Microtubule (MT)-binding protein that plays a role in the formation and maintenance of the spindle poles and the alignement and the segregation of chromosomes during mitotic cell division (PubMed:19255246, PubMed:24109598, PubMed:26765568). Functions to tether the minus ends of MTs at the spindle poles, which is critical for the establishment and maintenance of the spindle poles (PubMed:26765568). Plays a role in the establishment of the mitotic spindle orientation during metaphase and elongation during anaphase in a dynein-dynactin-dependent manner (PubMed:26765568). In metaphase, part of a ternary complex composed of GPSM2 and G(i) alpha proteins, that regulates the recruitment and anchorage of the dynein-dynactin complex in the mitotic cell cortex regions situated above the two spindle poles, and hence regulates the correct oritentation of the mitotic spindle (PubMed:24109598, PubMed:26765568). During anaphase, mediates the recruitment and accumulation of the dynein-dynactin complex at the cell membrane of the polar cortical region through direct association with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2), and hence participates in the regulation of the spindle elongation and chromosome segregation. Binds also to other polyanionic phosphoinositides, such as phosphatidylinositol 3-phosphate (PIP), lysophosphatidic acid (LPA) and phosphatidylinositol triphosphate (PIP3), in vitro (By similarity). Also required for proper orientation of the mitotic spindle during asymmetric cell divisions (PubMed:26765568). Plays a role in mitotic MT aster assembly. Involved in anastral spindle assembly. Positively regulates TNKS protein localization to spindle poles in mitosis. Highly abundant component of the nuclear matrix where it may serve a non-mitotic structural role, occupies the majority of the nuclear volume (By similarity). Required for epidermal differentiation and hair follicle morphogenesis (PubMed:26765568). Homodimer. Also forms multiarm oligomers by association of C-terminal tail domains, oligomers may further assemble to form a hexagonal nuclear lattice-like network. 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. Part of a spindle orientation complex at least composed of GNAI1, GPSM2 and NUMA1 (By similarity). 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. 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. 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. Does not interact with GPSM2 during anaphase. Interacts (via C-terminus) with the nuclear importin alpha/importin beta receptor; this interaction is inhibited by RanGTP. Interacts (via C-terminus) with KPNB1; this interaction is inhibited by RanGTP and the BRISC complex. Interacts with ABRAXAS2 and the BRISC complex; these interactions regulate mitotic spindle assembly. Interacts (via N-terminal end of the coiled-coil domain) with RAE1; this interaction promotes mitotic spindle formation. 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. Interacts with TNKS; this interaction occurs at the onset of mitosis. Interacts with TNKS2. Interacts with tubulin. Interacts with KHDC3 (via C-terminus) (PubMed:25936915). Mitotic cell cycle-dependent shuttling protein that relocalizes from the interphase nucleus to the spindle poles and cell cortex (PubMed:19255246, PubMed:24109598, PubMed:26765568). The localization to the spindle poles is regulated by AAAS (By similarity). In interphase, resides in the nuclear matrix (PubMed:19255246). In prophase, restricted to the interchromatin or condensed chromosome space. In prometaphase, after nuclear envelope disassembly, forms aggregates both in the spindle midzone and at duplicated centrosomes and astral microtubules (MTs) of the bipolar spindle apparatus. Translocates from the spindle midzone towards the spindle poles along spindle fibers in a MT- and dynein-dynactin-dependent manner until the anaphase onset (By similarity). In metaphase, recruited to the polar cortical region in a GPSM2- and GNAI1-dependent manner (PubMed:24109598). Excluded from the metaphase equatorial cortical region in a RanGTP-dependent manner. Phosphorylation on Thr-2037 by CDK1 results in its localization at spindle poles in metaphase, but not at the cell cortex (By similarity). In anaphase, recruited and anchored at the cell membrane of the polar cortical