1
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Kompaniiets D, Wang D, Yang Y, Hu Y, Liu B. Structure and molecular mechanism of bacterial transcription activation. Trends Microbiol 2024; 32:379-397. [PMID: 37903670 DOI: 10.1016/j.tim.2023.10.001] [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: 06/23/2023] [Revised: 09/27/2023] [Accepted: 10/03/2023] [Indexed: 11/01/2023]
Abstract
Transcription activation is an important checkpoint of regulation of gene expression which occurs in response to different intracellular and extracellular signals. The key elements in this signal transduction process are transcription activators, which determine when and how gene expression is activated. Recent structural studies on a considerable number of new transcription activation complexes (TACs) revealed the remarkable mechanistic diversity of transcription activation mediated by different factors, necessitating a review and re-evaluation of the transcription activation mechanisms. In this review, we present a comprehensive summary of transcription activation mechanisms and propose a new, elaborate, and systematic classification of transcription activation mechanisms, primarily based on the structural features of diverse TAC components.
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Affiliation(s)
- Dmytro Kompaniiets
- Section of Transcription and Gene Regulation, The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Dong Wang
- Section of Transcription and Gene Regulation, The Hormel Institute, University of Minnesota, Austin, MN 55912, USA
| | - Yang Yang
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, IA, USA
| | - Yangbo Hu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Center for Biosafety Mega-Science, Chinese Academy of Sciences, Wuhan 430071, China.
| | - Bin Liu
- Section of Transcription and Gene Regulation, The Hormel Institute, University of Minnesota, Austin, MN 55912, USA.
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2
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Cuba Samaniego C, Franco E. Ultrasensitive molecular controllers for quasi-integral feedback. Cell Syst 2021; 12:272-288.e3. [PMID: 33539724 DOI: 10.1016/j.cels.2021.01.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 09/22/2020] [Accepted: 01/11/2021] [Indexed: 12/24/2022]
Abstract
Feedback control has enabled the success of automated technologies by mitigating the effects of variability, unknown disturbances, and noise. While it is known that biological feedback loops reduce the impact of noise and help shape kinetic responses, many questions remain about how to design molecular integral controllers. Here, we propose a modular strategy to build molecular quasi-integral feedback controllers, which involves following two design principles. The first principle is to utilize an ultrasensitive response, which determines the gain of the controller and influences the steady-state error. The second is to use a tunable threshold of the ultrasensitive response, which determines the equilibrium point of the system. We describe a reaction network, named brink controller, that satisfies these conditions by combining molecular sequestration and an activation/deactivation cycle. With computational models, we examine potential biological implementations of brink controllers, and we illustrate different example applications.
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Affiliation(s)
- Christian Cuba Samaniego
- Mechanical and Aerospace Engineering, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Elisa Franco
- Mechanical and Aerospace Engineering, University of California at Los Angeles, Los Angeles, CA 90095, USA; Molecular Biology Institute, University of California at Los Angeles, Los Angeles, CA 90095, USA; Bioengineering, University of California at Los Angeles, Los Angeles, CA 90095, USA; Mechanical Engineering, University of California at Riverside, Riverside, CA 92521, USA.
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3
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Erlendsson S, Teilum K. Binding Revisited-Avidity in Cellular Function and Signaling. Front Mol Biosci 2021; 7:615565. [PMID: 33521057 PMCID: PMC7841115 DOI: 10.3389/fmolb.2020.615565] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Accepted: 12/09/2020] [Indexed: 12/16/2022] Open
Abstract
When characterizing biomolecular interactions, avidity, is an umbrella term used to describe the accumulated strength of multiple specific and unspecific interactions between two or more interaction partners. In contrast to the affinity, which is often sufficient to describe monovalent interactions in solution and where the binding strength can be accurately determined by considering only the relationship between the microscopic association and dissociation rates, the avidity is a phenomenological macroscopic parameter linked to several microscopic events. Avidity also covers potential effects of reduced dimensionality and/or hindered diffusion observed at or near surfaces e.g., at the cell membrane. Avidity is often used to describe the discrepancy or the "extra on top" when cellular interactions display binding that are several orders of magnitude stronger than those estimated in vitro. Here we review the principles and theoretical frameworks governing avidity in biological systems and the methods for predicting and simulating avidity. While the avidity and effects thereof are well-understood for extracellular biomolecular interactions, we present here examples of, and discuss how, avidity and the underlying kinetics influences intracellular signaling processes.
