Hiroshi Ochiai
The Division of Gene Expression Dynamics, Medical Research Center Initiativefor High Depth Omics, Medical Institute of Bioregulation, Kyushu University

Wednesday, January 17, 2024
16:00-17:00
1F Auditorium, DB Building C, Kobe / Broadcast online via Zoom
Zoom meeting URL will be announced on the event day by e-mail.
※This seminar is open only to BDR members

Regulation of gene expression dynamics inpluripotent stem cells revealed by imaging analysis
Summary

Our bodies are composed of a variety of cell types, each fulfilling unique functions through the specificexpression of particular groups of genes. These gene expressions are precisely regulated by the interaction
between the gene promoters and distal enhancers. This regulatory mechanism involves cell type-specific bindingsites for transcription factors, playing a crucial role in the recruitment of RNA Polymerase II and transcription cofactors.
Furthermore, these transcription regulatory factors possess numerous intrinsically disordered regions,promoting the formation of condensates within the cell nucleus. It is believed that the formation of thesecondensates facilitates the physical proximity of enhancers and promoters, thereby promoting continuoustranscriptional activation. Recent imaging analyses and single-cell RNA sequencing have confirmed dynamictranscriptional activation in various species, cell types, including mouse embryonic stem cells. Dynamictranscriptional activation, or transcriptional bursting, refers to the phenomenon where genes switch between atranscriptionally active state, continuously synthesizing RNA, and a transcriptionally inactive state, where little tono synthesis occurs. This transcriptional bursting is understood to gene expression levels and the heterogeneity
in gene expression among cells. However, the specifics of how the condensate formation of transcription-related
factors and the stability of enhancer-promoter interactions control transcriptional bursting remain unclear.
In this seminar, I will introduce transcriptional dynamics control mechanisms in mouse embryonic stem cells
elucidated using state-of-the-art imaging techniques, including live single-gene imaging and sequential
fluorescent in situ hybridization (FISH). In particular, I will provide the latest insights into the transcriptional
bursting and their regulatory mechanisms, discussing how transcriptional bursting controls gene expression
levels.
References:
1. Ochiai, H., Ohishi, H., Sato, Y. & Kimura, H. Organization of transcription and 3D genome as revealed by live-cell imaging. Curr Opin Struc Biol81, 102615 (2023).
2. Ohishi, H. et al. Transcription-coupled changes in higher-order genomic structure and transcription hub viscosity prolong enhancer-promoter
connectivity. bioRxiv 2023.11.27.568629 (2023) doi:10.1101/2023.11.27.568629.
3. Ohishi, H. et al. STREAMING-tag system reveals spatiotemporal relationships between transcriptional regulatory factors and transcriptionalactivity. Nat Commun 13, 7672 (2022).
4. Ochiai, H. et al. Genome-wide kinetic properties of transcriptional bursting in mouse embryonic stem cells. Sci Adv 6, eaaz6699 (2020).
5. Ochiai, H., Sugawara, T. & Yamamoto, T. Simultaneous live imaging of the transcription and nuclear position of specific genes. Nucleic Acids
Res 43, e127–e127 (2015).

Host: Ichiro Hiratani
Laboratory for Developmental Epigenetics, BDR
Contact: ichiro.hiratani@riken.jp, akie.tanigawa@riken.jp

RIKEN Center for Biosystems Dynamics Research (BDR)