Biology subjects

Yamazaki, H.

Publications and source records attributed to Yamazaki, H..

11 recordsLinked to original sources

bioRxiv2025

IDR-dependent MORC1 bodies limit chromatin accessibility to tune transposon repression

Germline-specific MORC1-mediated transposon repression intersects with the MIWI2-piRNA pathway and involves H3K9me3 deposition, yet the underlying mechanism remains unclear. Here, we show that MORC1 assembles nuclear bodies in gonocytes. Using a doxycycline-inducible MORC1 expression system in NIH3T3 cells, we find that condensate formation is confined to the nucleus via an IDR containing a bipartite NLS, and that TRIM28, a corepressor that recruits the H3K9 methyltransferase SETDB1, is enriched in these bodies through protein-protein interactions. An IDR-deficient MORC1 mutant fails to form nuclear condensates but retains TRIM28 binding. ChIP-seq analysis reveals that this mutant exhibits higher occupancy at heterochromatin-embedded transposons than wild-type MORC1, with a pronounced preference for evolutionarily young transposon subfamilies that strongly overlap endogenous MORC1 targets in gonocytes. Wild-type MORC1 shows weaker enrichment at these elements and instead exhibits a greater tendency to occupy open chromatin. Condensates formed by exogenous MORC1 expression in NIH3T3 cells are substantially larger than those observed in gonocytes. These findings support a model in which MORC1-dependent transposon repression is governed by physical engagement with TRIM28 and by IDR-dependent, yet quantitatively restrained, nuclear body formation, which limits MORC1 chromatin accessibility, curtails off-target binding, and concentrates repression on bona fide transposon targets.

molecular biology↗

bioRxiv2025

L-Phenylalanine restriction amplifies boron neutron capture therapy efficacy through increased L-boronophenylalanine uptake and induces activating transcription factor 4 stress response in tumor cell lines

Boron neutron capture therapy (BNCT) relies on the selective uptake of boron-10 compounds by tumor cells. L-boronophenylalanine (BPA) serves as a key carrier, and enhancing its accumulation is critical for improving BNCT efficacy. In this study, we investigated the effects of L-phenylalanine (Phe) restriction on the tumor cell lines SAS, U87-MG, PANC-1, and A375, and the immortalized keratinocyte line HaCaT on modulating BPA uptake and associated cellular responses. Quantitative analysis using inductively coupled plasma atomic emission spectroscopy (ICP-AES) showed that 24 h Phe restriction increased BPA uptake in the SAS, U87-MG, and PANC-1 cell lines. Colony formation assays confirmed enhanced sensitivity to neutron irradiation in these cells. RNA sequencing indicated that Phe restriction activated the integrated stress response downstream of activating transcription factor 4 (ATF4), although this pathway was not directly linked to increased BPA uptake. The L-type amino acid transporter 1 (LAT1)/4F2 heavy chain (4F2HC) complex was identified as the exclusive transport route for BPA. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis showed that Phe restriction altered intracellular levels of amino acids that serve as LAT1/4F2HC exchange substrates, suggesting a metabolic basis for enhanced BPA transport. Our results reveal that Phe restriction enhances BPA uptake and BNCT efficacy in a cell line-dependent manner, likely through the modulation of amino-acid metabolism. Therefore, targeted amino-acid manipulation prior to BNCT may represent a promising strategy to improve therapeutic outcomes.

cancer biology↗

bioRxiv2024

Diptera-specific Daedalus controls Zucchini endonucleolysis in piRNA biogenesis independent of exonucleases

piRNAs protect germline genomes and maintain fertility by repressing transposons. Daedalus and Gasz act together as a mitochondrial scaffold for Armitage, a necessary factor for Zucchini-dependent piRNA processing. However, the mechanism underlying this function remains unclear. Here, we find that the roles of Daedalus and Gasz in this process are distinct, although both are necessary: Daedalus physically interacts with Armitage, whereas Gasz supports Daedalus to maintain its function. Daedalus binds to Armitage through two distinct regions, an extended coiled-coil identified in this study, and a SAM. The former tethers Armitage to mitochondria, while the latter controls Zucchini endonucleolysis to define the length of piRNAs in an exonuclease-independent manner. piRNAs produced in the absence of Daedalus SAM do not exhibit full transposon silencing functionality. Daedalus is Diptera specific. Unlike Drosophila and mosquitoes, evolutionarily more complex species, such as mice, rely on exonucleases after Zucchini processing to specify the length of piRNAs.

