Fission yeast switches mating type by a replication-recombination coupled process.

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.