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Characterization of vertebrate cohesin complexes and their regulation in prophase.

Sumara I, Vorlaufer E, Gieffers C, Peters BH, Peters JM - J. Cell Biol. (2000)

Bottom Line: SA1 is also a subunit of 14S cohesin in Xenopus.The bulk of SA1- and SA2-containing complexes and PDS5 are chromatin-associated until they become soluble from prophase to telophase.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.

View Article: PubMed Central - PubMed

Affiliation: Research Institute of Molecular Pathology (IMP), A-1030 Vienna, Austria.

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.

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Immunofluorescence microscopy showing the intracellular distribution of SA1, SA2, and PDS5 in human cells at different stages of mitosis. Caco cells were stained with DAPI and with either the SA1/SA2 antibody 447 (A), or with PDS5 antibodies (B), or with the SA1-specific antibody 444. Similar results were obtained with the antibodies 445 and 446 (data not shown). Bars, 5 μm.
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Figure 6: Immunofluorescence microscopy showing the intracellular distribution of SA1, SA2, and PDS5 in human cells at different stages of mitosis. Caco cells were stained with DAPI and with either the SA1/SA2 antibody 447 (A), or with PDS5 antibodies (B), or with the SA1-specific antibody 444. Similar results were obtained with the antibodies 445 and 446 (data not shown). Bars, 5 μm.

Mentions: Yeast cohesin dissociates from chromatin at the onset of anaphase, whereas Xenopus 14S cohesin dissociates from chromatin already in prophase. Our observation that human cells contain two distinct 14S cohesin complexes containing either SA1 or SA2 therefore raised the possibility that in vertebrates different cohesin complexes may dissociate from chromatin at different times in mitosis. To test this hypothesis we analyzed the chromatin association of SA1 and SA2 in Xenopus egg extracts in vitro (Fig. 5) and in cultured cells by immunofluorescence microscopy in vivo (Fig. 6).


Characterization of vertebrate cohesin complexes and their regulation in prophase.

Sumara I, Vorlaufer E, Gieffers C, Peters BH, Peters JM - J. Cell Biol. (2000)

Immunofluorescence microscopy showing the intracellular distribution of SA1, SA2, and PDS5 in human cells at different stages of mitosis. Caco cells were stained with DAPI and with either the SA1/SA2 antibody 447 (A), or with PDS5 antibodies (B), or with the SA1-specific antibody 444. Similar results were obtained with the antibodies 445 and 446 (data not shown). Bars, 5 μm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2169443&req=5

Figure 6: Immunofluorescence microscopy showing the intracellular distribution of SA1, SA2, and PDS5 in human cells at different stages of mitosis. Caco cells were stained with DAPI and with either the SA1/SA2 antibody 447 (A), or with PDS5 antibodies (B), or with the SA1-specific antibody 444. Similar results were obtained with the antibodies 445 and 446 (data not shown). Bars, 5 μm.
Mentions: Yeast cohesin dissociates from chromatin at the onset of anaphase, whereas Xenopus 14S cohesin dissociates from chromatin already in prophase. Our observation that human cells contain two distinct 14S cohesin complexes containing either SA1 or SA2 therefore raised the possibility that in vertebrates different cohesin complexes may dissociate from chromatin at different times in mitosis. To test this hypothesis we analyzed the chromatin association of SA1 and SA2 in Xenopus egg extracts in vitro (Fig. 5) and in cultured cells by immunofluorescence microscopy in vivo (Fig. 6).

Bottom Line: SA1 is also a subunit of 14S cohesin in Xenopus.The bulk of SA1- and SA2-containing complexes and PDS5 are chromatin-associated until they become soluble from prophase to telophase.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.

View Article: PubMed Central - PubMed

Affiliation: Research Institute of Molecular Pathology (IMP), A-1030 Vienna, Austria.

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.

Show MeSH
Related in: MedlinePlus