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Nature Communications Jun 2024Mitochondrial transcription factor A (TFAM) employs DNA bending to package mitochondrial DNA (mtDNA) into nucleoids and recruit mitochondrial RNA polymerase (POLRMT) at...
Mitochondrial transcription factor A (TFAM) employs DNA bending to package mitochondrial DNA (mtDNA) into nucleoids and recruit mitochondrial RNA polymerase (POLRMT) at specific promoter sites, light strand promoter (LSP) and heavy strand promoter (HSP). Herein, we characterize the conformational dynamics of TFAM on promoter and non-promoter sequences using single-molecule fluorescence resonance energy transfer (smFRET) and single-molecule protein-induced fluorescence enhancement (smPIFE) methods. The DNA-TFAM complexes dynamically transition between partially and fully bent DNA conformational states. The bending/unbending transition rates and bending stability are DNA sequence-dependent-LSP forms the most stable fully bent complex and the non-specific sequence the least, which correlates with the lifetimes and affinities of TFAM with these DNA sequences. By quantifying the dynamic nature of the DNA-TFAM complexes, our study provides insights into how TFAM acts as a multifunctional protein through the DNA bending states to achieve sequence specificity and fidelity in mitochondrial transcription while performing mtDNA packaging.
Topics: DNA-Binding Proteins; Mitochondrial Proteins; Transcription Factors; DNA, Mitochondrial; DNA Packaging; Promoter Regions, Genetic; Fluorescence Resonance Energy Transfer; Humans; Nucleic Acid Conformation; Transcription Initiation, Genetic; Mitochondria; Single Molecule Imaging; DNA-Directed RNA Polymerases; Base Sequence; Protein Binding
PubMed: 38937458
DOI: 10.1038/s41467-024-49728-6 -
Cell Death & Disease Jun 2024In eukaryotes, the nucleolus is the critical non-membranous organelle within nuclei that is responsible for ribosomal DNA (rDNA) transcription and ribosome biogenesis....
In eukaryotes, the nucleolus is the critical non-membranous organelle within nuclei that is responsible for ribosomal DNA (rDNA) transcription and ribosome biogenesis. The transcription of rDNA, a rate-limiting step for ribosome biogenesis, is tightly regulated to meet the demand for global protein synthesis in response to cell physiology, especially in neurons, which undergo rapid changes in morphology and protein composition during development and synaptic plasticity. However, it is unknown how the pre-initiation complex for rDNA transcription is efficiently assembled within the nucleolus in neurons. Here, we report that the nucleolar protein, coronin 2B, regulates rDNA transcription and maintains nucleolar function through direct interaction with upstream binding factor (UBF), an activator of RNA polymerase I transcriptional machinery. We show that coronin 2B knockdown impairs the formation of the transcription initiation complex, inhibits rDNA transcription, destroys nucleolar integrity, and ultimately induces nucleolar stress. In turn, coronin 2B-mediated nucleolar stress leads to p53 stabilization and activation, eventually resulting in neuronal apoptosis. Thus, we identified that coronin 2B coordinates with UBF to regulate rDNA transcription and maintain proper nucleolar function in neurons.
Topics: Apoptosis; Cell Nucleolus; Neurons; Animals; Pol1 Transcription Initiation Complex Proteins; Humans; DNA, Ribosomal; Microfilament Proteins; Transcription, Genetic; Tumor Suppressor Protein p53; Mice; Stress, Physiological
PubMed: 38937439
DOI: 10.1038/s41419-024-06852-x -
Biochimie Jun 2024G-quadruplexes (G4s) are helical four-stranded nucleic acid structures that can form in guanine-rich sequences, which are mostly found in functional cellular regions,...
G-quadruplexes (G4s) are helical four-stranded nucleic acid structures that can form in guanine-rich sequences, which are mostly found in functional cellular regions, such as telomeres, promoters, and DNA replication origins. Great efforts are being made to target these structures towards the development of specific small molecule G4 binders for novel anti-cancer, neurological, and viral therapies. Here, we introduce an optical assay based on quenching of the intrinsic fluorescence of DNA G-quadruplexes for assessing and comparing the G4 binding affinity of various small molecule ligands in solutions. We show that the approach allows direct quantification of ligand binding towards distinctive G4 topologies. We believe that this method will facilitate quick and reliable evaluation of small molecule G4 ligands and support their development.
PubMed: 38936685
DOI: 10.1016/j.biochi.2024.06.009 -
Molecular Metabolism Jun 2024The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) continues to rise with the increasing obesity epidemic. Rezdiffra as an activator of a...
