Biology subjects

Murata, T.

Publications and source records attributed to Murata, T..

At least 19 recordsLinked to original sources

bioRxiv2026

Organelle-Specific pH Quantification Using a Protein-Based Quantum Sensor

Quantum sensing enables measurements of physicochemical changes within living cells at the organelle level. Conventional nanoparticle-based sensors, however, face limitations in subcellular targeting, intracellular tracking, and following dynamic biological processes across distinct intracellular environments. Here, we investigate MagLOV2, a genetically encoded quantum sensor, by examining its organelle-specific localization, magnetic field effects (MFEs) during mitophagy, and pH dependent response kinetics. MagLOV2 retained magnetic responsiveness in the cytoplasm, nucleus, and mitochondria, with fluorescence contrasts of 17.1%, 12.3%, and 28.0%, respectively. Optimization of mitochondrial targeting increased fluorescence 2.7 fold. During CCCP induced mitophagy, lysosomal colocalization of MagLOV2 increased from 20.75% to 89.73%, accompanied by slower MFE responses in acidic compartments. Purified MagLOV2 showed response times ranging from 8.27 s at pH 4.5 to 1.56 s at pH 9.5. Structural, spectral, and kinetic analyses suggested that protonation dependent flavin photochemistry and the surrounding protein environment contribute to this behavior. These measurements demonstrate that genetically targeted MagLOV2 can follow organelle transport and report local acidification through changes in magnetic-response kinetics.

biophysics↗

bioRxiv2026

Loss of NKX2-1 predisposes thyroid to neoplasm development through regulation of oxidative stress

Many factors including ionizing radiation and iodine deficiency are known to increase thyroid carcinogenesis risk. Our dataset analysis of The Cancer Genome Atlas (TCGA) showed that lower mRNA expression of NK2 homeobox 1 (NKX2-1) transcription factor, a master regulator of genesis, homeostasis, and function of thyroid, is linked to poor prognosis of papillary thyroid cancer patients. Here we provide the findings that thyroid-specific Nkx2-1 conditional knockout (Nkx2-1{Delta}T) mice develop thyroid adenoma and carcinoma in higher frequency with combined exposure to radiation and iodine deficiency than control Nkx2-1fl/fl mice. Iodine deficiency caused oxidative stress, which subsequently resulted in DNA damage, leading to transformation of thyroid follicular cells. RNA-seq gene set enrichment analysis indicated higher production of reactive oxygen species (ROS) in the thyroids of Nkx2-1{Delta}T as compared to Nkx2-1fl/fl mice with combined exposure to radiation and iodine deficiency. This was accompanied by a feedback induction of SOD3 (superoxide dismutase 3) and GPX2 (glutathione peroxidase 2). These antioxidants were naturally expressed at higher levels in the thyroids of Nkx2-1{Delta}T than Nkx2-1fl/fl mice without iodine deficiency or radiation. Nkx2-1{Delta}T thyroids exhibited abnormal follicle architecture and up-regulation of Acox2 (encoding acyl-CoA oxidase 2), which produces hydrogen peroxide. These results suggest that loss of NKX2-1 may contribute to excess ROS production, which elevates basal oxidative stress resulting in the promotion of ROS-induced carcinogenesis. We propose a role for NKX2-1 as a regulator of ROS production homeostasis in the thyroid. Its disturbance would dispose thyroid follicular cells more vulnerable to the ROS-producing carcinogens.

cancer biology↗

bioRxiv2026

Modeling Time to Visual Insight in Mooney Image Recognition with a Chaotic Recurrent Neural Network

