Biology subjects

Tsuruoka, T.

Publications and source records attributed to Tsuruoka, T..

4 recordsLinked to original sources

bioRxiv2026

Parental B-MYB/FOXM1 controls mitotic E2F to determine daughter cell fate

Mitogens trigger cell-cycle entry by activating E2F at the restriction point, which is followed by B-MYB/FOXM1 activation and progression to mitosis. How mitogens control continued cycling and cell-cycle exit after the restriction point is not well-understood. By developing an E2F and B-MYB/FOXM1 dual transcriptional biosensor system, we show that S/G2 phase duration is set by timed mitogen-regulated B-MYB/FOXM1 activation, while E2F activity gradually declines before mitosis. As a striking consequence, rapid B-MYB/FOXM1 activation shortens S/G2, delivering high mitotic E2F activity to daughter cells which keeps them cycling. Delayed B-MYB/FOXM1 activation prolongs S/G2, depleting mitotic E2F which drives daughters to quiescence. When S/G2 is further prolonged, partially activated B-MYB/FOXM1 frequently reverts, triggering mitotic bypass and polyploid quiescence. Thus, B-MYB/FOXM1 governs a tri-directional (G2 restriction point) where cells commit to continued cycling through early B-MYB/FOXM1 activation; cell-cycle exit through delayed B-MYB/FOXM1 activation; or mitotic bypass by B-MYB/FOXM1 inactivation.

cell biology↗

bioRxiv2026

Opto-MDMi: a dual-lock optogenetic system for robust activation of endogenous p53

Optogenetics has emerged as a powerful technology for manipulating biological functions with high spatiotemporal resolution, yet the precise control of endogenous molecules remains a significant challenge. In this study, we developed Opto-MDMi, a dual-lock optogenetic platform designed to control the activity of endogenous p53, a master regulator of cell cycle and apoptosis. The p53 pathway is strictly governed by its negative regulators, MDM2 and MDMX, which inhibit p53 through direct binding and ubiquitination. Our system integrates two distinct light-responsive modules: Opto-MDMi (LOVTRAP), which regulates the nuclear translocation of p53-activating peptides, and Opto-MDMi (LOV2-PMI), which controls the binding activity of these peptides by photocaging them within the AsLOV2 domain. Through extensive in vitro screening and live-cell assays, we discovered that truncating the J helix of LOV2 effectively restricts the movement of fused inhibitory peptides, thereby masking their interaction with MDM2/MDMX under dark conditions. By combining these two regulatory layers into a dual-lock system, we achieved robust light-dependent activation of endogenous p53 while significantly suppressing basal activity in the dark. Our findings not only provide a potent tool for p53 research but also establish a general design principle for optogenetically regulating functional peptides with the LOV2 domain, offering a versatile framework for the future development of optogenetic actuators.

systems biology↗

bioRxiv2025

Opto-p53: A Light-Controllable p53 Signaling for Regulating p53-Dependent Cell Fate.

p53 protein, a crucial transcription factor in cellular responses to a wide variety of stress, regulates multiple target genes involved in tumor suppression, senescence induction, and metabolic functions. However, it remains unclear how diverse cellular phenotypes are modulated by p53. In this study, we developed an optogenetic tool, Opto-p53, to control p53 signaling by light. Opto-p53 was designed to trigger p53 signaling by reconstituting p53 N-terminal and C-terminal fragments with a light-inducible dimerization (LID) system. Upon light exposure, cells expressing Opto-p53 demonstrated p53 transcriptional activation, resulting in cell death and cell cycle arrest. We further enhanced the efficacy of light-induced p53 activation by introducing specific mutations into Opto-p53 fragments. Our findings unveil the capability of Opto-p53 to serve as a powerful tool for dissecting the complex roles of p53 in cellular processes, thereby contributing to the field of synthetic biology and providing general design principles for optogenetic tools using endogenous transcription factors.

synthetic biology↗

bioRxiv2022

Development of a fluorescence reporter system to quantify transcriptional activity of endogenous p53 in living cells

The tumor suppressor p53 plays a central role in cellular stress responses by regulating transcription of multiple target genes. The temporal dynamics of p53 are thought to be important for its function: it encode input information and are decoded to induce distinct cellular phenotypes. However it remains unclear to what extent the temporal dynamics of p53 reflects the activity of p53-induced gene expression. In this study, we report a multiplexed reporter system that allows us to visualize the transcriptional activity of p53 at the single cell level. Our reporter system features simple and sensitive observation of the transcriptional activity of endogenous p53 to the response elements of various target genes. Using this system, we show that the transcriptional activation of p53 exhibits strong cell-to-cell heterogeneity. The transcriptional activation of p53 by etoposide is highly dependent on the cell cycle but not by UV-C. Finally, we show that our reporter system allows simultaneous visualization of the transcriptional activity of p53 and cell cycle. Our reporter system can thus be a useful tool for studying biological processes involving the p53 signaling pathway. Summary statementTumor suppressor protein p53 is one of the hub factor of the cellular stress responses. Our novel reporter system allows us to visualize the transcriptional activity of endogenous p53 easily and precisely.

cell biology↗