Publications by authors named "Katahira J"

Cell motility is related to the higher-order structure of chromatin. Stimuli that induce cell migration change chromatin organization; such stimuli include elevated histone H3 lysine 9 trimethylation (H3K9me3). We previously showed that depletion of histone H3 lysine 9 methyltransferase, SUV39H1, suppresses directional cell migration.

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To facilitate selfish replication, viruses halt host gene expression in various ways. The nuclear export of mRNA is one such process targeted by many viruses. SARS-CoV-2, the etiological agent of severe acute respiratory syndrome, also prevents mRNA nuclear export.

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Article Synopsis
  • - The LINC complex, made of SUN and nesprin proteins, connects the nucleus to the cytoskeleton and is crucial for processes like cell migration and mechanotransduction from external signals.
  • - SUN1 is essential for directional cell movement, and depletion of SUN1 affects the maturation of focal adhesions by disrupting the incorporation of proteins like vinculin and zyxin, even though it does not affect the initial recruitment of integrin β1.
  • - The study highlights that SUN1's role in the LINC complex is critical for actin organization and traction force generation, suggesting that SUN2 alone cannot compensate for SUN1's function in maintaining cellular adhesion and movement.
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  • The study investigates the oxidation of flavanone compounds (2'-Hydroxyflavanone and its derivatives) by human cytochrome P450 enzymes, focusing on CYP1A1, 1A2, 1B1.1, 1B1.3, and 2A6.
  • Various di-hydroxylated flavanone and flavone products were identified through LC-MS/MS analysis, revealing significant structural insights related to their formation.
  • Results indicate that CYP1 family enzymes demonstrated higher activity in catalyzing these oxidations compared to CYP2A6, with molecular docking studies supporting these findings.
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  • The nucleolar structure is influenced by internal factors like metabolism and external factors like mechanical stress, but how these factors shape nucleoli is not fully understood.
  • The study focuses on the role of SUN1 protein splicing variants in determining the shape and number of nucleoli, finding that variants SUN1_888 and SUN1_916 are vital but serve different functions.
  • Depletion of these SUN1 variants not only changes nucleolar morphology but also impacts chromatin structure and histone modification distribution, suggesting that the LINC complex is key in regulating nucleolar characteristics through chromatin interactions.
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2'-, 3'-, and 4'-Methoxyflavones (MeFs) were incubated with nine forms of recombinant human cytochrome P450 (P450 or CYP) enzymes in the presence of an NADPH-generating system and the products formed were analyzed with LC-MS/MS methods.CYP1B1.1 and 1B1.

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Article Synopsis
  • The THO/TREX multiprotein complex is crucial for processing pre-mRNA, exporting mRNA, and maintaining genome stability.
  • This study focused on THOC7, a component of THO, using chromatin immunoprecipitation sequencing to find that it binds to repetitive DNA sequences, particularly in transcriptionally active regions.
  • Knocking down another component, THOC5, led to DNA damage and instability in repeat regions, indicating that THO helps manage transcription-related instability in the human genome.
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Background: The authors report on surgical treatment for 20 patients with craniosynostosis in Japan in collaboration with neurosurgery department since 2007. They could safely expand the skull using distraction devices.

Methods: Total number of patients with craniosynostosis joint surgery was 20 (23 surgeries) at the time of this report.

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Biologically active plant flavonoids, including 5,7-dihydroxyflavone (57diOHF, chrysin), 4',5,7-trihydroxyflavone (4'57triOHF, apigenin), and 5,6,7-trihydroxyflavone (567triOHF, baicalein), have important pharmacological and toxicological significance, e.g., antiallergic, anti-inflammatory, antioxidative, antimicrobial, and antitumorgenic properties.

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A multiprotein complex, THO/TREX, couples the transcription, 3'-end formation and nuclear export of mRNAs. In this study, we report that crucial factors for mRNA processing, such as XRN2, DDX5/DDX17 and CstF64, are copurified with human THO (hTHO). Using chromatin immunoprecipitation, we found increased cross-linking of XRN2 and CstF64 to the RNA polymerase II (RNAP II) pause site of the HSPA1A gene upon down-regulation of THOC5, a metazoan-specific component of hTHO.

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Retrotransposon genes are silenced by DNA methylation because of potential harm due to insertional mutagenesis. DNA methylation of retrotransposon genes is erased and re-established during male germ cell development. Both piRNA-dependent and piRNA-independent mechanisms are active during the re-establishment process, with the piRNA-independent mechanism occurring first.

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The roles of human cytochrome P450 (P450 or CYP) 2A6 in the oxidation of flavanone [(2R)- and (2S)-enantiomers] and flavone were studied in human liver microsomes and recombinant human P450 enzymes. CYP2A6 was highly active in oxidizing flavanone to form flavone, 2'-hydroxy-, 4'-, and 6-hydroxyflavanones and in oxidizing flavone to form mono- and di-hydroxylated products, such as mono-hydroxy flavones M6, M7, and M11 and di-hydroxy flavones M3, M4, and M5. Liver microsomes prepared from human sample HH2, defective in coumarin 7-hydroxylation activity, were very inefficient in forming 2'-hydroxyflavanone from flavanone and a mono-hydroxylated product, M6, from flavone.

