Requirement for ESP1 in the nuclear division of Saccharomyces cerevisiae.

Abstract

Mutations in the ESP1 gene of Saccharomyces cerevisiae disrupt normal cell-cycle control and cause many cells in a mutant population to accumulate extra spindle pole bodies. To determine the stage at which the esp1 gene product becomes essential for normal cell-cycle progression, synchronous cultures of ESP1 mutant cells were exposed to the nonpermissive temperature for various periods of time. The mutant cells retained viability until the onset of mitosis, when their viability dropped markedly. Examination of these cells by fluorescence and electron microscopy showed the first detectable defect to be a structural failure in the spindle. Additionally, flow cytometric analysis of DNA content demonstrated that massive chromosome missegregation accompanied this failure of spindle function. Cytokinesis occurred despite the aberrant nuclear division, which often resulted in segregation of both spindle poles to the same cell. At later times, the missegregated spindle pole bodies entered a new cycle of duplication, thereby leading to the accumulation of extra spindle pole bodies within a single nucleus. The DNA sequence predicts a protein product similar to those of two other genes that are also required for nuclear division: the cut1 gene of Schizosaccharomyces pombe and the bimB gene of Aspergillus nidulans.

Anaphase initiation in Saccharomyces cerevisiae is controlled by the APC-dependent degradation of the anaphase inhibitor Pds1p.

“…In addition, Cut2p derivatives that lack the destruction box inhibit the onset of anaphase (Funabiki et al 1996). Interestingly, Cut2p associates with Cutlp (Funabiki et al 1996a), a homolog of the S. cerevisiae gene ESP1 (Uzawa et al 1990;McGrew et al 1992) with which Pdslp may have genetic interactions (V. Guacci, O. Cohen-Fix, and D. Koshland, unpubl.). The distribution of the charged amino acids in Cut2p resembles that of Pdslp, in that there is clustering of acidic and basic residues (Uzawa et al 1990;Yamamoto et al 1996a).…”

The Spindle Midzone Microtubule-Associated Proteins Ase1p and Cin8p Affect the Number and Orientation of Astral Microtubules in Saccharomyces cerevisiae

“…16 Budding yeast strains in which separase (Esp1p) has been inactivated exit mitosis with an undivided nucleus that segregates, almost exclusively, to the daughter cell. 17 The nuclear positioning function of Esp1p is independent of its role in chromosome segregation, because in strains that expressed a non-cleavable Scc1p subunit (Scc1-RRDD), the undivided nucleus is inherited by the mother cell. 15 Thus, Esp1p, as part of the FEAR pathway, is needed to activate a force that pulls the nucleus towards the mother cortex, possibly to facilitate the anaphase movement of the nuclear compartment containing the mother-bound chromosomes.…”

Cell cycle mechanisms of sister chromatid separation; Roles of Cut1/separin and Cut2/securin

“…Their close relationship is presumed by ®nding that Pds1 forms a stable complex with Esp1 (Ciosk et al 1998) in the same way as Cut2 forms the complex with Cut1. The C-terminal region of Esp1 is known to be quite similar to that of Cut1 (McGrew et al 1992). The Asperigillus nidulans BimB which is essential for mitosis is also similar to Cut1 and Esp1 (May et al 1992).…”

“…Phenotypes of ®ssion yeast cut1 and budding yeast esp1 mutants at the restrictive temperature are similar in many ways. Multiple spindle pole bodies (SPB) and the polyploidy nuclei are produced Baum et al 1988;Uzawa et al 1990;McGrew et al 1992). Both Esp1 and Cut1 are essential for viability.…”