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Designing enzymatic reaction networks capable of mimicking the complexity of biological information processing is challenging. Now, an in chemico reservoir sensor based on a recursive enzymatic competition network has been designed that can process diverse physical and chemical inputs and perform several information-processing tasks. Show less

Structured RNAs are increasingly explored as novel pharmacological targets for a range of diseases. Therefore, evaluating methods for RNA-focused hit discovery is crucial. Biolayer Interferometry (BLI), a label-free technique that detects biomolecular interactions by measuring changes in white light interference near the sensor surface, offers high throughput and multiplexing capabilities. While BLI has been widely adopted for protein-targeted screening, its application in RNA-targeted drug discovery remains largely unexplored. In this study, we demonstrate the effective use of BLI to investigate RNA–small molecule interactions using three different riboswitches, which are potential targets for novel antibiotics. Furthermore, we describe the successful use of BLI to identify fragment binders of these RNA targets. We combined the BLI experiments with ligand-based NMR as an orthogonal validation method and were able to identify seven competitive fragment binders of the flavin mononucleotide (FMN) riboswitch, each featuring scaffolds distinct from the previously known ligands. Show less

Differential and even opposing functions of two major antioxidant transcription factors Nrf1 and Nrf2 (encoded by Nfe2l1 and Nfe2l2, respectively) are determined by distinctions in their tempospatial positioning, topological repartitioning, proteolytic processing, and biochemical modification, as well as in their shared evolutionary origin. As a matter of fact, the allelopathic potentials of Nrf1 and Nrf2 (both resembling two entangled 'Yin-Yang' quanta that comply with a dialectic law of the unity of opposites) are fulfilled to coordinately control redox physiological homeostasis so as to be maintained within the presetting thresholds. By putative exponential curves of redox stress and intrinsic anti-redox capability, there is inferable to exist a set point at approaching zero with the 'Golden Mean' for the healthy survival (i.e., dubbed the 'zero theory'). A bulk of the hitherto accumulating evidence demonstrates that the set point of redox homeostasis is dictated selectively by multi-hierarchical threshold settings, in which the living fossil-like Nrf1 acts as a robust indispensable determinon, whereas Nrf2 serves as a versatile chameleon-like master regulon, in governing the redox homeodynamic ranges. This is attributable to the facts that Nrf2 has exerted certain 'double-edged sword' effects on life process, whereas Nrf1 executes its essential physiobiological functions, along with unique pathophysiological phenotypes, by integrating its 'three-in-one' roles elicited as a specific triplet of direct sensor, transducer and effector within multi-hierarchical stress responsive signaling to redox metabolism and target gene reprogramming. Here, we also critically reviewed redox regulation of physio-pathological functions from the eco-evo-devo perspectives, through those coding rules (redox code, stress-coping code, and topogenetic code). The evolving concepts on stress and redox stress were also further revisited by scientific principles of physics and chemistry. Besides, several novel concepts such as oncoprotists, Reverse Central Dogma, and Grand Redox-Unifying Theory' (GRUT) of life, together with diffusive reactive species (DRS)-based murburn concept integrating all stochastic electron-, proton- and/or moiety-transfer reactive and interactive processes (e.g., PCHEMS), are introduced in this interdisciplinary and synthetic review. Show less

ABSTRACTThe nucleolus, a prominent membrane‐less nuclear compartment, is organized around ribosomal RNA (rRNA) gene (rDNA) clusters, known as nucleolar organizing regions (NORs), located on the short arms of acrocentric chromosomes. It serves as the primary site for ribosome biogenesis, an energy‐intensive process crucial for cell growth and proliferation. This involves RNA polymerase I (Pol I)‐mediated transcription of 47S precursor rRNA (pre‐rRNA), pre‐rRNA processing, and ribosomal subunit assembly, reflected in its tripartite structure maintained by liquid–liquid phase separation. Recent evidence indicates that only about 30% of nucleolar proteins are exclusively involved in ribosome production. The remaining proteome participates in diverse cellular functions, establishing the nucleolus as a multifunctional organelle. It functions as a critical stress sensor and signaling hub, responding to various intracellular insults such as nutrient starvation, DNA damage, and viral infection. Many chemotherapeutic agents also induce the response called nucleolar stress via disruption of the nucleolar structure or function, potentially leading to rDNA instability. Nucleolar stress frequently leads to dynamic transition of nucleolar proteins, inducing nucleolar reorganization. Of these, the stress induced by transcriptional changes leads to the unique nucleolar structures termed nucleolar caps and nucleolar necklaces. In this review, we summarize the recent findings about the molecular mechanism of nucleolar changes upon stresses and discuss the possible relationship between rDNA instability and cancer. Show less