OBJECTIVE
The prevalence of metabolic dysfunction-associated steatotic liver disease (MASLD) continues to rise with the increasing obesity epidemic. Rezdiffra as an activator of a thyroid hormone receptor-beta is the only Food and Drug Administration approved therapy. As such, there is a critical need to improve our understanding of gene expression regulation and signaling transduction in MASLD to develop new therapies. Matrin-3 is a DNA- and RNA-binding protein involved in the pathogenesis of human diseases. Here we examined its previously uncharacterized role in limiting hepatic steatosis and stress response via the constitutive androstane receptor (CAR).
METHODS
Matrin-3 floxed and liver-specific knockout mice were fed either a chow diet or 60 kcal% high-fat diet (HFD) for up to 16 weeks. The mice were euthanized for different analysis including liver histology, lipid levels, and gene expression. Bulk RNA-seq, bulk ATAC-seq, and single-nucleus Multiome were used to examine changes of transcriptome and chromatin accessibility in the liver. Integrative bioinformatics analysis of our data and publicly available datasets and different biochemical assays were performed to identify underlying the molecular mechanisms mediating matrin-3's effects. Liver-tropic adeno-associated virus was used to restore the expression of CAR for lipid, acute phase genes, and histological analysis.
RESULTS
Matrin-3 expression is induced in the steatotic livers of mice. Liver-specific matrin-3 deletion exacerbated HFD-induced steatosis, acute phase response, and inflammation in the liver of female mice. The transcriptome and chromatin accessibility were re-programmed in the liver of these mice with signatures indicating that CAR signaling is dysregulated. Mechanistically, matrin-3 interacts with CAR mRNA, and matrin-3 deficiency promotes CAR mRNA degradation. Consequently, matrin-3 deletion impaired CAR signaling by reducing CAR expression. Matrin-3 levels positively correlate with CAR expression in human livers. Ces2a and Il1r1 were identified as new target genes of CAR. Interestingly, we found that CAR discords with the expression of its target genes including Cyp2b10 and Ces2a in response to HFD, indicating CAR signaling is dysregulated by HFD despite increased CAR expression. Dysregulated CAR signaling upon matrin-3 deficiency reduced Ces2a and de-repressed Il1r1 expression. CAR restoration partially abrogated the dysregulated gene expression, exacerbated hepatic steatosis, acute phase response, and inflammation in liver-specific matrin-3 knockout mice fed a HFD.
CONCLUSIONS
Our findings demonstrate that matrin-3 is a key upstream regulator maintaining CAR signaling upon metabolic stress, and the matrin-3-CAR axis limits hepatic steatosis and stress response signaling that may give insights for therapeutic intervention.
PubMed: 38936659
DOI: 10.1016/j.molmet.2024.101977 -
Journal of Hepatology Jun 2024Gut bacterial translocation contributes to immune dysfunction and spontaneous bacterial peritonitis (SBP) in cirrhosis. We hypothesized that exposure of peritoneal...
BACKGROUND & AIMS
Gut bacterial translocation contributes to immune dysfunction and spontaneous bacterial peritonitis (SBP) in cirrhosis. We hypothesized that exposure of peritoneal macrophages (PMs) to bacterial DNA results in type-I interferon (IFN) production, shaping subsequent immune responses, inflammasome activation, and the release of damage-associated molecular patterns (DAMPs).
METHODS
PMs from patients with cirrhosis were stimulated with E. coli single-stranded DNA (ssDNA), lipopolysaccharide LPS, and IFN or infected with E. coli, S. aureus, and Group B streptococcus in vitro. Cytokine release, inflammasome activation, and DAMP release were quantified by quantitative-PCR, ELISA, western blots, and reporter cells employing primary PMs, monocytes, and caspase-deficient THP-1 macrophages. Serum progranulin concentration was correlated with transplant-free survival in 77 patients with SBP.
RESULTS
E. coli ssDNA induced strong type-I IFN activity in PMs and monocytes, priming them for enhanced LPS-mediated tumor necrosis factor production without toll-like receptor 4 tolerance induction. During in vitro macrophage bacterial infection, type-I IFN release aligned with upregulated expression of IFN-regulatory factors (IRF)1/2 and guanylate binding proteins (GBP)2/5. PMs upregulated inflammasome-associated proteins and type-I IFN upon E. coli ssDNA exposure and released interleukin-1β upon bacterial infection. Proteomic screen in mouse macrophages revealed progranulin as being caspase-11-dependent during E. coli infection. PMs and THP-1 macrophages released significant amounts of progranulin when infected with S. aureus or E. coli via gasdermin-D in a type-I IFN and caspase-5-dependent manner. During SBP, PMs upregulated IRF1, GBP2/5 and caspase-5 and higher serum progranulin concentrations were indicative of lower 90-day transplant-free survival after SBP.