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The LINC complex is a multifunctional protein complex that is involved in various processes at the nuclear envelope, such as nuclear migration, mechanotransduction and chromatin tethering in the meiotic phase. However, it remains unknown how these functions are regulated in different cell contexts. An inner nuclear membrane component of the LINC complex, SUN1, is ubiquitously expressed.

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A supervised machine learning algorithm, which is qualified for image classification and analyzing similarities, is based on multiple discriminative morphological features that are automatically assembled during the learning processes. The algorithm is suitable for population-based analysis of images of biological materials that are generally complex and heterogeneous. Here we used the algorithm wndchrm to quantify the effects on nucleolar morphology of the loss of the components of nuclear envelope in a human mammary epithelial cell line.

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Transport of messenger RNA (mRNA) from the nucleus to the cytoplasm is an essential step of eukaryotic gene expression. In the cell nucleus, a precursor mRNA undergoes a series of processing steps, including capping at the 5' ends, splicing and cleavage/polyadenylation at the 3' ends. During this process, the mRNA associates with a wide variety of proteins, forming a messenger ribonucleoprotein (mRNP) particle.

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The NXF1:NXT1 complex (also known as TAP:p15) is a general mRNA nuclear export factor that is conserved from yeast to humans. NXF1 is a modular protein constructed from four domains (RRM, LRR, NTF2-like and UBA domains). It is currently unclear how NXF1:NXT1 binds transcripts and whether there is higher organization of the NXF1 domains.

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Metazoan Tap-p15 (also called Nxf1-Nxt1) and yeast Mex67-Mtr2 heterodimers are the general mRNA export receptors. The RNA binding activity of Tap-p15, which is essential for mRNA nuclear export, has been attributed to the amino-terminal RNA binding module of Tap consists of RNA recognition motif (RRM) and leucine-rich repeat. In this study, we identified a novel RNA interaction surface in the NTF2-like (NTF2L) domain of Tap, which is analogous to the rRNA binding platform of Mex67-Mtr2.

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The transcription-export complex (TREX) couples mRNA transcription, processing and nuclear export. We found that CFIm68, a large subunit of a heterotetrameric protein complex mammalian cleavage factor I (CFIm), which is implicated in alternative polyadenylation site choice, co-purified with Thoc5, a component of human TREX. Immunoprecipitation using antibodies against different components of TREX indicated that most likely both complexes interact via an interaction between Thoc5 and CFIm68.

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Influenza A viruses are a major cause of mortality. Given the potential for future lethal pandemics, effective drugs are needed for the treatment of severe influenza such as that caused by H5N1 viruses. Using mediator lipidomics and bioactive lipid screen, we report that the omega-3 polyunsaturated fatty acid (PUFA)-derived lipid mediator protectin D1 (PD1) markedly attenuated influenza virus replication via RNA export machinery.

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Ribosomal proteins are synthesized in the cytoplasm, before nuclear import and assembly with ribosomal RNA (rRNA). Little is known about coordination of nucleocytoplasmic transport with ribosome assembly. Here, we identify a transport adaptor, symportin 1 (Syo1), that facilitates synchronized coimport of the two 5S-rRNA binding proteins Rpl5 and Rpl11.

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The preservation of healthy tissue during surgical debridement is desirable as this may improve clinical outcomes. This study has estimated for the first time the amount of tissue lost during debridement using the VERSAJET system of tangential hydrosurgery. A multicenter, prospective case series was carried out on 47 patients with mixed wound types: 21 (45%) burns, 13 (28%) chronic wounds, and 13 (28%) acute wounds.

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mRNA export and the TREX complex.

Biochim Biophys Acta

June 2012

Over the past few decades, we have learned that eukaryotes have evolved sophisticated means to coordinate the nuclear export of mRNAs with different steps of gene expression. This functional orchestration is important for the maintenance of the efficiency and fidelity of gene expression processes. The TREX (TRanscription-EXport) complex is an evolutionarily conserved multiprotein complex that plays a major role in the functional coupling of different steps during mRNA biogenesis, including mRNA transcription, processing, decay, and nuclear export.

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Unlabelled: dendritic mRNA transport machines. Although Stau2 is thought to be involved in the dendritic targeting of several mRNAs in neurons, the mechanism whereby Stau2 regulates these mRNAs is unknown. To elucidate the functions of Stau2, we screened for novel binding partners by affinity purification of GST-tagged Stau2 from 293F cells.

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Small RNAs with lengths of 20-30 nucleotides, such as microRNAs (miRNAs), play important regulatory roles in various cellular processes. In conventional linear processing pathways, precursors of miRNAs are transported out of the nucleus by the specific nuclear transport receptor, exportin-5. The exported precursors are further processed and eventually incorporated into the RNA-induced silencing complex (RISC), which silences the expression of the target genes by posttranscriptional mechanisms in the cytoplasm.

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