The function of DCTN3 (dynactin subunit 3, ENSG00000137100) is as follows. Part of the dynactin complex that activates the molecular motor dynein for ultra-processive transport along microtubules (By similarity). Together with dynein may be involved in spindle assembly and cytokinesis (PubMed:9722614). {ECO:0000250|UniProtKB:F1SEC0, ECO:0000269|PubMed:9722614}.