Biology subjects

Kumar, A.

Publications and source records attributed to Kumar, A..

At least 307 records · Page 17Linked to original sources

bioRxiv2024

Curcumin Inhibits Zika Virus NS3 Helicase Activity

In the last decades, many efforts have been put forward in search of inhibitors/drugs specific to ZIKV-infected patients. These inhibitors include approved drugs, natural products, nucleosides, small molecules, and many others to inhibit Zika virus replication in cell and mouse models. In this regard, natural product curcumin has been widely explored in various disease conditions and found to have inhibition potential against ZIKV replication as well. Further, we investigated its inhibitory ability against the ZIKV NS3 helicase. We found that the curcumin interacts with the NS3 helicase domain by forming stable contacts at NTPase and RNA binding sites during molecular dynamic simulation. Furthermore, curcumin inhibits NTPase activity of NS3 helicase with an IC50 of 64.42 M. Altogether, the mechanistic insight into the action of curcumin will enlighten further drug discovery research in finding novel molecules.

biochemistry↗

bioRxiv2024

Synergistic Modulation of Macrophages by Methotrexate and RELA siRNA Folate-Liposome: A Precision Therapy to Prevent Joint Degradation in Collagen-Induced Arthritic Rats

Rheumatoid arthritis (RA) is a chronic autoimmune disorder characterized by inflammation and joint destruction. Current treatments, such as Methotrexate (MTX), while effective, often have therapeutic limitations like high plasma Cmax and lack of sustained release. This study explores a synergistic approach to RA therapy using folate-liposomal co-delivery of MTX and RELA siRNA, aimed at RAW264.7 macrophage repolarization through inhibition of the NF-{kappa}B pathway. Extensive invitro characterizations demonstrate the stability and biocompatibility of this combinatorial therapy in folate-liposomes. In collagen-induced arthritis (CIA) rat model, we observed a reduction in synovial inflammation and improved mobility following treatment. The combined MTX and RELA siRNA approach indirectly inhibits inflammatory cytokines and other biochemical parameters such as Rheumatoid factor (RF) and C-reactive protein (CRP). The targeted macrophage delivery yields a marked therapeutic effect in RAW264.7 murine macrophages, potentially modulating the M1 to M2 macrophage polarization. Overall, this research presents a promising avenue for innovative therapies in RA management by inhibiting the inflammatory cascade and preventing joint damage.

pharmacology and toxicology↗

bioRxiv2024

Light and temperature-dependent developmental role of Auxin Binding Protein 1 (ABP1) in Arabidopsis thaliana

Auxin Binding Protein 1 (ABP1) is a small glycoprotein of about 22 kDa that has long been debated as the auxin receptor, and has been put into question for its unclear functions. Despite its conservancy during land plant evolution, its precise role in plant development is still elusive. Historically, it has been implicated in various rapid responses such as membrane polarization, calcium fluxes, TMK1-based cell-surface signalling, auxin canalization, etc. A relatively recent observation questioning the role of ABP1 in plant development led us to explore its probable functions if any. In the current study, we reinvestigated the plausible function of ABP1 using its CRISPR-based loss-of-function mutants, namely abp1-C1 and abp1-C2. Here we show that, ABP1 acts as a positive regulator for primary root elongation under red and secondary root elongation under blue light in seedlings at 22 {degrees}C. Under red light at 18 {degrees}C, it has a negative effect on hypocotyl growth inhibition. Furthermore, it is involved in flowering time control at 18 {degrees}C irrespective of the photoperiod. We show that the transcript levels of Phytochrome B (phyB) and GIGANTEA (GI) are altered in the mutants of ABP1 under red light and low temperature (18 {degrees}C) regimes. Further, ABP1 show a pronounced role in tolerance to dehydration induced due to low temperature (18 {degrees}C), which correlates with an increase in endogenous abscisic acid (ABA), salicylic acid (SA), and a decrease in jasmonic acid (JA) content in leaves. The functional roles of ABP1 under red light, low temperature and dehydration tolerance in Arabidopsis thaliana once again frames it to be an important regulator under adverse and varied conditions that the plant can experience, and thus opened up new avenues for further studies.

plant biology↗

bioRxiv2023

Structure of the human systemic RNAi defective transmembrane protein 1 (hSIDT1) reveals the conformational flexibility of its lipid binding domain