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Affiliation(s)
- Simon Erlendsson
- Structural Studies Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, United Kingdom.,Structural Molecular Biology Group, Novo Nordisk Foundation Centre for Protein Research, Faculty of Health and Medical Sciences University of Copenhagen, Copenhagen, Denmark
| | - Kaare Teilum
- Structural Biology and NMR Laboratory and the Linderstrøm-Lang Centre for Protein Science, Department of Biology, University of Copenhagen, Copenhagen, Denmark
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4
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Abstract
Life is sustained by a variety of cyclic processes such as cell division, muscle contraction, and neuron firing. The periodic signals powering these processes often direct a variety of other downstream systems, which operate at different time scales and must have the capacity to divide or multiply the period of the master clock. Period modulation is also an important challenge in synthetic molecular systems, where slow and fast components may have to be coordinated simultaneously by a single oscillator whose frequency is often difficult to tune. Circuits that can multiply the period of a clock signal (frequency dividers), such as binary counters and flip-flops, are commonly encountered in electronic systems, but design principles to obtain similar devices in biological systems are still unclear. We take inspiration from the architecture of electronic flip-flops, and we propose to build biomolecular period-doubling networks by combining a bistable switch with negative feedback modules that preprocess the circuit inputs. We identify a network motif and we show it can be "realized" using different biomolecular components; two of the realizations we propose rely on transcriptional gene networks and one on nucleic acid strand displacement systems. We examine the capacity of each realization to perform period-doubling by studying how bistability of the motif is affected by the presence of the input; for this purpose, we employ mathematical tools from algebraic geometry that provide us with valuable insights on the input/output behavior as a function of the realization parameters. We show that transcriptional network realizations operate correctly also in a stochastic regime when processing oscillations from the repressilator, a canonical synthetic in vivo oscillator. Finally, we compare the performance of different realizations in a range of realistic parameters via numerical sensitivity analysis of the period-doubling region, computed with respect to the input period and amplitude. Our mathematical and computational analysis suggests that the motif we propose is generally robust with respect to specific implementation details: functionally equivalent circuits can be built as long as the species-interaction topology is respected. This indicates that experimental construction of the circuit is possible with a variety of components within the rapidly expanding libraries available in synthetic biology.
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Affiliation(s)
- Christian Cuba Samaniego
- Mechanical Engineering, University of California at Riverside , Riverside, California 92521, United States
| | - Elisa Franco
- Mechanical Engineering, University of California at Riverside , Riverside, California 92521, United States
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5
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Leng F. Protein-induced DNA linking number change by sequence-specific DNA binding proteins and its biological effects. Biophys Rev 2017; 8:123-133. [PMID: 28510217 DOI: 10.1007/s12551-016-0239-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 05/27/2016] [Indexed: 12/18/2022] Open
Abstract
Sequence-specific DNA-binding proteins play essential roles in many fundamental biological events such as DNA replication, recombination, and transcription. One common feature of sequence-specific DNA-binding proteins is to introduce structural changes to their DNA recognition sites including DNA-bending and DNA linking number change (ΔLk). In this article, I review recent progress in studying protein-induced ΔLk by several sequence-specific DNA-binding proteins, such as E. coli cAMP receptor protein (CRP) and lactose repressor (LacI). It was demonstrated recently that protein-induced ΔLk is an intrinsic property for sequence-specific DNA-binding proteins and does not correlate to protein-induced other structural changes, such as DNA bending. For instance, although CRP bends its DNA recognition site by 90°, it was not able to introduce a ΔLk to it. However, LacI was able to simultaneously bend and introduce a ΔLk to its DNA binding sites. Intriguingly, LacI also constrained superhelicity within LacI-lac O1 complexes if (-) supercoiled DNA templates were provided. I also discuss how protein-induced ΔLk help sequence-specific DNA-binding proteins regulate their biological functions. For example, it was shown recently that LacI utilizes the constrained superhelicity (ΔLk) in LacI-lac O1 complexes and serves as a topological barrier to constrain free, unconstrained (-) supercoils within the 401-bp DNA loop. These constrained (-) supercoils enhance LacI's binding affinity and therefore the repression of the lac promoter. Other biological functions include how DNA replication initiators λ O and DnaA use the induced ΔLk to open/melt bacterial DNA replication origins.
