The final cut: cell polarity meets cytokinesis at the bud neck in S. cerevisiae

Abstract

Cell division is a fundamental but complex process that gives rise to two daughter cells. It includes an ordered set of events, altogether called “the cell cycle”, that culminate with cytokinesis, the final stage of mitosis leading to the physical separation of the two daughter cells. Symmetric cell division equally partitions cellular components between the two daughter cells, which are therefore identical to one another and often share the same fate. In many cases, however, cell division is asymmetrical and generates two daughter cells that differ in specific protein inheritance, cell size, or developmental potential. The budding yeast Saccharomyces cerevisiae has proven to be an excellent system to investigate the molecular mechanisms governing asymmetric cell division and cytokinesis. Budding yeast is highly polarized during the cell cycle and divides asymmetrically, producing two cells with distinct sizes and fates. Many components of the machinery establishing cell polarization during budding are relocalized to the division site (i.e., the bud neck) for cytokinesis. In this review we recapitulate how budding yeast cells undergo polarized processes at the bud neck for cell division.

Mechanics and regulation of cytokinesis in budding yeast

“…Several MEN components, including the mitotic kinases Cdc15 and Dbf2 as well as the phosphatase Cdc14, localize to the division site to control cytokinesis [166, 171]. MEN regulates AMR constriction, as the ring can form but fails to constrict in MEN mutants [28, 32].…”

Septin-Associated Protein Kinases in the Yeast Saccharomyces cerevisiae

“…In S. cerevisiae , cytokinesis and cell separation proceed via the concerted action of actomyosin ring (AMR) formation and contraction (Bi et al, 1998) with concomitant synthesis of the chitinaceous primary septum (Nishihama et al, 2009). To permit these events to happen following anaphase, the septin collar is split into two gasket-like bands via a mechanism that is still completely unknown (McMurray and Thorner, 2009; Bi and Park, 2012; Wloka and Bi, 2012; Juanes and Piatti, 2016). However, after septin collar assembly and release from the morphogenesis checkpoint, the elevation of Clb2-Cdc28 activity commences the process of promoting AMR formation early in M phase and, once localized to the septin collar, Cdc5 generates a local pool of activated (GTP-bound) Rho1 at the bud neck via phosphorylation and activation of one of the primary Rho1 GEFs (Tus1) (Yoshida et al, 2006).…”

“…Recruitment of these three components to the bud neck requires MEN signaling activity (Meitinger et al, 2010), and thus presumably their phosphorylation, and all are required for efficient cytokinesis because they contribute to coordinating AMR contraction with primary septum formation (Meitinger et al, 2012; Wloka and Bi, 2012; Juanes and Piatti, 2016). As mentioned above, formation of the primary septum requires the localized activity of chitin synthase Chs2 between the bands of the split septin collar.…”

Mechanisms of cytokinesis in basidiomycetous yeasts

“…Several excellent reviews have been published recently that describe cytokinesis in S. cerevisiae and S. pombe and we refer the reader to these great resources for more information (Weiss 2012, Wloka and Bi 2012, Willet, McDonald et al 2015, Juanes and Piatti 2016, Meitinger and Palani 2016, Perez, Cortes et al 2016, Rincon and Paoletti 2016). Here we provide a brief overview of the mechanisms in both model yeasts and focus mostly on studies describing cytokinesis in basidiomycetous yeasts.…”