Condensin chromatin association is regulated by SMC head and hinge engagement and phosphorylation

The SMC condensin complex is essential for normal mitotic chromosome structure in eukaryotes. Here, we analyze how ATP binding and hydrolysis, SMC hinge stability, and condensin subunit phosphorylation influence condensin chromatin association in budding yeast. We show that mutations predicted to destabilize ATP binding and head-to-head engagement impair condensin chromatin association as assayed by ChIP. In contrast, mutations that inactivate the complex by destabilizing the hinge domain interaction, enhance chromatin association at known condensin loading sites. We find that condensin phosphorylation is enriched in enzymatic states associated with elevated chromatin binding. Moreover, phosphorylation and Aurora/Ipl1 kinase activity—but not Cdc5—are required to maintain condensin association with mitotic chromatin in early metaphase.