Biology subjects

Ogata, K.

Publications and source records attributed to Ogata, K..

17 recordsLinked to original sources

bioRxiv2026

The HBV basal core promoter mutation confers a replicative advantage and transcriptionally reprograms hepatocytes toward HCC subtypes

Background: Hepatitis B virus (HBV) basal core promoter (BCP) and precore (PC) mutations occur during chronic HBV infection with the BCP-mutant being associated with increased hepatocellular carcinoma (HCC) risk. Objectives: The effects of these mutants on viral replication, hepatocyte biology, and carcinogenesis remain poorly defined. To address this, we characterized BCP- and PC-mutants using human hepatocyte chimeric mice and asked whether the resulting infection-induced transcriptomes correspond to subsets of human HBV-related hepatocellular carcinomas (HBV-HCCs). Design: Isogenic wild-type (WT), BCP- and PC-mutants of HBV genotypes A, C, and D (HBV-A, -C, -D) were generated from recombinant covalently-closed circular DNA to infect chimeric mice. HBV-HCC transcriptomic datasets from The Cancer Genome Atlas (TCGA) were used to stratify association of HBV variants with HCC subtypes. Results: WT, BCP-mutant, and PC-mutant HBV sequences remained genetically stable. The BCP mutation, but not the PC mutation, accelerated the rise in serum viremia in HBV-D- and HBV-A-infected chimeras; in HBV-C, acceleration required both (PC+BCP) mutations. Further comparisons of HBV-D variants revealed that the BCP-mutant increased intrahepatic viral DNA, viral protein expression, and upregulated cancer-related pathways, including transcripts associated with a subset of HBV-HCCs. Analysis of HBV-HCC samples from the TCGA revealed that tumors often harbor a mixture of WT and mutant transcripts, and that WT- and BCP-mutant-associated HCCs exhibit distinct transcriptional profiles. Conclusions: The HBV BCP-mutant directly perturbs hepatocyte homeostasis via virus-intrinsic mechanisms, selectively activating cancer-related pathways and defining a molecularly distinct subset of HBV-HCC. These findings suggest that HBV variants form distinct subcategories of HBV-HCCs.

molecular biology↗

bioRxiv2026

A Multi-Omics Framework Reveals Phosphorylation-Dependent Control of Protein Interactions

Protein phosphorylation regulates nearly every cellular process, yet most of the hundreds of thousands of human phosphosites remain functionally uncharacterized. Rather than prioritising phosphosites by conservation or structural features, here we use the abundance of an interaction partner as a readout of whether a phosphosite affects that interaction. This idea exploits the fact that subunits of stable complexes are often degraded when unbound. Here, we apply a nested linear regression model to pan-cancer data from 1,006 tumours, while controlling for transcriptional and other covariates. We identified 6,160 associations between 3,038 phosphosites and the abundance of interacting proteins, including several known interaction-regulating sites. Mapping these onto AlphaFold-predicted complexes placed 239 sites at interaction interfaces, while another 402 were linked to compartment-specific localisation, indicating that phosphorylation can also tune interactions by relocating proteins between compartments. Affinity-purification mass spectrometry of NKAP and NUF2 phosphosite mutants experimentally supported some of these predictions. Together, this framework reveals a widespread coupling between phosphorylation and interaction-dependent protein abundance and provides a prioritized, structure-informed resource for characterizing the human phosphoproteome

bioinformatics↗

bioRxiv2026

Predicting cellular functions of human phosphosites

Protein phosphorylation is a regulatory switch that controls essentially all cellular processes, including metabolism, cell cycle progression, and DNA repair. Furthermore, by modulating specific regions and activities of a protein, phosphorylation sites can independently coordinate the proteins involvement in distinct cellular processes. Despite the importance of this regulatory mechanism, the majority of human phosphosites have not been functionally characterized. Here we have developed biologically informed predictors of phosphosite cellular function by integrating protein functional annotation, recognition by upstream kinases, and regulation across phosphoproteomics perturbations. To enable this we harmonized public phosphoproteomics data into an atlas of nearly 2,000 perturbations and more than 16 million quantifications, providing a powerful resource for studying phosphosite regulation. We applied our predictors to functionally characterise thousands of understudied phosphosites, revealing many phosphosite functions that could not be inferred from protein functional annotation, and functionally divergent phosphosites within the same protein. Using cancer multi-omics data we characterized connections between these phosphosites and other molecular layers. Finally, we illuminated novel signaling axes within the DNA repair pathway, and demonstrated that phosphosites on PPM1G and KHSRP modulate cell survival under DNA damage. Our work represents a powerful resource for dissecting the cellular consequences of protein phosphorylation.

