Evolutionary repair: Changes in multiple functional modules allow meiotic cohesin to support mitosis

Area of Science:

• Evolutionary biology
• Cell biology
• Molecular genetics

Background:

• Protein functions can change during evolution.
• Cellular adaptation mechanisms to altered protein roles are not well understood.

Purpose of the Study:

• To investigate how yeast cells adapt when a meiosis-specific protein (Rec8) is forced into the mitotic cell cycle.
• To identify genetic and phenotypic changes enabling adaptation to this perturbation.

Main Methods:

• Forced expression of meiosis-specific Rec8 during mitosis in Saccharomyces cerevisiae.
• Evolutionary experiment over 1,750 generations with 15 parallel yeast populations.
• Genotypic and phenotypic analysis of evolved populations.

Main Results:

• Forced Rec8 expression initially impaired chromosome linkage, advanced DNA replication, and reduced fitness by 45%.
• Evolved populations significantly increased fitness.
• Adaptation primarily involved mutations in transcriptional mediator complex, cohesin-related genes, and cell cycle regulators, not Rec8 itself.

Conclusions:

• Cells can adapt to using existing proteins in new biological functions by altering interacting partners.
• Changes in known and novel protein partners facilitate functional redeployment of proteins during evolution.