Positively regulates the activity of the minus-end directed microtubule motor protein dynein. May enhance dynein-mediated microtubule sliding by targeting dynein to the microtubule plus end. Required for several dynein- and microtubule-dependent processes. Localizes to the plus end of microtubules and to the centrosome. Dimerization mediated by the LisH domain may be required to activate dynein. Belongs to the WD repeat LIS1/nudF family. Extended N-terminus.