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Impact of Negative Feedbacks on De Novo Pyrimidines Biosynthesis in Escherichia coli. Int J Mol Sci 2023; 24:ijms24054806. [PMID: 36902235 PMCID: PMC10003070 DOI: 10.3390/ijms24054806] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 02/25/2023] [Accepted: 02/28/2023] [Indexed: 03/06/2023] Open
Abstract
Earlier studies aimed at investigating the metabolism of endogenous nucleoside triphosphates in synchronous cultures of E. coli cells revealed an auto-oscillatory mode of functioning of the pyrimidine and purine nucleotide biosynthesis system, which the authors associated with the dynamics of cell division. Theoretically, this system has an intrinsic oscillatory potential, since the dynamics of its functioning are controlled through feedback mechanisms. The question of whether the nucleotide biosynthesis system has its own oscillatory circuit is still open. To address this issue, an integral mathematical model of pyrimidine biosynthesis was developed, taking into account all experimentally verified negative feedback in the regulation of enzymatic reactions, the data of which were obtained under in vitro conditions. Analysis of the dynamic modes of the model functioning has shown that in the pyrimidine biosynthesis system, both the steady-state and oscillatory functioning modes can be realized under certain sets of kinetic parameters that fit in the physiological boundaries of the investigated metabolic system. It has been demonstrated that the occurrence of the oscillatory nature of metabolite synthesis depended on the ratio of two parameters: the Hill coefficient, hUMP1-the nonlinearity of the UMP effect on the activity of carbamoyl-phosphate synthetase, and the parameter r characterizing the contribution of the noncompetitive mechanism of UTP inhibition to the regulation of the enzymatic reaction of UMP phosphorylation. Thus, it has been theoretically shown that the E. coli pyrimidine biosynthesis system possesses its own oscillatory circuit whose oscillatory potential depends to a significant degree on the mechanism of regulation of UMP kinase activity.
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Abstract
Even if a species' phenotype does not change over evolutionary time, the underlying mechanism may change, as distinct molecular pathways can realize identical phenotypes. Here we use linear system theory to explore the consequences of this idea, describing how a gene network underlying a conserved phenotype evolves, as the genetic drift of small changes to these molecular pathways causes a population to explore the set of mechanisms with identical phenotypes. To do this, we model an organism's internal state as a linear system of differential equations for which the environment provides input and the phenotype is the output, in which context there exists an exact characterization of the set of all mechanisms that give the same input-output relationship. This characterization implies that selectively neutral directions in genotype space should be common and that the evolutionary exploration of these distinct but equivalent mechanisms can lead to the reproductive incompatibility of independently evolving populations. This evolutionary exploration, or system drift, is expected to proceed at a rate proportional to the amount of intrapopulation genetic variation divided by the effective population size ( Ne$N_e$ ). At biologically reasonable parameter values this could lead to substantial interpopulation incompatibility, and thus speciation, on a time scale of Ne$N_e$ generations. This model also naturally predicts Haldane's rule, thus providing a concrete explanation of why heterogametic hybrids tend to be disrupted more often than homogametes during the early stages of speciation.
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Affiliation(s)
- Joshua S. Schiffman
- New York Genome CenterNew YorkNew York 10013,Weill Cornell MedicineNew YorkNew York 10065,Department of Molecular and Computational BiologyUniversity of Southern CaliforniaLos AngelesCalifornia 90089
| | - Peter L. Ralph
- Department of Molecular and Computational BiologyUniversity of Southern CaliforniaLos AngelesCalifornia 90089,Department of Mathematics, Institute of Ecology and EvolutionUniversity of OregonEugeneOregon 97403,Department of Biology, Institute of Ecology and EvolutionUniversity of OregonEugeneOregon 97403
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Singh A, Mahesh A, Noack F, Cardoso de Toledo B, Calegari F, Tiwari VK. Tcf12 and NeuroD1 cooperatively drive neuronal migration during cortical development. Development 2022; 149:dev200250. [PMID: 35147187 PMCID: PMC8918803 DOI: 10.1242/dev.200250] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 12/31/2021] [Indexed: 01/06/2023]
Abstract
Corticogenesis consists of a series of synchronised events, including fate transition of cortical progenitors, neuronal migration, specification and connectivity. NeuroD1, a basic helix-loop-helix (bHLH) transcription factor (TF), contributes to all of these events, but how it coordinates these independently is still unknown. Here, we demonstrate that NeuroD1 expression is accompanied by a gain of active chromatin at a large number of genomic loci. Interestingly, transcriptional activation of these loci relied on a high local density of adjacent bHLH TFs motifs, including, predominantly, Tcf12. We found that activity and expression levels of Tcf12 were high in cells with induced levels of NeuroD1 that spanned the transition of cortical progenitors from proliferative to neurogenic divisions. Moreover, Tcf12 forms a complex with NeuroD1 and co-occupies a subset of NeuroD1 target loci. This Tcf12-NeuroD1 cooperativity is essential for gaining active chromatin and targeted expression of genes involved in cell migration. By functional manipulation in vivo, we further show that Tcf12 is essential during cortical development for the correct migration of newborn neurons and, hence, for proper cortical lamination.
