scholarly journals TNF stimulation primarily modulates transcriptional burst size of NF-κB-regulated genes

2020 ◽  
Author(s):  
Victor L. Bass ◽  
Victor C. Wong ◽  
M. Elise Bullock ◽  
Suzanne Gaudet ◽  
Kathryn Miller-Jensen
Keyword(s):  
Inflammatory Response ◽  
Rna Polymerase Ii ◽  
Computational Models ◽  
Target Genes ◽  
Burst Size ◽  
Inverse Correlation ◽  
Burst Frequency ◽  
Gene Expression Noise ◽  
Molecule Inhibitor ◽  
Single Transcript

AbstractCell-to-cell heterogeneity is a characteristic feature of the tumor necrosis factor (TNF)-stimulated inflammatory response mediated by the transcription factor NF-κB, motivating an exploration of the underlying sources of this noise. Here we combined single-transcript measurements with computational models to study transcriptional noise at six NF-κB-regulated inflammatory genes. In the basal state, NF-κB-target genes displayed an inverse correlation between mean and noise. TNF stimulation increased transcription while maintaining noise, except for the most repressed genes. By fitting transcript distributions to a two-state model of promoter activity, we found that TNF primarily stimulated transcription by increasing burst size while maintaining burst frequency. Burst size increases were associated with enrichment of initiated-but-paused RNA polymerase II at the promoter, and blocking the release of paused RNAPII with a small molecule inhibitor decreased TNF-stimulated burst size. Finally, we used a mathematical model to show that TNF positive feedback further amplified gene expression noise resulting from burst-size mediated transcription, leading to diverse TNF functional outputs. Our results reveal potential sources of noise underlying intercellular heterogeneity in the TNF-mediated inflammatory response.

scholarly journals Transcriptional bursting explains the noise-versus-mean relationship in mRNA and protein levels

2016 ◽  
Author(s):  
Roy D. Dar ◽  
Sydney M. Schaffer ◽  
Siddarth S. Dey ◽  
Jonathan E. Foley ◽  
Abhyudai Singh ◽  
...  
Keyword(s):  
Conflict Of Interest ◽  
Burst Size ◽  
Inverse Correlation ◽  
Recent Analysis ◽  
Mrna Levels ◽  
Burst Frequency ◽  
Expression Variability ◽  
Protein Levels ◽  
Transcriptional Bursting ◽  
Cell Expression

Recent analysis (Dey et al, 2015), demonstrates that the HIV-1 Long Terminal Repeat (HIV LTR) promoter exhibits a range of possible transcriptional burst sizes and frequencies for any mean-expression level. However, these results have also been interpreted as demonstrating that cell-to-cell expression variability (noise) and mean are uncorrelated, a significant deviation from previous results. Here, we re-examine the available mRNA and protein abundance data for the HIV LTR and find that noise in mRNA and protein expression scales inversely with the mean along analytically predicted transcriptional burst-size manifolds. We then experimentally perturb transcriptional activity to test a prediction of the multiple burst-size model: that increasing burst frequency will cause mRNA noise to decrease along given burst-size lines as mRNA levels increase. The data show that mRNA and protein noise decrease as mean expression increases, supporting the canonical inverse correlation between noise and mean.Conflict of InterestThe authors declare that they have no conflict of interest.

scholarly journals PRC1 drives Polycomb-mediated gene repression by controlling transcription initiation and burst frequency

2020 ◽  
Author(s):  
Paula Dobrinić ◽  
Aleksander T. Szczurek ◽  
Robert J. Klose
Keyword(s):  
Gene Expression ◽  
Rna Polymerase Ii ◽  
Transcription Initiation ◽  
Transcriptional Control ◽  
Target Genes ◽  
Gene Repression ◽  
Burst Frequency ◽  
Chromatin Domains ◽  
Time Resolved ◽  
Drive Gene

