The Aspergillus cytoplasmic dynein heavy chain and NUDF localize to microtubule ends and affect microtubule dynamics

Cytoplasmic dynein is a multisubunit, minus end-directed microtubule motor that uses dynactin as an accessory complex to perform various in vivo funct ions including vesicle transport, spindle assembly, and nuclear distributio n [1], We previously showed that in the filamentous fungus Aspergillus nidu lans, a GFP-tagged cytoplasmic dynein heavy chain (NUDA) forms comet-like s tructures that exhibited microtubule-dependent movement toward and back fro m the hyphal tip [2], Here we demonstrate that another protein in the NUDA pathway, NUDF, which is homologous to the human LIS1 protein involved in br ain development [3, 4], also exhibits such dynamic behavior. Both NUDA and NUDF are located at the ends of microtubules, and this observation suggests that the observed dynamic behavior is due to their association with the dy namic microtubule ends. To address whether NUDA and NUDF play a role in reg ulating microtubule dynamics in vivo, we constructed a GFP-labeled alpha -t ubulin strain and used it to compare microtubule dynamics in vivo in wildty pe A. nidulans versus temperature-sensitive loss-of-function mutants of nud A and nudF, The mutants showed a lower frequency of microtubule catastrophe , a lower rate of shrinkage during catastrophe, and a lower frequency of re scue, The microtubules in the mutant cells also paused longer at the hyphal tip than wild-type microtubules. These results indicate that cytoplasmic d ynein and the LIS1 homolog NUDF affect microtubule dynamics in vivo.