A BubR1-independent pathway for CENP-E targeting to the outer corona of kinetochores

For chromosome segregation to take place, unattached kinetochores expand in early mitosis, forming a fibrous structure called the fibrous corona that is captured by microtubules. The corona is assembled from the RZZ complex, Spindly, CENP-E and the Mad1/Mad2 spindle assembly checkpoint proteins. CENP-E aligns chromosomes along the mitotic spindle by moving them to the plus ends of microtubules. Here, we show that CENP-E is recruited to the outer corona independently of BubR1 in a dynein-dependent fashion. We determine the structure of this domain and show that a conserved loop is essential for CENP-E targeting to the outer corona. We show that both domains are essential for CENP-E recruitment to unattached kinetochores. We also report that the kinetochore-targeting domain of CENP-E contributes to the recruitment of the RZZ complex, Mad1 and Spindly, providing a feedback loop to assemble the outer corona. In this study, we propose that CENP-E uses 2 pathways to target to the kinetochore, which allows it to optimize kinetochore capture by microtubules for chromosome alignment and mitotic progression.