Dynein prevents erroneous kinetochore-microtubule attachments in mitosis

Abstract

Equal distribution of the genetic material during cell division relies on efficient congression of chromosomes to the metaphase plate. Prior to their alignment, the Dynein motor recruited to kinetochores transports a fraction of laterally-attached chromosomes along microtubules toward the spindle poles. By doing that, Dynein not only contributes to chromosome movements, but also prevents premature stabilization of end-on kinetochore-microtubule attachments. This is achieved by 2 parallel mechanisms: 1) Dynein-mediated poleward movement of chromosomes counteracts opposite polar-ejection forces (PEFs) on chromosome arms by the microtubule plus-end-directed motors chromokinesins. Otherwise, they could stabilize erroneous syntelic kinetochore-microtubule attachments and lead to the random ejection of chromosomes away from the spindle poles; and 2) By transporting chromosomes to the spindle poles, Dynein brings the former to the zone of highest Aurora A kinase activity, further destabilizing kinetochore-microtubule attachments. Thus, Dynein plays an important role in keeping chromosome segregation error-free by preventing premature stabilization of kinetochore-microtubule attachments near the spindle poles.

Keywords: Aurora A; Dynein; error correction; kinetochore; spindle pole.

Figure 1.

Dynein “locks” peripheral chromosomes at the spindle poles after CENP-E inhibition. High-resolution live-cell imaging (eleven 1μm-separated z-planes; 10 sec time interval) of HeLa cells stably expressing DHC-GFP (kind gift from Iain Cheeseman, Whitehead Institute, MIT, USA). Images were taken with an iXonEMC electron-multiplying CCD camera (Andor Technology), using a 100x 1.4 NA Plan-Apochromatic DIC objective on an inverted microscope (TE2000U; Nikon) equipped with a CSU-X1 spinning-disc confocal head (Yokogawa Corporation of America). Note that DHC-GFP is highly expressed at unattached kinetochores from polar chromosomes after CENP-E inhibition with 20 nM GSK92329 (MedChemexpress). Red circles indicate the position of the spindle poles. Scale bar: 10 μm. Time: hrs:mins

Figure 2.

Dynein prevents premature stabilization of erroneous kinetochore-microtubule attachments by counteracting PEFs and by bringing chromosomes closer to Aurora A activity at the spindle poles. Illustrative model depicting the dominant role of Dynein in bringing peripheral chromosomes toward the center of an Aurora A activity gradient at the spindle poles, against chromokinesin-mediated PEFs.