scholarly journals Modulating Fis and IHF binding specificity, crosstalk and regulatory logic through the engineering of complex promoters

2019 ◽  
Author(s):  
Lummy Maria Oliveira Monteiro ◽  
Ananda Sanches-Medeiros ◽  
Cauã Antunes Westmann ◽  
Rafael Silva-Rocha
Keyword(s):  
Gene Expression ◽  
Transcriptional Repression ◽  
Bacterial Genome ◽  
Binding Specificity ◽  
Regulatory Elements ◽  
Transcriptional Factors ◽  
Consensus Binding Site ◽  
Global Regulators ◽  
Gene Expression Control ◽  
Target Promoters

AbstractBacterial promoters are usually formed by multiplecis-regulatory elements recognized by a plethora of transcriptional factors (TFs). From those, global regulators are key elements since these TFs are responsible for the regulation of hundreds of genes in the bacterial genome. For instance, Fis and IHF are two global regulators which play a major role in gene expression control inEscherichia coliand usually multiplecis-regulatory elements for these proteins co-occur at target promoters. Here, we investigated the relationship between the architecture of thecis-regulatory elements for Fis and IHF inE. coli. For this, we constructed 42 synthetic promoter variants harboring consensuscis-elements for Fis and IHF at different distances from a core −35/−10 region and in different numbers and combinations. We first demonstrated that although Fis preferentially recognizes its consensuscis-element, it can also recognize, to some extent, the consensus binding site for IHF, and the same was true for IHF, which was also able of recognizing Fis binding sites. However, changing the arrangement of thecis-elements (i.e., the position or the number of sites) can completely abolish unspecific binding of both TFs. More remarkably, we demonstrate that combiningcis-elements for both TFs could result in Fis and IHF repressed or activated promoters depending on the final architecture of the promoters in an unpredictable way. Taken together, the data presented here demonstrate how small changes in the architecture of bacterial promoters could result in drastic changes in the final regulatory logic of the system, with important implications for the understanding of natural complex promoters in bacteria and their engineering for novel applications.ImportanceThe understanding of the regulatory complex in bacteria is a key issue in modern microbiology. Here, we constructed synthetic bacterial promoters in order to investigate how binding of transcriptional factors to multiple target sites at the promoters can influence gene expression. Our results demonstrate in a systematic way that the arrangement and number of thesecis-regulatory elements are crucial for the final expression dynamics of the target promoters. In particular, we show that TF binding specificity or promiscuity can be modulated using different promoter architectures based on consensuscis-regulatory elements, and that transcriptional repression and activation can also be affected by promoter architecture. These results are relevant both for the understanding of natural systems and for the construction of synthetic circuits for biotechnological applications.

scholarly journals Synthetic gene regulatory networks in the opportunistic human pathogen Streptococcus pneumoniae

2019 ◽  
Author(s):  
Robin A. Sorg ◽  
Clement Gallay ◽  
Jan-Willem Veening
Keyword(s):  
Gene Expression ◽  
Streptococcus Pneumoniae ◽  
Regulatory Networks ◽  
Expression Patterns ◽  
Combinatorial Libraries ◽  
Regulatory Elements ◽  
Expression Control ◽  
Gene Expression Control

AbstractStreptococcus pneumoniae can cause disease in various human tissues and organs, including the ear, the brain, the blood and the lung, and thus in highly diverse and dynamic environments. It is challenging to study how pneumococci control virulence factor expression, because cues of natural environments and the presence of an immune system are difficult to simulate in vitro. Here, we apply synthetic biology methods to reverse-engineer gene expression control in S. pneumoniae. A selection platform is described that allows for straightforward identification of transcriptional regulatory elements out of combinatorial libraries. We present TetR- and LacI-regulated promoters that show expression ranges of four orders of magnitude. Based on these promoters, regulatory networks of higher complexity are assembled, such as logic AND and IMPLY gates. Finally, we demonstrate single-copy genome-integrated toggle switches that give rise to bimodal population distributions. The tools described here can be used to mimic complex expression patterns, such as the ones found for pneumococcal virulence factors, paving the way for in vivo investigations of the importance of gene expression control on the pathogenicity of S. pneumoniae.