AbstractThe Polycomb repressive system plays a fundamental role in controlling gene expression during mammalian development. To achieve this, Polycomb repressive complexes 1 and 2 (PRC1 and PRC2) bind target genes and use histone modification-dependent feedback mechanisms to form Polycomb chromatin domains and repress transcription. The interrelatedness of PRC1 and PRC2 activity at these sites has made it difficult to discover the specific components of Polycomb chromatin domains that drive gene repression and to understand mechanistically how this is achieved. Here, by exploiting rapid degron-based approaches and time-resolved genomics we kinetically dissect Polycomb-mediated repression and discover that PRC1 functions independently of PRC2 to counteract RNA polymerase II binding and transcription initiation. Using single-cell gene expression analysis, we reveal that PRC1 acts uniformly within the cell population, and that repression is achieved by controlling transcriptional burst frequency. These important new discoveries provide a mechanistic and conceptual framework for Polycomb-dependent transcriptional control.

scholarly journals Flipping between Polycomb repressed and active transcriptional states introduces noise in gene expression

2017 ◽  
Author(s):  
Gozde Kar ◽  
Jong Kyoung Kim ◽  
Aleksandra A. Kolodziejczyk ◽  
Kedar Nath Natarajan ◽  
Elena Torlai Triglia ◽  
...  
Keyword(s):  
Gene Expression ◽  
Rna Polymerase Ii ◽  
Burst Size ◽  
Three Dimensions ◽  
Sequencing Data ◽  
Gene Expression Noise ◽  
Histone Modifiers ◽  
Transcriptional Bursting ◽  
Noise In Gene Expression ◽  
Active Genes

AbstractPolycomb repressive complexes (PRCs) are important histone modifiers, which silence gene expression, yet there exists a subset of PRC-bound genes actively transcribed by RNA polymerase II (RNAPII). It is likely that the role of PRC is to dampen expression of these PRC-active genes. However, it is unclear how this flipping between chromatin states alters the kinetics of transcriptional burst size and frequency relative to genes with exclusively activating marks. To investigate this, we integrate histone modifications and RNAPII states derived from bulk ChIP-seq data with single-cell RNA-sequencing data. We find that PRC-active genes have a greater cell-to-cell variation in expression than active genes with the same mean expression levels, and validate these results by knockout experiments. We also show that PRC-active genes are clustered on chromosomes in both two and three dimensions, and interactions with active enhancers promote a stabilization of gene expression noise. These findings provide new insights into how chromatin regulation modulates stochastic gene expression and transcriptional bursting, with implications for regulation of pluripotency and development.

scholarly journals High cooperativity in negative feedback can amplify noisy gene expression

2017 ◽  
Author(s):  
Pavol Bokes ◽  
Yen Ting Lin ◽  
Abhyudai Singh
Keyword(s):  
Gene Expression ◽  
Negative Feedback ◽  
Coefficient Of Variation ◽  
Burst Size ◽  
Burst Frequency ◽  
Gene Expression Noise ◽  
Protein Levels ◽  
Feedback Strength ◽  
Cell To Cell Variability ◽  
The Impact

AbstractBurst-like synthesis of protein is a significant source of cell-to-cell variability in protein levels. Negative feedback is a common example of a regulatory mechanism by which such stochasticity can be controlled. Here we consider a specific kind of negative feedback, which makes bursts smaller in the excess of protein. Increasing the strength of the feedback may lead to dramatically different outcomes depending on a key parameter, the noise load, which is defined as the squared coefficient of variation the protein exhibits in the absence of feedback. Combining stochastic simulation with asymptotic analysis, we identify a critical value of noise load: for noise loads smaller than critical, the coefficient of variation remains bounded with increasing feedback strength; contrastingly, if the noise load is larger than critical, the coefficient of variation diverges to infinity in the limit of ever greater feedback strengths. Interestingly, high-cooperativity feedbacks have lower critical noise loads, implying that low-cooperativity feedbacks in burst size can be preferable for noisy proteins. Finally, we discuss our findings in the context of previous results on the impact of negative feedback in burst size and burst frequency on gene-expression noise.

scholarly journals The Non-Canonical Aspects of MicroRNAs: Many Roads to Gene Regulation

Cells ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 1465 ◽  
Author(s):  
Christiaan J. Stavast ◽  
Stefan J. Erkeland
Keyword(s):  
Rna Polymerase Ii ◽  
Transcriptional Activation ◽  
Small Rnas ◽  
Target Genes ◽  
Biological Functions ◽  
Rnase Iii ◽  
Mrna Targets ◽  
Argonaute Proteins ◽  
Epigenetic Modifiers ◽  
Encoding Genes