genomics↗

bioRxiv2026

High Recovery Stop-and-Go Extraction Tips Using Polytetrafluoroethylene Disks Embedded with Poly(styrene-divinylbenzene) Particles for Proteomics

The stop-and-go extraction tip (StageTip) is widely used for peptide purification in bottom-up proteomics, yet the original 3M EmporeTM disk is no longer available, prompting the need to evaluate current alternatives. Two types of commercially available poly(styrene-divinylbenzene) (SDB)-containing polytetrafluoroethylene (PTFE) disks were used to fabricate StageTips. Desalting was performed on 500 ng and 20 ng of HeLa tryptic peptides, and the nanoLC/MS/MS results were compared. Both StageTips demonstrated equivalent performance for the 500 ng sample, but for the 20 ng sample, one StageTip identified 1.8 times more peptides, particularly longer and more hydrophobic peptides. Physical characterization and scanning electron microscope imaging of these disks revealed that the high-performing disk contains more PTFE fibers, partially covering the SDB particle surface. This likely prevents hydrophobic peptides from being trapped in small mesopores, improving recovery from low-input samples. These findings demonstrate that disk material properties critically influence performance in trace proteomics.

biochemistry↗

bioRxiv2025

Bottom-up proteomics under acidic conditions using protease type XIII from Aspergillus saitoi

Bottom-up proteomics is a powerful technique for comprehensive analysis of proteins by proteolytic cleavage followed by liquid chromatography/tandem mass spectrometry to identify the resulting peptides. Trypsin is the gold-standard protease for bottom-up proteomics, though its cleavage specificity limits peptide identification, depending on the protein sequence. In addition, its optimal pH is weakly alkaline, which can cause modification artifacts such as deamidation. We hypothesized that these limitations might be overcome by using protease type XIII (P13ase) from Aspergillus saitoi, which is active at low pH. P13ase has been used for protein structural analysis by hydrogen-deuterium exchange mass spectrometry, but its cleavage preferences have not been clarified. Here, we show that P13ase primarily cleaves the C-terminal side of Lys, Arg, and Leu, and the optimal P13ase digestion conditions for bottom-up proteomics are pH 3.5, 37{degrees}C for 60 min. Under these conditions, sequence coverage of more than 90% was achieved for several proteins in HeLa cell extracts, which is unachievable with trypsin. In addition, P13ase digestion reduced artifacts such as deamidation products generated by cyclization reactions and subsequent hydrolysis. These results indicate that P13ase is a promising new tool for precision proteomics.

biochemistry↗

bioRxiv2025

Detecting Protein Higher-Order Structural Changes Using Kinase as a Phospho-Labeler

We developed an approach to detect protein conformational changes on a proteome-wide scale by labeling proteins with phosphate groups through in vitro kinase reactions. This structural proteomics approach combines residue-specific labeling based on substrate recognition by protein kinases with quantitative phosphoproteomics using phosphopeptide enrichment, enabling proteome-wide and site-specific profiling of protein conformational changes. By performing in vitro phosphorylation of myoglobin with and without heat denaturation and of HEK293T cell extracts with and without protease treatment, we demonstrated that differences in substrate protein structure are reflected in in vitro phosphorylation efficiency. Moreover, we successfully identified protein conformational changes upon RNA digestion in non-denatured cell extract proteome samples on a proteome-wide scale with high sensitivity by comparing phosphorylation efficiencies. This approach enables residue-specific readout of structural dynamics within the intracellular proteome. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=119 SRC="FIGDIR/small/652599v1_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@b2c6c8org.highwire.dtl.DTLVardef@118b159org.highwire.dtl.DTLVardef@2374adorg.highwire.dtl.DTLVardef@1c14880_HPS_FORMAT_FIGEXP M_FIG C_FIG MotivationMass spectrometry (MS)-based structural analysis of proteins often involves labeling of exposed amino acid residues, followed by digestion and identification of labeled peptides by MS. However, the heterogeneity of labeled peptides and the complexity of biological samples hinder proteome-wide analysis of protein higher-order structures. To address this issue, we devised an approach that utilizes site-specific labeling with phosphate groups, taking advantage of the substrate recognition provided by protein kinases. The phosphate groups serve as enrichment handles, enabling selective extraction and highly sensitive analysis of labeled sites. HighlightsO_LIProtein labeling with phosphate groups using in vitro kinase reaction C_LIO_LIQuantitative MS-based readout of in vitro phosphorylation efficiency C_LIO_LIIn vitro phosphorylation efficiency reflects protein conformational changes C_LIO_LIProteome-wide and site-specific identification of protein conformational changes C_LI

biochemistry↗

bioRxiv2024

UniScore, a unified and universal measure for peptide identification by multiple search engines