New insights into promoter–enhancer communication mechanisms revealed by dynamic single-molecule imaging

2021 ◽  
Author(s):  
Jieru Li ◽  
Alexandros Pertsinidis
Keyword(s):  
Gene Expression ◽  
Single Molecule ◽  
Target Genes ◽  
Regulatory Elements ◽  
Specific Gene ◽  
Single Molecule Imaging ◽  
Cell Type ◽  
Regulatory Information ◽  
Cell Type Specific ◽  
Target Promoters

Establishing cell-type-specific gene expression programs relies on the action of distal enhancers, cis-regulatory elements that can activate target genes over large genomic distances — up to Mega-bases away. How distal enhancers physically relay regulatory information to target promoters has remained a mystery. Here, we review the latest developments and insights into promoter–enhancer communication mechanisms revealed by live-cell, real-time single-molecule imaging approaches.

scholarly journals Synthetic gene-regulatory networks in the opportunistic human pathogenStreptococcus pneumoniae

2020 ◽  
Vol 117 (44) ◽  
pp. 27608-27619 ◽  
Author(s):  
Robin A. Sorg ◽  
Clement Gallay ◽  
Laurye Van Maele ◽  
Jean-Claude Sirard ◽  
Jan-Willem Veening
Keyword(s):  
Gene Expression ◽  
Virulence Factor ◽  
Gene Regulatory Networks ◽  
Regulatory Networks ◽  
Combinatorial Libraries ◽  
Regulatory Elements ◽  
Synthetic Gene ◽  
Expression Control ◽  
Gene Expression Control ◽  
Gene Regulatory

Streptococcus pneumoniaecan cause disease in various human tissues and organs, including the ear, the brain, the blood, and the lung, and thus in highly diverse and dynamic environments. It is challenging to study how pneumococci control virulence factor expression, because cues of natural environments and the presence of an immune system are difficult to simulate in vitro. Here, we apply synthetic biology methods to reverse-engineer gene expression control inS. pneumoniae. A selection platform is described that allows for straightforward identification of transcriptional regulatory elements out of combinatorial libraries. We present TetR- and LacI-regulated promoters that show expression ranges of four orders of magnitude. Based on these promoters, regulatory networks of higher complexity are assembled, such as logic AND gates and IMPLY gates. We demonstrate single-copy genome-integrated toggle switches that give rise to bimodal population distributions. The tools described here can be used to mimic complex expression patterns, such as the ones found for pneumococcal virulence factors. Indeed, we were able to rewire gene expression of the capsule operon, the main pneumococcal virulence factor, to be externally inducible (YES gate) or to act as an IMPLY gate (only expressed in absence of inducer). Importantly, we demonstrate that these synthetic gene-regulatory networks are functional in an influenza A virus superinfection murine model of pneumonia, paving the way for in vivo investigations of the importance of gene expression control on the pathogenicity ofS. pneumoniae.

scholarly journals Transcriptional Regulation in Ebola Virus: Effects of Gene Border Structure and Regulatory Elements on Gene Expression and Polymerase Scanning Behavior

2015 ◽  
Vol 90 (4) ◽  
pp. 1898-1909 ◽  
Author(s):  
Kristina Brauburger ◽  
Yannik Boehmann ◽  
Verena Krähling ◽  
Elke Mühlberger
Keyword(s):  
Gene Expression ◽  
Ebola Virus ◽  
Rna Virus ◽  
Regulatory Elements ◽  
Minor Role ◽  
Transcript Levels ◽  
Reading Frame ◽  
Noncoding Regions ◽  
Expression Control ◽  
Gene Expression Control

