Chromosome congression is promoted by CENP-Q- and CENP-E-dependent pathways

Abstract

A key step of mitosis is the congression of chromosomes to the spindle equator. Congression is driven by at least two distinct mechanisms: (1) kinetochores slide along the microtubule lattice using the plus-end directed CENP-E motor, and (2) kinetochores biorientating near the pole move to the equator through microtubule depolymerisation-coupled pulling. Here, we show that CENP-Q - a subunit of the CENP-O/P/Q/U complex that targets polo-like kinase (Plk1) to kinetochores - is also required for the recruitment of CENP-E to kinetochores. We further reveal a CENP-E recruitment-independent role for CENP-Q in depolymerisation-coupled pulling. Both these functions are abolished by a single point mutation in CENP-Q (S50A) – a residue that is phosphorylated in vivo. Importantly, the S50A mutant does not affect Plk1 loading onto kinetochores and leaves the CENP-O complex intact. Thus, the function of CENP-Q in CENP-E loading and depolymerisation-coupled pulling are independent from its role in Plk1 recruitment and CENP-O/P/Q/U complex stabilization. Together, our data provide evidence that phospho-regulation of CENP-Q plays a central function in coordinating chromosome congression mechanisms.