-helix transcription factor dHAND and myocyte enhancer factor 2C regulates myocardial gene expression. J Biol Chem 2004; 279:54258-63. [PMID: 15485823 DOI: 10.1074/jbc.m408502200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cardiac-restricted transcription factors dHAND and myocyte enhancer factor 2C are expressed in the developing heart and activate several cardiac promoters. However, their regulatory mechanisms are still to be understood. To elucidate their exact regulatory functions, we have developed an RNA interference strategy to specifically inhibit dHAND and myocyte enhancer factor 2C protein production in H9c2 cells, which are derived from rat embryonic heart. Expression of endogenous cardiac genes atrial natriuretic peptide and alpha-myosin heavy chain was down-regulated in H9c2 cells lacking both dHAND and myocyte enhancer factor 2C, indicating that these factors are required for the maintenance of the cardiac genetic program. Consistent with these, expression of atrial natriuretic peptide and alpha-myosin heavy chain was up-regulated in H9c2 cells, which overexpressed dHAND and myocyte enhancer factor 2C. In addition, dHAND and myocyte enhancer factor 2C interact to synergistically activate atrial natriuretic peptide and alpha-myosin heavy chain transcription. Furthermore, chromatin immunoprecipitation analysis in H9c2 cells treated with phenylephrine showed that dHAND and myocyte enhancer factor 2C protein complex bind to the A/T sequence on atrial natriuretic peptide promoter. Taken together, these results not only suggest that the complex cis-trans interaction of dHAND, myocyte enhancer factor 2C, and the target gene may fine-tune gene expression in cardiac myocytes but also provide a molecular paradigm to elucidate the mechanisms of action of dHAND and myocyte enhancer factor 2C in the developing heart.
Collapse
Affiliation(s)
- Ming-Xi Zang
- Laboratory of Development Molecular Biology, Department of Nutrition and Food Hygiene, School of Public Health, Peking University Health Science Center, Beijing 100083, China
| | | | | | | | | |
Collapse
|
46
|
Kühn U, Wahle E. Structure and function of poly(A) binding proteins. ACTA ACUST UNITED AC 2004; 1678:67-84. [PMID: 15157733 DOI: 10.1016/j.bbaexp.2004.03.008] [Citation(s) in RCA: 246] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2004] [Revised: 03/30/2004] [Accepted: 03/31/2004] [Indexed: 01/01/2023]
Abstract
Poly (A) tails are found at the 3' ends of almost all eukaryotic mRNAs. They are bound by two different poly (A) binding proteins, PABPC in the cytoplasm and PABPN1 in the nucleus. PABPC functions in the initiation of translation and in the regulation of mRNA decay. In both functions, an interaction with the m7G cap at the 5' end of the message plays an important role. PABPN1 is involved in the synthesis of poly (A) tails, increasing the processivity of poly (A) polymerase and contributing to defining the length of a newly synthesized poly (A) tail.
Collapse
Affiliation(s)
- Uwe Kühn
- Institut für Biochemie, Martin-Luther-Universität Halle-Wittenberg, Kurt-Mothes-Stasse. 3, D-06120 Halle, Germany
| | | |
Collapse
|
47
|
Abstract
Great advances have been made in the past three decades in understanding the molecular mechanics underlying protein synthesis in bacteria, but our understanding of the corresponding events in eukaryotic organisms is only beginning to catch up. In this review we describe the current state of our knowledge and ignorance of the molecular mechanics underlying eukaryotic translation. We discuss the mechanisms conserved across the three kingdoms of life as well as the important divergences that have taken place in the pathway.
Collapse
Affiliation(s)
- Lee D Kapp
- Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, Maryland 21205-2185, USA.