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Affiliation(s)
- Fenfei Leng
- Biomolecular Sciences Institute and Department of Chemistry & Biochemistry, Florida International University, 11200 SW 8th Street, Miami, FL, 33199, USA.
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6
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Leng F. Protein-induced DNA linking number change by sequence-specific DNA binding proteins and its biological effects. Biophys Rev 2016; 8:197-207. [PMID: 28510223 DOI: 10.1007/s12551-016-0204-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 05/27/2016] [Indexed: 12/15/2022] Open
Abstract
Sequence-specific DNA-binding proteins play essential roles in many fundamental biological events such as DNA replication, recombination, and transcription. One common feature of sequence-specific DNA-binding proteins is to introduce structural changes to their DNA recognition sites including DNA-bending and DNA linking number change (ΔLk). In this article, I review recent progress in studying protein-induced ΔLk by several sequence-specific DNA-binding proteins, such as E. coli cAMP receptor protein (CRP) and lactose repressor (LacI). It was demonstrated recently that protein-induced ΔLk is an intrinsic property for sequence-specific DNA-binding proteins and does not correlate to protein-induced other structural changes, such as DNA bending. For instance, although CRP bends its DNA recognition site by 90°, it was not able to introduce a ΔLk to it. However, LacI was able to simultaneously bend and introduce a ΔLk to its DNA binding sites. Intriguingly, LacI also constrained superhelicity within LacI-lac O1 complexes if (-) supercoiled DNA templates were provided. I also discuss how protein-induced ΔLk help sequence-specific DNA-binding proteins regulate their biological functions. For example, it was shown recently that LacI utilizes the constrained superhelicity (ΔLk) in LacI-lac O1 complexes and serves as a topological barrier to constrain free, unconstrained (-) supercoils within the 401-bp DNA loop. These constrained (-) supercoils enhance LacI's binding affinity and therefore the repression of the lac promoter. Other biological functions include how DNA replication initiators λ O and DnaA use the induced ΔLk to open/melt bacterial DNA replication origins.
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Affiliation(s)
- Fenfei Leng
- Biomolecular Sciences Institute and Department of Chemistry & Biochemistry, Florida International University, 11200 SW 8th Street, Miami, FL, 33199, USA.
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7
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Fulcrand G, Dages S, Zhi X, Chapagain P, Gerstman BS, Dunlap D, Leng F. DNA supercoiling, a critical signal regulating the basal expression of the lac operon in Escherichia coli. Sci Rep 2016; 6:19243. [PMID: 26763930 PMCID: PMC4725879 DOI: 10.1038/srep19243] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Accepted: 12/10/2015] [Indexed: 12/20/2022] Open
Abstract
Escherichia coli lac repressor (LacI) is a paradigmatic transcriptional factor that controls the expression of lacZYA in the lac operon. This tetrameric protein specifically binds to the O1, O2 and O3 operators of the lac operon and forms a DNA loop to repress transcription from the adjacent lac promoter. In this article, we demonstrate that upon binding to the O1 and O2 operators at their native positions LacI constrains three (−) supercoils within the 401-bp DNA loop of the lac promoter and forms a topological barrier. The stability of LacI-mediated DNA topological barriers is directly proportional to its DNA binding affinity. However, we find that DNA supercoiling modulates the basal expression from the lac operon in E. coli. Our results are consistent with the hypothesis that LacI functions as a topological barrier to constrain free, unconstrained (−) supercoils within the 401-bp DNA loop of the lac promoter. These constrained (−) supercoils enhance LacI’s DNA-binding affinity and thereby the repression of the promoter. Thus, LacI binding is superhelically modulated to control the expression of lacZYA in the lac operon under varying growth conditions.
