Recruitment of the kinesin CENP-E to the kinetochore during mitosis is essential for the capture and alignment of chromosomes that are located outside the interpolar region. Although it has been shown that CENP-E can depend on spindle checkpoint proteins to localise to the kinetochore, such as the mitotic checkpoint serine-threonine kinase BubR1 (also known as BUB1B), the molecular mechanism is still unclear. In this study, Julie Welburn and colleagues (Legal et al., 2020) identify the molecular details of the interaction between CENP-E and the kinetochore-localised BubR1. By analysing different truncations of these proteins in vitro and in vivo, the authors determine that a small acidic patch, located between residues 2313 and 2319 in the kinetochore-targeting domain of CENP-E (residues 2091 to 2358), and the C-terminal helix of BubR1 are essential for the interaction between these two proteins. Moreover, the expression of truncated BubR1 variants unable to bind CENP-E leads to impaired chromosome congression. Finally, although CENP-E can localise to the kinetochore in the absence of BubR1, this does not allow for stable end-on attachment of the chromosomes and their alignment. Taken together, these data uncover the molecular determinants that allow for the recruitment of CENP-E to the kinetochore by BubR1 and reveal the importance of their interaction for chromosome congression during mitosis.
