Orderly termination of sister-chromatid cohesion during mitosis is critical for 
accurate chromosome segregation. During prophase, mitotic kinases phosphorylate 
cohesin and its protector sororin, triggering Wapl-dependent cohesin release 
from chromosome arms. The shugoshin (Sgo1)-PP2A complex protects centromeric 
cohesin until its cleavage by separase at anaphase onset. Here, we report the 
crystal structure of a human cohesin subcomplex comprising SA2 and Scc1. 
Multiple HEAT repeats of SA2 form a dragon-shaped structure. Scc1 makes 
extensive contacts with SA2, with one binding hotspot. Sgo1 and Wapl compete for 
binding to a conserved site on SA2-Scc1. At this site, mutations of SA2 residues 
that disrupt Wapl binding bypass the Sgo1 requirement in cohesion protection. 
Thus, in addition to recruiting PP2A to dephosphorylate cohesin and sororin, 
Sgo1 physically shields cohesin from Wapl. This unexpected, direct antagonism 
between Sgo1 and Wapl augments centromeric cohesion protection.