region in a EPB41-, EPB41L2-, phosphatidylinositol-dependent and GPSM2- and G(i) alpha proteins-independent manner (PubMed:24109598). Excluded from the anaphase equatorial region of the cell cortex in a RACGAP1- and KIF23-dependent and RanGTP-independent manner. Associated with astral MTs emanating from the spindle poles during anaphase. Nonphosphorylated Thr-2037 localizes at the cell cortex, weakly during metaphase and more prominently during anaphase in a phosphatase PPP2CA-dependent manner. As mitosis progresses it reassociates with telophase chromosomes very early during nuclear reformation, before substantial accumulation of lamins on chromosomal surfaces is evident. Localizes to the tips of cortical MTs in prometaphase (By similarity). Localizes along MTs and specifically to both MT plus and minus ends (PubMed:26765568). Accumulates also at MT tips near the cell periphery. Colocalizes with GPSM2 at mitotic spindle poles during mitosis. Colocalizes with SPAG5 at mitotic spindle at prometaphase and at mitotic spindle poles at metaphase and anaphase. Colocalizes with ABRO1 at mitotic spindle poles. Colocalized with TNKS from prophase through to anaphase in mitosis. Colocalizes with tubulin alpha. CCSAP is essential for its centrosomal localization (By similarity). In horizontally retinal progenitor dividing cells, localized to the lateral cortical region (PubMed:26766442). Expressed in testis, speen, liver, lung, spinal cord and brain. Expressed in Purkinje neurons (at protein level) (PubMed:19255246). The C-terminal tubulin-binding domain mediates direct binding to microtubules, independently of dynein-dynactin complex, and induces their bundling and stabilization. The 4.1-binding domain is necessary for its cortical stability and spindle orientation. Phosphorylation and dephosphorylation on Thr-2037 regulates the extent of cortical NUMA1 and the dynein-dynactin complex localization during mitotic metaphase and anaphase. In metaphase, phosphorylation on Thr-2037 occurs in a kinase CDK1-dependent manner; this phosphorylation maintains low levels of cortical dynein-dynactin complex at metaphase, and hence proper spindle positioning. In anaphase, dephosphorylated on Thr-2037 by phosphatase PPP2CA; this dephosphorylation stimulates its membrane association and with the dynein-dynactin complex its enrichment at the cell cortex, and hence robust spindle elongation. Probably also phosphorylated on Thr-1997 and Ser-2069 by CDK1; these phosphorylations may regulate its cell cortex recruitment during metaphase and anaphase. Phosphorylated on Ser-1751, Ser-1754, Ser-1771 and Ser-1816 by PLK1; these phosphorylations induce cortical dynein-dynactin complex dissociation from the NUMA1-GPSM2 complex and negatively regulates cortical dynein-dynactin complex localization. ADP-ribosylated by TNKS at the onset of mitosis; ADP-ribosylation is not required for its localization to spindle poles. O-glycosylated during cytokinesis at sites identical or close to phosphorylation sites, this interferes with the phosphorylation status. Ubiquitinated with 'Lys-63'-linked polyubiquitin chains. Deubiquitination by the BRISC complex is important for the incorporation of NUMA1 into mitotic spindle poles and normal spindle pole function, probably by modulating interactions between NUMA1, dynein-dynactin complex and importin-beta. Mutant mice with an internal in-frame deletion of exon 22 exhibit early embryonic lethality (PubMed:19255246). Mutant mice with a conditional internal in-frame deletion of exon 22 show embryonic lethality and display inhibition of primary embryonic fibroblast proliferation that display mitotic centrosome-spindle coupling, microtubule-focusing at the spindle poles and equatorial metaphase chromosome alignement defects (PubMed:19255246). Mutant mice with a conditional internal in-frame deletion of exon 22 in the embryonic epidermis show neonatal lethality and display perturbation of epidermis differentiation characterized by increased suprabasal cell divisions and mitotic spindle orientation defects (PubMed:26765568). Adult mutant mice with a conditional internal in-frame deletion of exon 22 in interfollicular and hair follicles display an almost complete absence of hair regrowth and mitotic spindle orientation defects in hair follicle matrix cells (PubMed:26765568).