The role of proteolysis in cell cycle progression in Schizosaccharomyces pombe.

Abstract

A cell‐free system derived from Xenopus eggs was used to identify the ‘destruction box’ of the Schizosaccharomyces pombe B‐type cyclin, Cdc13, as residues 59–67: RHALDDVSN. Expression of indestructible Cdc13 from a regulated promoter in S.pombe blocked cells in anaphase and inhibited septation, showing that destruction of Cdc13 is necessary for exit from mitosis, but not for sister chromatid separation. In contrast, strong expression of a polypeptide comprising the N‐terminal 70 residues of Cdc13, which acts as a competitive inhibitor of destruction box‐mediated proteolysis, inhibited both sister chromatid separation and the destruction of Cdc13, whereas an equivalent construct with a mutated destruction box did not. Appropriately timed expression of this N‐terminal fragment of Cdc13 overcame the G1 arrest seen in cdc10 mutant strains, suggesting that proteins required for the initiation of S phase are subject to destruction by the same proteolytic machinery as cyclin.

Fission Yeast Ste9, a Homolog of Hct1/Cdh1 and Fizzy-related, Is a Novel Negative Regulator of Cell Cycle Progression during G1-Phase

“…In the absence of this control, fission yeast cells in G 1 can initiate mitosis without having undergone DNA replication. Proteolysis is indispensable for normal cell cycle progression (King et al, 1996), and expression of undegradable Cdc13 resulted in the cell cycle arrest at anaphase (Yamano et al, 1996). The fact that ste9 ϩ and rum1 ϩ are dispensable for normal growth is curious because Cdc13 protein remains in the ste9 or rum1 mutant arrested in G 1 (Moreno and Nurse, 1994; this study).…”

“…Third, the population in G 1 at the semipermissive temperature is considerably less in the ste9 cdc10 double mutant than in the control cdc10 strain. Because inhibition of the ubiquitin-dependent proteolytic activity overcomes Start arrest and induces DNA synthesis in fission yeast (Yamano et al, 1996), it is possible that deregulation of the Start-promoting activity is related to the proteolytic defect. In this aspect, it is intriguing that the G 1 arrest induced by mating pheromone exposure is overridden in the budding yeast hct1 mutant (Schwab et al, 1997).…”

“…The amount of Cdc13 protein, a major mitotic B-type cyclin in S. pombe, culminates in the late G 2 /M and is very low in the G 1 -phase due to selective degradation by the proteasome (Hayles et al, 1994;Yamano et al, 1996). Strong activation of the Cdc2/Cdc13 complex in G 1 -arrested cells leads to mitosis in the absence of DNA synthesis (Hayles et al, 1994;Yamano et al, 1996).…”

“…Strong activation of the Cdc2/Cdc13 complex in G 1 -arrested cells leads to mitosis in the absence of DNA synthesis (Hayles et al, 1994;Yamano et al, 1996). Because similar premature mitosis occurs in the G 1 -arrested ste9 cdc10 cells, we quantified the level of the Cdc13 protein at the restrictive temperature.…”

Regulation of the Anaphase-promoting Complex/Cyclosome bybimAAPC3and Proteolysis of NIMA

“…It has been proposed that some checkpoint controls over mitosis are switched from the APC/C during G1 to include tyrosine phosphorylation of p34 cdc2 upon initiation of DNA replication (Ye et al, 1997a). BIME APC1 may therefore normally play a role to prevent activation of NIMA kinase, and other mitotic regulators, during interphase to prevent premature mitosis.The levels of NIME cyclinB and NIMA proteins oscillate once each cell cycle in a strikingly similar manner (Evans et al, 1983;Alfa et al, 1990;Draetta et al, 1990;Ghiara et al, 1991;Hunt et al, 1992;Richardson et al, 1992;Grandin and Reed, 1993;Pu and Osmani, 1995;Ye et al, 1995;Yamano et al, 1996). Both proteins accumulate during late S to G2, peak at early M, and are rapidly degraded as cells progress out of mitosis with slightly different kinetics Ye et al, 1995).…”