Spatial regulation of Aurora A activity during mitotic spindle assembly requires RHAMM to correctly localize TPX2

Abstract

Construction of a mitotic spindle requires biochemical pathways to assemble spindle microtubules and structural proteins to organize these microtubules into a bipolar array. Through a complex with dynein, the receptor for hyaluronan-mediated motility (RHAMM) cross-links mitotic microtubules to provide structural support, maintain spindle integrity, and correctly orient the mitotic spindle. Here, we locate RHAMM to sites of microtubule assembly at centrosomes and non-centrosome sites near kinetochores and demonstrate that RHAMM is required for the activation of Aurora kinase A. Silencing of RHAMM delays the kinetics of spindle assembly, mislocalizes targeting protein for XKlp2 (TPX2), and attenuates the localized activation of Aurora kinase A with a consequent reduction in mitotic spindle length. The RHAMM–TPX2 complex requires a C-terminal basic leucine zipper in RHAMM and a domain that includes the nuclear localization signal in TPX2. Together, our findings identify RHAMM as a critical regulator for Aurora kinase A signaling and suggest that RHAMM ensures bipolar spindle assembly and mitotic progression through the integration of biochemical and structural pathways.

Keywords: :

• Aurora kinase A
• mitosis
• RHAMM
• spindle assembly
• TPX2

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Author Contributions

H.C., P.M., O.N., D.H., and J.J. performed all experiments and data analysis. M.C.F., D.N., L.M.P., and C.J.L. provided reagents and expertise. C.A.M. designed the study, assisted in the analysis, and, along with H.C., wrote the manuscript.

Funding

These studies were supported by an operating grant from the Canadian Institutes of Health Research (CIHR), in partnership with the Avon Foundation for Women- Canada (Grant No. 201309OBC). H.C. was supported by a graduate studentship from the Child and Family Research Institute (CFRI). O.N. was supported by graduate studentships from the CFRI and a Banting and Best MSc studentship from CIHR.