In C. elegans, inter-cellular transport of the small non-coding RNA causing systemic RNA interference (RNAi) is mediated by the transmembrane protein SID1, encoded by the sid1 gene in the systemic RNA interference-defective (sid) loci. SID1 shares structural and sequence similarity with cholesterol uptake protein 1 (CHUP1) and is classified as a member of the cholesterol uptake family (ChUP). Although systemic RNAi is not an evolutionarily conserved process, the sid gene products are found across the animal kingdom, suggesting the existence of other novel gene regulatory mechanisms mediated by small non-coding RNAs. Human homologs of sid gene products - hSIDT1 and hSIDT2 - mediate contact-dependent lipophilic small non-coding dsRNA transport. Here, we report the structure of recombinant human SIDT1. We find that the extra- cytosolic domain (ECD) of hSIDT1 adopts a double jelly roll fold, and the transmembrane domain (TMD) exists as two modules - a flexible lipid binding domain (LBD) and a rigid TMD core. Our structural analyses provide insights into the inherent conformational dynamics within the lipid binding domain in cholesterol uptake (ChUP) family members.

biophysics↗

bioRxiv2023

Intronic miR-6741-3p is involved in oral squamous cell carcinoma pathogenesis by targeting the oncogene SRSF3

Epigenetic silencing through methylation is one of the major mechanisms for downregulation of tumor suppressor miRNAs in various malignancies. The aim of this study was to identify novel tumor suppressor miRNAs which are silenced by DNA hypermethylation and investigate the role of at least one of these in oral squamous cell carcinoma (OSCC) pathogenesis. We treated cells from an OSCC cell line SCC131 with 5-Azacytidine, a DNA methyltransferase inhibitor, to reactivate tumor suppressor miRNA genes silenced/downregulated due to DNA methylation. At 5-day post-treatment, total RNA was isolated from the 5-Azacytidine and vehicle control-treated cells. The expression of 2,459 mature miRNAs was analysed between 5-Azacytidine and control-treated OSCC cells by the microRNA microarray analysis. Of the 50 miRNAs which were found to be upregulated following 5-Azacytidine treatment, we decided to work with miR-6741-3p in details for further analysis, as it showed a mean fold expression of >4.0. The results of qRT-PCR, Western blotting, and dual-luciferase reporter assay indicated that miR-6741-3p directly targets the oncogene SRSF3 at the translational level only. The tumor-suppressive role of miR-6741-3p was established by various in vitro and in vivo assays. Our results revealed that miR-6741-3p plays a tumor-suppressive role in OSCC pathogenesis, in part, by directly regulating SRSF3. Based on our observations, we propose that miR-6741-3p may serve as a potential biological target in tumor diagnostics, prognostic evaluation, and treatment of OSCC and perhaps other malignancies.

cancer biology↗

bioRxiv2023

Fluvoxamine maleate ameliorates Alzheimer disease pathology by mitigating amyloid-beta load and neuroinflammation in 5XFAD mice

BackgroundAlzheimer pathology (AD) is accompanied by the deposition of amyloid beta (A{beta}) and chronic neuroinflammation, where NLRP3 inflammasome is particularly involved. In this study, we found that the OCD drug fluvoxamine maleate (FXN) can potently ameliorate AD pathology in 5XFAD mice by autophagy-mediated clearance of A{beta} and inhibition of NLRP3 inflammasome. MethodsWe used mice primary astrocytes to establish the mechanism of action of FXN against NLRP3 inflammasome by using various techniques like ELISA, Western blotting, confocal microscopy, Immunofluorescence, etc. The validation of the anti-AD activity of FXN was done in transgenic 5XFAD mice after two months of treatment followed by behavior analysis and studying inflammatory and autophagy proteins along with immunohistochemistry analysis for A{beta} load in the hippocampi. ResultsOur data showed that FXN induces autophagy to inhibit NF-{kappa}B and NLRP3 inflammasome at a low concentration of 78 nM apart from directly inhibiting NLRP3 inflammasome in primary astrocytes. FXN activated the PRKAA2 pathway through CAMKK2 signaling, which led to the induction of autophagy in primary astrocytes. FXN inhibited the ATP-mediated NLRP3 inflammasome through autophagic degradation of NF-{kappa}B and thus caused the downregulation of pro-IL-1{beta} and NLRP3. The anti-NLRP3 inflammasome effect of FXN was reversed when autophagy was inhibited either by genetic knockdown of the PRKAA2 pathway or by bafilomycin A1. Furthermore, FXN treatment led to improved AD pathology in 5XFAD mice, which displayed a significant improvement in multiple behavior parameters like working memory and neuromuscular coordination and they behaved more like wild-type animals. We found that FXN improved behavior in 5XFAD mice by clearing the A{beta} deposits from the hippocampi along with a significant reduction in multiple inflammatory proteins, including NF-{kappa}B, GFAP, IBA1, IL-1{beta}, TNF-, and IL-6 associated with NF-{kappa}B and NLRP3 inflammasome in the brain. Moreover, these changes were accompanied by increased expression of autophagic proteins. ConclusionOur data suggest that to ameliorate AD pathology, FXN simultaneously targets two key pathological features of AD that is A{beta} deposits and neuroinflammation. Being an approved drug, FXN can be pushed as a potential drug candidate for human studies against AD.

