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

Abstract

The fission yeast Schizosaccharomyces pombe divides through constriction of an actomyosin-based contractile ring followed by formation and degradation of a medial septum. Formation of an organized septin ring is also important for the completion of S. pombe cell division and this event relies on the production of Mid2p. mid2 + mRNA and protein accumulate in mitosis. Recent microarray analyses identified mid2 + as a target of the Ace2p transcription factor, and ace2 + as a target of the Sep1p transcription factor. In this study, we find that Mid2p production is controlled by Ace2p functioning downstream of Sep1p. Consequently, both Sep1p and Ace2p are required for septin ring assembly and genetic analyses indicate that septin rings function in parallel with other Ace2p targets to achieve efficient cell division. Conversely, forced overproduction of Sep1p or Ace2p prevents septin ring disassembly. We find that Ace2p levels peak during anaphase and Ace2p is post-translationally modified by phosphorylation and ubiquitylation. Ace2p localizes symmetrically to dividing nuclei and functions independently of the septation initiation network.

Role of Hcn1 and Its Phosphorylation in Fission Yeast Anaphase-promoting Complex/Cyclosome Function

“…To test this prediction, pREP3Xace2 or a control plasmid was transformed into hcn1-S48A cells. Plasmid pREP3Xace2 expresses Ace2 levels that complement the ace2⌬ phenotype and that are not deleterious to cell growth (52). As expected, there was significant rescue of the cell separation phenotype in cells transformed with the ace2-containing vector (Fig.…”

“…In the case of swm1⌬ cells, however, it is present at normal levels, but mislocalized to the cytoplasm (53,58). S. pombe Ace2 is regulated differently from its S. cerevisiae counterpart (52). ace2 ϩ is a direct target of the Sep1 transcription factor (59 -61), the activity of which appears to be primarily responsible for dictating Ace2 abundance and activity (52).…”

“…S. pombe Ace2 is regulated differently from its S. cerevisiae counterpart (52). ace2 ϩ is a direct target of the Sep1 transcription factor (59 -61), the activity of which appears to be primarily responsible for dictating Ace2 abundance and activity (52). What controls Sep1 activity and S. pombe Ace2 post-translationally is still unknown, and therefore, it is presently unclear how the APC/C might influence S. pombe Ace2 levels.…”

A Cds1-Mediated Checkpoint Protects the MBF Activator Rep2 from Ubiquitination by Anaphase-Promoting Complex/Cyclosome-Ste9 at S-Phase Arrest in Fission Yeast

“…1E). Turnover of cell cycle-specific TFs such as Ace2 (46), Rep2 (this study), and Sep1 (16) has been linked to the ubiquitin-proteasomes. The cell cycle is known to be controlled by CDK activities that are regulated through both (de)phosphorylation and ubiquitin-mediated proteolysis.…”

Cooperation Between the Septins and the Actomyosin Ring and Role of a Cell-Integrity Pathway During Cell Division in Fission Yeast

“…pombe has seven septins, four of which (Spn1, Spn2, Spn3, and Spn4) are expressed in vegetative cells and localize to the division site shortly before AMR constriction and septum formation (Longtine et al 1996;Berlin et al 2003;Tasto et al 2003;Wu et al 2003;An et al 2004;Petit et al 2005;Pan et al 2007;Onishi et al 2010). Spn1 and Spn4 appear to be the core members of the septin complex McMurray and Thorner 2008), and mutants lacking either of these proteins do not assemble the others at the division site.…”