A new essential gene of Saccharomyces cerevisiae, a defect in it may result in instability of nucleus

We identified a new essential gene of Saccharomyces cerevisiae, designated NIN1 (nuclear integrity). The nin1-1 mutant cells showed temperature-sensitive growth, and their nuclei underwent deformation and eventually were broken down upon a temperature shift. When the nin1-1 cells growing at 25°C were transferred to a nonpermissive temperature, the nucleus moved to the isthmus and cells with a large bud accumulated. Flow cytometry proved that G2 nuclei accumulated during incubation at a nonpermissive temperature. NIN1 is mapped on chromosome VI, 16 cM centromere-distal to PHO4. Cloning and sequencing of NIN1 revealed that this is a new gene. Disruption of NIN1 resulted in cell death; however, a dead spore clone contained about 30 dead cells, indicating that spores that received the disrupted nin1 allele divided approximately five times before their death. Western blotting using anti-Nin1 antibody reveals that NIN1 produces a doublet consisting of 32 and 34 kDa whose size is close enough to that calculated from the predicted amino acid sequence of Nin1.