1
|
Nakajima RT, Costa PR, Lemke N. Cooperative and sequence-dependent model for RNAP dynamics: Application to ribosomal gene transcription. J Theor Biol 2020; 488:110134. [PMID: 31874133 DOI: 10.1016/j.jtbi.2019.110134] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 11/11/2019] [Accepted: 12/19/2019] [Indexed: 11/29/2022]
Abstract
Escherichia coli ribosomal genes are a well-established experimental model used to investigate the transcription process. These genes are essential to cell physiology and are therefore strongly expressed. Multiple transcription units collaborate in rrn expression. Experiments involving electron microscopy have shown the non-uniform density of the RNA polymerases transcribing these ribosomal operons. Here, we investigate RNAP collaborative transcription in E. coli ribosomal genes using a stochastic sequence-dependent model that included interactions among the RNAPs. We achieved results consistent with experimental data using a model with variable parametrization for genic and intergenic regions, compared with previous attempts that used uniform parameters for genic and intergenic regions. Our model also showed that cooperative behaviour reduced the dwell times in pause sites predicted by the single-round approach but induced a new pausing event at an upstream position. This work may stimulate new experimental research and provide other scenarios to test our model predictions.
Collapse
Affiliation(s)
- Rafael Takahiro Nakajima
- Institute of Biosciences, UNESP - Univ Estadual Paulista, Department of Physics and Biophysics, Botucatu, 18618-689, Brazil.
| | - Pedro Rafael Costa
- Institute of Biosciences, UNESP - Univ Estadual Paulista, Department of Physics and Biophysics, Botucatu, 18618-689, Brazil.
| | - Ney Lemke
- Institute of Biosciences, UNESP - Univ Estadual Paulista, Department of Physics and Biophysics, Botucatu, 18618-689, Brazil.
| |
Collapse
|
2
|
Belitsky V, Schütz G. RNA Polymerase interactions and elongation rate. J Theor Biol 2019; 462:370-380. [DOI: 10.1016/j.jtbi.2018.11.025] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2018] [Revised: 11/19/2018] [Accepted: 11/26/2018] [Indexed: 11/30/2022]
|
3
|
Belitsky V, Schütz GM. Stationary RNA polymerase fluctuations during transcription elongation. Phys Rev E 2019; 99:012405. [PMID: 30780341 DOI: 10.1103/physreve.99.012405] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Indexed: 06/09/2023]
Abstract
We study fluctuation effects of nonsteric molecular interactions between RNA polymerase (RNAP) motors that move simultaneously on the same DNA track during transcription elongation. Based on a stochastic model that allows for the exact analytical computation of the stationary distribution of RNAPs as a function of their density, interaction strength, nucleoside triphosphate concentration, and rate of pyrophosphate release we predict an almost geometric headway distribution of subsequent RNAP transcribing on the same DNA segment. The localization length which characterizes the decay of the headway distribution depends directly only the average density of RNAP and the interaction strength, but not on specific single-RNAP properties. Density correlations are predicted to decay exponentially with the distance (in units of DNA base pairs), with a correlation length that is significantly shorter than the localization length.
Collapse
Affiliation(s)
- V Belitsky
- Instituto de Matemática e Estátistica, Universidade de São Paulo, Rua do Matão, 1010, CEP 05508-090 São Paulo, São Paulo, Brazil
| | - G M Schütz
- Institute of Complex Systems II, Theoretical Soft Matter and Biophysics, Forschungszentrum Jülich, 52425 Jülich, Germany
| |
Collapse
|
4
|
Abstract
The frequencies of transcription initiation of regulated and constitutive genes depend on the concentration of free RNA polymerase holoenzyme [Rf] near their promoters. Although RNA polymerase is largely confined to the nucleoid, it is difficult to determine absolute concentrations of [Rf] at particular locations within the nucleoid structure. However, relative concentrations of free RNA polymerase at different growth rates, [Rf]rel, can be estimated from the activities of constitutive promoters. Previous studies indicated that the rrnB P2 promoter is constitutive and that [Rf]rel in the vicinity of rrnB P2 increases with increasing growth rate. Recently it has become possible to directly visualize Rf in growing Escherichia coli cells. Here we examine some of the important issues relating to gene expression based on these new observations. We conclude that: (i) At a growth rate of 2 doublings/h, there are about 1000 free and 2350 non-specifically DNA-bound RNA polymerase molecules per average cell (12 and 28%, respectively, of 8400 total) which are in rapid equilibrium. (ii) The reversibility of the non-specific binding generates more than 1000 free RNA polymerase molecules every second in the immediate vicinity of the DNA. Of these, most rebind non-specifically to the DNA within a few ms; the frequency of non-specific binding is at least two orders of magnitude greater than specific binding and transcript initiation. (iii) At a given amount of RNA polymerase per cell, [Rf] and the density of non-specifically DNA-bound RNA polymerase molecules along the DNA both vary reciprocally with the amount of DNA in the cell. (iv) At 2 doublings/h an E. coli cell contains, on the average, about 1 non-specifically bound RNA polymerase per 9 kbp of DNA and 1 free RNA polymerase per 20 kbp of DNA. However some DNA regions (i.e. near active rRNA operons) may have significantly higher than average [Rf].
