Characterization of Vertebrate Cohesin Complexes and Their Regulation in Prophase

Abstract

In eukaryotes, sister chromatids remain connected from the time of their synthesis until they are separated in anaphase. This cohesion depends on a complex of proteins called cohesins. In budding yeast, the anaphase-promoting complex (APC) pathway initiates anaphase by removing cohesins from chromosomes. In vertebrates, cohesins dissociate from chromosomes already in prophase. To study their mitotic regulation we have purified two 14S cohesin complexes from human cells. Both complexes contain SMC1, SMC3, SCC1, and either one of the yeast Scc3p orthologs SA1 and SA2. SA1 is also a subunit of 14S cohesin in Xenopus. These complexes interact with PDS5, a protein whose fungal orthologs have been implicated in chromosome cohesion, condensation, and recombination. The bulk of SA1- and SA2-containing complexes and PDS5 are chromatin-associated until they become soluble from prophase to telophase. Reconstitution of this process in mitotic Xenopus extracts shows that cohesin dissociation does neither depend on cyclin B proteolysis nor on the presence of the APC. Cohesins can also dissociate from chromatin in the absence of cyclin-dependent kinase 1 activity. These results suggest that vertebrate cohesins are regulated by a novel prophase pathway which is distinct from the APC pathway that controls cohesins in yeast.

Roles of the sister chromatid cohesion apparatus in gene expression, development, and human syndromes

“…Pds5 is not a stable subunit of cohesin, but colocalizes with cohesin on chromosomes in fungi and Drosophila (Hartman et al 2000;Panizza et al 2000;Tanaka et al 2001; Z. Misulovin, J.C. Eissenberg, D. Dorsett, unpublished). Association of Pds5 with chromatin depends on cohesin (Hartman et al 2000;Panizza et al 2000; and human Pds5 interacts with cohesin (Sumara et al 2000). The S. pombe Pds5 protein also interacts with the Eso1 (Ctf7/ Eco1) cohesin factor discussed below (Tanaka et al 2001).…”

“…Most of the cohesin bound to chromosome arms is removed during mitotic prophase (Losada et al 1998;Sumara et al 2000;Waizenegger et al 2000), while the shugosin protein protects the cohesin at the centromeres (Salic et al 2004;McGuinness et al 2005; reviewed by Watanabe 2005). The Rad21 (Mcd1/Scc1) subunit of the centromeric cohesin is proteolytically cleaved at the metaphase to anaphase transition to dissolve cohesion and permit chromosome segregation (Hauf et al 2001;Tomonaga et al 2000;Uhlmann et al 1999;Uhlmann et al 2000;Waizenegger et al 2000).…”

Association of cohesin and Nipped-B with transcriptionally active regions of the Drosophila melanogaster genome

“…The Pds5 protein, which is also conserved from fungi to man, interacts with cohesin and plays roles in establishment and/or maintenance of sister chromatid cohesion (Dorsett et al 2005;Hartman et al 2000;Losada et al 2005;Panizza et al 2000;Stead et al 2003;Sumara et al 2007;Tanaka et al 2001). In mammals, there are two Pds5 proteins, and the mice lacking Pds5B that show developmental abnormalities do not have cohesion defects.…”

Cohesin Associates with Spindle Poles in a Mitosis-specific Manner and Functions in Spindle Assembly in Vertebrate Cells

“…During G2/prophase, the majority of cohesin dissociates from chromosomes as an intact complex in a Polo-like kinase-reguThis article was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E08 -04 -0419) on January 7, 2009. Address correspondence to: Kyoko Yokomori (kyokomor@uci.edu).Abbreviations used: histone H3 lysine 9 methylation (H3K9me), histone methyltransferase (HMTase), microtubules (MTs), nuclear mitotic apparatus protein (NuMA), polo-like kinase 1 (plk1), structural maintenance of chromosomes (SMC).© 2009 by The American Society for Cell Biology 1289 lated manner (Losada et al, 2000;Sumara et al, 2000;Gregson et al, 2001). Only a small amount of cohesin (ϳ5%) remains at the chromosome-pairing domain to mediate sister chromatid cohesion, which is eventually terminated by the cleavage of Rad21 at the onset of anaphase leading to chromosome segregation (Waizenegger et al, 2000;Hoque and Ishikawa, 2001;Gimenez-Abian et al, 2004).…”