neuroscience↗

bioRxiv2023

Phylogenomic and phenotypic analyses highlight the diversity of antibiotic resistance and virulence in both human and non-human Acinetobacter baumannii

Acinetobacter baumannii is a Gram-negative opportunistic pathogen causing infections of the immunocompromised. With a high incidence of muti-drug resistance, carbapenem-resistant A. baumannii is as a priority 1 pathogen designated by the WHO. The current literature has expertly characterized clinical isolates of A. baumannii. As the challenge of these infections has recently been classified as a One Health issue, we set out to explore the diversity of isolates from human and non-clinical sources such as agricultural surface water, urban streams, various effluents from wastewater-treatment plants and tank milk; and, importantly, these isolates came from a wide geographic distribution. Phylogenomic analysis considering almost 200 isolates showed that our diverse set is well-differentiated from the main international clones of A. baumannii. We discovered novel sequence types in both hospital and non-clinical settings, and five strains that overexpress the RND efflux pump adeIJK without changes in susceptibility. Further, we detected a blaADC-79 in a non-human isolate despite its sensitivity to all antibiotics. There was no significant differentiation between the virulence profiles of clinical and non-clinical isolates in the Galleria mellonella insect model of virulence suggesting that virulence is neither dependent on geographic origin nor isolation source. Detection of antibiotic resistance and virulence genes in non-human strains suggests that these isolates may act as a genetic reservoir for clinical strains. This endorses the notion that in order to combat multi-drug resistant infection caused by A. baumannii, a One Health approach is required, and a deeper understanding of non-clinical strains must be achieved. ImportanceThe global crisis of antibiotic resistance is a silent one. More and more bacteria are becoming resistant to all antibiotics available for treatment, leaving no options remaining. This includes Acinetobacter baumannii. This Gram-negative opportunistic pathogen shows a high frequency of multi-drug resistance, and many strains are resistant to last-resort drugs carbapenem and colistin. Research has focused on strains of clinical origin, but there is a knowledge gap regarding virulence traits, particularly, how A. baumannii become the notorious pathogen of today. Antibiotic resistance and virulence genes have been detected in strains from animals, and environmental locations such as grass and soil. As such, A. baumannii is a One Health concern which includes the health of humans, animals and the environment. Thus, in order to truly combat the antibiotic resistance crisis, we need to understand antibiotic resistance and virulence gene reservoirs of this pathogen under the One Health continuum. RepositoriesNCBI GenBank Accession numbers: Bioproject PRJNA819071, Biosamples SAMN26898552 - SAMN26898587.

microbiology↗

bioRxiv2023

Structural Basis of μ-Opioid Receptor-Targeting by a Nanobody Antagonist

The -opioid receptor (OR), a prototypical member of the G protein-coupled receptor (GPCR) family, is the molecular target of opioid analgesics such as morphine and fentanyl. Due to the limitations and severe side effects of currently available opioid drugs, there is considerable interest in developing novel modulators of OR function. Most GPCR ligands today are small molecules, however biologics, including antibodies and nanobodies, are emerging as alternative therapeutics with clear advantages such as affinity and target selectivity. Here, we describe the nanobody NbE, which selectively binds to the OR and acts as an antagonist. We functionally characterize NbE as an extracellular and genetically encoded {micro}OR ligand and uncover the molecular basis for {micro}OR antagonism by solving the cryo-EM structure of the NbE-{micro}OR complex. NbE displays a unique ligand binding mode and achieves {micro}OR selectivity by interactions with the orthosteric pocket and extracellular receptor loops. Based on a {beta}-hairpin loop formed by NbE that deeply inserts into the {micro}OR and centers most binding contacts, we design short peptide analogues that retain {micro}OR antagonism. The work illustrates the potential of nanobodies to uniquely engage with GPCRs and describes novel OR ligands that can serve as a basis for therapeutic developments.

