NuMA: a protein involved in nuclear structure, spindle assembly, and nuclear re-formation.

The abundant coiled-coil protein NuMA is located in the nucleus during interphase, but when the nuclear envelope disassembles in prometaphase it rapidly redistributes to the developing spindle poles. Microinjection of antibodies to NuMA at or before metaphase can block spindle assembly or cause spindle collapse, indicating a role for NuMA in spindle function. NuMA must also play a key role in telophase, as NuMA antibodies or truncations of NuMA cause aberrant nuclear reassembly despite apparently normal chromosome segregation. Consistent with a structural role for NuMA in the nucleus, immunoelectron microscopy reveals NuMA to be a component of nuclear filaments.