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Updated: Aug 6, 2025
07:47
Microscopy of Fission Yeast Sexual Lifecycle
Published on: March 9, 2016
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Fission yeast Swi2 designates cell-type specific donor and stimulates Rad51-driven strand exchange for mating-type
Takahisa Maki1, Geneviève Thon2, Hiroshi Iwasaki1,3
1Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan.
Nucleic Acids Research
|March 23, 2023
Summary
The Swi2-Swi5 complex controls yeast mating-type switching by binding specific DNA sites. This mechanism directs gene conversion, ensuring accurate inheritance of mating-type information in Schizosaccharomyces pombe.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Fission yeast (Schizosaccharomyces pombe) mating-type switching relies on Rad51-driven gene conversion.
- The Swi2-Swi5 complex is a key regulator, selecting donor DNA cassettes (mat2-P or mat3-M) for mating-type switching.
- Donor selection is mediated by cell-type-specific activation of recombination enhancers (SRE2 and SRE3).
Purpose of the Study:
- To elucidate the molecular mechanisms by which the Swi2-Swi5 complex mediates cell-type-specific donor selection.
- To identify functional motifs within the Swi2 protein involved in localization and donor choice.
- To investigate the role of Swi2-Swi5 in promoting the strand exchange activity of Rad51.
Main Methods:
- Identification of functional motifs in Swi2, including a Swi6 (HP1 homolog)-binding site and AT-hooks.
- Genetic analysis to assess the requirement of these motifs for Swi2 localization and donor selection.
- In vitro assays to evaluate the effect of Swi2-Swi5 on Rad51-driven strand exchange.
Main Results:
- The AT-hooks in Swi2 are essential for its localization to SRE3, promoting mat3-M donor selection in P cells.
- The Swi6-binding site in Swi2 is crucial for localization to SRE2, facilitating mat2-P donor selection in M cells.
- The Swi2-Swi5 complex was shown to stimulate Rad51-driven strand exchange in vitro.
Conclusions:
- The Swi2-Swi5 complex utilizes cell-type-specific binding mechanisms via its identified motifs to localize to recombination enhancers.
- This precise localization enables the stimulation of Rad51-driven gene conversion at the targeted donor locus.
- The study reveals a detailed mechanism for regulated DNA recombination in mating-type switching.
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