Microtubule-associated protein with the capacity to bundle and stabilize microtubules (By similarity). May associate with chromosomes and promote the organization of mitotic spindle microtubules around them. Interacts with DNA and microtubules. Microtubule bundling is inhibited by IPO7, KPNA2 and KPNB1 while association with DNA is also inhibited by IPO7 and KPNA2 (By similarity). Found in the cytoplasm and nucleolus during interphase and redistributes to the mitotic spindle in prometaphase (By similarity). Localizes to the mitotic spindle during anaphase and telophase then disappears from around the chromosomes during cytokinesis (By similarity). Localizes to multiple distinct regions of chromosomes throughout mitosis. The KEN box is required for the FZR1-dependent degradation of this protein subsequent to ubiquitination. Ubiquitinated. Ubiquitination by FZR1 may lead to proteasome-dependent degradation of this protein. Phosphorylation by ATM in G2/M-phase induces mitotic arrest. Belongs to the NUSAP family.