Biology subjects

Takashima, K.

Publications and source records attributed to Takashima, K..

9 recordsLinked to original sources

bioRxiv2024

Cholesterol Restriction Primes RIG-I Antiviral Responses Through a Noncanonical Type I IFN Pathway

Cholesterol metabolism is associated with innate immune responses; however, the mechanisms underlying this have not been fully elucidated. Here, we performed a chemical screening to isolate small molecules affecting the activity of RIG-I, a cytoplasmic viral RNA sensor, and found that statins, which inhibit cholesterol synthesis, dramatically enhanced RIG-I-dependent antiviral responses in specific cell types. The restriction of cholesterol synthesis induced the expression of noncanonical type I interferons (IFNs), such as IFN-{omega}, in an SREBP1 transcription factor-dependent manner. This noncanonical type I IFN expression pathway subsequently enhanced RIG-I-mediated signaling following viral infection. Administration of statins in mice augmented RIG-I-dependent cytokine expression in the lungs. Conversely, a mouse obesity model exhibited reduced RIG-I response in the lungs compared to wild-type mice. Single-cell transcriptome analyses revealed a subset of alveolar macrophages that increased the RIG-I expression in response to inhibited cholesterol synthesis in vivo. This study revealed the noncanonical type I IFN pathway linking cholesterol metabolism and RIG-I signaling. Targeting this pathway could offer valuable insights for developing novel treatment approaches to address future viral pandemics.

immunology↗

bioRxiv2024

Single-cell genotype-phenotype mapping identifies therapeutic vulnerabilities in VEXAS syndrome

Somatic evolution leads to the emergence of clonal diversity across tissues with broad implications for human health. A striking example of somatic evolution is the VEXAS (Vacuoles E1 enzyme X-linked Autoinflammatory Somatic) syndrome, caused by somatic UBA1 mutations in hematopoietic stem cells (HSCs), inducing treatment-refractory, systemic inflammation. However, the mechanisms that lead to survival and expansion of mutant HSCs are unknown, limiting the development of effective therapies. The lack of animal or cellular models of UBA1-mutant HSCs has hindered such mechanistic understanding, mandating analysis of primary human VEXAS samples, which harbor admixtures of wild-type and UBA1-mutant HSCs. To address these challenges, we applied single-cell multi-omics to comprehensively define mutant UBA1-induced transcriptome, chromatin accessibility and signaling pathway alterations in VEXAS patients, allowing for the direct comparison of mutant versus wild-type cells within the same environment. We confirmed the expected enrichment of UBA1M41V/T mutations in myeloid cells, and additionally discovered that these mutations were also prevalent in Natural Killer (NK) cells in VEXAS patients, providing new insights into disease phenotypes. Through mapping genotypes to molecular phenotypes, including transcriptome, chromatin accessibility, cell surface protein or intracellular protein profiles, in HSCs, we found that UBA1M41V/T-mutant cells showed an increased inflammation signature (interferon alpha and gamma response pathways), as well as activation of unfolded protein response (UPR) via pro-survival, but not pro-apoptotic, mediators of the PERK pathway, compared to UBA1 wild-type HSCs. Ex vivo validation experiments showed that inhibiting UBA1 in normal CD34+ or using UBA1-mutant HSCs led to PERK pathway up-regulation, increased myeloid differentiation and cell survival, which was reversed by PERK inhibition. Thus, we demonstrated that human VEXAS HSCs show cell-intrinsic inflammatory phenotypes and survive the proteomic stress caused by compromised ubiquitination through PERK-mediated activation of the UPR. Together, these analyses nominate PERK pathway inhibition as a potential new therapeutic strategy for eradicating the VEXAS-inducing clone, demonstrating the power of single-cell multi-omics profiling of primary patient sample to enable genotype-to-phenotype somatic mapping for the discovery of novel candidates for clinical intervention.

genomics↗

bioRxiv2023

NOP16 is a histone mimetic that regulates Histone H3K27 methylation and gene repression