Abstract Neuroblastoma, a transcriptionally driven pediatric malignancy, exhibits a remarkable clinical and biological heterogeneity. Two major subtypes, the adrenergic and mesenchymal, are differentially governed by a subset of transcription factors that comprise the core regulatory circuit (CRC). The former subtype is often associated with MYCN amplification and is particularly aggressive and therapy-resistant, underscoring the need for novel targets. Here, we identify the multifunctional non-POU domain-containing octamer-binding (NONO) protein as a guardian of individual CRC genes, thereby contributing to survival of neuroblastoma cells with different MYCN copy numbers. Intracellular oxidation in response to auranofin, an inhibitor of thioredoxin reductase 1, rapidly down-regulated the amounts of NONO mRNA and protein in MYCN -amplified Kelly cell line. Conversely, NONO knockdown with RNA interference (siNONO) also triggered intracellular oxidation. These effects were less pronounced in the SK-N-AS cell line carrying a single MYCN copy, as well as in non-malignant HS5 fibroblasts. In Kelly cells, siNONO attenuated auranofin-induced activation of CRC genes HAND2 and PHOX2B . In line with preferential effects on NONO abundance, the Kelly cells were more sensitive than single MYCN copy counterparts to combinations of a sublethal concentration of auranofin with siNONO. Importantly, MYCN -amplified cells demonstrated a significantly suppressed clonogenic survival 14 days after transient exposure to these combinations compared with each agent alone; HS5 fibroblasts were largely spared. Our findings 1) establish NONO as a redox sensor, a non-trivial role for transcriptional proteins, and 2) justify the strategy of therapeutic targeting of MYCN -amplified tumors vulnerable to oxidative stress. Key points NONO, a master regulator of the core regulatory circuit (CRC) in MYCN -amplified neuroblastoma, is rapidly down-regulated by auranofin-induced intracellular oxidation. NONO knockdown synergizes with auranofin in triggering individual CRC gene deregulation and lethal oxidative stress preferentially in MYCN -amplified cells. Show less

Z-nucleic acid binding protein 1 (ZBP1) is an innate immune sensor recognizing nucleic acids in Z-conformation. Upon Z-nucleic acid sensing, ZBP1 triggers innate immune activation, inflammation, and programmed cell death during viral infections, mice development, and inflammation-associated diseases. The Zα domains of ZBP1 sense Z-nucleic acids and promote RIP-homotypic interaction motif (RHIM)-dependent signaling complex assembly to mount cell death and inflammation. The studies on ZBP1 spurred an understanding of the role of Z-form RNA and DNA in cellular and physiological functions. In particular, short viral genomic segments, endogenous retroviral elements, and 3'UTR regions are likely sources of Z-RNAs that orchestrate ZBP1 functions. Recent seminal studies identify an intriguing association of ZBP1 with adenosine deaminase acting on RNA-1 (ADAR1), and cyclic GMP-AMP synthase (cGAS) in regulating aberrant nucleic acid sensing, chronic inflammation, and cancer. Thus, ZBP1 is an attractive target to aid the development of specific therapeutic regimes for disease biology. Here, we discuss the role of ZBP1 in Z-RNA sensing, activation of programmed cell death, and inflammation. Also, we discuss how ZBP1 coordinates intracellular perturbations in homeostasis, and Z-nucleic acid formation to regulate chronic diseases and cancer. Show less

DNA crosslinking agents such as cisplatin and related platinum(II) analogs are effective drugs to treat solid tumors. However, these therapeutics can cause high toxicity in the body, and tumors can develop resistance to them. To develop less toxic and more effective DNA crosslinkers, medicinal chemists have focused on tuning the ligands in square planar platinum(II) complexes to modulate their bioavailability, targeted cell penetration, and DNA binding rates. Unfortunately, linking in vitro DNA binding capacity of DNA crosslinkers with their in vivo efficacy has proven challenging. Here we report an electrochemical biosensor strategy that allows the study of platinum(II)-DNA binding in real time. Our biosensors contain a purine-rich deoxynucleotide sequence, T6 (AG)10 , modified with a 5' hexylthiol linker for easy self-assembly onto gold electrodes. The 3' terminus is functionalized with the redox reporter methylene blue. Electron transfer from methylene blue to the sensor is a function of platinum(II) compound concentration and reaction time. Using these biosensors, we resolve DNA binding mechanisms including monovalent and bivalent binding, as well as base stacking. Our approach can measure DNA binding kinetics in buffers and in 50 % serum, offering a single-step, real-time approach to screen therapeutic compounds during drug development. Show less