ABSTRACTThe highly pathogenic Ebola virus (EBOV) has a nonsegmented negative-strand (NNS) RNA genome containing seven genes. The viral genes either are separated by intergenic regions (IRs) of variable length or overlap. The structure of the EBOV gene overlaps is conserved throughout all filovirus genomes and is distinct from that of the overlaps found in other NNS RNA viruses. Here, we analyzed how diverse gene borders and noncoding regions surrounding the gene borders influence transcript levels and govern polymerase behavior during viral transcription. Transcription of overlapping genes in EBOV bicistronic minigenomes followed the stop-start mechanism, similar to that followed by IR-containing gene borders. When the gene overlaps were extended, the EBOV polymerase was able to scan the template in an upstream direction. This polymerase feature seems to be generally conserved among NNS RNA virus polymerases. Analysis of IR-containing gene borders showed that the IR sequence plays only a minor role in transcription regulation. Changes in IR length were generally well tolerated, but specific IR lengths led to a strong decrease in downstream gene expression. Correlation analysis revealed that these effects were largely independent of the surrounding gene borders. Each EBOV gene contains exceptionally long untranslated regions (UTRs) flanking the open reading frame. Our data suggest that the UTRs adjacent to the gene borders are the main regulators of transcript levels. A highly complex interplay between the differentcis-acting elements to modulate transcription was revealed for specific combinations of IRs and UTRs, emphasizing the importance of the noncoding regions in EBOV gene expression control.IMPORTANCEOur data extend those from previous analyses investigating the implication of noncoding regions at the EBOV gene borders for gene expression control. We show that EBOV transcription is regulated in a highly complex yet not easily predictable manner by a set of interactingcis-active elements. These findings are important not only for the design of recombinant filoviruses but also for the design of other replicon systems widely used as surrogate systems to study the filovirus replication cycle under low biosafety levels. Insights into the complex regulation of EBOV transcription conveyed by noncoding sequences will also help to interpret the importance of mutations that have been detected within these regions, including in isolates of the current outbreak.

scholarly journals Enhancer Deregulation in Myeloma

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. SCI-38-SCI-38
Author(s):  
Paola Neri
Keyword(s):  
Gene Expression ◽  
Transcriptional Repression ◽  
Gene Expression Regulation ◽  
Therapeutic Targets ◽  
Regulatory Elements ◽  
Dependent Manner ◽  
Cellular Viability ◽  
Direct Role ◽  
Myeloma Cells ◽  
Bet Inhibitors

Abstract The complexity of gene expression regulation is the result of a composite interplay between promoters, enhancers and other cis-acting regulatory elements bound by transcription factors (TFs) that controls the transcriptional activity of genes. Primary tumor cells, in comparison to their healthy counterparts, are known to display altered enhancer repertoires that are associated with tumor-specific transcription. Large groups of transcriptional enhancers cluster together to form super-enhancers (SEs). These elements have been shown to control genes that are important for maintaining cell identity but are also frequently associated with oncogenes as well as translocations that result in aberrant gene expression in cancer. Immunoglobulin (IGH, IGL, IGK) and non-immunoglobulin (PVT1, FAM46C, DUSP22, etc.) enhancers hijacking by variable genes (MYC, MAF, CCND1/2/3, MMSET, IRF4) is a recognized oncogenic driver event in multiple myeloma (MM). However, the identity of the TFs or transcriptional regulatory complexes binding and regulating the activity of these enhancers remains to be fully elucidated and may yield valuable therapeutic targets. In this regard, the bromodomain and extra-terminal (BET) inhibitors have emerged as promising molecules for the treatment of hematologic malignancies. BET family proteins are chromatin adaptors, functionally linked to important pathways for cellular viability and cancer signaling. In particular, BRD4 has a direct role in the transcription regulation of different genes involved in the cell cycle progression and cellular viability. The BET inhibitor JQ1 selectively inhibits BRD4 by competitively binding to the acetyl-lysine recognition pocket of BET bromodomains from chromatin leading to the inhibition of MYC transcription in a dose- and time-dependent manner. Thus, BRD4 has been recently described as a therapeutic target for MM, among other hematologic diseases. Constitutive activation of MYC signaling is detected in more than 60% of patient-derived MM cells and can be involved in the pathogenesis of MM through different mechanisms. One of the most common somatic genomic aberrations in early and late-stage MM is rearrangement or translocation of MYC. Regardless of whether MYC rearrangements occur at early or late stages of MM pathogenesis, MYC rearrangements may provide one of several critical events contributing to increased autonomy and a more aggressive phenotype. Moreover promiscuous rearrangements of the MYC locus are known to hijack enhancers and super-enhancers to dysregulate MYC expression in MM and are involved in its pathogenesis. The development of the immunomodulatory drugs (IMiDs) has contributed significantly to improve the outcomes of MM patients. They possess pleiotropic anti-MM properties and through CRBN binding they induce Ikaros and Aiolos ubiquitylation and proteasomal degradation with an ensuing transcriptional repression of MYC and IRF4, two essential factors for myeloma cells survival. However, is not clear how IKZF1/IKZF3 regulate MYC transcription and how myeloma cells acquire resistance to IMIDs, "beyond CRBN". In addition, acquired resistance to IMIDs and the loss of the transcriptional repression of MYC are nearly universal and occur in spite of sustained IKZF1/3 degradation suggesting that transcriptional rewiring may be sustaining hijacked enhancers activity and transcription of driver oncogenes. In this contest we have recently demonstrated that IMiDs are repressors of IKZF1/3-depedent oncogenic enhancers. Transcriptional plasticity with expression of extra-lineage TFs such as the ETS family member ETV4 sustains oncogenic enhancers in MM overcoming IKAROS and AIOLOS dependency and promoting IMiDs resistance. Therefore defining TFs occupancy and their circuitry at enhancers identifies "non-canonical" (aberrant) myeloma TFs dependency that may be linked to potential therapeutic targets. Disclosures Neri: Janssen: Consultancy, Honoraria; Celgene: Consultancy, Honoraria.