molecular biology↗

bioRxiv2023

Epigenetic and transcriptional regulation of the human angiotensinogen gene by high salt

Hypertension is caused by a combination of genetic and environmental factors. Angiotensinogen (AGT) is a component of RAAS, that regulates blood pressure. The human angiotensinogen (hAGT) gene has -6A/-6G polymorphism and -6A variant is associated with human hypertension. In this study, we have investigated the epigenetic regulation of the hAGT. To understand transcriptional regulation of the hAGT, we have made transgenic animals containing -6A. We show that HS affects DNA methylation and modulates transcriptional regulation of this gene in liver and kidney. High salt (HS) increases hAGT gene expression in -6A TG mice. We have observed that the number of CpG sites in the hAGT promoter is decreased after HS treatment. In the liver, seven CpG sites are methylated whereas after HS treatment, only three CpG sites remain methylated. In the kidney, five CpG sites are methylated, whereas after HS treatment, only three CpG sites remain methylated. These results suggest that HS promotes DNA demethylation and increasing AGT gene expression. RT-PCR and immunoblot analysis show that hAGT gene expression is increased by HS. Chip assay has shown that transcription factors bind strongly after HS treatment. RNA-Seq identified differentially expressed genes, novel target genes associated with hypertension, top canonical pathways, upstream regulators. One of the plausible mechanisms for HS induced up-regulation of the hAGT gene is through IL-6/JAK/STAT3/AGT axis.

molecular biology↗

bioRxiv2023

Immuno-informatics Study Identifies Conserved T Cell Epitopes in Non-structural Proteins of Bluetongue Virus Serotypes: Formulation of Computationally Optimized Next-Generation Broad-spectrum Multiepitope Vaccine

Bluetongue (BT) is a significant arboviral disease affecting sheep, cattle, goats, and wild ruminants, posing serious economic challenges to livestock industry. Control efforts have been hampered by the existence of over 32 distinct BT virus (BTV) serotypes and the absence of broad-spectrum vaccines. Some key non-structural proteins of BTV, including NS1, NS2, and NS3, exhibit notable amino acid sequence conservation. Our findings reveal that mouse MHC class I (MHC-I) CD8+ T cell epitopes are highly conserved in NS1 and NS3, while MHC-II epitopes are prevalent in all the three non-structural NS 1-3 proteins. Similarly, both class I and II Bovine Leukocyte antigen-restricted CD8+ and CD4+ T cell epitopes are conserved within NS1, NS2, and NS3 proteins. To construct in silico broad-spectrum vaccine, we subsequently screened these conserved epitopes based on antigenicity, allergenicity, toxicity, and solubility. Modeling and Refinement of the 3D structure models of vaccine constructs were achieved using protein modeling web servers. Our analysis revealed promising epitopes that exhibit strong binding affinities with low energies against two TLR receptors (TLR3 and TLR4). To ensure atomic-level stability, we evaluated the docking complexes of epitopes and receptors through all-atom molecular dynamics simulations (MDS). Encouragingly, our 100 nanoseconds MDS showed stable complexes with minimal RMSF values. Our study offers valuable insights into these conserved T cell epitopes as promising candidates for a broad-spectrum BT vaccine. We therefore encourage for their evaluation in animal models and natural hosts to assess their immunogenicity, safety, and efficacy for field use in the livestock.

bioinformatics↗

bioRxiv2023

Focal adhesion-derived liquid-liquid phase separations regulate mRNA translation

Liquid-liquid phase separation (LLPS) has emerged as a major organizing principle in cells. Recent work showed that multiple components of integrin-mediated focal adhesions including p130Cas can form LLPS, which govern adhesion dynamics and related cell behaviors. In this study, we found that the focal adhesion protein p130Cas drives formation of structures with the characteristics of LLPS that bud from focal adhesions into the cytoplasm. Condensing concentrated cytoplasm around p130Cas-coated beads allowed their isolation, which were enriched in a subset of focal adhesion proteins, mRNAs and RNA binding proteins, including those implicated in inhibiting mRNA translation. Plating cells on very high concentrations of fibronectin to induce large focal adhesions inhibited message translation which required p130Cas and correlated with droplet formation. Photo-induction of p130Cas condensates using the Cry2 system also reduced translation. These results identify a novel regulatory mechanism in which high adhesion limits message translation via induction of p130Cas-dependent cytoplasmic LLPS. This mechanism may contribute to the quiescent state of very strongly adhesive myofibroblasts and senescent cells.

cell biology↗

bioRxiv2023

Intricate mechanism (s) of substrate specificity and loss of function on disease mutation (K211N) of Parkin