Insight is often described as a sudden shift in or formation of a conceptual representation, enabling humans to restructure existing knowledge and solve problems beyond conventional analytical approaches. Although prior computational studies have modeled aspects of insight using deep neural networks (DNNs) or reinforcement learning, few have captured the dynamic emergence of insight through autonomous neural computation. Here, we present a neural network model that simulates the time required to reach visual insight in the Mooney image recognition task, a widely used paradigm for studying visual insight and perceptual reorganization. The model couples a DNN module for perceptual feature extraction with a recurrent neural network (RNN) that implements a chaotic search process for recognition. The RNN is formulated as a continuous-time dynamical system, autonomously explores internal states, and stabilizes when the missing visual features required for recognition are internally reconstructed. Using the same image set as in human psychophysical experiments, the model reproduces key statistical properties of human search times (STs), including (i) lognormal-like ST distributions across participants for each image, (ii) a proportional relationship between the log-scale mean and standard deviation estimated from lognormal fits across images, and (iii) discrete levels of the fitted log-scale mean across images (a proxy for image difficulty). Importantly, these properties emerge without assuming any lognormal distribution for participant-to-participant variability, whereas previous models reproduced similar signatures by positing lognormal-distributed individual differences. We further show that lognormal-like signatures can arise from exponential search dynamics when combined with both standard experimental preprocessing and finite observation windows, highlighting the need to distinguish generative mechanisms from measurement and analysis effects. Together, these results motivate a mechanistic link between chaotic neural dynamics and insight-related search and provide a computational framework for implementing insight in artificial systems.

neuroscience↗

bioRxiv2025

Superior colliculus coordinates whole-brain dynamics for sudden unconscious visual insight

The human capacity for sudden insight, often marked by abrupt and illuminating "eureka" moments, has long intrigued neuroscientists seeking to understand its elusive neural basis1-6. Mooney image recognition offers a compelling behavioral paradigm of this phenomenon, in which ambiguous black-and-white patterns are abruptly perceived as coherent objects7-13. Whole-brain cortical involvement, which is mainly revealed by the contrast between recognition and nonrecognition, is well established8,14-27. However, the neural dynamics underlying the transition from nonrecognition to recognition, particularly the contributions of noncortical structures, have remained largely unknown. Here, we show that the transition in whole-brain dynamics can be effectively characterized by three large-scale activity patterns and that the superior colliculus (SC) emerges as a structure with a distinct temporal profile that is potentially critical for insight. Using functional clustering of functional magnetic resonance imaging data comprising 41,446 time points from 14 human participants performing this insight task, we identified three distinct functional clusters exhibiting stimulus-driven activation, suppression, and recognition-associated patterns. Notably, the SC in the third cluster displayed a distinct activation peak immediately before the recognition response. Furthermore, empirical dynamic modeling revealed that the SC was the only region in the whole brain that exhibited mutual positive directed interactions with all three clusters and was functionally embedded within higher-order cortical interactions mediating the transformation from stimulus input to motor output. Our findings provide compelling experimental evidence that the SC plays a critical role in orchestrating whole-brain dynamics for sudden insight, calling for a reappraisal of this evolutionarily conserved structure as a key player supporting unconscious but high-level cognitive processing.

neuroscience↗

bioRxiv2024

Engineering of ATP synthase for enhancement of proton-to-ATP ratio

FoF1-ATP synthase (FoF1) interconverts the energy of the proton motive force (pmf) and that of ATP via mechanical rotation of the rotor complex. The H+/ATP ratio, one of the most crucial parameters in bioenergetics, varies among species due to the different number of H+-binding c-subunits, resulting in H+/ATP ratios ranging from 2.7 to 5. The present study attempted to enhance the H+/ATP ratio significantly by employing a novel approach that differs from that of nature. We engineered FoF1 to form multiple peripheral stalks, each bound to a proton-conducting a-subunit. Engineered FoF1 showed an H+/ATP ratio of 5.9, beyond the highest among naturally occurring FoF1s, enabling ATP synthesis at a low pmf, at which wild-type enzymes are unable to synthesize ATP. Structural analysis showed that the engineered FoF1 formed up to three peripheral stalks and the a-subunits. This study not only provides important insights into the H+-transport mechanism of FoF1 but also opens the possibility of engineering the foundation of cell bioenergetics.

