FISSION YEAST MAL2(+) IS REQUIRED FOR CHROMOSOME SEGREGATION

By a screen designed to isolate new fission yeast genes required for c hromosome segregation, we have identified mal2(+). The conditionally l ethal mal2-1 allele gives rise to increased loss of a nonessential min ichromosome at the permissive temperature and leads to severe missegre gation of the chromosomes at the non-permissive temperature. Cloning b y complementation and subsequent sequence analysis revealed that mal2 is a novel protein with a mass of 34 kDa. Cells containing a mal2 null allele were inviable, indicating that mal2(+) is an essential gene. F usion of mal2 protein to the green fluorescent protein (GFP) showed th at mal2 was predominantly localized in the nucleus. Sensitivity to mic rotubule-destabilizing drugs and strong genetic interactions with alph a 1-tubulin suggest an interaction of the mal2 protein with the microt ubule system. Spindle formation and elongation were not detectably aff ected in the mal2-1 mutant as determined by indirect immunofluorescenc e. However, anomalous chromosome movement on the spindle leading to ab errant distribution of the chromosomal material was observed.