摘要
For proper chromosome segregation, all kinetochores must achieve bipolar microtubule （MT） attachment and subsequently align at the spindle equator before anaphase onset. The MT minus end-directed motor dynein/dynactin binds kinetoehores in prometaphase and has long been implicated in chromosome congression. Unfortunately, inactivation of dynein usually disturbs spindle organization, thus hampering evaluation of its kinetochore roles. Here we specifically eliminated kinetochore dynein/dynactin by RNAi-mediated depletion of ZW10, a protein essential for kinetochore localization of the motor. Time-lapse microscopy indicated markedly-reduced congression efficiency, though congressing chromosomes displayed similar velocities as in control cells. Moreover, cells frequently failed to achieve full chromosome alignment, despite their normal spindles. Confocal microcopy revealed that the misaligned kinetochores were monooriented or unattached and mostly lying outside the spindle, suggesting a difficulty to capture MTs from the opposite pole. Kinetoehores on monoastral spindles were dispersed farther away from the pole and exhibited only mild oscillation. Furthermore, inactivating dynein by other means generated similar phenotypes. Therefore, kinetochore dynein produces on monooriented kinetochores a poleward pulling force, which may contribute to efficient bipolar attachment by facilitating their proper microtubule captures to promote congression as well as full chromosome alignment.
基金
Acknowledgments The authors thank Qiongping Huang, Lirong Liu, and Wei Bian for technical assistance. We are grateful to Drs G Chan （Cross Cancer Institute, University of Alberta, Edmonton Alberta, Canada） for antibodies to human ZW 10 and Rod, KH Choo （Murdoch Children＇s Research Institute, Royal Children＇s Hospital, Melbourne, Australia） for anti-CREST serum, and E Fuchs （Rockefeller University, USA） for mRFP cDNA. This work was supported by the National Science Foundation of China （30330330, 30421005, and 30623003）, Ministry of Science and Technology of China （2005CB522703 and 2007CB914501）, and the Shanghai Municipal Council for Science and Technology （S048014317, 06DZ22032, and 058014578）.
