Abstract
In vertebrate cells, chromosomes oscillate to align precisely during metaphase. NuSAP, a microtubule-associated protein, plays a critical role in stabilizing spindle microtubules. In this study, we utilize 3D time-lapse live-cell imaging to monitor the role of NuSAP in chromosome oscillation and identify NuSAP as a novel regulator of the chromokinesin, Kid. Depletion of NuSAP significantly suppresses the amplitude and velocity of chromosome oscillation. We analyse the effects of NuSAP and Kid depletion in monopolar and bipolar cells with or without kinetochore microtubule depletion. Twelve postulated conditions are deciphered to reveal the contribution of NuSAP to the polar force generated at kinetochore microtubules and to the regulation of the polar ejection force generated by Kid, thus revealing a pivotal role of NuSAP in chromosome oscillation.
Highlights
In vertebrate cells, chromosomes oscillate to align precisely during metaphase
Poleward motion is produced by the polar force (PF), which is predominantly generated by the depolymerization of kinetochore microtubules[3], while anti-poleward motion is produced by the polar ejection force (PEF), which is dependent on motor proteins sliding along the chromosome arms at interpolar microtubules[4]
To simplify the factors involved in chromosome oscillation further, we studied the movement of centromeres in monastroltreated monopolar cells with both interpolar microtubules (iMTs) and kinetochore microtubules (kMTs) from one spindle pole with a single direction[2,4,10,38]
Summary
Chromosomes oscillate to align precisely during metaphase. NuSAP, a microtubule-associated protein, plays a critical role in stabilizing spindle microtubules. Poleward motion is produced by the polar force (PF), which is predominantly generated by the depolymerization of kinetochore microtubules (kMTs)[3], while anti-poleward motion is produced by the polar ejection force (PEF), which is dependent on motor proteins sliding along the chromosome arms at interpolar microtubules (iMTs)[4]. Microtubule-associated proteins (MAPs) play vital roles in regulating chromosome oscillation by tightly maintaining both the dynamics of kMTs and the surface properties of iMTs13. Human chromokinesins are plus-end-directed motors contributing to anti-poleward movement[26,27,28] These include Kid (kinesin-like DNA-binding protein), which contains an N-terminal microtubule-binding domain and a C-terminal chromosome-interacting domain[29]. A functional relationship has been reported between NuMA and Kid in spindle morphology and chromosome alignment[32], and the microtubule localization of Kid is known to be mediated by the spindle protein CHICA33, the regulatory mechanism of Kid in chromosome oscillation remains unclear
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