Recognizes a phosphorylated protein of 228kDa, identified as nuclear mitotic apparatus protein (NuMA). Its epitope is resistant to phosphatases. NuMA is intra-nuclear protein and present in nucleus during interphase. At the onset of mitosis, it redistributes from the nucleus to two centrosomal structures that later will become part of the mitotic spindle pole. After anaphase, the protein redistributes from the spindle polar region into reforming nucleus. NuMA is an essential protein during mitosis for the terminal phases of chromosome separation and/or nuclear reassembly. Recently a study shows that NuMA is cleaved to a 180 to 200kDa during apoptosis. Chromosomal translocation of this gene with the RARA (retinoic acid receptor, alpha) gene on chromosome 17 has been detected in patients with acute promyelocytic leukemia.