MicroRNAs (miRNAs) are critical regulators of gene expression. As miRNAs are frequently deregulated in many human diseases, including cancer and immunological disorders, it is important to understand their biological functions. Typically, miRNA-encoding genes are transcribed by RNA Polymerase II and generate primary transcripts that are processed by RNase III-endonucleases DROSHA and DICER into small RNAs of approximately 21 nucleotides. All miRNAs are loaded into Argonaute proteins in the RNA-induced silencing complex (RISC) and act as post-transcriptional regulators by binding to the 3′- untranslated region (UTR) of mRNAs. This seed-dependent miRNA binding inhibits the translation and/or promotes the degradation of mRNA targets. Surprisingly, recent data presents evidence for a target-mediated decay mechanism that controls the level of specific miRNAs. In addition, several non-canonical miRNA-containing genes have been recently described and unexpected functions of miRNAs have been identified. For instance, several miRNAs are located in the nucleus, where they are involved in the transcriptional activation or silencing of target genes. These epigenetic modifiers are recruited by RISC and guided by miRNAs to specific loci in the genome. Here, we will review non-canonical aspects of miRNA biology, including novel regulators of miRNA expression and functions of miRNAs in the nucleus.

scholarly journals Live-cell imaging reveals the spatiotemporal organization of endogenous RNA polymerase II phosphorylation at a single gene

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Linda S. Forero-Quintero ◽  
William Raymond ◽  
Tetsuya Handa ◽  
Matthew N. Saxton ◽  
Tatsuya Morisaki ◽  
...  
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Single Molecule ◽  
Computational Models ◽  
Spatial Organization ◽  
Fluorescent Antibody ◽  
Single Gene ◽  
Single Copy ◽  
Living Cells ◽  
Live Cell

AbstractThe carboxyl-terminal domain of RNA polymerase II (RNAP2) is phosphorylated during transcription in eukaryotic cells. While residue-specific phosphorylation has been mapped with exquisite spatial resolution along the 1D genome in a population of fixed cells using immunoprecipitation-based assays, the timing, kinetics, and spatial organization of phosphorylation along a single-copy gene have not yet been measured in living cells. Here, we achieve this by combining multi-color, single-molecule microscopy with fluorescent antibody-based probes that specifically bind to different phosphorylated forms of endogenous RNAP2 in living cells. Applying this methodology to a single-copy HIV-1 reporter gene provides live-cell evidence for heterogeneity in the distribution of RNAP2 along the length of the gene as well as Serine 5 phosphorylated RNAP2 clusters that remain separated in both space and time from nascent mRNA synthesis. Computational models determine that 5 to 40 RNAP2 cluster around the promoter during a typical transcriptional burst, with most phosphorylated at Serine 5 within 6 seconds of arrival and roughly half escaping the promoter in ~1.5 minutes. Taken together, our data provide live-cell support for the notion of efficient transcription clusters that transiently form around promoters and contain high concentrations of RNAP2 phosphorylated at Serine 5.

scholarly journals The Integrator complex regulates microRNA abundance through RISC loading

2021 ◽  
Author(s):  
Nina Kirstein ◽  
Sadat Dokaneheifard ◽  
Pradeep Reddy Cingaram ◽  
Monica Guiselle Valencia ◽  
Felipe Beckedorff ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Molecular Mechanisms ◽  
Target Genes ◽  
Mature Mirnas ◽  
Mirna Biogenesis ◽  
Important Regulator ◽  
Rna Maturation ◽  
Nascent Transcripts ◽  
Post Transcriptional Regulation ◽  
Mirna Duplex

MicroRNA (miRNA) homeostasis is crucial for the post-transcriptional regulation of their target genes and miRNA dysregulation has been linked to multiple diseases, including cancer. The molecular mechanisms underlying miRNA biogenesis from processing of primary miRNA transcripts to formation of mature miRNA duplex are well understood. Loading of miRNA duplex into members of the Argonaute (Ago) protein family, representing the core of the RNA-induced silencing complex (RISC), is pivotal to miRNA-mediated gene silencing. The Integrator complex has been previously shown to be an important regulator of RNA maturation, RNA polymerase II pause-release, and premature transcriptional termination. Here, we report that loss of Integrator results in global diminution of mature miRNAs. By incorporating 4-Thiouridine (s4U) in nascent transcripts, we traced miRNA fate from biogenesis to stabilization and identified Integrator to be essential for proper miRNA assembly into RISC. Enhanced UV crosslinking and immunoprecipitation (eCLIP) of Integrator confirms a robust association with mature miRNAs. Indeed, Integrator potentiates Ago2-mediated cleavage of target RNAs. These findings highlight an essential role for Integrator in miRNA abundance and RISC function.