biophysics↗

bioRxiv2023

Structural basis of anticancer drug recognition and amino acid transport by LAT1

LAT1 (SLC7A5) transports large neutral amino acids and their derivatives across the plasma membrane and plays pivotal roles in cancer cell proliferation, immune response and drug delivery across the blood-brain barrier. Despite recent advances in structural understanding of LAT1, how it discriminates substrates and inhibitors including the clinically relevant anticancer drugs remains elusive. Here we report six structures of LAT1, captured in three different conformations and bound with diverse bioactive ligands, elucidating its substrate transport and inhibitory mechanisms. JPH203, also known as nanvuranlat or KYT-0353 and currently in clinical trials as an anticancer drug, binds to the wide-open substrate-binding pocket of LAT1. It adopts a U-shaped conformer, with its amino-phenylbenzoxazol moiety pushing against transmembrane helix 3 (TM3), bending TM10 and arresting the transporter in the outward-facing conformation. In contrast, the physiological substrate L-Phe does not exhibit such inhibitory interactions, whereas melphalan, a slow substrate, poses steric hindrance in the pocket, explaining its inhibitory activity. Unexpectedly, the "classical" system L inhibitor BCH induces an occluded state, a key structural intermediate required for substrate transport. Trans stimulation assays show that BCH facilitates transporter turnover and is therefore a transportable substrate. These findings provide a structural framework for the intricate mechanisms of substrate recognition and inhibition of LAT1, paving the way for developing more specific and effective drugs against it.

biochemistry↗

bioRxiv2023

Brefeldin A and M-COPA block the export of RTKs from the endoplasmic reticulum via simultaneous inactivation of ARF1, ARF4, and ARF5

Normal receptor tyrosine kinases (RTKs) need to reach the plasma membrane (PM) for ligand-induced activation, whereas its cancer-causing mutants can be activated before reaching the PM in organelles, such as the Golgi/trans-Golgi network (TGN). Inhibitors of protein export from the endoplasmic reticulum (ER), such as brefeldin A (BFA) and 2-methylcoprophilinamide (M-COPA), can suppress the activation of mutant RTKs in cancer cells, suggesting that RTK mutants cannot initiate signaling in the ER. BFA and M-COPA block the function of ADP-ribosylation factors (ARFs) that play a crucial role in ER-Golgi protein trafficking. However, which ARFs among AFR family proteins are inhibited by BFA or M-COPA, that is, which ARFs are involved in RTKs transport from the ER, remain unclear. In this study, we showed that M-COPA blocked the export of not only KIT but also PDGFRA/EGFR/MET RTKs from the ER. ER-retained RTKs could not fully transduce anti-apoptotic signals, thereby leading to cancer cell apoptosis. Moreover, single knockdown of ARF1, ARF3, ARF4, ARF5, or ARF6 could not block ER export of RTKs, indicating that BFA/M-COPA treatment cannot be mimicked by knockdown of only one ARF member. Interestingly, simultaneous transfection of ARF1, ARF4, and ARF5 siRNAs mirrored the effect of BFA/M-COPA treatment. Consistent with these results, in vitro pulldown assays showed that BFA/M-COPA blocked the function of ARF1, ARF4, and ARF5. Taken together, these results suggest that BFA/M-COPA targets at least ARF1, ARF4, and ARF5; in other words, RTKs require the simultaneous activation of ARF1, ARF4, and ARF5 for their ER export.

cell biology↗

bioRxiv2023

Akr1b7 functions as a master regulator in ovarian aging

At the beginning of ovarian aging, the ovulation of immature oocytes is accelerated, leading to the arrest of ovulation despite the remaining oocytes. Here, RNA expression in the ovarian aging of mice is comprehensively analyzed during the estrous cycle after ovulation stimulation. The aldo-keto reductase Akr1b7 pathway transiently activated in the ovaries of young mice disappears in those of old mice. Akr1b7--/-- mice attenuate oocyte Akt activation essential for the follicular development in primordial follicles, and enhanced ovulation in immature oocytes. The estrous cycle is extended because of the prolonged diestrous stage by a sustained progesterone level in Akr1b7--/--mice ovaries, which is caused by the decline of Cyp17a1, a major metabolic enzyme of progesterone in Akr1b7-expressed theca cell layers. In summary, the decreased Akr1b7 pathway causes ovulation of immature oocytes and a prolonged estrous cycle, typical symptoms of ovarian aging.

