NUF2, A SPINDLE POLE BODY-ASSOCIATED PROTEIN REQUIRED FOR NUCLEAR DIVISION IN YEAST

The NUF2 gene of the yeast Saccharomyces cerevisiae encodes an essenti al 53-kd protein with a high content of potential coiled-coil structur e similar to myosin. Nuf2 is associated with the spindle pole body (SP B) as determined by coimmunofluorescence with known SPB proteins. Nuf2 appears to be localized to the intranuclear region and is a candidate for a protein involved in SPB separation. The nuclear association of Nuf2 can be disrupted, in part, by 1 M salt but not by the detergent T riton X-100. All Nuf2 can be removed from nuclei by 8 M urea extractio n. In this regard, Nuf2 is similar to other SPB-associated proteins in cluding Nuf1/SPC110, also a coiled-coil protein. Temperature-sensitive alleles of NUF2 were generated within the coiled-coil region of Nuf2 and such NUF2 mutant cells rapidly arrest after temperature shift with a single undivided or partially divided nucleus in the bud neck, a sh ortened mitotic spindle and their DNA fully replicated. In sum, Nuf2 i s a protein associated with the SPB that is critical for nuclear divis ion. Anti-Nuf2 antibodies also recognize a mammalian 73-kd protein and display centrosome staining of mammalian tissue culture cells suggest ing the presence of a protein with similar function.