Biology subjects

Mishima, Y.

Publications and source records attributed to Mishima, Y..

8 recordsLinked to original sources

bioRxiv2025

Ultra-parallel ribosome profiling platform with RNA-dependent RNA amplification

Translation regulation plays a pivotal role in the diversification of gene expression and the response to intra- and extracellular environmental cues. Ribosome profiling (or Ribo-Seq) serves as a sensitive, quantitative, comprehensive, and data-rich technique to survey ribosome traversal across the cellular transcriptome. However, due to the intricacy of library preparation, applications to low-input and a large number of samples have presented analytic challenges. Here, we developed the semi-automated platform of Ribo-Seq and Disome-Seq, which allowed us to assess the translation status from a vast collection of samples with reduced amounts in a plate format. Through an siRNA-mediated knockdown screen for ribosome-associated proteins, this technique identified factors that (i) mediate regulation via RNA elements such as the TOP motif, (ii) assist efficient ribosome recycling, (iii) support ribosome-associated quality control (RQC), (iv) enhance translation elongation across inhibitory G-quadruplex sequences, and (v) repress mitochondrial translation. The application to human-derived samples revealed that stop codon readthrough and mitochondrial translation deficiency are associated with severe symptoms in COVID-19. Our approach provides a versatile option to investigate the translatome in a highly parallel manner.

molecular biology↗

bioRxiv2025

Posttranscriptional activity of the eukaryotic translation initiation factoreIF4E contributes to HoxA9-driven leukemogenesis

HoxA9, a homeodomain-containing transcription factor, is mis-expressed in over half of acute myeloid leukemia (AML) cases, and is associated with poor prognosis. Previous studies indicated that HoxA9 binds to the eukaryotic translation initiation factor eIF4E in primary specimens and that HoxA9 stimulated the RNA export and translation efficiency of selected RNAs via eIF4E. However, the relevance of this to its leukemogenic transformation capacity was unknown. Here, we used a double point mutation (HoxA9AA) to disrupt the physical and functional interaction between eIF4E and HoxA9 while retaining the HoxA9 transcriptional signature. Surprisingly, the mutation dramatically increased AML latency from a median of 90 to 280 days and resulted in incomplete penetrance. Re-transplantation of bone marrow cells from leukemic animals demonstrated even more pronounced differences in disease kinetics and penetrance with all animals succumbing to disease by day 60 in the wildtype group, while some HoxA9AA mice never developed leukemia. Collectively, these findings uncover a novel, transcription-independent mechanism of HoxA9-driven leukemogenesis through eIF4E and positions eIF4E as a potential therapeutic target AML patients expressing high levels of HoxA9. Key PointsO_LIA double point mutation in HoxA9 disrupted the physical and functional interaction between eIF4E and HoxA9 while retaining the HoxA9 transcriptional signature. C_LIO_LIEukaryotic translation initiation factor eIF4E contributes to HoxA9-driven leukemogenesis and is important for the maintenance of acute myeloid leukemia. C_LI

molecular biology↗

bioRxiv2024

Label-free imaging of cellular organization in living mammalian cells via external apodization phase-contrast microscopy

Developing techniques to visualize intracellular structures, which influence the spatiotemporal functionality of biomolecules, is essential for elucidating mechanisms governing cellular behavior. In this study, we demonstrate that label-free external apodization phase-contrast (ExAPC) microscopy serves as a valuable tool for the simultaneous observation of various intracellular structures with high spatiotemporal resolution, while successfully mitigating halo artifacts. Additionally, through quantitative analysis of images obtained by combining ExAPC microscopy with fluorescence microscopy, we identified distinct heterogeneities in biomolecular condensates, lipid droplets, and mitochondria. Our findings highlight the potential of ExAPC microscopy to provide detailed insights into alterations in intracellular structures associated with diverse cellular processes, corroborating the existing knowledge and potentially contributing to the discovery of novel cellular mechanisms.

cell biology↗

bioRxiv2023

No-go decay dampens zinc finger protein mRNAs in vertebrates

Quality control of translation is crucial for maintaining cellular and organismal homeostasis. Obstacles in translation elongation induce ribosome collision, which is monitored by multiple sensor mechanisms in eukaryotes. The E3 ubiquitin ligase Znf598 recognizes collided ribosomes, triggering ribosome-associated quality control (RQC) to rescue stalled ribosomes and no-go decay (NGD) to degrade stall-prone mRNAs. However, the impact of RQC and NGD on maintaining the translational homeostasis of endogenous mRNAs has remained unclear. In this study, we investigated the endogenous substrate mRNAs of NGD during the maternal-to-zygotic transition (MZT) of zebrafish development. RNA-Seq analysis of zebrafish znf598 mutant embryos revealed that Znf598 downregulates mRNAs encoding the C2H2-type zinc finger domain (C2H2-ZF) during the MZT. Reporter assays and disome profiling indicated that ribosomes stall and collide while translating tandem C2H2-ZFs, leading to mRNA degradation by Znf598. We further showed that mRNAs encoding C2H2-ZF were degraded in a ZNF598-dependent manner in HEK293T cells. Our results suggest that NGD maintains the quality of the translatome by mitigating the risk of ribosome collision at the abundantly present C2H2-ZF sequences in the vertebrate genome.