molecular biology↗

bioRxiv2022

Six states of Enterococcus hirae V-type ATPase reveals non-uniform rotor rotation during turnover

The vacuolar-type ATPase from Enterococcus hirae (EhV-ATPase) is a thus-far unique adaptation of V-ATPases, as it performs Na+ transport and demonstrates an off-axis rotor assembly. Recent single molecular studies of the isolated V1 domain have indicated that there are subpauses within the three major states of the pseudo three-fold symmetric rotary enzyme. However, there was no structural evidence for these. Herein we activated the EhV-ATPase complex with ATP and identified multiple structures consisting of a total of six states of this complex by using cryo-electron microscopy. The orientations of the rotor complex during turnover, especially in the intermediates, were not as perfectly uniform as expected. The densities in the nucleotide binding pockets in the V1 domain indicated the different catalytic conditions for the six conformations. The off-axis rotor and its interactions with the stator a-subunit during rotation suggests that this non-uniform rotor rotation is performed through the entire complex.

molecular biology↗

bioRxiv2022

Direct Observation of Stepping Rotation of V-ATPase Reveals Rigid Coupling between Vo and V1 Motors

V-ATPases are rotary motor proteins which convert chemical energy of ATP into electrochemical potential of ions across the cell membrane. V-ATPases consist of two rotary motors, Vo and V1, and Enterococcus hirae V-ATPase (EhVoV1) actively transports Na+ in Vo (EhVo) by using torque generated by ATP hydrolysis in V1 (EhV1). Here, we observed ATP-driven stepping rotation of detergent-solubilized EhVoV1 wild-type, aE634A, and BR350K mutants under the various Na+ and ATP concentrations ([Na+] and [ATP], respectively) by using a 40-nm gold nanoparticle as a low-load probe. When [Na+] was low and [ATP] was high, under the condition that only Na+ binding to EhVo is the rate-limiting, wild-type and aE634A exhibited 10-pausing positions reflecting 10-fold symmetry of the EhVo rotor and almost no backward steps. Duration time before forward steps was inversely proportional to [Na+], confirming that Na+ binding triggers the steps. When both [ATP] and [Na+] were low, under the condition that both Na+ and ATP bindings are rate-limiting, aE634A exhibited 13-pausing positions reflecting 10- and 3-fold symmetries of EhVo and EhV1, respectively. Distribution of duration time before forward step was well fitted by a sum of two exponential decay functions with distinct time constants. Furthermore, frequent backward steps smaller than 36{degrees} were observed. Small backward steps were also observed during long, three ATP cleavage pauses of BR350K. These results indicate that EhVo and EhV1 do not share pausing positions and Na+ and ATP bindings occur at different angles, and the coupling between EhVo and EhV1 is not elastic but rigid. Significance StatementV-ATPases are ion pumps consisting of two rotary motor proteins Vo and V1, and actively transport ions across the cell membrane by using chemical energy of ATP. To understand how V-ATPases transduce the energy in the presence of structural symmetry mismatch between Vo and V1, we simultaneously visualized rotational pauses and forward and backward steps of Vo and V1 coupled with ion transport and ATP hydrolysis reaction, respectively. Our results indicate rigid coupling of a V-ATPase which has multiple peripheral stalks, in contrast to elastic coupling of F-ATPases with only one peripheral stalk, which work as ATP synthase. Our high-speed/high-precision single-molecule imaging of rotary ATPases in action will pave the way for a comprehensive understanding of their energy transduction mechanisms.

biophysics↗

bioRxiv2022

Chemical screen of Arabidopsis zygote and proteomics in tobacco BY-2 cells identify general plant cell division inhibitors