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Affiliation(s)
- Aditi Singh
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry & Biomedical Science, Queens University Belfast, Belfast BT9 7BL, UK
| | - Arun Mahesh
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry & Biomedical Science, Queens University Belfast, Belfast BT9 7BL, UK
| | - Florian Noack
- CRTD-Center for Regenerative Therapies, School of Medicine, Technische Universität Dresden, 01307 Dresden, Germany
| | - Beatriz Cardoso de Toledo
- CRTD-Center for Regenerative Therapies, School of Medicine, Technische Universität Dresden, 01307 Dresden, Germany
| | - Federico Calegari
- CRTD-Center for Regenerative Therapies, School of Medicine, Technische Universität Dresden, 01307 Dresden, Germany
| | - Vijay K. Tiwari
- Wellcome-Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry & Biomedical Science, Queens University Belfast, Belfast BT9 7BL, UK
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Garbuzov FE, Gursky VV. Nonequilibrium model of short-range repression in gene transcription regulation. Phys Rev E 2021; 104:014407. [PMID: 34412298 DOI: 10.1103/physreve.104.014407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2020] [Accepted: 06/24/2021] [Indexed: 11/07/2022]
Abstract
Transcription factors are proteins that regulate gene activity by activating or repressing gene transcription. A special class of transcriptional repressors operates via a short-range mechanism, making local DNA regions inaccessible to binding by activators, and thus providing an indirect repressive action on the target gene. This mechanism is commonly modeled assuming that repressors interact with DNA under thermodynamic equilibrium and neglecting some configurations of the gene regulatory region. We elaborate on a more general nonequilibrium model of short-range repression using the graph formalism for transitions between gene states, and we apply analytical calculations to compare it with the equilibrium model in terms of the repression strength and expression noise. In contrast to the equilibrium approach, the new model allows us to separate two basic mechanisms of short-range repression. The first mechanism is associated with the recruiting of factors that mediate chromatin condensation, and the second one concerns the blocking of factors that mediate chromatin loosening. The nonequilibrium model demonstrates better performance on previously published gene expression data obtained for transcription factors controlling Drosophila development, and furthermore it predicts that the first repression mechanism is the most favorable in this system. The presented approach can be scaled to larger gene networks and can be used to infer specific modes and parameters of transcriptional regulation from gene expression data.
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Affiliation(s)
- F E Garbuzov
- Ioffe Institute, 26 Polytekhnicheskaya, St. Petersburg 194021, Russia
| | - V V Gursky
- Ioffe Institute, 26 Polytekhnicheskaya, St. Petersburg 194021, Russia
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Makashov AA, Myasnikova EM, Spirov AV. Fuzzy Linguistic Modeling of the Regulation of Drosophila Segmentation Genes. Biophysics (Nagoya-shi) 2021. [DOI: 10.1134/s0006350921010073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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Chertkova AA, Schiffman JS, Nuzhdin SV, Kozlov KN, Samsonova MG, Gursky VV. In silico evolution of the Drosophila gap gene regulatory sequence under elevated mutational pressure. BMC Evol Biol 2017; 17:4. [PMID: 28251865 PMCID: PMC5333172 DOI: 10.1186/s12862-016-0866-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Cis-regulatory sequences are often composed of many low-affinity transcription factor binding sites (TFBSs). Determining the evolutionary and functional importance of regulatory sequence composition is impeded without a detailed knowledge of the genotype-phenotype map. RESULTS We simulate the evolution of regulatory sequences involved in Drosophila melanogaster embryo segmentation during early development. Natural selection evaluates gene expression dynamics produced by a computational model of the developmental network. We observe a dramatic decrease in the total number of transcription factor binding sites through the course of evolution. Despite a decrease in average sequence binding energies through time, the regulatory sequences tend towards organisations containing increased high affinity transcription factor binding sites. Additionally, the binding energies of separate sequence segments demonstrate ubiquitous mutual correlations through time. Fewer than 10% of initial TFBSs are maintained throughout the entire simulation, deemed 'core' sites. These sites have increased functional importance as assessed under wild-type conditions and their binding energy distributions are highly conserved. Furthermore, TFBSs within close proximity of core sites exhibit increased longevity, reflecting functional regulatory interactions with core sites. CONCLUSION In response to elevated mutational pressure, evolution tends to sample regulatory sequence organisations with fewer, albeit on average, stronger functional transcription factor binding sites. These organisations are also shaped by the regulatory interactions among core binding sites with sites in their local vicinity.