Cyclic guanosine monophosphate (GMP)-AMP (cGAMP) synthase (cGAS) is a universal double-stranded DNA (dsDNA) sensor that recognizes foreign and self-DNA in the cytoplasm and initiates innate immune responses and has been implicated in various infectious and non-infectious contexts. cGAS binds to the backbone of dsDNA and generates the second messenger, cGAMP, which activates the stimulator of interferon genes (STING). Here, we show that the endogenous polyamines spermine and spermidine attenuated cGAS activity and innate immune responses. Mechanistically, spermine and spermidine induced the transition of B-form DNA to Z-form DNA (Z-DNA), thereby decreasing its binding affinity with cGAS. Spermidine/spermine N1-acetyltransferase 1 (SAT1), the rate-limiting enzyme in polyamine catabolism that decreases the cellular concentrations of spermine and spermidine, enhanced cGAS activation by inhibiting cellular Z-DNA accumulation; SAT1 deficiency promoted herpes simplex virus 1 (HSV-1) replication in vivo. The results indicate that spermine and spermidine induce dsDNA to adopt the Z-form conformation and that SAT1-mediated polyamine metabolism orchestrates cGAS activity. Show less

KEAP1 (Kelch-like ECH-associated protein), a cytoplasmic repressor of the oxidative stress responsive transcription factor Nuclear factor erythroid 2-related factor 2 (NRF2), senses the presence of electrophilic agents by modification of its sensor cysteine residues. In addition to xenobiotics, several reactive metabolites have been shown to covalently modify key cysteines on KEAP1, although the full repertoire of these molecules and their respective modifications remain undefined. Here, we report the discovery of sAKZ692, a small molecule identified by high-throughput screening that stimulates NRF2 transcriptional activity in cells by inhibiting the glycolytic enzyme pyruvate kinase. sAKZ692 treatment promotes the buildup of glyceraldehyde 3-phosphate, a metabolite which leads to S-lactate modification of cysteine sensor residues of KEAP1, resulting in NRF2-dependent transcription. This work identifies a posttranslational modification of cysteine derived from a reactive central carbon metabolite and helps further define the complex relationship between metabolism and the oxidative stress-sensing machinery of the cell. Show less

Z-form nucleic acid-binding protein 1 (ZBP1) detects viral Z-form RNAs (Z-RNAs), activates receptor-interacting protein kinase 3, and triggers cell death during both RNA and DNA virus infections. Such cell death promotes virus clearance by eliminating infected cells and galvanizing antiviral immunity, and is thus often targeted for evasion by virus-encoded suppressors. Recent evidence demonstrates that ZBP1 can also be activated by cellular Z-RNAs transcribed from endogenous retroelements within mammalian genomes. These cellular Z-RNAs, if not edited and neutralized by adenosine deaminase RNA-specific 1, trigger ZBP1-dependent cell death and inflammation, which may drive disease in Aicardi-Goutière's syndrome and related interferonopathies. Thus, while well-controlled activation of ZBP1 by viral Z-RNAs during infections is beneficial, the same pathway can have harmful consequences when inappropriately triggered by cellular Z-RNAs in other disease settings. Show less

The accumulation of lipid peroxides is recognized as a determinant of the occurrence of ferroptosis. However, the sensors and amplifying process of lipid peroxidation linked to ferroptosis remain obscure. Here we identify PKCβII as a critical contributor of ferroptosis through independent genome-wide CRISPR-Cas9 and kinase inhibitor library screening. Our results show that PKCβII senses the initial lipid peroxides and amplifies lipid peroxidation linked to ferroptosis through phosphorylation and activation of ACSL4. Lipidomics analysis shows that activated ACSL4 catalyses polyunsaturated fatty acid-containing lipid biosynthesis and promotes the accumulation of lipid peroxidation products, leading to ferroptosis. Attenuation of the PKCβII-ACSL4 pathway effectively blocks ferroptosis in vitro and impairs ferroptosis-associated cancer immunotherapy in vivo. Our results identify PKCβII as a sensor of lipid peroxidation, and the lipid peroxidation-PKCβII-ACSL4 positive-feedback axis may provide potential targets for ferroptosis-associated disease treatment. Show less

