Cohesin's ATPase activity is stimulated by the C-terminal Winged-Helix domain of its kleisin subunit.
BACKGROUND
Cohesin, a multisubunit protein complex conserved from yeast to humans, holds sister chromatids together from the onset of replication to their separation during anaphase. Cohesin consists of four core subunits, namely Smc1, Smc3, Scc1, and Scc3. Smc1 and Smc3 proteins are characterized by 50-nm-long anti-parallel coiled coils flanked by a globular hinge domain and an ABC-like ATPase head domain. Whereas Smc1 and Smc3 heterodimerize via their hinge domains, the kleisin subunit Scc1 connects their ATPase heads, and this results in the formation of a large ring. Biochemical studies suggest that cohesin might trap sister chromatids within its ring, and genetic evidence suggests that ATP hydrolysis is required for the stable association of cohesin with chromosomes. However, the precise role of the ATPase domains remains enigmatic.


RESULTS
Characterization of cohesin's ATPase activity suggests that hydrolysis depends on the binding of ATP to both Smc1 and Smc3 heads. However, ATP hydrolysis at the two active sites is not per se cooperative. We show that the C-terminal winged-helix domain of Scc1 stimulates the ATPase activity of the Smc1/Smc3 heterodimer by promoting ATP binding to Smc1's head. In contrast, we do not detect any effect of Scc1's N-terminal domain on Smc1/Smc3 ATPase activity.


CONCLUSIONS
Our studies reveal that Scc1 not only connects the Smc1 and Smc3 ATPase heads but also regulates their ATPase activity.
Arumugam
Prakash
P
Research Institute of Molecular Pathology, Dr. Bohr Gasse 7, A-1030 Vienna, Austria.
Nishino
Tatsuya
T
Haering
Christian H
CH
Gruber
Stephan
S
Nasmyth
Kim
K
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000302:isolation & purification / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000302:isolation & purification / Q000378:metabolism*; D011508:Chondroitin Sulfate Proteoglycans / Q000302:isolation & purification / Q000378:metabolism*; D002868:Chromosomal Proteins, Non-Histone / Q000302:isolation & purification / Q000378:metabolism*; D003001:Cloning, Molecular; D019281:Dimerization; D005822:Genetic Vectors / Q000235:genetics; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000302:isolation & purification / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012441:Saccharomyces cerevisiae; D029701:Saccharomyces cerevisiae Proteins / Q000302:isolation & purification / Q000378:metabolism*; D000098550:Structural Maintenance of Chromosome Protein 1
D018797:Cell Cycle Proteins; D011508:Chondroitin Sulfate Proteoglycans; D002868:Chromosomal Proteins, Non-Histone; D018832:Molecular Chaperones; C120372:SMC3 protein, S cerevisiae; C101767:SSC1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D000098550:Structural Maintenance of Chromosome Protein 1; D000255:Adenosine Triphosphate; D000252:Calcium-Transporting ATPases