Regulates prospindle assembly during late prophase and at the onset of mitosis, before nuclear envelope breakdown (NEB). Is exported from the nucleus shortly before NEB and organized into two polar crescents. After NEB, is progressively associated with the forming spindle. Probably mediates AUR1 activation and localization to spindle microtubules. Has a microtubule binding capability and is able to trigger microtubule assembly induced by RanGTP in a heterologous system. Not involved in phragmoplast assembly, nuclear envelope reformation, and cortical microtubule assembly at the onset of G1 (PubMed:18941054). Involved in the formation of specific nuclear and perinuclear microtubular arrays in the nuclei of acentrosomal plant cells. Fungi and plants have acentrosomal microtubule arrays because they lack centrosomes. They use other microtubule organizing center (MTOC) structures to organize their microtubules. May function through interaction with importin (PubMed:24006426). Interacts with AUR1. Located in the nucleoplasm during interphase until late G2, in the perinuclear region during early prophase, and at the spindle during mitosis. Localized on a specific subset of phragmoplast microtubules in early telophase. The N-terminal part of the protein is required for the interaction with AUR1. Two regions (220-463 and 684-758) seem involved in the targeting to the microtubule cytoskeleton. Lethal when homozygous. TPX2 over-expressing cells display formation of nuclear and perinuclear microtubular arrays which are not specific for the transition to mitosis and occur independently of AUR1 kinase. Belongs to the TPX2 family.