Cellular DNA is continuously transcribed into RNA by multisubunit RNA polymerases (RNAPs). The continuity of transcription can be disrupted by DNA lesions that arise from the activities of cellular enzymes, reactions with endogenous and exogenous chemicals or irradiation. Here, we review available data on translesion RNA synthesis by multisubunit RNAPs from various domains of life, define common principles and variations in DNA damage sensing by RNAP, and consider existing controversies in the field of translesion transcription. Depending on the type of DNA lesion, it may be correctly bypassed by RNAP, or lead to transcriptional mutagenesis, or result in transcription stalling. Various lesions can affect the loading of the templating base into the active site of RNAP, or interfere with nucleotide binding and incorporation into RNA, or impair RNAP translocation. Stalled RNAP acts as a sensor of DNA damage during transcription-coupled repair. The outcome of DNA lesion recognition by RNAP depends on the interplay between multiple transcription and repair factors, which can stimulate RNAP bypass or increase RNAP stalling, and plays the central role in maintaining the DNA integrity. Unveiling the mechanisms of translesion transcription in various systems is thus instrumental for understanding molecular pathways underlying gene regulation and genome stability. Show less

Mitochondria are important organelles that present extensively in cells, serving diverse functions. In addition to controlling cell energy production and metabolism, mitochondria are also involved in various biological processes, including anti-infection, apoptosis, and autophagy. Harmful stimuli from external environment or those generated by the cells themselves can damage mitochondria and cause mitochondrial stress response, during which the mitochondrial matrix containing mitochondrial DNA (mtDNA) can leak into the cytoplasm. Cytoplasmic mtDNA, acting as a damage-associated molecular pattern (DAMP), can activate a panel of DNA sensors and elicit innate immune response in organisms. Cyclic GMP-AMP synthase (cGAS), a key intracellular DNA sensor, can catalyze the conversion of GTP and ATP to cyclic GMP-AMP (2'3'-cGAMP), which serves as second messenger to bind and activate stimulator of interferon gene (STING), an endoplasmic adaptor protein. Beyond its critical roles in anti-microbial immunity, cGAS-STING pathway also serves important functions in many pathological and physiological processes such as autoimmunity, tumor and senescence. In this review, we focus on how the mtDNA released during mitochonrial stress response activates the cGAS-STING innate immune signaling pathway and the associated diseases, in order to help promote basic research about the role of mitochondria in innate immunity and provide new strategies for developing mitochondria-targeting drugs. Show less

Mechanisms that integrate the metabolic state of a cell with regulatory pathways are necessary to maintain cellular homeostasis. Endogenous, intrinsically reactive metabolites can form functional, covalent modifications on proteins without the aid of enzymes1,2, and regulate cellular functions such as metabolism3-5 and transcription6. An important 'sensor' protein that captures specific metabolic information and transforms it into an appropriate response is KEAP1, which contains reactive cysteine residues that collectively act as an electrophile sensor tuned to respond to reactive species resulting from endogenous and xenobiotic molecules. Covalent modification of KEAP1 results in reduced ubiquitination and the accumulation of NRF27,8, which then initiates the transcription of cytoprotective genes at antioxidant-response element loci. Here we identify a small-molecule inhibitor of the glycolytic enzyme PGK1, and reveal a direct link between glycolysis and NRF2 signalling. Inhibition of PGK1 results in accumulation of the reactive metabolite methylglyoxal, which selectively modifies KEAP1 to form a methylimidazole crosslink between proximal cysteine and arginine residues (MICA). This posttranslational modification results in the dimerization of KEAP1, the accumulation of NRF2 and activation of the NRF2 transcriptional program. These results demonstrate the existence of direct inter-pathway communication between glycolysis and the KEAP1-NRF2 transcriptional axis, provide insight into the metabolic regulation of the cellular stress response, and suggest a therapeutic strategy for controlling the cytoprotective antioxidant response in several human diseases. Show less

The regulation of hydrogen ion concentration (pH) is fundamental to cell viability, metabolism, and enzymatic function. Within the nervous system, the control of pH is also involved in diverse and dynamic processes including development, synaptic transmission, and the control of network excitability. As pH affects neuronal activity, and can also itself be altered by neuronal activity, the existence of tools to accurately measure hydrogen ion fluctuations is important for understanding the role pH plays under physiological and pathological conditions. Outside of their use as a marker of synaptic release, genetically encoded pH sensors have not been utilized to study hydrogen ion fluxes associated with network activity. By combining whole-cell patch clamp with simultaneous two-photon or confocal imaging, we quantified the amplitude and time course of neuronal, intracellular, acidic transients evoked by epileptiform activity in two separate in vitro models of temporal lobe epilepsy. In doing so, we demonstrate the suitability of three genetically encoded pH sensors: deGFP4, E(2)GFP, and Cl-sensor for investigating activity-dependent pH changes at the level of single neurons. Show less