Cell division is essential for growth and development and involves events such as spindle assembly, chromosome separation, and cell plate formation. In plants, the tools used to control these events at the desired time are still poor because the genetic approach is ineffective owing to a high redundancy and lethality, as well as harmful side effects. Accordingly, we screened cell division-affecting compounds, with a focus on Arabidopsis thaliana zygotes, which individually develop in maternal ovules; the cell division was reliably traceable without time-lapse observations. We then identified the target events of the identified compounds using tobacco BY-2 cells for live-cell imaging and proteomics. As a result, we isolated two compounds, PD-180970 and PP2. PD-180970 disrupts microtubule (MT) organization and, thus, nuclear separation, presumably by inhibiting MT-associated proteins (MAP70). PP2 affected class II Kinesin-12 localization at the phragmoplast emerging site and impaired cytokinesis. Moreover, neither chemical caused irreversible damage to viability but they were effective in multiple plant species such as cucumber (Cucumis sativus) and moss (Physcomitrium patens). We propose that the combination of chemical screening based on Arabidopsis zygotes and target event specification focusing on tobacco BY-2 cells can be used to effectively identify novel tools and transiently control specific cell division events that are conserved in diverse plant species.

plant biology↗

bioRxiv2021

Revealing a hidden intermediate of rotatory catalysis with X-ray crystallography and Molecular simulations

The mechanism of rotatory catalysis in ATP-hydrolyzing molecular motors remain an unresolved puzzle in biological energy transfer. Notwith standing the wealth of available biochemical and structural information inferred from years of experiments, knowledge on how the coupling between the chemical and mechanical steps within motors enforces directional rotatory movements remains fragmentary. Even more contentious is to pinpoint the rate-limiting step of a multi-step rotation process. Here, using Vacuolar or V1-type hexameric ATPase as an exemplary rotational motor, we present a model of the complete 4-step conformational cycle involved in rotatory catalysis. First, using X-ray crystallography a new intermediate or dwell is identified, which enables the release of an inorganic phosphate (or Pi) after ATP hydrolysis. Using molecular dynamics simulations, this new dwell is placed in a sequence with three other crystal structures to derive a putative cyclic rotation path. Free-energy simulations are employed to estimate the rate of the hexameric protein transformations, and delineate allosteric effects that allow new reactant ATP entry only after hydrolysis product exit. An analysis of transfer entropy brings to light how the sidechain-level interactions transcend into larger-scale reorganizations, highlighting the role of the ubiquitous arginine-finger residues in coupling chemical and mechanical information. Inspection of all known rates encompassing the 4-step rotation mechanism implicates overcoming of the ADP interactions with V1-ATPase to be the rate-limiting step of motor action.

biophysics↗

bioRxiv2021

Design of complicated all-α protein structures

A wide range of de novo protein structure designs have been achieved, but the complexity of naturally occurring protein structures is still far beyond these designs. To expand the diversity and complexity of de novo designed protein structures, we sought to develop a method for designing "difficult-to-describe"-helical protein structures composed of irregularly aligned -helices like globins. Backbone structure libraries consisting of a myriad of -helical structures with 5- or 6-helices were generated by combining 18 helix-loop-helix motifs and canonical -helices, and five distinct topologies were selected for de novo design. The designs were found to be monomeric with high thermal stability in solution and fold into the target topologies with atomic accuracy. This study demonstrated that complicated -helical proteins are created using typical building blocks. The method we developed would enable us to explore the universe of protein structures for designing novel functional proteins.

biophysics↗

bioRxiv2021

Discovery of the fastest myosin, its amino acid sequence, and structural features