Post-translational modifications of histone tails alter chromatin accessibility to regulate gene expression. Some viruses exploit the importance of histone modifications by expressing histone mimetic proteins that contain histone-like sequences to sequester complexes that recognize modified histones. Here we identify an evolutionarily conserved and ubiquitously expressed, endogenous mammalian protein Nucleolar protein 16 (NOP16) that functions as a H3K27 mimic. NOP16 binds to EED in the H3K27 trimethylation PRC2 complex and to the H3K27 demethylase JMJD3. NOP16 knockout selectively globally increases H3K27me3, a heterochromatin mark, without altering methylation of H3K4, H3K9, or H3K36 or acetylation of H3K27. NOP16 is overexpressed and linked to poor prognosis in breast cancer. Depletion of NOP16 in breast cancer cell lines causes cell cycle arrest, decreases cell proliferation and selectively decreases expression of E2F target genes and of genes involved in cell cycle, growth and apoptosis. Conversely, ectopic NOP16 expression in triple negative breast cancer cell lines increases cell proliferation, cell migration and invasivity in vitro and tumor growth in vivo, while NOP16 knockout or knockdown has the opposite effect. Thus, NOP16 is a histone mimic that competes with Histone H3 for H3K27 methylation and demethylation. When it is overexpressed in cancer, it derepresses genes that promote cell cycle progression to augment breast cancer growth.

cancer biology↗

bioRxiv2023

Cotranscriptional demethylation induces global loss of H3K4me2 from active genes in Arabidopsis

Based on studies of animals and yeasts, methylation of histone H3 lysine 4 (H3K4me1/2/3, for mono-, di-, and tri-methylation, respectively) is regarded as the key epigenetic modification of transcriptionally active genes. In plants, however, H3K4me2 correlates negatively with transcription, and the regulatory mechanisms of this counterintuitive H3K4me2 distribution in plants remain largely unexplored. A previous genetic screen for factors regulating plant regeneration identified Arabidopsis LYSINE-SPECIFIC DEMETHYLASE 1-LIKE 3 (LDL3), which is a major H3K4me2 demethylase. Here, we show that LDL3-mediated H3K4me2 demethylation depends on the transcription elongation factor Paf1C and phosphorylation of the C-terminal domain (CTD) of RNA polymerase II (RNAPII). In addition, LDL3 binds to phosphorylated RNAPII. These results suggest that LDL3 is recruited to transcribed genes by binding to elongating RNAPII and demethylates H3K4me2 cotranscriptionally. Importantly, the negative correlation between H3K4me2 and transcription is disrupted in the ldl3 mutant, demonstrating the genome-wide impacts of the transcription-driven LDL3 pathway to control H3K4me2 in plants. Our findings implicate H3K4me2 in plants as chromatin memory for transcriptionally repressive states, which ensures robust gene control.

plant biology↗

bioRxiv2021

Transcription-coupled and epigenome-encoded mechanisms direct H3K4 methylation

Mono-, di-, and trimethylation of histone H3 lysine 4 (H3K4me1/2/3) are associated with transcription, yet it remains controversial whether H3K4me1/2/3 promote or result from transcription. Our previous characterizations of Arabidopsis H3K4 demethylases suggest roles for H3K4me1 in transcription. However, the control of H3K4me1 remains unexplored in Arabidopsis, in which no methylase for H3K4me1 has been identified. Here, we identified three Arabidopsis methylases that direct H3K4me1. Analyses of their genome-wide localization using ChIP-seq and machine learning revealed that one of the enzymes cooperates with the transcription machinery, while the other two are associated with specific histone modifications and DNA sequences. Importantly, these two types of localization patterns are also found for the other H3K4 methylases in Arabidopsis and mice. These results suggest that H3K4me1/2/3 are established and maintained via interplay with transcription as well as inputs from other chromatin features, presumably enabling elaborate gene control.

molecular biology↗

bioRxiv2020

Role of Epigenetics in Unicellular to Multicellular Transition in Dictyostelium

The evolution of multicellularity is a critical event that remains incompletely understood. We use the social amoeba, Dictyostelium discoideum, one of the rare organisms that exists in both unicellular and multicellular stages, to examine the role of epigenetics in regulating multicellularity. While transitioning to multicellular states, patterns of H3K4 methylation and H3K27 acetylation significantly change. By combining transcriptomics, epigenomics, chromatin accessibility, and syntenic analyses with other unicellular and multicellular organisms, we identify 52 conserved genes, which are specifically accessible and expressed during multicellular states. We validated that four of these genes, including the H3K27 deacetylase hdaD, are necessary and that an SMC-like gene, smcl1, is sufficient for multicellularity. These results highlight the importance of epigenetics in reorganizing chromatin architecture to facilitate the evolution of multicellularity. One Sentence SummaryEpigenetic regulation of multicellularity

genetics↗

bioRxiv2020

The effects of temporal continuities of grasslands on the diversity and species composition of plants

