Tokyo Institute of Technology · Biochemistry, Genetics and Molecular Biology
Professor Hiroshi Kimurâ's research lab specializes in chromatin dynamics and transcription regulation in eukaryotic cells, focusing on the epigenetic mechanisms governing gene expression and genome stability. The lab employs advanced live-cell imaging techniques, such as photobleaching and fluorescent protein tagging, to study the dynamics of histones, RNA polymerase II, and their associated complexes in real time. Key research directions include histone modifications (e.g., acetylation and methylation of H3), nucleosome assembly, and the functional organization of transcription machinery in interphase and mitosis. The lab also investigates the kinetic behavior and assembly states of RNA polymerase II holoenzymes, providing insights into transcriptional regulation and elongation.
Figures are computed from collected data and may differ slightly.
Histones H2A and H2B form part of the same nucleosomal structure as H3 and H4. Stable HeLa cell lines expressing histones H2B, H3, and H4 tagged with green fluorescent protein (GFP) were established; the tagged molecules were assembled into nucleosomes. Although H2B-GFP was distributed like DNA, H3-GFP and H4-GFP were concentrated in euchromatin during interphase and in R-bands in mitotic chromosomes. These differences probably result from an unregulated production of tagged histones and differe
Histone modifications play critical roles in the epigenetic regulation of gene expression and in the maintenance of genome integrity. Acetylation and methylation of histone H3 are particularly important in gene activation and silencing. We generated and characterized a panel of mouse monoclonal antibodies that specifically recognize different modifications on K4, K9, and K27 residues on histone H3. By using these antibodies for chromatin immunoprecipitation and immunoblotting, we analyzed the re
RNA polymerase II transcribes most eukaryotic genes. Its catalytic subunit was tagged with green fluorescent protein and expressed in Chinese hamster cells bearing a mutation in the same subunit; it complemented the defect and so was functional. Photobleaching revealed two kinetic fractions of polymerase in living nuclei: approximately 75% moved rapidly, but approximately 25% was transiently immobile (association t1/2 approximately 20 min) and transcriptionally active, as incubation with 5,6-dic
Various complexes that contain the core subunits of RNA polymerase II associated with different transcription factors have been isolated from eukaryotes; their precise molecular constitution depends on the purification procedure. We estimated the numbers of various components of such complexes in an HeLa cell by quantitative immunoblotting. The cells were lysed with saponin in a physiological buffer; approximately 140,000 unengaged polymerases (mainly of form IIA) were released. Only approximate
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