PURPOSE: Cancer cell survival depends on adaptive mechanisms that include modulation of oxidative stress. One such mechanism may be via up-regulation of uncoupling protein-2 (UCP2), a mitochondrial inner membrane anion carrier recently found to provide cytoprotection in nontumor cells by acting as a sensor and negative regulator of reactive oxygen species production. We hypothesized that UCP2 expression may be increased in colon cancer as part of tumor adaptation. EXPERIMENTAL DESIGN: UCP2 expression was characterized by real-time polymerase chain reaction and Western blotting using paired human colon adenocarcinoma and peritumoral specimens. Oxidant production was characterized by tissue malondialdehyde levels. Tissue microarrays constructed of 107 colon adenocarcinomas as well as representative specimens of hyperplastic polyps and tubular adenomas were used for UCP2 immunohistochemistry. RESULTS: UCP2 mRNA and protein levels were 3- to 4-fold higher in adenocarcinomas, and UCP2 mRNA levels showed significant correlation with increased tumor tissue malondialdehyde contents. Immunohistochemistry on tissue microarrays showed positive staining for UCP2 in most adenocarcinomas (86.0%); positive staining for UCP2 was seen less often in tubular adenomas (58.8%) and rarely seen in hyperplastic polyps (11.1%). CONCLUSIONS: UCP2 expression is increased in most human colon cancers, and the level of expression appears to correlate with the degree of neoplastic changes. These findings may foster the idea that UCP2 is part of a novel adaptive response by which oxidative stress is modulated in colon cancer. Show less

Transcription factor Nrf2 is a major regulator of genes encoding phase 2 detoxifying enzymes and antioxidant stress proteins in response to electrophilic agents and oxidative stress. In the absence of such stimuli, Nrf2 is inactive owing to its cytoplasmic retention by Keap1 and rapid degradation through the proteasome system. We examined the contribution of Keap1 to the rapid turnover of Nrf2 (half-life of less than 20 min) and found that a direct association between Keap1 and Nrf2 is required for Nrf2 degradation. In a series of domain function analyses of Keap1, we found that both the BTB and intervening-region (IVR) domains are crucial for Nrf2 degradation, implying that these two domains act to recruit ubiquitin-proteasome factors. Indeed, Cullin 3 (Cul3), a subunit of the E3 ligase complex, was found to interact specifically with Keap1 in vivo. Keap1 associates with the N-terminal region of Cul3 through the IVR domain and promotes the ubiquitination of Nrf2 in cooperation with the Cul3-Roc1 complex. These results thus provide solid evidence that Keap1 functions as an adaptor of Cul3-based E3 ligase. To our knowledge, Nrf2 and Keap1 are the first reported mammalian substrate and adaptor, respectively, of the Cul3-based E3 ligase system. Show less

Transcription factor Nrf2 is a major regulator of genes encoding phase 2 detoxifying enzymes and antioxidant stress proteins in response to electrophilic agents and oxidative stress. In the absence of such stimuli, Nrf2 is inactive owing to its cytoplasmic retention by Keap1 and rapid degradation through the proteasome system. We examined the contribution of Keap1 to the rapid turnover of Nrf2 (half-life of less than 20 min) and found that a direct association between Keap1 and Nrf2 is required for Nrf2 degradation. In a series of domain function analyses of Keap1, we found that both the BTB and intervening-region (IVR) domains are crucial for Nrf2 degradation, implying that these two domains act to recruit ubiquitin-proteasome factors. Indeed, Cullin 3 (Cul3), a subunit of the E3 ligase complex, was found to interact specifically with Keap1 in vivo. Keap1 associates with the N-terminal region of Cul3 through the IVR domain and promotes the ubiquitination of Nrf2 in cooperation with the Cul3-Roc1 complex. These results thus provide solid evidence that Keap1 functions as an adaptor of Cul3-based E3 ligase. To our knowledge, Nrf2 and Keap1 are the first reported mammalian substrate and adaptor, respectively, of the Cul3-based E3 ligase system. Show less