Cohesin at active genes: a unifying theme for cohesin and gene expression from model organisms to humans

Cohesin is an evolutionarily ancient multisubunit protein complex with a deeply conserved function: it provides cohesion between sister chromatids from the time of DNA replication in S-phase until mitosis. This cohesion facilitates repair of damage that occurs during DNA replication, and, crucially, enforces faithful segregation of chromosomes upon cell division. Cohesin also influences gene expression, and relative to sister chromatid cohesion, gene expression is exquisitely sensitive to moderate changes in cohesin activity. Early studies revealed differences in cohesin's roles in gene expression between various organisms. In all organisms examined, however, cohesin marks a subset of active genes. This review focuses on the roles of cohesin at active genes, and to what extent these roles are conserved between organisms.