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 such as nuclear migration during cell division. Required for neuronal cell differentiation. {ECO:0000255|HAMAP-Rule:MF_03141; ECO:0000269|PubMed:11685578; ECO:0000269|PubMed:15254012; ECO:0000269|PubMed:15331665}.