H. Funabiki et al., FISSION YEAST CUT1 AND CUT2 ARE ESSENTIAL FOR SISTER-CHROMATID SEPARATION, CONCENTRATE ALONG THE METAPHASE SPINDLE AND FORM LARGE COMPLEXES, EMBO journal, 15(23), 1996, pp. 6617-6628
Fission yeast Schizosaccharomyces pombe temperature-sensitive (ts) cut
1 mutants fail to separate sister chromatids in anaphase but the cells
continue to divide, leading to bisection of the undivided nucleus (th
e cut phenotype). If cytokinesis is blocked, replication continues, fo
rming a giant nucleus with polyploid chromosomes, We show here that th
e phenotype of ts cut2-364 is highly similar to that of cut1 and that
the functions of the gene products of cut1(+) and cut2(+) are closely
interrelated. The cut1(+) and cut2(+) genes are essential for viabilit
y and interact genetically. Cut1 protein concentrates along the short
spindle in metaphase as does Cut2. Cut1 (similar to 200 kDa) and Cut2
(42 kDa) associate, as shown by immunoprecipitation, and cosediment as
large complexes (30 and 40S) in sucrose gradient centrifugation, Thei
r behavior in the cell cycle is strikingly different, however: Cut2 is
degraded in anaphase by the same proteolytic machinery used for the d
estruction of cyclin B, whereas Cut1 exists throughout the cell cycle.
The essential function of the Cut1-Cut2 complex which ensures sister
chromatid separation may be regulated by Cut2 proteolysis. The C-termi
nal region of Cut1 is evolutionarily conserved and similar to that of
budding yeast Esp1, filamentous fungi BimB and a human protein.