We propose UniScore as a metric for integrating and standardizing the outputs of multiple search engines in the analysis of data-dependent acquisition (DDA) data from LC/MS/MS-based bottom-up proteomics. UniScore is calculated from the annotation information attached to the product ions alone by matching the amino acid sequences of candidate peptides suggested by the search engine with the product ion spectrum. The acceptance criteria are controlled independently of the score values by using the false discovery rate based on the target-decoy approach. Compared to other rescoring methods that use deep learning-based spectral prediction, larger amounts of data can be processed using minimal computing resources. When applied to large-scale global proteome data and phosphoproteome data, the UniScore approach outperformed each of the conventional single search engines examined (Comet, X! Tandem, Mascot and MaxQuant). Furthermore, UniScore could also be directly applied to peptide matching in chimeric spectra without any additional filters.

bioinformatics↗

bioRxiv2024

Prediction of Protein Half-lives from Amino Acid Sequences by Protein Language Models

We developed a protein half-life prediction model, PLTNUM, based on a protein language model using an extensive dataset of protein sequences and protein half-lives from the NIH3T3 mouse embryo fibroblast cell line as a training set. PLTNUM achieved an accuracy of 71% on validation data and showed robust performance with an ROC of 0.73 when applied to a human cell line dataset. By incorporating Shapley Additive Explanations (SHAP) into PLTNUM, we identified key factors contributing to shorter protein half-lives, such as cysteine-containing domains and intrinsically disordered regions. Using SHAP values, PLTNUM can also predict potential degron sequences that shorten protein half-lives. This model provides a platform for elucidating the sequence dependency of protein half-lives, while the uncertainty in predictions underscores the importance of biological context in influencing protein half-lives.

bioinformatics↗

bioRxiv2024

Leveraging Pretrained Deep Protein Language Model to Predict Peptide Collision Cross Section

Collision cross section (CCS) of peptide ions provides an important separation dimension in liquid chromatography/tandem mass spectrometry-based proteomics that incorporates ion mobility spectrometry (IMS), and its accurate prediction is the basis for advanced proteomics workflows. This paper describes novel experimental data and a novel prediction model for challenging CCS prediction tasks including longer peptides that tend to have higher charge states. The proposed model is based on a pretrained deep protein language model. While the conventional prediction model requires training from scratch, the proposed model enables training with less amount of time owing to the use of the pretrained model as a feature extractor. Results of experiments with the novel experimental data show that the proposed model succeeds in drastically reducing the training time while maintaining the same or even better prediction performance compared with the conventional method. Our approach presents the possibility of prediction in a "greener" manner of various peptide properties in proteomic liquid chromatography/tandem mass spectrometry experiments.

bioinformatics↗

bioRxiv2024

Highly Sequence-specific, Timing-controllable m6A Demethylation by Modulating RNA-binding Affinity of m6A Erasers

In recent years, significant progress has been made in developing tools that consist of programmable RNA binding proteins and m6A-erasers to selectively demethylate m6A at specific sites. Especially, timing-controllable demethylation tools using stimulus-inducible dimerization show promise in understanding the impact of individual m6A modifications on dynamic physiological processes. However, a critical issue with these technologies is the possible off-target effects, wherein wild-type m6A-erasers constituting the tools may decrease methylation levels at sites other than the intended target m6A. In this study, we addressed this issue by reducing the intrinsic RNA-binding ability of m6A-erasers to prevent off-target effects and by fusing with PUF RNA-binding protein to provide recognition ability of arbitrary RNA sequences. Taking advantage of the reduced RNA-binding ability of the m6A-erasers themselves, we employed a rapamycin-based switching system in the linker connecting the PUF and m6A-eraser domains. The resulting m6A-erasers exhibited superior precision in demethylating targeted sites while minimizing off-target effects, presenting a novel approach for precise temporal control over m6A modification dynamics.

biochemistry↗

bioRxiv2023

One thousand samples per day capillary-flow LC/MS/MS for high-speed, high-sensitivity and in-depth proteomics

