Centrosomes [1, 2] play a central role during spindle assembly in most animal cells [3]. In early mitosis, they organize two symmetrical microtubule arrays that upon separation define the two poles of the forming spindle. Centrosome separation is tightly regulated [4, 5], occurring through partially redundant mechanisms that rely on the action of microtubule-based dynein and kinesin motors and the actomyosin system [6]. While centrosomes can separate in prophase or in prometaphase after nuclear envelope breakdown (NEBD), prophase centrosome separation optimizes spindle assembly and minimizes the occurrence of abnormal chromosome attachments that could end in aneuploidy [7, 8]. Prophase centrosome separation relies on the activity of Eg5/KIF11, a mitotic kinesin [9] that accumulates around centrosomes in early mitosis under the control of CDK1 and the Nek9/Nek6/7 kinase module [10-17]. Here, we show that Eg5 localization and centrosome separation in prophase depend on the nuclear microtubule-associated protein TPX2 [18], a pool of which localizes to the centrosomes before NEBD. This localization involves RHAMM/HMMR [19] and the kinase Nek9 [20], which phosphorylates TPX2 nuclear localization signal (NLS) preventing its interaction with importin and nuclear import. The pool of centrosomal TPX2 in prophase has a critical role for both microtubule aster organization and Eg5 localization, and thereby for centrosome separation. Our results uncover an unsuspected role for TPX2 before NEBD and define a novel regulatory mechanism for centrosome separation in prophase. They furthermore suggest NLS phosphorylation as a novel regulatory mechanism for spindle assembly factors controlled by the importin/Ran system.
The activity of dynein is regulated by a number of adaptors that mediate its interaction with dynactin, effectively activating the motor complex while also connecting it to different cargos. The regulation of adaptors is consequently central to dynein physiology but remains largely unexplored. We now describe that one of the best-known dynein adaptors, BICD2, is effectively activated through phosphorylation. In G2, phosphorylation of BICD2 by CDK1 promotes its interaction with PLK1. In turn, PLK1 phosphorylation of a single residue in the N-terminus of BICD2 results in a structural change that facilitates the interaction with dynein and dynactin, allowing the formation of active motor complexes. Moreover, modified BICD2 preferentially interacts with the nucleoporin RanBP2 once RanBP2 has been phosphorylated by CDK1. BICD2 phosphorylation is central for dynein recruitment to the nuclear envelope, centrosome tethering to the nucleus and centrosome separation in the G2 and M phases of the cell cycle. This work reveals adaptor activation through phosphorylation as crucial for the spatiotemporal regulation of dynein activity.
SummaryThe activity of dynein is regulated by a number of adaptors that mediate its interaction with dynactin, effectively activating the motor complex while also connecting it to different cargos. The regulation of adaptors is consequently central to dynein physiology, but remains largely unexplored. We now describe that one of the best-known dynein adaptors, BICD2, is effectively activated through phosphorylation. In G2 phosphorylation of BICD2 by CDK1 promotes its interaction with PLK1. In turn, PLK1 phosphorylation of a single residue in the N-terminus of BICD2 results in a conformational change that facilitates interaction with dynein and dynactin, allowing the formation of active motor complexes. BICD2 phosphorylation is central for dynein recruitment to the nuclear envelope, centrosome tethering to the nucleus and centrosome separation in G2/M. This work reveals adaptor activation through phosphorylation as crucial for the spatiotemporal regulation of dynein activity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.