CONCLUSIONS
Type-I IFN shapes peritoneal immune responses and regulates caspase-5-mediated progranulin release during SBP.
IMPACT AND IMPLICATIONS
Patients with cirrhosis exhibit impaired immune responses and increased susceptibility to bacterial infections. This study reveals that type-I interferon responses, triggered by pathogen-associated molecular patterns, are crucial in regulating macrophage activation and priming them for inflammatory responses. Additionally, we elucidate the mechanisms by which type-I interferons promote the release of progranulin from macrophages during spontaneous bacterial peritonitis. Our findings enhance understanding of how bacterial translocation affects immune responses, identify novel biomarkers for inflammasome activation during infections, and point to potential therapeutic targets.
PubMed: 38936554
DOI: 10.1016/j.jhep.2024.06.019 -
Molecular Cell Jun 2024The bacterial world offers diverse strains for understanding medical and environmental processes and for engineering synthetic biological chassis. However, genetically...
The bacterial world offers diverse strains for understanding medical and environmental processes and for engineering synthetic biological chassis. However, genetically manipulating these strains has faced a long-standing bottleneck: how to efficiently transform DNA. Here, we report imitating methylation patterns rapidly in TXTL (IMPRINT), a generalized, rapid, and scalable approach based on cell-free transcription-translation (TXTL) to overcome DNA restriction, a prominent barrier to transformation. IMPRINT utilizes TXTL to express DNA methyltransferases from a bacterium's restriction-modification systems. The expressed methyltransferases then methylate DNA in vitro to match the bacterium's DNA methylation pattern, circumventing restriction and enhancing transformation. With IMPRINT, we efficiently multiplex methylation by diverse DNA methyltransferases and enhance plasmid transformation in gram-negative and gram-positive bacteria. We also develop a high-throughput pipeline that identifies the most consequential methyltransferases, and we apply IMPRINT to screen a ribosome-binding site library in a hard-to-transform Bifidobacterium. Overall, IMPRINT can enhance DNA transformation, enabling the use of sophisticated genetic manipulation tools across the bacterial world.
PubMed: 38936361
DOI: 10.1016/j.molcel.2024.06.003 -
Biomedicine & Pharmacotherapy =... Jun 2024Deciphering how hesperadin, a repurposed mammalian aurora kinase B inhibitor, affects the cellular pathways in Leishmania donovani might be beneficial. This...
Deciphering how hesperadin, a repurposed mammalian aurora kinase B inhibitor, affects the cellular pathways in Leishmania donovani might be beneficial. This investigation sought to assess the physiological effects of hesperadin on promastigotes of L. donovani, by altering the duration of treatment following exposure to hesperadin. Groups pre-treated with inhibitors such as EGTA, NAC, and z-VAD-fmk before hesperadin exposure were also included. Morphological changes by microscopy, ATP and ROS changes by luminometry; DNA degradation using agarose gel electrophoresis and metacaspase levels through RT-PCR were assessed. Flow cytometry was used to study mitochondrial depolarization using JC-1 and MitoTracker Red; mitochondrial-superoxide accumulation using MitoSOX; plasma membrane modifications using Annexin-V and propidium iodide, and lastly, caspase activation using ApoStat. Significant alterations in promastigote morphology were noted. Caspase activity and mitochondrial-superoxide rose early after exposure whereas mitochondrial membrane potential demonstrated uncharacteristic variations, with significant functional disturbances such as leakage of superoxide radicals after prolonged treatments. ATP depletion and ROS accumulation demonstrated inverse patterns, genomic DNA showed fragmentation and plasma membrane showed Annexin-V binding, soon followed by propidium iodide uptake. Multilobed macronuclei and micronuclei accumulated in hesperadin exposed cells before they disintegrated into necrotic debris. The pathologic alterations were unlike the intrinsic or extrinsic pathways of classical apoptosis and suggest a caspase-mediated cell death most akin to mitotic-catastrophe. Most likely, a G2/M transition block caused accumulation of death signals, disorganized spindles and mechanical stresses, causing changes in morphology, organellar functions and ultimately promastigote death. Thus, death was a consequence of mitotic-arrest followed by ablation of kinetoplast functions, often implicated in L. donovani killing.
