In situ architecture of human kinetochore-microtubule interface visualized by cryo-electron tomography

Faithful segregation of chromosomes during mitosis relies on a carefully coordinated and intricate interplay between the centromere, kinetochore, and spindle microtubules. Despite its importance, the architecture of this interface remains elusive. Here we used in situ cryo-electron tomography to visualize the native architecture of the kinetochore-microtubule interface in human U2OS cells at different stages of mitosis. We find that the centromere forms a pocket-like structure around kinetochore microtubules. Two morphologically distinct fibrillar densities form end-on and side-on connections to the plus-ends of microtubules within this centromeric pocket. Our data suggest a dynamic kinetochore-microtubule interface with multiple interactions between outer kinetochore components and spindle microtubules.