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Affiliation(s)
- Geraldine Fulcrand
- Biomolecular Sciences Institute, Florida International University, Miami, FL 33199.,Department of Chemistry &Biochemistry, Florida International University, Miami, FL 33199
| | - Samantha Dages
- Biomolecular Sciences Institute, Florida International University, Miami, FL 33199.,Department of Chemistry &Biochemistry, Florida International University, Miami, FL 33199
| | - Xiaoduo Zhi
- Biomolecular Sciences Institute, Florida International University, Miami, FL 33199.,Department of Chemistry &Biochemistry, Florida International University, Miami, FL 33199
| | - Prem Chapagain
- Biomolecular Sciences Institute, Florida International University, Miami, FL 33199.,Department of Physics, Florida International University, Miami, FL 33199
| | - Bernard S Gerstman
- Biomolecular Sciences Institute, Florida International University, Miami, FL 33199.,Department of Physics, Florida International University, Miami, FL 33199
| | - David Dunlap
- Department of Physics, Emory University, Atlanta, GA 30322
| | - Fenfei Leng
- Biomolecular Sciences Institute, Florida International University, Miami, FL 33199.,Department of Chemistry &Biochemistry, Florida International University, Miami, FL 33199
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8
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Schroeder LA, Gries TJ, Saecker RM, Record MT, Harris ME, DeHaseth PL. Evidence for a tyrosine-adenine stacking interaction and for a short-lived open intermediate subsequent to initial binding of Escherichia coli RNA polymerase to promoter DNA. J Mol Biol 2008; 385:339-49. [PMID: 18976666 DOI: 10.1016/j.jmb.2008.10.023] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2008] [Revised: 09/30/2008] [Accepted: 10/03/2008] [Indexed: 11/18/2022]
Abstract
Bacterial RNA polymerase and a "sigma" transcription factor form an initiation-competent "open" complex at a promoter by disruption of about 14 base pairs. Strand separation is likely initiated at the highly conserved -11 A-T base pair. Amino acids in conserved region 2.3 of the main Escherichia coli sigma factor, sigma(70), are involved in this process, but their roles are unclear. To monitor the fates of particular bases upon addition of RNA polymerase, promoters bearing single substitutions of the fluorescent A-analog 2-aminopurine (2-AP) at -11 and two other positions in promoter DNA were examined. Evidence was obtained for an open intermediate on the pathway to open complex formation, in which these 2-APs are no longer stacked onto their neighboring bases. The tyrosine at residue 430 in region 2.3 of sigma(70) was shown to be involved in quenching the fluorescence of a 2-AP substituted at -11, presumably through a stacking interaction. These data refine the structural model for open complex formation and reveal a novel interaction involved in DNA melting by RNA polymerase.
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Affiliation(s)
- Lisa A Schroeder
- Center for RNA Molecular Biology, Case Western Reserve University, Cleveland, OH 44106-4973, USA
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9
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Wade JT, Struhl K. The transition from transcriptional initiation to elongation. Curr Opin Genet Dev 2008; 18:130-6. [PMID: 18282700 DOI: 10.1016/j.gde.2007.12.008] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Accepted: 12/20/2007] [Indexed: 11/26/2022]
Abstract
Transcription is the first step in gene expression, and its regulation underlies multicellular development and the response to environmental changes. Most studies of transcriptional regulation have focused on the recruitment of RNA polymerase to promoters. However, recent work has shown that, for many promoters, post-recruitment steps in transcriptional initiation are likely to be rate limiting. The rate at which RNA polymerase transitions from transcriptional initiation to elongation varies dramatically between promoters and between organisms and is the target of multiple regulatory proteins that can function to both repress and activate transcription.
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Affiliation(s)
- Joseph T Wade
- Wadsworth Center, New York State Department of Health, Albany, NY 12208, United States.
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10
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Reppas NB, Wade JT, Church GM, Struhl K. The transition between transcriptional initiation and elongation in E. coli is highly variable and often rate limiting. Mol Cell 2007; 24:747-757. [PMID: 17157257 DOI: 10.1016/j.molcel.2006.10.030] [Citation(s) in RCA: 169] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Revised: 10/10/2006] [Accepted: 10/24/2006] [Indexed: 10/23/2022]
Abstract
We perform a genome-wide analysis of the transition between transcriptional initiation and elongation in Escherichia coli by determining the association of core RNA polymerase (RNAP) and the promoter-recognition factor sigma70 with respect to RNA transcripts. We identify 1286 sigma70-associated promoters, including many internal to known operons, and demonstrate that sigma70 is usually released very rapidly from elongating RNAP complexes. On average, RNAP density is higher at the promoter than in the coding sequence, although the ratio is highly variable among different transcribed regions. Strikingly, a significant fraction of RNAP-bound promoters is not associated with transcriptional activity, perhaps due to an intrinsic energetic barrier to promoter escape. Thus, the transition from transcriptional initiation to elongation is highly variable, often rate limiting, and in some cases is essentially blocked such that RNAP is effectively "poised" to transcribe only under the appropriate environmental conditions. The genomic pattern of RNAP density in E. coli differs from that in yeast and mammalian cells.