biochemistry↗

bioRxiv2023

Acto3D: user- and budget-friendly software for multichannel high-resolution three-dimensional imaging

Advances in fluorescence microscopy and tissue-clearing technology have revolutionized three-dimensional (3D) imaging of fluorescently labeled tissues, organs, and embryos. However, the complexity and high cost of existing software and computer solutions for such imaging limit its widespread adoption by researchers with limited resources. We here introduce Acto3D as a user- and budget-friendly, open-source computer software application designed to streamline the generation and observation of high-resolution 3D images of targets labeled with multiple fluorescent probes. Acto3D features an intuitive interface that simplifies the importation, visualization, and analysis of data sets, has an associated tool for annotation of vascular lumens, and incorporates multiple fluorescence channels for comprehensive imaging. Underpinned by an integrated graphics processing unit, Acto3D allows accurate image reconstruction and efficient data processing without the need for expensive high-performance computers. We validated the software by imaging mouse embryonic structures. Acto3D thus constitutes a cost-effective and efficient platform to support biological research.

developmental biology↗

bioRxiv2023

Statistical mining of triple-negative breast cancer-specific nanobodies among huge libraries from immunized alpacas

Breast cancer can be classified into several types according to the expression patterns of human epidermal growth factor receptor 2 (Her2), oestrogen receptor (ER), and progesterone receptor (PgR) proteins. The prognosis of patients with tumors showing low Her2 expression and no ER and PgR expression--categorized as triple-negative breast cancer (TNBC)--is worst among these groups. Due to the lack of specific antibodies for TNBC, curative treatments for TNBC remain limited. Antibodies targeting TNBC have potential as diagnostic and therapeutic tools. Here, we generate a panel of nanobodies targeting TNBC cell lines by immunizing alpacas and subsequently panning the resulting phage libraries with TNBC cell lines. We show that several clones exclusively stain Her2-negative cells in tissues of breast cancer patients, and a few clones stain both Her2-positive and Her2-negative regions in these tissues. These clones can be applied to patient-specific therapies using drug-conjugated antibodies, radiolabelled antibodies, chimaera antigen receptor T cells, or drug delivery components, as well as to TNBC diagnosis.

cancer biology↗

bioRxiv2022

Recycling of uridylated mRNAs in starfish embryos

In eukaryotes, mRNAs with long poly(A) tails are translationally active, whereas deadenylation of the tails decreases translation and uridylation of the short poly(A) tails causes the mRNA to be degraded. In this study, we confirmed that maternal cyclin B mRNAs with long poly(A) tails in blastula embryos of invertebrate starfish were deadenylated and uridylated, followed by decay. In starfish oocytes, however, cyclin B mRNAs with uridylated short poly(A) tails are stable. They are polyadenylated and translationally active immediately following hormonal stimulation for resumption of meiosis. Similarly, maternal ribosomal protein mRNAs, Rps29 and Rpl27a, which become uridylated following deadenylation upon hormonal stimulation, remain stable even after fertilisation and early development. At the morula stage, the uridylated maternal ribosomal protein mRNAs are modified to yield non-canonical poly (A) tails rich in U and G residues in the 5 region and in A residues at the 3 end, rendering them translationally active. These results indicate that the fates of uridylated mRNAs in starfish are decay and/or recycling.

