Abstract
ABSTRACTBipolar spindle organization is essential for the faithful segregation of chromosomes during cell division. This organization relies on the collective activities of motor proteins. The minus-end-directed dynein motor complex generates spindle inward forces and plays a major role in spindle pole focusing. The dynactin complex regulates many dynein functions, increasing its processivity and force production. Here, we show that DnaJB6 is a novel RanGTP-regulated protein. It interacts with the dynactin subunit p150Glued (also known as DCTN1) in a RanGTP-dependent manner specifically in M-phase, and promotes spindle pole focusing and dynein force generation. Our data suggest a novel mechanism by which RanGTP regulates dynein activity during M-phase.
Highlights
Spindle assembly involves the organization of microtubules into two antiparallel arrays with interdigitating plus-ends, and two focused minus-ends forming the spindle poles
We used a Xenopus egg extract system to directly test whether the long isoform of DnaJB6 (DnaJB6-L; xDnaJB6-L refers to the Xenopus form), which contains an NLS, could be regulated by RanGTP during mitosis
Here, we showed that the nuclear protein DnaJB6 interacts with dynactin p150Glued in a RanGTP-dependent way during mitosis by performing pulldown experiments
Summary
Spindle assembly involves the organization of microtubules into two antiparallel arrays with interdigitating plus-ends, and two focused minus-ends forming the spindle poles This organization is highly dependent on the collective activities of microtubuledependent motor proteins. Impairing dynein activity rescues spindle bipolarity in Eg5-inhibited cells (Ferenz et al, 2009; Mitchison et al, 2005; Raaijmakers et al, 2013; Tanenbaum et al, 2008) This suggests that a fine balance between outward forces generated by Eg5 and inward forces generated by dynein defines spindle length and bipolarity (Ferenz et al, 2009; Florian and Mayer, 2012; Gaglio et al, 1997, 1996; Heald et al, 1996; Tanenbaum et al, 2008; Walczak et al, 1998)
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