Swi4-dependent SWI4 transcription couples cell size to cell cycle commitment
Pooja Goswami1, Abhishek Ghimire1, Carleton Coffin1
1Department of Biological Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
Iscience
|March 24, 2025
Summary
Budding yeast cell size at division (Start) is controlled by the transcription factor SBF (Swi4 and Swi6). Auto-production of Swi4 refines this cell cycle transition, impacting cell size.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Cell cycle progression in budding yeast is regulated by the G1/S transcription factor SBF (Swi4/Swi6).
- SBF accumulation in G1 phase is crucial for commitment to cell division (Start) and is size-dependent.
Purpose of the Study:
- To investigate the mechanisms underlying the size dependence of Swi4 accumulation.
- To understand how Swi4 auto-production influences cell size control at Start.
Main Methods:
- Utilized quantitative scanning number and brightness microscopy.
- Employed genetic manipulation, including promoter mutation and disruption of SBF activation.
- Performed ectopic inducible expression of Swi4.
Main Results:
- Mutations in SWI4 promoter or SBF activation decreased Swi4 accumulation rate by 33-50%, increasing cell size at Start.
- Ectopic Swi4 expression accelerated Start and upregulated the G1/S regulon.
- A threshold model accurately predicted cell size responses to genetic and nutrient variations.
Conclusions:
- Transcription factor auto-production, exemplified by Swi4, is a key mechanism for refining cell state transitions like Start.
- Swi4 auto-regulation contributes to the precise control of cell size at the G1/S transition.
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