Cytoplasmic dynein’s mitotic-spindle-pole localization requires a functional anaphase-promoting complex, γ-tubulin and NUDF/LIS1 in Aspergillus nidulans

In Aspergillus nidulans, cytoplasmic dynein and NUDF/LIS1 are found at the spindle poles during mitosis, but they appear to be targeted to this location via different mechanisms. The spindle-pole localization of cytoplasmic dynein requires the function of the anaphase-promoting complex (APC), while that of NUDF does not. Moreover, while NUDF's localization to the spindle poles does not require a fully functional dynein motor, the function of NUDF is important for cytoplasmic dynein's targeting to the spindle poles. Interestingly, a γ-tubulin mutation, mipAR63, nearly eliminates the localization of cytoplasmic dynein to the spindle poles, but has no apparent effect on NUDF’s spindlepole localization. Live cell analysis of the mipAR63 mutant revealed a defect in chromosome separation accompanied by unscheduled spindle elongation before the completion of anaphase A, suggesting that γ-tubulin may recruit regulatory proteins to the spindle poles for mitotic progression. In A. nidulans, dynein is not apparently required for mitotic progression. In the presence of a low amount of benomyl, a microtubule depolymerizing agent, however, a dynein mutant diploid strain exhibits a more pronounced chromosome-loss phenotype than the control, indicating that cytoplasmic dynein plays a role in chromosome segregation.