CENP-E initiates chromosome congression by opposing Aurora kinases to promote end-on attachments

Abstract

Chromosome congression to the spindle equator, which recurrently fails in cancer cells leading to aneuploidy, requires the kinetochore motor protein CENP-E/kinesin-7. Current models state that chromosomes congress by CENP-E-driven gliding along spindle microtubules. Here, we show that CENP-E is not essential for the congression movement, but for initiating movement through the formation of end-on attachments. We reached this conclusion by large-scale live-cell imaging under varying activity of CENP-E using lattice light-sheet microscopy. We found that congression without CENP-E is delayed by the activity of centriole-dependent Aurora A and outer-kinetochore-localized Aurora B kinases, which limit the formation of end-on attachments. CENP-E bypasses this inhibition by causing a decrease in Aurora B activity and in phosphorylation of its outer-kinetochore targets. Chromosomally unstable cancer cells rely on CENP-E more than non-cancer cells, leading to segregation errors specifically in cancer cells with prolonged mitosis, thereby exposing a mitotic timing-dependent vulnerability of cancer cells.

Motor proteins in antiparallel microtubule overlaps drive chromosome congression during mitotic spindle assembly

“…We also show that plus-end-directed motor proteins at kinetochores assist congression. Taken together, our model provides a systematic approach to understanding key forces relevant to chromosome congression and reproduces experimentally measured kinetochore velocities, including duration of chromosome congression [25].…”

“…These calculations show that the kinetochore velocity reaches a maximum value for the average MT length around 1 µm. The kinetochore velocity has values comparable to biologically relevant values, which are around 0.5 µm/min [25], for an average MT length between 0.6 µm and 3.8 µm. To understand how the kinetochore velocity reaches the maximum value, we explore the dependence of the number of motor proteins on the average MT lengths (Fig.…”

“…We solve the MT distribution equations in a steadystate limit (see Appendix C), which is reasonable due to the difference in time scales. For non-kinetochore MTs, the MT growth time, k −1 ps ≈ 0.1 min, is much shorter than the time needed for congression, usually 5-10 min [25,64]. We also calculate the kinetochore MT distributions in a steady-state limit (see Appendix D), because the kinetochore MT detachment time, k −1 off ≈ 3.5 min [59], is shorter than the congression time.…”

“…In experiments in cells with altered concentrations of CENP-E proteins, chromosomes can be found in the metaphase plane, as well as near the poles [25]. Such states can persist for long periods of time, even after inhibiting Aurora B (which detaches kinetochore MTs at low inter-kinetochore tension), suggesting that there are several stable locations along the spindle where kinetochores tend to accumulate.…”

“…Forces oriented toward the spindle midplane are also exerted by plus-end-directed kinetochore motor proteins, such as CENP-E, which move along non-kinetochore MTs [24]. A recent study has shown that chromosome congression relies on end-on kinetochore-MT attachments and in their absence, chromosomes do not congress [25]. Pulling forces on kinetochores are generated by depolymerization of end-on attached MTs, as shown in vitro and in vivo [26][27][28][29].…”