Collapse
|
5
|
Fange D, Mellenius H, Dennis PP, Ehrenberg M. Thermodynamic modeling of variations in the rate of RNA chain elongation of E. coli rrn operons. Biophys J 2014; 106:55-64. [PMID: 24411237 DOI: 10.1016/j.bpj.2013.11.4487] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Revised: 11/07/2013] [Accepted: 11/25/2013] [Indexed: 11/15/2022] Open
Abstract
Previous electron-microscopic imaging has shown high RNA polymerase occupation densities in the 16S and 23S encoding regions and low occupation densities in the noncoding leader, spacer, and trailer regions of the rRNA (rrn) operons in E. coli. This indicates slower transcript elongation within the coding regions and faster elongation within the noncoding regions of the operon. Inactivation of four of the seven rrn operons increases the transcript initiation frequency at the promoters of the three intact operons and reduces the time for RNA polymerase to traverse the operon. We have used the DNA sequence-dependent standard free energy variation of the transcription complex to model the experimentally observed changes in the elongation rate along the rrnB operon. We also model the stimulation of the average transcription rate over the whole operon by increasing rate of transcript initiation. Monte Carlo simulations, taking into account initiation of transcription, translocation, and backward and forward tracking of RNA polymerase, partially reproduce the observed transcript elongation rate variations along the rrn operon and fully account for the increased average rate in response to increased frequency of transcript initiation.
Collapse
Affiliation(s)
- David Fange
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Harriet Mellenius
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden
| | - Patrick P Dennis
- Janelia Farm Research Campus, Howard Hughes Medical Institute, Ashburn, Virginia
| | - Måns Ehrenberg
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, Sweden.
| |
Collapse
|
6
|
Hunt RC, Simhadri VL, Iandoli M, Sauna ZE, Kimchi-Sarfaty C. Exposing synonymous mutations. Trends Genet 2014; 30:308-21. [PMID: 24954581 DOI: 10.1016/j.tig.2014.04.006] [Citation(s) in RCA: 230] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Revised: 04/16/2014] [Accepted: 04/17/2014] [Indexed: 12/12/2022]
Abstract
Synonymous codon changes, which do not alter protein sequence, were previously thought to have no functional consequence. Although this concept has been overturned in recent years, there is no unique mechanism by which these changes exert biological effects. A large repertoire of both experimental and bioinformatic methods has been developed to understand the effects of synonymous variants. Results from this body of work have provided global insights into how biological systems exploit the degeneracy of the genetic code to control gene expression, protein folding efficiency, and the coordinated expression of functionally related gene families. Although it is now clear that synonymous variants are important in a variety of contexts, from human disease to the safety and efficacy of therapeutic proteins, there is no clear consensus on the approaches to identify and validate these changes. Here, we review the diverse methods to understand the effects of synonymous mutations.
Collapse
Affiliation(s)
- Ryan C Hunt
- Division of Hematology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD, USA.
| | - Vijaya L Simhadri
- Division of Hematology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD, USA
| | - Matthew Iandoli
- Division of Hematology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD, USA
| | - Zuben E Sauna
- Division of Hematology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD, USA.
| | - Chava Kimchi-Sarfaty
- Division of Hematology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD, USA.
| |
Collapse
|
7
|
Cooperative RNA polymerase molecules behavior on a stochastic sequence-dependent model for transcription elongation. PLoS One 2013; 8:e57328. [PMID: 23437369 PMCID: PMC3578854 DOI: 10.1371/journal.pone.0057328] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Accepted: 01/21/2013] [Indexed: 12/02/2022] Open
Abstract
The transcription process is crucial to life and the enzyme RNA polymerase (RNAP) is the major component of the transcription machinery. The development of single-molecule techniques, such as magnetic and optical tweezers, atomic-force microscopy and single-molecule fluorescence, increased our understanding of the transcription process and complements traditional biochemical studies. Based on these studies, theoretical models have been proposed to explain and predict the kinetics of the RNAP during the polymerization, highlighting the results achieved by models based on the thermodynamic stability of the transcription elongation complex. However, experiments showed that if more than one RNAP initiates from the same promoter, the transcription behavior slightly changes and new phenomenona are observed. We proposed and implemented a theoretical model that considers collisions between RNAPs and predicts their cooperative behavior during multi-round transcription generalizing the Bai et al. stochastic sequence-dependent model. In our approach, collisions between elongating enzymes modify their transcription rate values. We performed the simulations in Mathematica® and compared the results of the single and the multiple-molecule transcription with experimental results and other theoretical models. Our multi-round approach can recover several expected behaviors, showing that the transcription process for the studied sequences can be accelerated up to 48% when collisions are allowed: the dwell times on pause sites are reduced as well as the distance that the RNAPs backtracked from backtracking sites.