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Affiliation(s)
- Nikos B Reppas
- Harvard University Biophysics Program, Harvard Medical School, Boston, Massachusetts 02115; Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115
| | - Joseph T Wade
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115
| | - George M Church
- Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115
| | - Kevin Struhl
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115.
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11
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Bintu L, Buchler NE, Garcia HG, Gerland U, Hwa T, Kondev J, Phillips R. Transcriptional regulation by the numbers: models. Curr Opin Genet Dev 2005; 15:116-24. [PMID: 15797194 PMCID: PMC3482385 DOI: 10.1016/j.gde.2005.02.007] [Citation(s) in RCA: 511] [Impact Index Per Article: 26.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The expression of genes is regularly characterized with respect to how much, how fast, when and where. Such quantitative data demands quantitative models. Thermodynamic models are based on the assumption that the level of gene expression is proportional to the equilibrium probability that RNA polymerase (RNAP) is bound to the promoter of interest. Statistical mechanics provides a framework for computing these probabilities. Within this framework, interactions of activators, repressors, helper molecules and RNAP are described by a single function, the "regulation factor". This analysis culminates in an expression for the probability of RNA polymerase binding at the promoter of interest as a function of the number of regulatory proteins in the cell.
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12
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Roy S, Semsey S, Liu M, Gussin GN, Adhya S. GalR represses galP1 by inhibiting the rate-determining open complex formation through RNA polymerase contact: a GalR negative control mutant. J Mol Biol 2005; 344:609-18. [PMID: 15533432 DOI: 10.1016/j.jmb.2004.09.070] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2004] [Revised: 09/23/2004] [Accepted: 09/23/2004] [Indexed: 11/19/2022]
Abstract
GalR represses the galP1 promoter by a DNA looping-independent mechanism. Equilibrium binding of GalR and RNA polymerase to DNA, and real-time kinetics of base-pair distortion (isomerization) showed that the equilibrium dissociation constant of RNA polymerase-P1 closed complexes is largely unaffected in the presence of saturating GalR, indicating that mutual antagonism (steric hindrance) of the regulator and the RNA polymerase does not occur at this promoter. In fluorescence kinetics with 2-AP labeled P1 DNA, GalR inhibited the slower of the two-step base-pair distortion process. We isolated a negative control GalR mutant, S29R, which while bound to the operator DNA was incapable of repression of P1. Based on these results and previous demonstration that repression requires the C-terminal domain of the alpha subunit (alpha-CTD) of RNA polymerase, we propose that GalR establishes contact with alpha-CTD at the last resolved isomerization intermediate, forming a kinetic trap.
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Affiliation(s)
- Siddhartha Roy
- Laboratory of Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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13
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Liu M, Garges S, Adhya S. lacP1 promoter with an extended -10 motif. Pleiotropic effects of cyclic AMP protein at different steps of transcription initiation. J Biol Chem 2004; 279:54552-7. [PMID: 15385551 DOI: 10.1074/jbc.m408609200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cyclic AMP receptor protein (CRP), which activates transcription from the wild-type lacP1 promoter and most of its mutants, represses productive RNA synthesis from a lacP1 promoter variant that contains an extended -10 element, although CRP enhances RNA polymerase binding as well as open complex formation in both promoters. Moreover, abortive RNA synthesis, which is already higher in the extended -10 variant compared with the parent promoter, was further enhanced by CRP. These results, together with the observed decrease in productive RNA synthesis, indicate that CRP, while facilitating the earlier steps of initiation, inhibits transcription from the extended -10 lacP1 by hindering promoter clearance. We propose that CRP decreases energetic barriers to RNA polymerase binding, isomerization, and abortive RNA synthesis but stabilizes the abortive RNA initiating complex, which results in increasing the activation energy of the transition state before the elongation complex. The results demonstrate for the first time that a DNA-binding regulatory protein acts as an activator or a repressor in different steps of the transcription initiation pathway because of the energetic differences of the intermediate complex in the same promoter.
