Homodimer (PubMed:10075938). Also forms multiarm oligomers by association of C-terminal tail domains, oligomers may further assemble to form a hexagonal nuclear lattice-like network (PubMed:10075938). Associates with the dynein-dynactin complex; this association promotes the transport and accumulation of
NUMA1 at the mitotic spindle poles that is inhibited by the BRISC complex in a
PLK1-dependent manner (PubMed:10811826, PubMed:17172455, PubMed:23027904, PubMed:22327364, PubMed:26195665). Part of a spindle orientation complex at least composed of
GNAI1,
GPSM2 and
NUMA1 (PubMed:26766442). Interacts (via C-terminus) with microtubules (MTs); this interaction is direct and promotes both MT bundle formation and stability in a dynein-dynactin complex- and
CDK1-independent manner (PubMed:12445386, PubMed:11956313, PubMed:26765568). Interacts with
EPB41 and
EPB41L2; these interactions are negatively regulated by
CDK1 during metaphase and are important for anaphase-specific localization of
NUMA1 in symmetrically dividing cells (PubMed:23870127, PubMed:24996901). Interacts (via C-terminus) with
GPSM2 (via
TPR repeats); this interaction is direct, prevented by competitive binding of
INSC, is inhibited in a
PLK1-dependent manner, blocks the association of
NUMA1 with MTs and inhibits
NUMA1-induced MT bundle formation, prevents the association of
NUMA1 with
SPAG5, induces mitotic spindle pole localization of
GPSM2, both metaphase cell cortex localization of
NUMA1 and mitotic spindle organization (PubMed:11781568, PubMed:12445386, PubMed:22327364, PubMed:24109598, PubMed:27462074, PubMed:21816348). Does not interact with
GPSM2 during anaphase (PubMed:23870127). Interacts (via C-terminus) with the nuclear importin alpha/importin beta receptor; this interaction is inhibited by RanGTP (PubMed:11163243). Interacts (via C-terminus) with
KPNB1; this interaction is inhibited by RanGTP and the BRISC complex (PubMed:11229403, PubMed:26195665). Interacts with
ABRAXAS2 and the BRISC complex; these interactions regulate mitotic spindle assembly (PubMed:26195665). Interacts (via N-terminal end of the coiled-coil domain) with
RAE1; this interaction promotes mitotic spindle formation (PubMed:17172455). Interacts (via C-terminus) with
SPAG5 (via C-terminus); this interaction promotes the recruitment of
SPAG5 to the MTs at spindle poles in a dynein-dynactin-dependent manner and regulates mitotic spindle organization and proper chromosome alignment during mitosis (PubMed:27462074). Interacts with
TNKS; this interaction occurs at the onset of mitosis (PubMed:12080061, PubMed:16076287). Interacts with
TNKS2 (PubMed:12080061). Interacts with tubulin (PubMed:11956313).
UniProt