A NudE/14-3-3 Pathway Coordinates Dynein and the Kinesin Khc73 to Position the Mitotic Spindle

•The N terminus of the kinesin Khc73 provides a cortical-microtubule connection•A 14-3-3 binding motif in the Khc73 stalk is required for robust spindle orientation•Khc73 forms a quaternary complex with 14-3-3 ε, 14-3-3ζ, and NudE•Khc73 delivers NudE to the cortex, where it activates cortically localized Dynein

SummaryMitotic spindle position is controlled by interactions of cortical molecular motors with astral microtubules. In animal cells, Partner of Inscuteable (Pins) acts at the cortex to coordinate the activity of Dynein and Kinesin-73 (Khc73; KIF13B in mammals) to orient the spindle. Though the two motors move in opposite directions, their synergistic activity is required for robust Pins-mediated spindle orientation. Here, we identify a physical connection between Dynein and Khc73 that mediates cooperative spindle positioning. Khc73’s motor and MBS domains link Pins to microtubule plus ends, while its stalk domain is necessary for Dynein activation and precise positioning of the spindle. A motif in the stalk domain binds, in a phospho-dependent manner, 14-3-3ζ, which dimerizes with 14-3-3ε. The 14-3-3ζ/ε heterodimer binds the Dynein adaptor NudE to complete the Dynein connection. The Khc73 stalk/14-3-3/NudE pathway defines a physical connection that coordinates the activities of multiple motor proteins to precisely position the spindle.

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