Semi-natural grasslands are ecosystems rich in biodiversity. However, their decline has been reported worldwide, and identification of grasslands with high conservation priority is urgently required. Recently, an increasing number of studies have reported that past vegetation history affects current biological communities. To evaluate whether the temporal continuity of grasslands promotes biodiversity, and thus can be an indicator of conservation priority, we studied vascular plant communities in old (160- 1000s years) and new (52-70 years after deforestation) grasslands, as well as in forests, of Sugadaira Highland in central Japan. The number of plant species was highest in old grasslands, followed by new grasslands and forests. This pattern was much clearer in the number of grassland-dependent native and grassland-dependent endangered species, indicating the role of old grasslands as refugia for those species. The species composition differed between old and new grasslands. New grasslands had species compositions in between those of old grasslands and forests, suggesting that the plant community in new grasslands retains the influence of past forestation for more than 52 years after deforestation. Eleven indicator species were detected in old grasslands, but none in new grasslands, suggesting the uniqueness of the plant community in old grasslands. We conclude that the temporal continuity of grasslands increases plant diversity and can be an indicator of grasslands with high conservation priority.

ecology↗

bioRxiv2020

Chromatin-based mechanisms to coordinate convergent overlapping transcription

In eukaryotic genomes, transcription units of genes often overlap with other protein-coding and/or noncoding transcription units1,2. In such intertwined genomes, coordinated transcription of nearby or overlapping genes would be important to ensure integrity of genome function; however, the mechanisms underlying this coordination are largely unknown3-6. Here, we show in Arabidopsis thaliana that genes with convergent orientation of transcription are major sources of overlapping bidirectional transcripts and that these bidirectionally transcribed genes are regulated by a putative LSD1 family histone demethylase, FLD7,8. Our genome-wide chromatin profiling revealed that FLD downregulated histone H3K4me1 in regions with convergent overlapping transcription. FLD localizes to actively transcribed genes where it colocalizes with elongating RNA polymerase II phosphorylated at Ser-2 or Ser-5 sites. Genome-wide transcription analyses suggest that FLD-mediated H3K4me1 removal negatively regulates bidirectional transcription by retaining the elongating transcription machinery. Furthermore, this effect of FLD on transcription dynamics is mediated by DNA topoisomerase I. Our study has revealed chromatin-based mechanisms to cope with overlapping bidirectional transcription, likely by modulating DNA topology. This global mechanism to cope with bidirectional transcription could be co-opted for specific epigenetic processes, such as cellular memory of responses to environment9.

molecular biology↗

bioRxiv2018

Identification of the m6Am methyltransferase PCIF1 reveals the location and functions of m6Am in the transcriptome

mRNAs are regulated by nucleotide modifications that influence their cellular fate. Two of the most abundant modified nucleotides are N6-methyladenosine (m6A), found within mRNAs, and N6,2-O-dimethyladenosine (m6Am), which is found at the first-transcribed nucleotide. A long-standing challenge has been distinguishing these similar modifications in transcriptome-wide mapping studies. Here we identify and biochemically characterize, PCIF1, the methyltransferase that generates m6Am. We find that PCIF1 binds and is dependent on the m7G cap. By depleting PCIF1, we definitively identified m6Am sites and generated transcriptome-wide maps that are selective for m6Am and m6A. We find that m6A and m6Am misannotations largely arise from mRNA isoforms with alternate transcription-start sites. These isoforms contain m6Am that appear to map to \"internal\" sites, increasing the likelihood of misannotation. Using the new m6Am annotations, we find that depleting m6Am does not affect mRNA translation but reduces the stability of a subset of m6Am-annotated mRNAs. The discovery of PCIF1 and our accurate mapping technique will facilitate future studies to characterize m6Ams function.

molecular biology↗