scholarly journals Elucidating the Mechanisms of Hugan Buzure Granule in the Treatment of Liver Fibrosis via Network Pharmacology

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Yi Zhu ◽  
Ming Qiao ◽  
Jianhua Yang ◽  
Junping Hu
Keyword(s):  
Liver Fibrosis ◽  
Rna Polymerase Ii ◽  
Molecular Mechanisms ◽  
Target Genes ◽  
Docking Simulation ◽  
Interaction Network ◽  
Network Pharmacology ◽  
Transcription Activator ◽  
Active Ingredients ◽  
Oxidoreductase Activity

Objective. To holistically explore the latent active ingredients, targets, and related mechanisms of Hugan buzure granule (HBG) in the treatment of liver fibrosis (LF) via network pharmacology. Methods. First, we collected the ingredients of HBG by referring the TCMSP server and literature and filtered the active ingredients though the criteria of oral bioavailability ≥30% and drug-likeness index ≥0.18. Second, herb-associated targets were predicted and screened based on the BATMAN-TCM and SwissTargetPrediction platforms. Candidate targets related to LF were collected from the GeneCards and OMIM databases. Furthermore, the overlapping target genes were used to construct the protein-protein interaction network and “drug-compound-target-disease” network. Third, GO and KEGG pathway analyses were carried out to illustrate the latent mechanisms of HBG in the treatment of LF. Finally, the combining activities of hub targets with active ingredients were further verified based on software AutoDock Vina. Results. A total of 25 active ingredients and 115 overlapping target genes of HBG and LF were collected. Besides, GO enrichment analysis exhibited that the overlapping target genes were involved in DNA-binding transcription activator activity, RNA polymerase II-specific, and oxidoreductase activity. Simultaneously, the key molecular mechanisms of HBG against LF were mainly involved in PI3K-AKT, MAPK, HIF-1, and NF-κB signaling pathways. Also, molecular docking simulation demonstrated that the key targets of HBG for antiliver fibrosis were IL6, CASP3, EGFR, VEGF, and MAPK. Conclusion. This work validated and predicted the underlying mechanisms of multicomponent and multitarget about HBG in treating LF and provided a scientific foundation for further research.

scholarly journals A Transcription Factor Pulse Can Prime Chromatin for Heritable Transcriptional Memory

2016 ◽  
Vol 37 (4) ◽  
Author(s):  
Aimee Iberg-Badeaux ◽  
Samuel Collombet ◽  
Benoit Laurent ◽  
Chris van Oevelen ◽  
Kuo-Kai Chin ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Rna Polymerase Ii ◽  
Target Genes ◽  
Short Term Memory ◽  
Epigenetic Mechanism ◽  
Short Term ◽  
Term Memory ◽  
Pol Ii ◽  
Transcriptional Memory

ABSTRACT Short-term and long-term transcriptional memory is the phenomenon whereby the kinetics or magnitude of gene induction is enhanced following a prior induction period. Short-term memory persists within one cell generation or in postmitotic cells, while long-term memory can survive multiple rounds of cell division. We have developed a tissue culture model to study the epigenetic basis for long-term transcriptional memory (LTTM) and subsequently used this model to better understand the epigenetic mechanisms that enable heritable memory of temporary stimuli. We find that a pulse of transcription factor CCAAT/enhancer-binding protein alpha (C/EBPα) induces LTTM on a subset of target genes that survives nine cell divisions. The chromatin landscape at genes that acquire LTTM is more repressed than at those genes that do not exhibit memory, akin to a latent state. We show through chromatin immunoprecipitation (ChIP) and chemical inhibitor studies that RNA polymerase II (Pol II) elongation is important for establishing memory in this model but that Pol II itself is not retained as part of the memory mechanism. More generally, our work reveals that a transcription factor involved in lineage specification can induce LTTM and that failure to rerepress chromatin is one epigenetic mechanism underlying transcriptional memory.

Sign in / Sign up

Export Citation Format

Share Document