We developed a capillary-flow LC/MS/MS system with ultrahigh speed, enabling a throughput of 1,000 samples per day while maintaining high sensitivity and depth of analysis. In targeted LC/MS mode, 36 endogenous phosphopeptides in HeLa cells, including EphA2- derived phosphopeptide isomers, were successfully quantified with high selectivity and linearity by combining ion mobility separation. When 500 ng of HeLa cell digest was measured 100 times repeatedly in data-dependent acquisition mode, the coefficient of variation of retention time, peak intensity and number of identified peptides were on average 3.4%, 19.8%, and 6.0%, respectively. In data-independent acquisition mode, this system achieved the identification and quantification of 3,139 protein groups from a 100 ng HeLa cell digest and 2,145 protein groups from a sample of only 10 ng. The coefficient of variation of protein commonly quantified in the triplicate analysis ranged from 12 to 24% for HeLa digest samples ranging from 10 to 1000 ng. Finally, we applied this high-speed system to the spatial proteomics of the mouse brain, and succeeded in capturing the proteome distribution along a 96-sectioned brain structure in 135 minutes. This is the first LC/MS/MS system to achieve both more than 500 samples per day and more than 3000 identified protein groups ID with less than 100 ng human cultured cells simultaneously.

systems biology↗

bioRxiv2023

Structure of the human Bre1 complex bound to the nucleosome

Histone H2B monoubiquitination (at Lys120 in humans) regulates transcription elongation and DNA repair. In humans, H2B monoubiquitination is catalyzed by the heterodimeric Bre1 complex composed of Bre1A/RNF20 and Bre1B/RNF40. The Bre1 proteins generally function as tumor suppressors, while in certain cancers, they facilitate cancer cell proliferation. To reveal the structural basis of H2BK120 ubiquitination and its regulation, we determined the cryo-EM structure of the human Bre1 complex bound to the nucleosome. The two RING domains of Bre1A and Bre1B recognize the acidic patch and the nucleosomal DNA phosphates around SHL 6.0, which are ideally located to recruit the E2 enzyme and ubiquitin for H2BK120-specific ubiquitination. Mutational experiments suggest that the two RING domains bind in both orientations and that ubiquitination occurs when Bre1A binds to the acidic patch. Our results provide insights into the relationships between Bre1 proteins and cancer and suggest that H2B monoubiquitination can be regulated by nuclesomal DNA flexibility.

biochemistry↗

bioRxiv2021

Conservation of the direct and indirect pathways dichotomy in mouse caudal striatum with uneven distribution of dopamine receptor D1- and D2-expressing neurons

The striatum is one of the key nuclei for adequate control of voluntary behaviors and reinforcement learning. Two striatal projection neuron types, expressing either dopamine receptor D1 (D1R) or dopamine receptor D2 (D2R) constitute two independent output routes: the direct or indirect pathways, respectively. These pathways co-work in balance to achieve coordinated behavior. Two projection neuron types are equivalently intermingled in most striatal space. However, recent studies revealed two atypical zones in the caudal striatum: the zone in which D1R-neurons are the minor population (D1R-poor zone) and that in which D2R-neurons are the minority (D2R-poor zone). It remains obscure as to whether these imbalanced zones have similar properties on axonal projections and electrophysiology compared to other striatal regions. Based on morphological experiments in mice using immunofluorescence, in situ hybridization, and neural tracing, here, we revealed that the poor zones densely projected to the globus pallidus and substantia nigra pars lateralis, with a few collaterals in substantia nigra pars reticulata and compacta. Similar to that in other striatal regions, D1R-neurons were the direct pathway neurons. We also showed membrane properties of projection neurons in the poor zones were largely similar to those in the conventional striatum using in vitro electrophysiological recording. In addition, the poor zones existed irrespective of the age or sex of mice. We also identified the poor zones in the common marmoset as well as other rodents. These results suggest that the poor zones in the caudal striatum follow the conventional projection patterns irrespective of imbalanced distribution of projection neurons. The poor zones could be an innate structure and common in mammals. The unique striatal zones possessing highly restricted projections could relate to functions different from those of motor-related striatum.

neuroscience↗

bioRxiv2021

IRAK1-dependent Regnase-1-14-3-3 complex formation controls Regnase-1-mediated mRNA decay