molecular biology↗

bioRxiv2021

Nanobodies recognizing conserved hidden clefts of all SARS-CoV-2 spike variants

We are in the midst of the historic coronavirus infectious disease 2019 (COVID-19) pandemic caused by severe respiratory syndrome coronavirus 2 (SARS-CoV-2). Although countless efforts to control the pandemic have been attempted--most successfully, vaccination1-3--imbalances in accessibility to vaccines, medicines, and diagnostics among countries, regions, and populations have been problematic. Camelid variable regions of heavy chain-only antibodies (VHHs or nanobodies)4 have unique modalities: they are smaller, more stable, easier to customize, and, importantly, less expensive to produce than conventional antibodies5, 6. We present the sequences of nine alpaca nanobodies that detect the spike proteins of four SARS-CoV-2 variants of concern (VOCs)--namely, the alpha, beta, gamma, and delta variants. We show that they can quantify or detect spike variants via ELISA and lateral flow, kinetic, flow cytometric, microscopy, and Western blotting assays7. The panel of nanobodies broadly neutralized viral infection by pseudotyped SARS-CoV-2 VOCs. Structural analyses showed that a P86 clone targeted epitopes that were conserved yet unclassified on the receptor-binding domain (RBD) and located inside the N-terminal domain (NTD). Human antibodies have hardly accessed both regions; consequently, the clone buries hidden crevasses of SARS-CoV-2 spike proteins undetected by conventional antibodies and maintains activity against spike proteins carrying escape mutations.

molecular biology↗

bioRxiv2021

Electrical Unfolding of Cytochrome c During Translocation Through a Nanopore Constriction

Many small proteins move across cellular compartments through narrow pores. In order to thread a protein through a constriction, free energy must be overcome to either deform or completely unfold the protein. In principle, the diameter of the pore, along with the effective driving force for unfolding the protein, as well as its barrier to translocation, should be critical factors that govern whether the process proceeds via squeezing, unfolding/threading, or both. To probe this for a well-established protein system, we studied the electric-field-driven translocation behavior of cytochrome c (cyt c) through ultrathin silicon nitride (SiNx) solid-state nanopores of diameters ranging from 1.5 to 5.5 nm. For a 2.5 nm diameter pore we find that, in a threshold electric field regime of [~]30-100 MV/m, cyt c is able to squeeze through the pore. As electric fields inside the pore are increased, the unfolded state of cyt c is thermodynamically stabilized, facilitating its translocation. In contrast, for 1.5 nm and 2.0 nm diameter pores, translocation occurs only by threading of the fully unfolded protein after it transitions through a higher energy unfolding intermediate state at the mouth of the pore. The relative energies between the metastable, intermediate, and unfolded protein states are extracted using a simple thermodynamic model that is dictated by the relatively slow ([~]ms) protein translocation times for passing through the nanopore. These experiments map the various modes of protein translocation through a constriction, which opens new avenues for exploring protein folding structures, internal contacts, and electric field-induced deformability. Significance StatementCan localized electric fields drive the complete unfolding of a protein molecule? Protein unfolding prior to its translocation through a nanopore constriction is an important step in protein transport across biological membranes and also an important step in nanopore-based protein sequencing. We studied here the electric-field-driven translocation behavior of a model protein (cyt c) through nanopores of diameters ranging from 1.5 to 5.5 nm. These single molecule measurements show that electric fields at the nanopore constriction can select both partially and fully unfolded protein conformations. Zero-field free energy gaps between these conformations, found using a simple thermodynamic model, are in remarkable agreement with previously reported studies of cyt c unfolding energetics.

biophysics↗

bioRxiv2020

Development of Microsatellite Markers for a Soricid Water Shrew Chimarrogale platycephalus, and the Success of Individual Identification Using It.

The soricid water shrew, Chimarrogale platycephalus, is a mammal species endemic to the Japanese Islands. They inhabit the islands of Honshu and Kyushu, and are considered to be extinct in Shikoku. Information on this water shrew from Honshu and Kyushu is also scarce, and C. platycephalus is registered on the Japanese Governments red list as an endangered species. Almost all study areas such as regarding their ethology, ecology, also their phylogenetics are lacking. The delay in these foundational studies is due to difficulties related to them being both nocturnal and aquatic. In order to study of C. platycephalus, it is essential to conduct field research in mountain streams at night under such circumstances. In response to such difficult circumstances, we established a genetic analysis method using the feces of C. platycephalus, and as a result the accumulation of data on their phylogenetic evolution and phylogeography has increased which has improved our understanding of this species. Furthermore in this study, development of microsatellite markers was carried out, and a total of 21 loci marker analyses were performed. In addition, in order to confirm the credibility of these 21 microsatellite markers, as being able to validly differentiate individuals, all markers were examined using the fecal and tissues specimens from verified separately reared individuals (12 individuals) with the known history of having been reared in an aquarium. As a result, it was revealed that if analyses of the 12 loci were possible, individual differentiation with 100% accuracy was possible. The development of microsatellite markers in this study, and the establishment of individual identification methods by means of this will be expected to greatly contribute to future ecological and ethological research, population genetics and biogeographical research of the water shrew, C. platycephalus.

