Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, United States; Biomedical Sciences Graduate Program, University of California, San Francisco, San Francisco, United States
Samuel J Kenny
Department of Chemistry, University of California, Berkeley, Berkeley, United States
Department of Cell and Tissue Biology, University of California, San Francisco, San Francisco, United States; Biomedical Sciences Graduate Program, University of California, San Francisco, San Francisco, United States; Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, United States
To build the spindle at mitosis, motors exert spatially regulated forces on microtubules. We know that dynein pulls on mammalian spindle microtubule minus-ends, and this localized activity at ends is predicted to allow dynein to cluster microtubules into poles. How dynein becomes enriched at minus-ends is not known. Here, we use quantitative imaging and laser ablation to show that NuMA targets dynactin to minus-ends, localizing dynein activity there. NuMA is recruited to new minus-ends independently of dynein and more quickly than dynactin; both NuMA and dynactin display specific, steady-state binding at minus-ends. NuMA localization to minus-ends involves a C-terminal region outside NuMA’s canonical microtubule-binding domain and is independent of minus-end binders γ-TuRC, CAMSAP1, and KANSL1/3. Both NuMA’s minus-end-binding and dynein-dynactin-binding modules are required to rescue focused, bipolar spindle organization. Thus, NuMA may serve as a mitosis-specific minus-end cargo adaptor, targeting dynein activity to minus-ends to cluster spindle microtubules into poles.
