A conserved CENP-E region mediates BubR1-independent recruitment to the outer corona at mitotic onset.

The outer corona plays an essential role at the onset of mitosis by expanding to maximize microtubule attachment to kinetochores. ^{1 , 2} The low-density structure of the corona forms through the expansion of unattached kinetochores. It comprises the RZZ complex, the dynein adaptor Spindly, the plus-end directed microtubule motor centromere protein E (CENP-E), and the Mad1/Mad2 spindle-assembly checkpoint proteins. ^{3 , 4 , 5 , 6 , 7 , 8 , 9 , 10} CENP-E specifically associates with unattached kinetochores to facilitate chromosome congression, ^{11 , 12 , 13 , 14 , 15 , 16} interacting with BubR1 at the kinetochore through its C-terminal region (2091-2358). ^{17 , 18 , 19 , 20 , 21} We recently showed that CENP-E recruitment to BubR1 at the kinetochores is both rapid and essential for correct chromosome alignment. However, CENP-E is also recruited to the outer corona by a second, slower pathway that is currently undefined. ¹⁹ Here, we show that BubR1-independent localization of CENP-E is mediated by a conserved loop that is essential for outer-corona targeting. We provide a structural model of the entire CENP-E kinetochore-targeting domain combining X-ray crystallography and Alphafold2. We reveal that maximal recruitment of CENP-E to unattached kinetochores critically depends on BubR1 and the outer corona, including dynein. Ectopic expression of the CENP-E C-terminal domain recruits the RZZ complex, Mad1, and Spindly, and prevents kinetochore biorientation in cells. We propose that BubR1-recruited CENP-E, in addition to its essential role in chromosome alignment to the metaphase plate, contributes to the recruitment of outer corona proteins through interactions with the CENP-E corona-targeting domain to facilitate the rapid capture of microtubules for efficient chromosome alignment and mitotic progression.
Competing Interests: Declaration of interests The authors declare no competing interests.
(Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)