Project description:Cohesin holds sister chromatids together to enable their accurate segregation in mitosis. How, and where, cohesin binds to chromosomes are still poorly understood, and recent genome-wide surveys have revealed an apparent disparity between its chromosomal association patterns in different organisms. Here, we present the high-resolution analysis of cohesin localisation along fission yeast chromosomes. This reveals that several determinants, thought specific for distinct organisms, come together to shape the overall distribution. Cohesin is detected at chromosomal loading sites, characterised by the cohesin loader Mis4/Ssl3, in regions of strong transcriptional activity. Cohesin also responds to transcription by downstream translocation and accumulation at convergent transcriptional terminators surrounding the loading sites. As cells enter mitosis, a fraction of cohesin leaves chromosomes in a cleavage-independent reaction, while a substantial pool of cohesin dissociates when it is cleaved at anaphase onset. As a unique feature, centromeric cohesin spreads out onto chromosome arms during mitosis as the heterochromatin protein Swi6 dissociates from centromeres. Together, this allows us to suggest conserved mechanisms for chromosomal cohesin binding in eukaryotes.