PubMed: 38936193
DOI: 10.1016/j.biopha.2024.116960 -
Briefings in Bioinformatics May 2024Advances in chromatin mapping have exposed the complex chromatin hierarchical organization in mammals, including topologically associating domains (TADs) and their...
Advances in chromatin mapping have exposed the complex chromatin hierarchical organization in mammals, including topologically associating domains (TADs) and their substructures, yet the functional implications of this hierarchy in gene regulation and disease progression are not fully elucidated. Our study delves into the phenomenon of shared TAD boundaries, which are pivotal in maintaining the hierarchical chromatin structure and regulating gene activity. By integrating high-resolution Hi-C data, chromatin accessibility, and DNA double-strand breaks (DSBs) data from various cell lines, we systematically explore the complex regulatory landscape at high-level TAD boundaries. Our findings indicate that these boundaries are not only key architectural elements but also vibrant hubs, enriched with functionally crucial genes and complex transcription factor binding site-clustered regions. Moreover, they exhibit a pronounced enrichment of DSBs, suggesting a nuanced interplay between transcriptional regulation and genomic stability. Our research provides novel insights into the intricate relationship between the 3D genome structure, gene regulation, and DNA repair mechanisms, highlighting the role of shared TAD boundaries in maintaining genomic integrity and resilience against perturbations. The implications of our findings extend to understanding the complexities of genomic diseases and open new avenues for therapeutic interventions targeting the structural and functional integrity of TAD boundaries.
Topics: DNA Repair; Humans; DNA Breaks, Double-Stranded; Chromatin; Gene Expression Regulation; Transcription Factors; Animals; Genomics; Genomic Instability; Chromatin Assembly and Disassembly
PubMed: 38935071
DOI: 10.1093/bib/bbae306 -
Genome Biology and Evolution Jun 2024De novo genes emerge from non-coding regions of genomes via succession of mutations. Among others, such mutations activate transcription and create a new open reading...
De novo genes emerge from non-coding regions of genomes via succession of mutations. Among others, such mutations activate transcription and create a new open reading frame (ORF). Although the mechanisms underlying ORF emergence are well documented, relatively little is known about the mechanisms enabling new transcription events. Yet, in many species a continuum between absent and very prominent transcription has been reported for essentially all regions of the genome. In this study we searched for de novo transcripts by using newly assembled genomes and transcriptomes of seven inbred lines of Drosophila melanogaster, originating from six European and one African population. This setup allowed us to detect sample specific de novo transcripts, and compare them to their homologous non-transcribed regions in other samples, as well as genic and intergenic control sequences. We studied the association with transposable elements and the enrichment of transcription factor motifs upstream of de novo emerged transcripts and compared them with regulatory elements. We found that de novo transcripts overlap with TEs more often than expected by chance. The emergence of new transcripts correlates with regions of high GC content and TE expression. Moreover, upstream regions of de novo transcripts are highly enriched with regulatory motifs. Such motifs are more enriched in new transcripts overlapping with TEs, particularly DNA TEs, and are more conserved upstream de novo transcripts than upstream their 'non-transcribed homologs'. Overall, our study demonstrates that TE insertion is important for transcript emergence, partly by introducing new regulatory motifs from DNA TE families.
PubMed: 38934893
DOI: 10.1093/gbe/evae134 -
Indian Journal of Public Health Oct 2023LAMP assay is widely used for detecting pathogens. We observed that the conventional and gradient polymerase chain reaction (PCR) could not detect the extracted...
Electrophoresis of Amplicons is a Better Method to Understand the Performance of Loop-mediated Isothermal Amplification Assay for Screening the Presence of Escherichia coli in Water.
LAMP assay is widely used for detecting pathogens. We observed that the conventional and gradient polymerase chain reaction (PCR) could not detect the extracted Escherichia coli DNA; real-time PCR was able to detect up to a certain limit (10-8 bacterial dilution). At the same time, the LAMP assay could detect the bacteria at a much lower concentration (10-14 dilution). The results of the LAMP assay were evaluated using agarose gel electrophoresis and DNA binding dye (PicoGreen), but only gel electrophoresis gave reliable results. Therefore, we propose using electrophoresis-based amplicon detection to overcome the limitations of dye-based detection. We believe that this amplicon detection will go a long way in the screening of potable drinking water.
Topics: Escherichia coli; Nucleic Acid Amplification Techniques; Water Microbiology; Real-Time Polymerase Chain Reaction; Humans; Electrophoresis, Agar Gel; DNA, Bacterial; Molecular Diagnostic Techniques; Drinking Water
PubMed: 38934812
DOI: 10.4103/ijph.ijph_1628_22