As predicted by the notion that sister chromatid cohesion is mediated by 
entrapment of sister DNAs inside cohesin rings, there is perfect correlation 
between co-entrapment of circular minichromosomes and sister chromatid cohesion. 
In most cells where cohesin loads without conferring cohesion, it does so by 
entrapment of individual DNAs. However, cohesin with a hinge domain whose 
positively charged lumen is neutralized loads and moves along chromatin despite 
failing to entrap DNAs. Thus, cohesin engages chromatin in non-topological, as 
well as topological, manners. Since hinge mutations, but not Smc-kleisin 
fusions, abolish entrapment, DNAs may enter cohesin rings through hinge opening. 
Mutation of three highly conserved lysine residues inside the Smc1 moiety of 
Smc1/3 hinges abolishes all loading without affecting cohesin's recruitment to 
CEN loading sites or its ability to hydrolyze ATP. We suggest that loading and 
translocation are mediated by conformational changes in cohesin's hinge driven 
by cycles of ATP hydrolysis.