Swm1p subunit of the APC/cyclosome is required for activation of the daughter-specific gene expression program mediated by Ace2p during growth at high temperature inSaccharomyces cerevisiae

Abstract

SWM1 was originally identified for its role in the late steps of the sporulation process, being required for spore wall assembly. This protein, recently identified as one of the core subunits of the anaphase-promoting complex (APC) is also required to complete cell separation in vegetative cells during growth at high temperature. Mutants lacking SWM1 show a thermosensitive growth defect that is suppressed by osmotic support in the culture medium. At the restrictive temperature, swm1 mutants are unable to complete separation, forming chains of cells that remain associated and, with prolonged incubation times, the stability of the cell wall is compromised, resulting in cell lysis. This separation defect is due to a reduction in expression of CTS1 (the gene encoding chitinase) and a group of genes involved in cell separation (such as ENG1, SCW11, DSE1 and DSE2). Interestingly, these genes are specifically regulated by the transcription factor Ace2p, suggesting that Swm1p is required for normal expression of Ace2p-dependent genes during growth at high temperatures. Although no defect in Ace2p localization can be observed at 28°C, this transcription factor is unable to enter the nucleus of the daughter cell during growth at 38°C. Under these growth conditions, swm1 cells undergo a delay in exit from mitosis, as determined by analysis of Clb2p degradation and Cdc28p-Clb2p kinase assays, and this could be the reason for the cytoplasmic localization of Ace2p.

Ace2p contributes to fission yeast septin ring assembly by regulating mid2+ expression

“…Protein abundance peaks at late anaphase and then diminishes as mitosis is completed. This timing would be consistent with Ace2p nuclear accumulation requiring activation of the anaphase-promoting complex (APC), which is a multisubunit E3 ubiquitin ligase (Harper et al, 2002;Peters, 2002), as seems to be the case in budding yeast (Ufano et al, 2004). In S. cerevisiae, cells with a mutant version of the APC component Swm1p, do not accumulate Ace2p in the daughter nucleus.…”

“…In S. cerevisiae, cells with a mutant version of the APC component Swm1p, do not accumulate Ace2p in the daughter nucleus. These mutant cells do not express genes under Ace2p control and exhibit mitotic exit and cell separation defects (Ufano et al, 2004). It remains to be determined, however, whether the APC affects S. pombe Ace2p.…”

Swm1/Apc13 Is an Evolutionarily Conserved Subunit of the Anaphase-Promoting Complex Stabilizing the Association of Cdc16 and Cdc27

“…It might be important that translocation of Ace2 occurs abruptly because nuclear Ace2 is unstable (29). While this paper was being revised, Ufano et al reported experiments showing that the cell separation phenotype stems from a defect in nuclear accumulation of Ace2 (42). The SWM1 deletion also reduced the activity of APC/C-Cdh1, causing a stabilization of Clb2 in G 1 -arrested cells.…”

Ace2p Controls the Expression of Genes Required for Cell Separation inSchizosaccharomyces pombe

“…However, suppression of the separation defect was not complete, indicating that Ace2p might be regulated by other mechanisms. Although we have ruled out the contribution of the SIN in controlling Ace2p function, it is possible that, by analogy with S. cerevisiae Ace2p, Cdk1p, or Orb6p (similar to S. cerevisiae Cbk1p) phosphorylation might be involved in its regulation (O'Conallain et al, 1999;Weiss et al, 2002;Nelson et al, 2003;Ufano et al, 2004). It is also possible that Sep1p not only regulates ace2 ϩ transcription, but also the activity or localization of Ace2p.…”