| | | |
Collapse
|
48
|
Nguyên TLA, Calomme C, Wijmeersch G, Nizet S, Veithen E, Portetelle D, de Launoit Y, Burny A, Van Lint C. Deacetylase inhibitors and the viral transactivator TaxBLV synergistically activate bovine leukemia virus gene expression via a cAMP-responsive element- and cAMP-responsive element-binding protein-dependent mechanism. J Biol Chem 2004; 279:35025-36. [PMID: 15163662 DOI: 10.1074/jbc.m404081200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Efficient bovine leukemia virus (BLV) transcription requires the virus-encoded transactivator Tax(BLV), which acts through three Tax(BLV)-responsive elements located in the 5' long terminal repeat. It has been proposed that the binding of the CRE-binding protein (CREB) and the activating transcription factor (ATF) to the three imperfect cAMP-responsive elements (CREs) located in each Tax(BLV)-responsive element mediates Tax(BLV) transactivation. Here we demonstrated that deacetylase inhibitors (HDACis) synergistically enhanced the transcriptional activation of the BLV promoter by Tax(BLV) in a CRE-dependent manner. Tax(BLV) was acetylated in vivo at its N(alpha) terminus but not at internal lysine residues. Rather, HDACi potentiation of Tax(BLV) transactivation was mediated by an HDACi indirect action that requires new protein synthesis. Mechanistically, using a dominant-negative form of CREB, we showed that Tax(BLV) and HDACi synergistically activated BLV gene expression via a CREB-dependent mechanism. Moreover, electrophoretic mobility shift assay and Western blot experiments revealed that HDACi increased the in vitro DNA binding activity of CREB/ATF but did not alter CREB/ATF intranuclear presence. Remarkably, chromatin immunoprecipitation assays demonstrated that HDACi treatment increased the level of CREB bound to the BLV promoter in vivo. Our results together suggest that an increase in CREB/ATF occupancy of the viral CREs in response to HDACi potentiates Tax(BLV) transactivation of the BLV promoter.
Collapse
Affiliation(s)
- Thi Liên-Anh Nguyên
- Université Libre de Bruxelles, Institut de Biologie et de Médecine Moléculaires, Service de Chimie Biologique, Laboratoire de Virologie Moléculaire, Rue des Profs Jeener et Brachet 12, 6041 Gosselies, Belgium
| | | | | | | | | | | | | | | | | |
Collapse
|
49
|
Bhargava A, Pearce D. Mechanisms of mineralocorticoid action: determinants of receptor specificity and actions of regulated gene products. Trends Endocrinol Metab 2004; 15:147-53. [PMID: 15109612 DOI: 10.1016/j.tem.2004.03.009] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The mineralocorticoid receptor (MR) and its close cousin, the glucocorticoid receptor (GR), share considerable structural and functional similarity, including indistinguishable DNA binding properties, yet they mediate distinct physiological responses in some tissues. Specificity is determined by their distinct interactions with other protein factors and modification by peptides, including the small ubiquitin modifier SUMO1. Serum and glucocorticoid-regulated kinase 1 (sgk1) is one key target gene of both MR and GR, and encodes a serine-threonine kinase that stimulates the apical membrane localization of the epithelial sodium channel ENaC. Sgk1 exerts its effects, at least in part, by inhibiting an isoform of the ENaC inhibitory ubiquitin ligase Nedd4-2. This review briefly summarizes two areas of mineralocorticoid research: molecular determinants of MR specificity, and the role of Sgk1 in mediating the effects of aldosterone on epithelial Na(+) transport.
Collapse
Affiliation(s)
- Aditi Bhargava
- Departments of Medicine and Cellular and Molecular Pharmacology, Box 2140, N272C Genentach Hall, University of California, San Francisco, CA 94143-2140, USA
| | | |
Collapse
|
50
|
Goutsias J, Kim S. A nonlinear discrete dynamical model for transcriptional regulation: construction and properties. Biophys J 2004; 86:1922-45. [PMID: 15041638 PMCID: PMC1304049 DOI: 10.1016/s0006-3495(04)74257-5] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2003] [Accepted: 11/17/2003] [Indexed: 10/21/2022] Open
Abstract
Transcriptional regulation is a fundamental mechanism of living cells, which allows them to determine their actions and properties, by selectively choosing which proteins to express and by dynamically controlling the amounts of those proteins. In this article, we revisit the problem of mathematically modeling transcriptional regulation. First, we adopt a biologically motivated continuous model for gene transcription and mRNA translation, based on first-order rate equations, coupled with a set of nonlinear equations that model cis-regulation. Then, we view the processes of transcription and translation as being discrete, which, together with the need to use computational techniques for large-scale analysis and simulation, motivates us to model transcriptional regulation by means of a nonlinear discrete dynamical system. Classical arguments from chemical kinetics allow us to specify the nonlinearities underlying cis-regulation and to include both activators and repressors as well as the notion of regulatory modules in our formulation. We show that the steady-state behavior of the proposed discrete dynamical system is identical to that of the continuous model. We discuss several aspects of our model, related to homeostatic and epigenetic regulation as well as to Boolean networks, and elaborate on their significance. Simulations of transcriptional regulation of a hypothetical metabolic pathway illustrate several properties of our model, and demonstrate that a nonlinear discrete dynamical system may be effectively used to model transcriptional regulation in a biologically relevant way.
Collapse
Affiliation(s)
- John Goutsias
- The Whitaker Biomedical Engineering Institute, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
| | | |
Collapse
|