Cytoplasmic streaming with extremely high velocity (~70 m s-1) occurs in cells of the characean algae (Chara). Because cytoplasmic streaming is caused by organelle-associated myosin XI sliding along actin filaments, it has been suggested that a myosin XI, which has a velocity of 70 m s-1, the fastest myosin measured so far, exists in Chara cells. However, the previously cloned Chara corallina myosin XI (CcXI) moved actin filaments at a velocity of around 20 m s-1, suggesting that an unknown myosin XI with a velocity of 70 m s-1 may be present in Chara. Recently, the genome sequence of Chara braunii has been published, revealing that this alga has four myosin XI genes. In the work reported in this paper, we cloned these four myosin XIs (CbXI-1, 2, 3, and 4) and measured their velocities. While the velocities of CbXI-3 and CbXI-4 were similar to that of CcXI, the velocities of CbXI-1 and CbXI-2 were estimated to be 73 and 66 m s-1, respectively, suggesting that CbXI-1 and CbXI-2 are the main contributors to cytoplasmic streaming in Chara cells and showing that CbXI-1 is the fastest myosin yet found. We also report the first atomic structure (2.8 [A] resolution) of myosin XI using X-ray crystallography. Based on this crystal structure and the recently published cryo-EM structure of acto-myosin XI at low resolution (4.3 [A]), it appears that the actin-binding region contributes to the fast movement of Chara myosin XI. Mutation experiments of actin-binding surface loop 2 support this hypothesis. Significance statementIt has been suggested for more than 50 years that the fastest myosin in the biological world, with a velocity of 70 m s-1, exists in the alga Chara because cytoplasmic streaming with a velocity of 70 m s-1 occurs in Chara cells. However, a myosin with that velocity has not yet been identified. In this work, we succeeded in cloning a myosin XI with a velocity of 73 m s-1, the fastest myosin so far measured. We also successfully crystallized myosin XI for the first time. Structural analyses and mutation experiments suggest that the central regions that define the fast movement of Chara myosin XI are the actin-binding sites.

cell biology↗

bioRxiv2021

A triple-negative matrix-producing breast carcinoma is arrested by tumor-targeting Salmonella typhimurium A1-R in a PDOX model

Background/AimMatrix-producing breast carcinoma (MPBC), is a rare, recalcitrant and highly aggressive. The present study aimed to determine the efficacy of tumor-targeting Salmonella typhimurium (S. typhimurium) A1-R on a triple-negative MPBC in a patient-derived orthotopic xenograft (PDOX) model. MethodsThe PDOX model was established in the left second mammary gland of a nude mouse by surgical orthotopic implantation (SOI) of the patient triple-negative MPBC PDOX models were randomized into two groups: G1, control group (n=6); G2, tumor-targeting S. typhimurium A1-R group (n=7, intravenous (i.v.) injection via tail vein, weekly, for two weeks). All mice were sacrificed on day 15. Tumor volume and body weight were measured one time per week. ResultsS. typhimurium A1-R arrested tumor growth compared to the control group (P = 0.016). ConclusionThe results of the present study suggest that S. typhimurium A1-R has future clinical potential in triple-negative MPBC patients.

cancer biology↗

bioRxiv2021

FLT3-ITD transduces autonomous growth signals during its biosynthetic trafficking in acute myelogenous leukemia cells.

FMS-like tyrosine kinase 3 (FLT3) in hematopoietic cells binds to its ligand at the plasma membrane (PM), then transduces growth signals. FLT3 gene alterations that lead the kinase to assume its permanently active form, such as internal tandem duplication (ITD) and D835Y substitution, are found in 30~40% of acute myelogenous leukemia (AML) patients. Thus, the drugs for molecular targeting of FLT3 mutants have been developed for the treatment of AML. Several groups have reported that compared with wild-type FLT3 (FLT3-wt), FLT3 mutants are retained in organelles, resulting in low levels of PM localization of the receptor. However, the precise subcellular localization of mutant FLT3 remains unclear, and the relationship between oncogenic signaling and the mislocalization is not completely understood. In this study, we show that in cell lines established from AML patients, endogenous FLT3-ITD but not FLT3-wt clearly accumulates in the perinuclear region. Our co-immunofluorescence assays demonstrate that Golgi markers are co-localized with the perinuclear region, indicating that FLT3-ITD mainly localizes to the Golgi region in AML cells. FLT3-ITD biosynthetically traffics to the Golgi apparatus and remains there in a manner dependent on its tyrosine kinase activity. A tyrosine kinase inhibitor midostaurin (PKC412) markedly decreases in FLT3-ITD retention and increases in the PM levels of the mutant. FLT3-ITD activates downstream in the endoplasmic reticulum (ER) and the Golgi apparatus during its biosynthetic trafficking. Results of our trafficking inhibitor treatment assays show that FLT3-ITD in the ER activates STAT5, whereas that in the Golgi can cause the activation of AKT and ERK. We provide evidence that FLT3-ITD signals from the early secretory compartments before reaching the PM in AML cells.