Regnase-1 is an endoribonuclease crucial for controlling inflammation by degrading mRNAs encoding cytokines and inflammatory mediators in mammals. However, it is unclear how Regnase-1-mediated mRNA decay is controlled in interleukin (IL)-1{beta} or Toll-like receptor (TLR) ligand-stimulated cells. Here, by analyzing the Regnase-1 interactome, we found that IL-1{beta} or TLR stimulus dynamically induced the formation of Regnase-1-{beta}-transducin repeat-containing protein ({beta}TRCP) complex. Importantly, we also uncovered a novel interaction between Regnase-1 and 14-3-3 in both mouse and human cells. Strikingly, both interactions occur in a mutually exclusive manner, underscoring the importance of modulating Regnase-1s activity. Additionally, we show that in IL-1R/TLR-stimulated cells, the Regnase-1-14-3-3 interaction is mediated by IRAK1 through a previously uncharacterized C-terminal structural domain. Phosphorylation of Regnase-1 at S494 and S513 is critical for Regnase-1-14-3-3 interaction, while a different set of phosphorylation sites of Regnase-1 are known to be required for the recognition by {beta}TRCP and proteasome-mediated degradation. 14-3-3 stabilizes Regnase-1 but abolishes its activity by inhibiting Regnase-1-mRNA association. Furthermore, nuclear-cytoplasmic shuttling of Regnase-1 is abrogated by 14-3-3 interaction. Taken together, the results suggest that a novel inflammation-induced interaction of 14-3-3 with Regnase-1 stabilizes inflammatory mRNAs by sequestering Regnase-1 in the cytoplasm to prevent mRNA recognition.

immunology↗

bioRxiv2021

Motif-centric phosphoproteomics to target kinase-mediated signaling pathways

Identifying cellular phosphorylation pathways based on kinase-substrate relationships is a critical step to understanding the regulation of physiological functions in cells. Mass spectrometry-based phosphoproteomics workflows have made it possible to comprehensively collect information on individual phosphorylation sites in a variety of samples. However, there is still no generic approach to uncover phosphorylation networks based on kinase-substrate relationships in rare cell populations. Here, we describe a motif-centric phosphoproteomics approach combined with multiplexed isobaric labeling, in which in vitro kinase reaction is used to generate the targeted phosphopeptides, which are spiked into one of the isobaric channels to increase detectability. Proof-of-concept experiments demonstrate selective and comprehensive quantification of targeted phosphopeptides by using multiple kinases for motif-centric channels. Over 7,000 tyrosine phosphorylation sites were quantified from several tens of {micro}g of starting materials. This approach enables the quantification of multiple phosphorylation pathways under physiological or pathological regulation in a motif-centric manner. MotivationSensitivity for detecting phosphopeptides with a particular phosphorylation motif is limited, especially for tyrosine phosphopeptides.

systems biology↗

bioRxiv2020

Structural basis of the regulation of normal and oncogenic methylation of nucleosomal histone H3 Lys36 by NSD2

Dimethylated histone H3 Lys36 (H3K36me2) regulates gene expression by antagonizing the repressive effect of polycomb-group proteins. Aberrant upregulation of H3K36me2, either by overexpression or point mutations of NSD2/MMSET, an H3K36 dimethyltransferase, is found in various cancers, including multiple myeloma. To understand the mechanism underlying its regulation, here we report the cryo-electron microscopy structure of the catalytic fragment of NSD2 bound to the nucleosome at 2.8 [A] resolution. The nucleosomal DNA is partially unwrapped at superhelix location +5.5, facilitating the access of NSD2 to H3K36. NSD2 interacts with DNA and H2A along with H3. The autoinhibitory loop of NSD2 changes its conformation upon nucleosome binding to accommodate H3 in its substrate-binding cleft. Kinetic analysis revealed two oncogenic mutations, E1099K and T1150A, to aberrantly activate NSD2 by increasing its catalytic turnover but not the nucleosome affinity. Molecular dynamics simulations suggested that in both mutants, the autoinhibitory loop adopts an open state that can accommodate H3 more often than the wild type. We propose that E1099K and T1150A destabilize the interactions that keep the autoinhibitory loop closed, thereby enhancing the catalytic turnover. Our analyses would guide the development of specific inhibitors of NSD2 for the treatment of various cancers.

biochemistry↗

bioRxiv2020

Effect of Phosphorylation on the Collision Cross Sections of Peptide Ions in Ion Mobility Spectrometry

The insertion of ion mobility spectrometry (IMS) between LC and MS can improve peptide identification in both proteomics and phosphoproteomics by providing structural information that is complementary to LC and MS, because IMS separates ions on the basis of differences in their shapes and charge states. However, it is necessary to know how phosphate groups affect the peptide collision cross sections (CCS) in order to accurately predict phosphopeptide CCS values and to maximize the usefulness of IMS. In this work, we systematically characterized the CCS values of 4,433 pairs of mono-phosphopeptide and corresponding unphosphorylated peptide ions using trapped ion mobility spectrometry (TIMS). Nearly one-third of the mono-phosphopeptide ions evaluated here showed smaller CCS values than their unphosphorylated counterparts, even though phosphorylation results in a mass increase of 80 Da. Significant changes of CCS upon phosphorylation occurred mainly in structurally extended peptides with large numbers of basic groups, possibly reflecting intramolecular interactions between phosphate and basic groups.

biochemistry↗