PINK1 and Parkin mutations lead to the early onset of Parkinsons disease. PINK1-mediated phosphorylation of its substrates such as ubiquitin (Ub), ubiquitin-like protein (NEDD8), and ubiquitin-like (Ubl) domain of Parkin activate autoinhibited Parkin E3 ligase. The mechanism of various phospho-Ubls binding on Parkin and conformational changes leading to Parkin activation remain elusive. Herein, we determine the first crystal structure of human Parkin E3 ligase bound with phospho (p)-NEDD8, which shows that NEDD8 has evolved over Ub to bind and activate Parkin more robustly. X-ray crystal structures and supporting biophysical/biochemical data reveal specific recognition and underlying mechanisms of pUb/pNEDD8 and pUbl domain binding to the RING1 and RING0 domains, respectively. This new data also shows that pUb/pNEDD8 binding in the RING1 pocket causes allosteric conformational changes in Parkins catalytic domain (RING2), leading to Parkin activation. Furthermore, Parkinsons disease mutation K211N in the RING0 domain of Parkin was believed to lose its activation due to loss of interaction with pUb. However, our data reveal allosteric conformational changes due to N211 that lock RING2 with RING0 to inhibit Parkin K211N activity without disrupting pNEDD8/pUb binding. This study would aid the design of small-molecule Parkin activators for the treatment of Parkinsons disease.

biochemistry↗

bioRxiv2023

Discovery of the sEH Inhibitor Epoxykynin as Potent Kynurenine Pathway Modulator

Disease-related phenotypic assays enable unbiased discovery of novel bioactive small molecules and may provide novel insights into physiological systems and unprecedented molecular modes-of-action (MMOA). Herein we report the identification and characterization of epoxykynin, a potent inhibitor of the soluble epoxide hydrolase (sEH). Epoxykynin was discovered by means of a cellular assay monitoring modulation of kynurenine (Kyn) levels in BxPC-3 cells upon stimulation with the cytokine interferon-{gamma} (IFN-{gamma}) and subsequent target identification employing affinity-based chemical proteomics. Increased Kyn levels are associated with immune suppression in the tumor microenvironment and, thus, the Kyn pathway and its key player indoleamine 2,3-dioxygenase 1 (IDO1) are appealing targets in immuno-oncology. However, targeting IDO1 directly has led to limited success in clinical investigations, demonstrating that alternative approaches to reduce Kyn levels are in high demand. We uncover a cross-talk between sEH and the Kyn pathway that may provide new opportunities to revert cancer-induced immune tolerance.

cell biology↗

bioRxiv2023

Competition and Cooperation of Assembly Sequences in Recurrent Neural Networks

Neural activity sequences are ubiquitous in the brain and play pivotal roles in functions such as long-term memory formation and motor control. While conditions for storing and reactivating individual sequences have been thoroughly characterized, it remains unclear how multiple sequences may interact when activated simultaneously in recurrent neural networks. This question is especially relevant for weak sequences, comprised of fewer neurons, competing against strong sequences. Using a non-linear rate model with discrete, pre-configured assemblies, we demonstrate that weak sequences can compensate for their competitive disadvantage either by increasing excitatory connections between subsequent assemblies or by cooperating with other co-active sequences. Further, our model suggests that such cooperation can negatively affect sequence speed unless subsequently active assemblies are paired. Our analysis, validated by an analytically tractable linear approximation, characterizes the conditions for successful sequence progression in isolated, competing, and cooperating sequences, and identifies the distinct contributions of recurrent and feed-forward projections. This proof-of-principle study shows how even disadvantaged sequences can be prioritized for reactivation, a process which has recently been implicated in hippocampal memory processing.

neuroscience↗

bioRxiv2023

Drug-Target-Interaction Prediction with Contrastive and Siamese Transformers.

