Abstract
PP2A-B56 is a serine/threonine phosphatase complex that regulates several major processes during mitosis, including sister chromatid cohesion, kinetochore-microtubule attachment and the spindle assembly checkpoint. We show here that these key functions are controlled by distinct B56 isoforms that localise differentially to either the centromere or kinetochore. The centromeric B56 isoforms rely on a specific interaction with Sgo2, whereas the kinetochore isoforms bind preferentially to proteins containing an LxxIxE motif, including the kinetochore B56 receptor BubR1. The molecular basis for this differential localisation can be mapped to a small C-terminal region in B56 that defines whether PP2A-B56 complexes bind to either Sgo2 at the centromere or BubR1 at the kinetochore. Together, this study describes how different PP2A-B56 complexes utilise isoform-specific interactions to control distinct processes during mitosis.