Fig 7. Summary of the mechanism that allows budding yeast to use the meiotic kleisin, Rec8, for mitosis.

Yeast cells expressing Rec8 in place of Scc1 cannot build robust cohesion to hold sister chromosomes together before anaphase due to the weak association of cohesin with chromosomes and Rec8 protein instability. Rec8-expressing cells induce earlier firing of replication origins compared to what wild type does and start S phase earlier. After experimental evolution, adaptive mutations in different functional modules delay origin firing and improve sister chromosome cohesion of Rec8-expressing cells, potentially by allowing more time for Rec8-containing cohesin to load onto chromosomes prior to the passage of replication forks. Rec8, recombination 8; Scc1, sister chromosome cohesion 1; WT, wild type.