scholarly journals The KZFP/KAP1 system controls transposable elements-embedded regulatory sequences in adult T cells

2019 ◽  
Author(s):  
Flavia Marzetta ◽  
Laia Simó-Riudalbas ◽  
Julien Duc ◽  
Evarist Planet ◽  
Sonia Verp ◽  
...  
Keyword(s):  
Gene Expression ◽  
T Cells ◽  
Transposable Elements ◽  
Transcriptional Repression ◽  
Regulation Of Gene Expression ◽  
Embryonic Stem ◽  
Cell Receptor ◽  
Regulatory Elements ◽  
Regulatory Sequences ◽  
Adult Human

ABSTRACTTransposable elements-embedded regulatory sequences (TEeRS) are subjected to early embryonic repression through sequence-specific recruitment of KRAB zinc finger proteins (KZFPs), their cofactor KAP1/TRIM28 and associated chromatin modifiers. This modulates the TEeRS-mediated regulation of gene expression in embryonic stem cells (ESCs) and leads to DNA methylation-induced silencing. However, KZFPs are broadly expressed in adult tissues, suggesting that they control TEeRS throughout life. Confirming this hypothesis, we reveal here that the KZFP/KAP1 system exerts a highly dynamic control of TEeRS in adult human CD4+ T lymphocytes. First, we observed that in these cells many TEs are still bound by KAP1, the recruitment of which is dynamically regulated upon T cell receptor stimulation. Second, we found that KAP1 depletion induces broad transcriptional alterations in T cells, with de-repression of TE-based regulatory elements leading to the illegitimate activation of nearby genes. Finally, we show that the tissue-restricted expression of KZFPs correlates with KAP1-mediated lineage-specific chromatin signatures and transcriptional repression. These data support a model where TE-targeting KZFPs and KAP1 are important regulators of gene expression in adult human cells.

scholarly journals Emergent properties in complex synthetic bacterial promoters

2017 ◽  
Author(s):  
Lummy Maria Oliveira Monteiro ◽  
Letícia Magalhães Arruda ◽  
Rafael Silva-Rocha
Keyword(s):  
Gene Expression ◽  
Escherichia Coli ◽  
Binding Sites ◽  
Consensus Sequence ◽  
Regulation Of Gene Expression ◽  
Emergent Properties ◽  
Global Regulators ◽  
Up Elements ◽  
The Individual ◽  
Target Promoters

