Anillin‐related protein Mid1 regulates timely formation of the contractile ring in the fission yeast Schizosaccharomyces japonicus

Abstract

In the fission yeast Schizosaccharomyces pombe (Sp), Mid1/Dmf1 plays an important role in positioning the division site by inducing formation of the contractile ring (CR). Mid1, emanating from the nucleus located in the cell center, forms a dozen of nodes in the middle cell cortex ahead of mitosis, and actin filaments and myosin II accumulated at each node interact and assemble the CR in metaphase. Curiously, in another fission yeast S. japonicus (Sj), CR formation begins after nuclear segregation in late anaphase. Here, we investigated the role of S. japonicus Mid1 during mitosis to compare the molecular mechanisms that determine the cell division site in Schizosaccharomyces. Similar to Sp Mid1, Sj Mid1 often accumulated in the nucleus of interphase cells. Moreover, Sj Mid1 localized to cortical dots with myosin II in the future division site and formed a medial ring in mitotic cells. However, S. japonicus cells without Mid1 function still carried out symmetrical binary division. Therefore, the Mid1 dependency for positional control of the cell division site is possibly different between the two species. Meanwhile, we found that Sj Mid1 enhanced CR formation, in a manner possibly similar to that by Sp Mid1.

The actin networks of chytrid fungi reveal evolutionary loss of cytoskeletal complexity in the fungal kingdom

“…48 We find Bni-type formins in all other dikaryotic fungi included in our analyses ( Figure 5A), as well as references to their assembly of actin cables. [49][50][51][52] We also find that some chytrids have at least one bni1-type formin, including Sp, whose sporangia we recently found can build actin cables within the cell body. 2 Other chytrids, including Bd and Bs, are missing these formins, an interesting finding given the lack of actin cables in the cell bodies of Bd zoospores and sporangia ( Figure 1).…”

Regulation and Assembly of Actomyosin Contractile Rings in Cytokinesis and Cell Repair

“…The mammalian anillin and the yeast Mid1 both bind the PM via cryptic C2 domains, but unlike anillin, Mid1 is capable of Rho GTPase-independent furrow localization via dimerization-induced interaction with PI(4,5)P 2 (Sun et al, 2015). Interestingly, though it enhances CR formation, Mid1 is not required for proper CR positioning in S. japonicus (Yasuda et al, 2016), but along with Efr3 (Snider et al, 2017) and suppressor of beta glucan synthase 1 (Sbg1p; Sethi et al, 2016), is still probably involved in CR anchoring to the PM.…”

Identification of a new p53 responsive element in the promoter region of anillin

“…However with the dissolution of the nuclear membrane at the onset of mitosis, anillin becomes phosphorylated (2) and relocates to the cell cortex, associating with the cell membrane prior to being accumulated at the developing cleavage furrow (5). Here, it serves as a scaffold, associating with actin (6), septins (7) myosin II (8) and also Rho like signaling complexes, including racGAP components (9) and a range of other proteins (10). The ubiquitin-mediated degradation of anillin, occurring at the end of mitosis, is facilitated by anaphase-promoting complex (11).…”