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Affiliation(s)
- Mofang Liu
- Laboratory of Molecular Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892-4264, USA
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14
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Liu M, Tolstorukov M, Zhurkin V, Garges S, Adhya S. A mutant spacer sequence between -35 and -10 elements makes the Plac promoter hyperactive and cAMP receptor protein-independent. Proc Natl Acad Sci U S A 2004; 101:6911-6. [PMID: 15118087 PMCID: PMC406441 DOI: 10.1073/pnas.0401929101] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To determine whether the spacer region between the -35 and -10 elements plays any sequence-specific role, we randomized the GC-rich sequence ((-20)CCGGCTCG(-13)) within the spacer region of the cAMP-dependent lac promoter and selected an activator-independent mutant, which showed extraordinarily high intrinsic activity. The hyperactive promoter is obtained by incorporation of a specific 10-bp-long AT-rich DNA sequence within the spacer, referred to as the -15 sequence, which must be juxtaposed to the upstream end of the -10 sequence for the hyperactivity. The transcription enhancement functions only in the presence of a -35 element. The spacer sequence enhanced both RNA polymerase binding and open complex formation. Isolated in the lac promoter, it also enhanced transcription when placed at two other unrelated promoters. Sequence analysis shows a low GC content and an abundance of stereochemically flexible TG:CA and TA:TA dimeric steps in the -18/-9 region and a strong correlation between the presence of flexible dimeric steps in this region and the intrinsic strength of the promoter.
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Affiliation(s)
- Mofang Liu
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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15
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Seredick SD, Spiegelman GB. The Bacillus subtilis response regulator Spo0A stimulates sigmaA-dependent transcription prior to the major energetic barrier. J Biol Chem 2004; 279:17397-403. [PMID: 14976210 DOI: 10.1074/jbc.m311190200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
At the spoIIG promoter phosphorylated Spo0A (Spo0A approximately P) binds 0A boxes overlapping the -35 element, interacting with RNA polymerase to facilitate open complex formation. We have compared in vitro transcription from a series of heteroduplex templates containing denatured regions within the promoters. Transcription from heteroduplex templates with 12, 8, or 6 base pairs denatured was independent of Spo0A approximately P, but heteroduplexes with 4 or 2 base pairs denatured required Spo0A approximately P for maximal levels of transcription. Investigation of the thermal dependence of transcription suggested that strand separation was the primary thermodynamic barrier to transcription initiation but indicated that Spo0A approximately P does not reduce this energetic barrier. Kinetic assays revealed that Spo0A approximately P stimulated both the rate of formation of initiated complexes as well as increasing the number of complexes capable of initiating transcription. These results imply that Spo0A approximately P stimulates transcription at least in part by stabilizing the RNA polymerase-spoIIG complex until contacts between RNA polymerase and the -10 element induce strand separation.
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Affiliation(s)
- Steve D Seredick
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
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16
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Roy S, Lim HM, Liu M, Adhya S. Asynchronous basepair openings in transcription initiation: CRP enhances the rate-limiting step. EMBO J 2004; 23:869-75. [PMID: 14963488 PMCID: PMC381006 DOI: 10.1038/sj.emboj.7600098] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2003] [Accepted: 12/15/2003] [Indexed: 11/08/2022] Open
Abstract
The mechanism of isomerization (basepair openings) during transcription initiation by RNA polymerase at the galP1 promoter of Escherichia coli was investigated by 2-aminopurine (2,AP) fluorescence. The fluorescence of 2,AP is quenched in DNA duplex and enhanced when the basepair is distorted or deformed. The increase of 2,AP fluorescence was used to monitor basepair distortion at several individual positions in the promoter. We observed that basepair distortions during isomerization are a multi-step process. Three distinct hitherto unresolved steps in kinetic terms were observed, where significant fluorescence change occurs: a fast step with a half-life of around 1 s, which is followed by two slower steps occurring with a half-life in the range of minutes at 25 degrees C. Contrary to commonly held expectations, basepairs at different positions opened by 2,AP assays without any obvious pattern, suggesting that basepair opening is an asynchronous multi-step process. cAMP.CRP, which activates transcription at galP1, enhanced the rate-limiting step.
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Affiliation(s)
- Siddhartha Roy
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
- Department of Biophysics, Bose Institute, Calcutta, India
| | - Heon Man Lim
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
- Department of Biology, Chungnam National University, Taejon, South Korea
| | - Mofang Liu
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Sankar Adhya
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
- Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, 37 Convent Dr., Rm 5138, Bethesda, MD 20892-4264, USA. Tel.: +1 301 496 2495; Fax: +1 301 480 7687; E-mail:
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