SummaryRegulation of gene expression in bacteria results from the interplay between transcriptional factors (TFs) at target promoters, and how the arrangement of binding sites determines the regulatory logic of promoters is not well known. Here, we generated and fully characterized a library of synthetic complex promoters for the global regulators, CRP and IHF, inEscherichia coli, formed by a weak -35/-10 consensus sequence preceded by four combinatorial binding sites for these TFs. We found that whilecis-elements for CRP preferentially activate promoters when located immediately upstream of the promoter consensus, binding sites for IHF mainly function as “UP” elements and stimulate transcription in several different architectures in the absence of this protein. However, the combination of CRP- and IHF-binding sites resulted in emergent properties in these complex promoters, where the activity of combinatorial promoters cannot be predicted from the individual behavior of its components. Taken together, the results presented here add to the information on architecture-logic of complex promoters in bacteria.

scholarly journals Chemical Inhibition of Apurinic-Apyrimidinic Endonuclease 1 Redox and DNA Repair Functions Affects the Inflammatory Response via Different but Overlapping Mechanisms

2021 ◽  
Vol 9 ◽  
Author(s):  
Thais Teixeira Oliveira ◽  
Fabrícia Lima Fontes-Dantas ◽  
Rayssa Karla de Medeiros Oliveira ◽  
Daniele Maria Lopes Pinheiro ◽  
Leonam Gomes Coutinho ◽  
...  
Keyword(s):  
Gene Expression ◽  
Dna Repair ◽  
Inflammatory Response ◽  
Target Genes ◽  
Transcriptional Factors ◽  
Dna Lesions ◽  
Master Regulator ◽  
Gene Expression Control ◽  
Chemical Inhibition ◽  
Upregulated Genes

The presence of oxidized DNA lesions, such as 7,8-dihydro-8-oxoguanine (8-oxoG) and apurinic/apyrimidinic sites (AP sites), has been described as epigenetic signals that are involved in gene expression control. In mammals, Apurinic-apyrimidinic endonuclease 1/Redox factor-1 (APE1/Ref-1) is the main AP endonuclease of the base excision repair (BER) pathway and is involved in active demethylation processes. In addition, APE1/Ref-1, through its redox function, regulates several transcriptional factors. However, the transcriptional control targets of each APE1 function are not completely known. In this study, a transcriptomic approach was used to investigate the effects of chemical inhibition of APE1/Ref-1 redox or DNA repair functions by E3330 or methoxyamine (MX) in an inflammatory cellular model. Under lipopolysaccharide (LPS) stimulation, both E3330 and MX reduced the expression of some cytokines and chemokines. Interestingly, E3330 treatment reduced cell viability after 48 h of the treatment. Genes related to inflammatory response and mitochondrial processes were downregulated in both treatments. In the E3330 treatment, RNA processing and ribosome biogenesis genes were downregulated, while they were upregulated in the MX treatment. Furthermore, in the E3330 treatment, the cellular stress response was the main upregulated process, while the cellular macromolecule metabolic process was observed in MX-upregulated genes. Nuclear respiratory factor 1 (NRF1) was predicted to be a master regulator of the downregulated genes in both treatments, while the ETS transcription factor ELK1 (ELK1) was predicted to be a master regulator only for E3330 treatment. Decreased expression of ELK1 and its target genes and a reduced 28S/18S ratio were observed, suggesting impaired rRNA processing. In addition, both redox and repair functions can affect the expression of NRF1 and GABPA target genes. The master regulators predicted for upregulated genes were YY1 and FLI1 for the E3330 and MX treatments, respectively. In summary, the chemical inhibition of APE1/Ref-1 affects gene expression regulated mainly by transcriptional factors of the ETS family, showing partial overlap of APE1 redox and DNA repair functions, suggesting that these activities are not entirely independent. This work provides a new perspective on the interaction between APE1 redox and DNA repair activity in inflammatory response modulation and transcription.

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