evolutionary biology↗

bioRxiv2019

APOBEC3B reporter myeloma cell lines identify DNA damage response pathways leading to APOBEC3B expression

Apolipoprotein B mRNA-editing enzyme catalytic polypeptide-like (APOBEC) DNA cytosine deaminase 3B (A3B) is a DNA editing enzyme which induces genomic DNA mutations in multiple myeloma and various other cancers. APOBEC family proteins are highly homologous so it is especially difficult to investigate the biology of A3B alone in cancer cells. To investigate A3B function in myeloma cells easily and comprehensively, we used CRISPR/Cas9 to generate A3B reporter cells that contain 3xFLAG tag and IRES-EGFP sequences integrated at the end of the A3B gene. These reporter cells stably express 3xFLAG tagged A3B and the reporter EGFP and this expression is enhanced under known stimuli, such as PMA. Conversely, shRNA knockdown of A3B decreased EGFP fluorescence and 3xFLAG tagged A3B protein levels. We screened a series of anticancer treatments using these cell lines and identified that most conventional therapies, such as antimetabolites or radiation, exacerbated endogenous A3B expression, but recent molecular targeting drugs, including bortezomib, lenalidomide and elotuzumab, did not. Furthermore, chemical inhibition of ATM, ATR and DNA-PK suppressed the EGFP expression upon treatment with antimetabolites. These results suggest that DNA damage response triggers A3B expression through ATM, ATR and DNA-PK signaling.

cancer biology↗

bioRxiv2019

Quantitative proteomics revealed a tight correlation between mitotic phosphorylation/dephosphorylation and structural properties of substrate domains

Protein phosphorylation plays a critical role in the regulation and progression of mitosis. More than 10,000 phosphorylated residues and the associated kinases have been identified to date via proteomic analyses. Although some of these phosphosites are associated with regulation of either protein-protein interactions or the catalytic activity of the substrate protein, the roles of most mitotic phosphosites remain unclear. In this study, we examined structural properties of mitotic phosphosites and neighboring residues to understand the role of heavy phosphorylation in non-structured domains. Quantitative mass spectrometry analysis of mitosis-arrested and non-arrested HeLa cells revealed >4,100 and >2,200 residues either significantly phosphorylated or dephosphorylated, respectively, at mitotic entry. The calculated disorder scores of amino acid sequences of neighboring individual phosphosites revealed that >70% of dephosphorylated phosphosites exist in disordered regions, whereas 50% of phosphorylated sites exist in non-structured domains. A clear inverse correlation was observed between probability of phosphorylation in non-structured domain and increment of phosphorylation in mitosis. These results indicate that at entry to mitosis, a significant number of phosphate groups are removed from non-structured domains and transferred to more-structured domains. Gene ontology term analysis revealed that mitosis-related proteins are heavily phosphorylated, whereas RNA-related proteins are both dephosphorylated and phosphorylated, suggesting that heavy phosphorylation/dephosphorylation in non-structured domains of RNA-binding proteins plays a role in dynamic rearrangement of RNA-containing organelles, as well as other intracellular environments.\n\nSignificance StatementProgression of mitosis is tightly regulated by protein phosphorylation/dephosphorylation. Although proteomic studies have identified tens of thousands of phosphosites in mitotic cells, the roles of them remain to be answered. We approached this question from the viewpoint of the higher-order structure of phosphosites. Quantitative proteomics and bioinformatic analyses revealed that more than 70% of mitotic dephosphorylation events occurred in non-structured regions. Non-structured regions of cellular proteins are attracting considerable attention in terms of their involvement in dynamic rearrangements of intracellular membrane-less organelles and protein assembly/disassembly processes. Our results suggest the possibility that a vast amount of mitosis-associated dephosphorylation/phosphorylation at non-structured regions plays a role in regulating the dynamic assembly/disassembly of intracellular architectures and organelles such as chromosomes and nucleolus.

cell biology↗