AO_SCPLOWBSTRACTC_SCPLOWAs machine learning (ML) becomes increasingly integrated into the drug development process, accurately predicting Drug-Target Interactions (DTI) becomes a necessity for pharmaceutical research. This prediction plays a crucial role in various aspects of drug development, including virtual screening, repurposing of drugs, and proactively identifying potential side effects. While Deep Learning has made significant progress in enhancing DTI prediction, challenges related to interpretability and consistent performance persist in the field. This study introduces two innovative methodologies that combine Generative Pretraining and Contrastive Learning to specialize Transformers for bio-chemical modeling. These systems are designed to best incorporate cross-attention, which enables a nuanced alignment of multi-representation embeddings. Our empirical evaluation will showcase the effectiveness and interpretability of this proposed framework. Through a series of experiments, we provide compelling evidence of its superior predictive accuracy and enhanced interpretability. The primary objective of this research is not only to contribute to the advancement of novel DTI prediction methods but also to promote greater transparency and reliability within the drug discovery pipeline.

bioinformatics↗

bioRxiv2023

Neuro-Cognitive Multilevel Causal Modeling: A Framework that Bridges the Explanatory Gap between Neuronal Activity and Cognition

Explaining how neuronal activity gives rise to cognition arguably remains the most significant challenge in cognitive neuroscience. We introduce neuro-cognitive multilevel causal modeling (NC-MCM), a framework that bridges the explanatory gap between neuronal activity and cognition by construing cognitive states as (behaviorally and dynamically) causally consistent abstractions of neuronal states. Multilevel causal modeling allows us to interchangeably reason about the neuronal- and cognitive causes of behavior while maintaining a physicalist (in contrast to a strong dualist) position. We introduce an algorithm for learning cognitive-level causal models from neuronal activation patterns and demonstrate its ability to learn cognitive states of the nematode C. elegans from calcium imaging data. We show that the cognitive-level model of the NC-MCM framework provides a concise representation of the neuronal manifold of C. elegans and its relation to behavior as a graph, which, in contrast to other neuronal manifold learning algorithms, supports causal reasoning. We conclude the article by arguing that the ability of the NC-MCM framework to learn causally interpretable abstractions of neuronal dynamics and their relation to behavior in a purely data-driven fashion is essential for understanding more biological systems whose complexity prohibits the development of hand-crafted computational models.

neuroscience↗

bioRxiv2023

Structure of the human heparan-α-glucosaminide N-acetyltransferase (HGSNAT)

Degradation of heparan sulfate (HS), a glycosaminoglycan (GAG) comprised of repeating units of N-acetylglucosamine and glucuronic acid, begins in the cytosol and is completed in the lysosomes. Acetylation of the terminal non-reducing amino group of -D-glucosamine of HS is essential for its complete breakdown into monosaccharides and free sulfate. Heparan--glucosaminide N-acetyltransferase (HGSNAT), a resident of the lysosomal membrane, catalyzes this essential acetylation reaction by accepting and transferring the acetyl group from cytosolic acetyl-CoA to terminal -D-glucosamine of HS in the lysosomal lumen. Mutation-induced dysfunction in HGSNAT causes abnormal accumulation of HS within the lysosomes and leads to an autosomal recessive neurodegenerative lysosomal storage disorder called mucopolysaccharidosis IIIC (MPS IIIC). There are no approved drugs or treatment strategies to cure or manage the symptoms of, MPS IIIC. Here, we use cryo-electron microscopy (cryo-EM) to determine a high-resolution structure of the HGSNAT-acetyl-CoA complex, the first step in HGSNAT catalyzed acetyltransferase reaction. In addition, we map the known MPS IIIC mutations onto the structure and elucidate the molecular basis for mutation-induced HGSNAT dysfunction.

biophysics↗

bioRxiv2023

Missense mutations in Myc Box I influence MYC cellular localization, mRNA partitioning and turnover to promote leukemogenesis

Somatic missense mutations in the phosphodegron domain of the MYC gene (MYC Box I) are detected in the dominant clones of a subset of acute myeloid leukemia (AML) patients, but the mechanisms by which they contribute to AML are unknown. To unveil unique proprieties of MBI MYC mutant proteins, we systematically compared the cellular and molecular consequences of expressing similar oncogenic levels of wild type and MBI mutant MYC. We found that MBI MYC mutants can accelerate leukemia by driving unique transcriptional signatures in highly selected, myeloid progenitor subpopulations. Although these mutations increase MYC stability, they overall dampen MYC chromatin localization and lead to a cytoplasmic accumulation of the mutant proteins. This phenotype is coupled with increased translation of RNA binding proteins and nuclear export machinery, which results in altered RNA partitioning and accelerated decay of select transcripts encoding proapoptotic and proinflammatory genes. Heterozygous knockin mice harboring the germline MBI mutation Myc p.T73N exhibit cytoplasmic MYC localization, myeloid progenitors expansion with similar transcriptional signatures to the overexpression model, and eventually develop hematological malignancies. This study uncovers that MBI MYC mutations alter MYC localization and disrupt mRNA subcellular distribution and turnover of select transcripts to accelerate tumor initiation and growth.

cancer biology↗