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Affiliation(s)
- Aleksandra A. Chertkova
- Systems Biology and Bioinformatics Laboratory, Peter the Great St. Petersburg Polytechnic University, Polytechnicheskaya, 29, St. Petersburg, 195251 Russia
| | - Joshua S. Schiffman
- Molecular and Computational Biology, University of Southern California, Los Angeles, 90089 CA USA
| | - Sergey V. Nuzhdin
- Systems Biology and Bioinformatics Laboratory, Peter the Great St. Petersburg Polytechnic University, Polytechnicheskaya, 29, St. Petersburg, 195251 Russia
- Molecular and Computational Biology, University of Southern California, Los Angeles, 90089 CA USA
| | - Konstantin N. Kozlov
- Systems Biology and Bioinformatics Laboratory, Peter the Great St. Petersburg Polytechnic University, Polytechnicheskaya, 29, St. Petersburg, 195251 Russia
| | - Maria G. Samsonova
- Systems Biology and Bioinformatics Laboratory, Peter the Great St. Petersburg Polytechnic University, Polytechnicheskaya, 29, St. Petersburg, 195251 Russia
| | - Vitaly V. Gursky
- Systems Biology and Bioinformatics Laboratory, Peter the Great St. Petersburg Polytechnic University, Polytechnicheskaya, 29, St. Petersburg, 195251 Russia
- Theoretical Department, Ioffe Institute, Polytechnicheskaya, 26, St. Petersburg, 194021 Russia
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Boeva V. Analysis of Genomic Sequence Motifs for Deciphering Transcription Factor Binding and Transcriptional Regulation in Eukaryotic Cells. Front Genet 2016; 7:24. [PMID: 26941778 PMCID: PMC4763482 DOI: 10.3389/fgene.2016.00024] [Citation(s) in RCA: 87] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 02/05/2016] [Indexed: 12/27/2022] Open
Abstract
Eukaryotic genomes contain a variety of structured patterns: repetitive elements, binding sites of DNA and RNA associated proteins, splice sites, and so on. Often, these structured patterns can be formalized as motifs and described using a proper mathematical model such as position weight matrix and IUPAC consensus. Two key tasks are typically carried out for motifs in the context of the analysis of genomic sequences. These are: identification in a set of DNA regions of over-represented motifs from a particular motif database, and de novo discovery of over-represented motifs. Here we describe existing methodology to perform these two tasks for motifs characterizing transcription factor binding. When applied to the output of ChIP-seq and ChIP-exo experiments, or to promoter regions of co-modulated genes, motif analysis techniques allow for the prediction of transcription factor binding events and enable identification of transcriptional regulators and co-regulators. The usefulness of motif analysis is further exemplified in this review by how motif discovery improves peak calling in ChIP-seq and ChIP-exo experiments and, when coupled with information on gene expression, allows insights into physical mechanisms of transcriptional modulation.
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Affiliation(s)
- Valentina Boeva
- Centre de Recherche, Institut CurieParis, France; INSERM, U900Paris, France; Mines ParisTechFontainebleau, France; PSL Research UniversityParis, France; Department of Development, Reproduction and Cancer, Institut CochinParis, France; INSERM, U1016Paris, France; Centre National de la Recherche Scientifique UMR 8104Paris, France; Université Paris Descartes UMR-S1016Paris, France
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Baranova AV, Orlov YL. The papers presented at 7th Young Scientists School "Systems Biology and Bioinformatics" (SBB'15): Introductory Note. Introduction. BMC Genet 2016; 17 Suppl 1:20. [PMID: 26822407 PMCID: PMC4895277 DOI: 10.1186/s12863-015-0326-5] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Affiliation(s)
- Ancha V Baranova
- Research Center for Medical Genetics RAMS, Moscow, Russian Federation. .,Center for the Study of Chronic Metabolic Diseases, School of System Biology, George Mason University, Fairfax, VA, USA.
| | - Yuriy L Orlov
- Institute of Cytology and Genetics, Siberian Branch, Russian Academy of Sciences, Lavrentieva ave., 10, Novosibirsk, 630090, Russian Federation.,Novosibirsk State University, Pirogova, 2, Novosibirsk, 630090, Russian Federation
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