Collapse
|
8
|
Ehrenberg M, Bremer H, Dennis PP. Medium-dependent control of the bacterial growth rate. Biochimie 2012; 95:643-58. [PMID: 23228516 DOI: 10.1016/j.biochi.2012.11.012] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 11/22/2012] [Indexed: 11/26/2022]
Abstract
By combining results from previous studies of nutritional up-shifts we here re-investigate how bacteria adapt to different nutritional environments by adjusting their macromolecular composition for optimal growth. We demonstrate that, in contrast to a commonly held view the macromolecular composition of bacteria does not depend on the growth rate as an independent variable, but on three factors: (i) the genetic background (i.e. the strain used), (ii) the physiological history of the bacteria used for inoculation of a given growth medium, and (iii) the kind of nutrients in the growth medium. These factors determine the ribosome concentration and the average rate of protein synthesis per ribosome, and thus the growth rate. Immediately after a nutritional up-shift, the average number of ribosomes in the bacterial population increases exponentially with time at a rate which eventually is attained as the final post-shift growth rate of all cell components. After a nutritional up-shift from one minimal medium to another minimal medium of higher nutritional quality, ribosome and RNA polymerase syntheses are co-regulated and immediately increase by the same factor equal to the increase in the final growth rate. However, after an up-shift from a minimal medium to a medium containing all 20 amino acids, RNA polymerase and ribosome syntheses are no longer coregulated; a smaller rate of synthesis of RNA polymerase is compensated by a gradual increase in the fraction of free RNA polymerase, possibly due to a gradual saturation of mRNA promoters. We have also analyzed data from a recent publication, in which it was concluded that the macromolecular composition in terms of RNA/protein and RNA/DNA ratios is solely determined by the effector molecule ppGpp. Our analysis indicates that this is true only in special cases and that, in general, medium adaptation also depends on factors other than ppGpp.
Collapse
Affiliation(s)
- Måns Ehrenberg
- Department of Cell and Molecular Biology, BMC, Uppsala University, Box 596, S-751 24 Uppsala, Sweden.
| | | | | |
Collapse
|
9
|
Sauna ZE, Kimchi-Sarfaty C. Understanding the contribution of synonymous mutations to human disease. Nat Rev Genet 2011; 12:683-91. [PMID: 21878961 DOI: 10.1038/nrg3051] [Citation(s) in RCA: 679] [Impact Index Per Article: 52.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Synonymous mutations - sometimes called 'silent' mutations - are now widely acknowledged to be able to cause changes in protein expression, conformation and function. The recent increase in knowledge about the association of genetic variants with disease, particularly through genome-wide association studies, has revealed a substantial contribution of synonymous SNPs to human disease risk and other complex traits. Here we review current understanding of the extent to which synonymous mutations influence disease, the various molecular mechanisms that underlie these effects and the implications for future research and biomedical applications.
Collapse
Affiliation(s)
- Zuben E Sauna
- Laboratory of Hemostasis, Division of Hematology, Center for Biologics Evaluation and Research, Food and Drug Administration, 29 Lincoln Drive, Bethesda, Maryland 20892, USA.
| | | |
Collapse
|
10
|
Fredrick K, Ibba M. How the sequence of a gene can tune its translation. Cell 2010; 141:227-9. [PMID: 20403320 PMCID: PMC2866089 DOI: 10.1016/j.cell.2010.03.033] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Revised: 03/22/2010] [Accepted: 03/23/2010] [Indexed: 11/21/2022]
Abstract
Sixty-one codons specify 20 amino acids, offering cells many options for encoding a polypeptide sequence. Two new studies (Cannarrozzi et al., 2010; Tuller et al., 2010) now foster the idea that patterns of codon usage can control ribosome speed, fine-tuning translation to increase the efficiency of protein synthesis.
Collapse
Affiliation(s)
- Kurt Fredrick
- Department of Microbiology, Ohio State Biochemistry Program, and Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA.
| | | |
Collapse
|