Spindle microtubules generate tension-dependent changes in the distribution of inner kinetochore proteins

Abstract

The kinetochore forms a dynamic interface with microtubules from the mitotic spindle. Live-cell light microscopy-based observations on the dynamic structural changes within the kinetochore suggest that molecular rearrangements within the kinetochore occur upon microtubule interaction. However, the source of these rearrangements is still unclear. In this paper, we analyze vertebrate kinetochore ultrastructure by immunoelectron microscopy (EM) in the presence or absence of tension from spindle microtubules. We found that the inner kinetochore region defined by CENP-A, CENP-C, CENP-R, and the C-terminal domain of CENP-T is deformed in the presence of tension, whereas the outer kinetochore region defined by Ndc80, Mis12, and CENP-E is not stretched even under tension. Importantly, based on EM, fluorescence microscopy, and in vitro analyses, we demonstrated that the N and C termini of CENP-T undergo a tension-dependent separation, suggesting that CENP-T elongation is at least partly responsible for changes in the shape of the inner kinetochore.