molecular biology↗

bioRxiv2023

Znf598-mediated Rps10/eS10 ubiquitination contributes to the ribosome ubiquitination dynamics during zebrafish development

Ribosome is a translational apparatus that comprises about 80 ribosomal proteins and four rRNAs. Recent studies reported that ribosome ubiquitination is crucial for translational regulation and ribosome-associated quality control (RQC). However, little is known about the dynamics of ribosome ubiquitination under complex biological processes of multicellular organisms. To explore ribosome ubiquitination during animal development, we generated a zebrafish strain that expresses a FLAG-tagged ribosomal protein Rpl36/eL36 from its endogenous locus. We examined ribosome ubiquitination during zebrafish development by combining affinity purification of ribosomes from rpl36-FLAG zebrafish embryos with immunoblotting analysis. Our findings showed that ubiquitination of ribosomal proteins dynamically changed as development proceeded. We also showed that during zebrafish development, the ribosome was ubiquitinated by Znf598, an E3 ubiquitin ligase that activates RQC. Ribosomal protein Rps10/eS10 was found to be a key ubiquitinated protein during development. Furthermore, we showed that Rps10/eS10 ubiquitination-site mutations reduced the overall ubiquitination pattern of ribosome. These results demonstrate the complexity and dynamics of ribosome ubiquitination during zebrafish development.

molecular biology↗

bioRxiv2021

pSNAP: Proteome-wide analysis of elongating nascent polypeptide chains

Cellular global translation is often measured using ribosome profiling or quantitative mass spectrometry, but these methods do not provide direct information at the level of elongating nascent polypeptide chains (NPCs) and associated co-translational events. Here we describe pSNAP, a method for proteome-wide profiling of NPCs by affinity enrichment of puromycin- and stable isotope-labeled polypeptides. pSNAP does not require ribosome purification and/or chemical labeling, and captures bona fide NPCs that characteristically exhibit protein N-terminus-biased positions. We applied pSNAP to evaluate the effect of silmitasertib, a potential molecular therapy for cancer, and revealed acute translational repression through casein kinase II and mTOR pathways. We also characterized modifications on NPCs and demonstrated that the combination of different types of modifications, such as acetylation and phosphorylation in the N-terminal region of histone H1.5, can modulate interactions with ribosome-associated factors. Thus, pSNAP provides a framework for dissecting co-translational regulations on a proteome-wide scale.

biochemistry↗

bioRxiv2021

Transient ribosome slowdown at the decoding step triggers mRNA degradation independent of Znf598 in zebrafish

The control of mRNA stability plays a central role in regulating gene expression patterns. Recent studies have revealed that codon composition in the open reading frame (ORF) determines mRNA stability in multiple organisms. Based on genome-wide correlation approaches, this previously unrecognized role of the genetic code is attributable to the kinetics of the codon-decoding process by the ribosome. However, complementary experimental analysis is required to define the codon effects on mRNA stability apart from the related cotranslational mRNA decay pathways such as those triggered by aberrant ribosome stalls. In the current study, we performed a set of reporter-based analyses to define codon-mediated mRNA decay and ribosome stall-dependent mRNA decay in zebrafish embryos. Our analysis showed that the effect of codons on mRNA stability stems from the decoding process, independent of Znf598 and stall-dependent mRNA decay. We propose that codon-mediated mRNA decay is triggered by transiently slowed ribosomes engaging in a productive translation cycle in zebrafish embryos.

molecular biology↗

bioRxiv2019

Genome-wide survey of ribosome collision

In protein synthesis, ribosome movement is not always smooth and is rather often impeded for numerous reasons. Although the deceleration of the ribosome defines the fates of the mRNAs and synthesizing proteins, fundamental issues remain to be addressed, including where ribosomes pause in mRNAs, what kind of RNA/amino acid sequence causes this pause, and the physiological significance of this slowdown of protein synthesis. Here, we surveyed the positions of ribosome collisions caused by ribosome pausing in humans and zebrafish on a genome-wide level using modified ribosome profiling. The collided ribosomes, i.e., disomes, emerged at various sites: the proline-proline-lysine motif, stop codons, and the 3' untranslated region (UTR). The number of ribosomes involved in a collision is not limited to two, but rather four to five ribosomes can form a queue of ribosomes. In particular, XBP1, a key modulator of the unfolded protein response, shows striking queues of collided ribosomes and thus acts as a substrate for ribosome-associated quality control (RQC) to avoid the accumulation of undesired proteins in the absence of stress. Our results provide an insight into the causes and consequences of ribosome slowdown by dissecting the specific architecture of ribosomes.

molecular biology↗