Reis, R., Feijão, T., Gouveia, S., Pereira, A.J., Matos, I., Sampaio, P., Maiato, H., Sunkel, C.E. (2009). Dynein and Mast/Orbit/CLASP have antagonistic roles in regulating kinetochore-microtubule plus-end dynamics.  J. Cell Sci. 122(14): 2543--2553.

FBrf0208223

Research paper

Establishment and maintenance of the mitotic spindle requires the balanced activity of microtubule-associated proteins and motors. In this study we have addressed how the microtubule plus-end tracking protein mast/orbit/CLASP and cytoplasmic dynein regulate this process in Drosophila melanogaster embryos and S2 cells. We show that mast accumulates at kinetochores early in mitosis, which is followed by a poleward streaming upon microtubule attachment. This leads to a reduction of mast levels at kinetochores during metaphase and anaphase that depends largely on the microtubule minus end-directed motor cytoplasmic dynein. Surprisingly, we also found that co-depletion of dynein rescues spindle bipolarity in mast-depleted cells, while restoring normal microtubule poleward flux. Our results suggest that mast and dynein have antagonistic roles in the local regulation of microtubule plus-end dynamics at kinetochores, which are important for the maintenance of spindle bipolarity and normal spindle length.