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Fission yeast switches mating type by a replication-recombination coupled process
1Unite des Virus Oncogenes, URA 1644 du CNRS, Departement des Biotechnologies, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris, Cedex 15, France.
Abstract:
Fission yeast exhibits a homothallic life cycle, in which the mating type of the cell mitotically alternates in a highly regulated fashion. Pedigree analysis of dividing cells has shown that only one of the two sister cells switches mating type. It was shown recently that a site- and strand-specific DNA modification at the mat1 locus precedes mating-type switching. By tracking the fate of mat1 DNA throughout the cell cycle with a PCR assay, we identified a novel DNA intermediate of mating-type switching in S-phase. The time and rate of appearance and disappearance of this DNA intermediate are consistent with a model in which mating-type switching occurs through a replication-recombination coupled pathway. Such a process provides experimental evidence in support of a copy choice recombination model in Schizosaccharomyces pombe mating-type switching and is reminiscent of the sister chromatid recombination used to complete replication in the presence of certain types of DNA damage.
Insights
Fission yeast mating-type switching involves a novel DNA intermediate during S-phase. This discovery supports a replication-recombination pathway for mating-type switching in Schizosaccharomyces pombe.
Area of Science:
- Molecular Biology
- Genetics
- Cell Biology
Background:
- Fission yeast (Schizosaccharomyces pombe) has a homothallic life cycle with regulated mitotic mating-type alternation.
- Mating-type switching in one of two sister cells is a key feature of this life cycle.
- Previous research identified site- and strand-specific DNA modification at the mat1 locus preceding switching.
Purpose of the Study:
- To investigate the molecular mechanism and timing of mating-type switching in fission yeast.
- To identify and characterize any DNA intermediates involved in the mating-type switching process.
- To provide experimental evidence for proposed models of mating-type switching.
Main Methods:
- Tracking the fate of mat1 DNA throughout the cell cycle.
- Utilizing a Polymerase Chain Reaction (PCR) assay to detect DNA intermediates.
- Analyzing the timing and rate of appearance and disappearance of the identified DNA intermediate.
Main Results:
- A novel DNA intermediate of mating-type switching was identified during the S-phase of the cell cycle.
- The temporal dynamics of this intermediate align with a replication-recombination coupled pathway.
- Experimental evidence supports a copy choice recombination model for mating-type switching in Schizosaccharomyces pombe.
Conclusions:
- Mating-type switching in fission yeast occurs via a replication-recombination coupled pathway.
- The identified S-phase DNA intermediate is crucial for this process.
- The mechanism is analogous to sister chromatid recombination observed during DNA damage repair.