cancer biology↗

bioRxiv2020

MafF is an anti-viral host factor that suppresses transcription from Hepatitis B Virus and Epstein Barr Virus promoters

Hepatitis B Virus (HBV) is a stealth virus that exhibits only minimal induction of the interferon system that is required for both innate and adaptive immune responses. However, 90% of acutely infected adults can clear the virus, suggesting the presence of additional mechanisms that facilitate viral clearance. Herein, we report that Maf bZIP transcription factor F (MafF) promotes host defense against infection with HBV. Using siRNA library and an HBV/NL reporter virus, we screened to identify anti-HBV host factors. Our data showed that silencing of MafF led to a 6-fold increase in luciferase activity after HBV/NL infection. Overexpression of MafF reduced HBV core promoter transcriptional activity, which was relieved upon mutating the putative MafF binding region. Loss of MafF expression by CRISPR/CAS9 (in HepG2-hNTCP-C4 cells) or siRNA silencing (in primary hepatocytes [PXB]), induced HBV core and HBV pregenomic RNA (pgRNA) levels, respectively, after HBV infection. MafF physically binds to HBV core promoter and competitively inhibits HNF-4 binding to an overlapping sequence in HBV enhancer II sequence (EnhII) as seen by ChIP analysis. MafF expression was induced by IL-1{beta}/TNF- treatment in both HepG2 and PXB cells, in an NF-{kappa}B-dependent manner. Consistently, MafF expression levels were significantly enhanced and positively correlated with the levels of these cytokines in patients with chronic HBV infection, especially in the immune clearance phase. ImportanceHBV is a leading cause of chronic liver diseases, infecting about 250 million people worldwide. HBV has developed strategies to escape interferon-dependent innate immune responses. Hence, the identification of other anti-HBV mechanisms is important for understanding HBV pathogenesis, and developing anti-HBV strategies. MafF was shown to suppress transcription from HBV core promoter, leading to a significant suppression of HBV life cycle. Furthermore, MafF expression was induced in chronic HBV patients and in primary human hepatocytes (PXB). This induction correlated with the levels of inflammatory cytokines (IL-1{beta} and TNF-). These data suggest that the induction of MafF contributes to the hosts antiviral defense by suppressing transcription from selected viral promoters. Our data shed light on a novel role for MafF as anti-HBV host restriction factor.

microbiology↗

bioRxiv2020

Epstein-Barr virus tegument protein BGLF2 in exosomes released from virus-producer cells assists de novo infection by enhancing viral gene expression

Viruses must adapt to the environment of their host cells to establish infection and persist. Diverse mammalian cells, including virus-infected cells, secrete extracellular vesicles such as exosomes containing proteins and miRNAs, and use these vesicles to mediate intercellular communications. However, the roles of exosomes in viral infection remain unclear. Here we screened viral proteins to identify those responsible for the exosome-mediated upregulation of Epstein-Barr virus (EBV) infection. We found BGLF2 protein encapsulated in exosomes, which were released from EBV-infected cells. BGLF2 protein is a tegument protein that exists the space between the envelope and the nucleocapsid, and it is released into the cytoplasm shortly after infection. BGLF2 protein-containing exosomes enhanced viral gene expression and repressed innate immunity, thereby assisting the EBV infection. In summary, the EBV tegument protein BGLF2 is encapsulated not only encapsulated in viral particles, but also in exosomes secreted from infected cells. Therefore, BGLF2 may play a crucial role in establishing EBV latent infection.

microbiology↗