Research Themes

• 化学遺伝学的データを用いた新規プロテアソーム阻害剤の探索
  01 Apr. 2023 - 31 Mar. 2026
• Elucidation of the mechanism for the proteasome assembly regulated by
  Grant-in-Aid for Scientific Research (C)
  The University of Tokyo
  01 Apr. 2016 - 31 Mar. 2019
  TIF6 was isolated as a gene related to the ubiquitin-proteasome system (UPS) in S. cerevisiae. TIF6 (translation initiation factor 6) is an essential gene, and encodes one of the chaperone proteins involved in the biogenesis of the 60S ribosome. DAmP (decreased abundance by mRNA perturbation) mutant cells of Tif6 showed three phenotypes, all of which indicate the relation between Tif6 and the UPS. 1) tif6-DAmP cells are sensitive to the amino acid analogs. 2) The model substrates of the 26S proteasome are not efficiently degraded in the tif6-DAmP mutant. 3) Double mutations of TIF6 and the proteasome genes cause synthetic growth defects. Tif6 is a highly conserved among eukaryotes, and its human ortholog is eIF6 (>70% identity). Thus, we next investigated the relation between eIF6 and the UPS. Knockdown of eIF6 led to retardation of the assembly of proteasomes, and yeast two-hybrid assays indicated that eIF6 interacts with some proteasome subunits.
• Why is the 26S proteasome essential for eukaryotic cell viability?
  Grant-in-Aid for Scientific Research (C)
  The University of Tokyo
  01 Apr. 2012 - 31 Mar. 2015
  The 26S proteasome is a eukaryotic protease complex conserved from yeast to human. In eukaryotes, the 26S proteasome is essential for growth, but where this essentiality comes from remains unknown. To address this issue, I examined two peptidase activities, which reside only in eukaryotic proteasomes, the functional relationship between the 26S proteasome and mitochondria, which are the essential eukaryotic organelles, and some proteasome subunits, whose functions have not been clarified yet.
• プロテアソームに結合する蛋白質の探索と解析
  2009 - 2010
• 正の選択を制御するペプチドの解析
  2008 - 2009
• Analysis of the proteaosme assembly pathway
  Grant-in-Aid for Young Scientists (B)
  2007 - 2008
• Studies on proteolysis mediated by the proteasomes and ubiquitin
  Grant-in-Aid for Specially Promoted Research
  Tokyo Metropolitan Organization for Medical Research
  2001 - 2005
  The proteasome (a eukaryotic ATP-dependent protease complex) is a sophisticated cellular apparatus capable of shredding unnecessary proteins modified by ubiquitin (a posttranslational modifier serving a destination signal for proteolysis) selectively. It plays a central role in the control of a diverse array of cellular activities by catalyzing biological reactions rapidly, orderly, exhaustively, and uni-directionally. Over the past 25 years, we have been aiming to elucidate comprehensively the divergent roles of the ubiquitin-proteasome system (UPS) in the life science field. In the present project named "Studies on proteolysis mediated by the proteasomes and ubiquitin", our research projects on the proteasomes were (1) the analysis of the tertiary structure of the mammalian proteasome as a unusually large multi-protein complex, (2) the clarification of assembling mechanisms, focusing on the newly-discovered PAC (proteasome assembling chaperone) 1/2 heterodimeric complex and Hsp90, and (3) immunogenetic analysis of the new proteasome activator family proteins of PA28α, PA28β and PA28γ. In the ubiquitin project, we were interested in analyzing the quality-control ubiquitin-protein ligases (E3s) in cells: CHIP is a molecular chaperone-dependent E3, Parkin is encoded by the causative gene of eating of oneself") and two novel ubiquitin-like (UBL) modifying systems, such as NEDD8 and Ufml pathways, by generation of model mice with impairment of various related genes. Recently, various diseases, such as cancers, infectious diseases, and neurodegenerative diseases, have been increasing in the aged society of the 21st century. Considering such circumstances, it has been clarified, as a central scenario, that dysfunctioning of UPS causes these intractable diseases. Thus, our studies may contribute to the development of new bio-science field as well as to that of therapies for intractable diseases.
• ユビキチン様蛋白質Rub1による細胞周期制御
  2001 - 2002
• Functional analysis of PML protein in the ubiquitin system
  Grant-in-Aid for Scientific Research (C)
  2001 - 2002
  PML protein has a typical RING finger domain and there is in the nuclei-inclusion body known as POD. A RING ringer motif is found in typical ubiquitin ligase (E3). The translocation on PML and retinoic acid-receptor alpha (RARα) gene working as a transcription iactor is occurred in APL patients. The chemical therapy with retinoic acid-inoculation resulted, somehow, in reconstitution of POD and degradation of PML-RARa fusion protein depending on ubiquitin-proteasome pathway. However the molecular mechanism of PML-RARα protein degradation has not been clear.
  We investigated the relationships between a ubiquity conjugation enzyme (E2) and PML protein, therefore, imrnunoprecipitation and western blotting analysis were carried out after transfection with PML and each E2 gene. As a result, only UbcH9 could be detected to bind PML protein for SUMOylation. It takes it for granted because PML is typical targeted for SUMOylation and the system is required for UbcH9 as E2 protein. PML, PML-RARα, and E2 genes were transfected into HEK293 cells and analyzed on protein stability on PML and PML-RARα proteins. The stability of the proteins was pretty well in the presence of retinoic acid The PML protein was hyper SUMOylated in the presence of retinoic acid and pory-SUMOylated. It does not seem that PML protein has E3 ligase activity in spite of typical RING finger motif. The investigation will be required to the role for SUMOylation in the pathogenesis of APL.
• 神経細胞変性とユビキチンープロテアソームシステム
  2000 - 2000