Category: Fission Yeast

Fission yeast cells divide precisely at their middle. Once the cell reaches a critical size, the scaffolding protein anillin/Mid1p accumulates at the cell’s equator, where it anchors to the plasma membrane to form “nodes”, the precursors for actomyosin contractile ring (ACR) assembly (Upper Figure 4). These nodes then coalesce and recruit the necessary contractile ring machinery. Following its assembly, the ring constricts, as its name implies, driving ingression of the plasma membrane while simultaneously directing the deposition of septum material. This newly synthesized cell wall is ultimately remodeled to generate the two daughter cells (Lower Figure 4).

Figure 4: Finding the Middle and Building the Wall: Cytokinesis in Fission Yeast.

1. Paoletti A, Chang F. Analysis of mid1p, a protein required for placement of the cell division site, reveals a link between the nucleus and the cell surface in fission yeast. Mol Biol Cell. 2000;11(8):2757-73. doi: 10.1091/mbc.11.8.2757

2. Wu JQ, Sirotkin V, Kovar DR, Lord M, Beltzner CC, Kuhn JR, Pollard TD. Assembly of the cytokinetic contractile ring from a broad band of nodes in fission yeast. J Cell Biol. 2006;174(3):391-402. doi: 10.1083/jcb.200602032

3. Campbell BF, Hercyk BS, Williams AR, San Miguel E, Young HG, Das ME. Cdc42 GTPase activating proteins Rga4 and Rga6 coordinate septum synthesis and membrane trafficking at the division plane during cytokinesis. Traffic. 2022;23(10):478-495. doi: 10.1111/tra.12864

4. Rezig IM, Yaduma WG, McInerny CJ. Processes Controlling the Contractile Ring during Cytokinesis in Fission Yeast, Including the Role of ESCRT Proteins. J Fungi (Basel). 2024;10(2):154. doi: 10.3390/jof10020154

Fission yeast are single-celled, simple eukaryotes that undergo closed mitosis where the nuclear envelope stays intact throughout division (Upper Figure 1). During mitosis, an actin‑myosin contractile ring (ACR) assembles and constricts, then cytokinesis finishes via septation, where a cell-wall-like structure, the septum, forms between the two daughter cells, separating them completely (Lower Figure 1).

Figure 1: Fission Yeast Cell Division From Closed Mitosis to Cytokinesis.

1. Hayles J, Nurse P. A review of mitosis in the fission yeast Schizosaccharomyces pombe. Exp Cell Res. 1989;184(2):273-86. doi: 10.1016/0014-4827(89)90327-3

2. Gallardo P, Barrales RR, Daga RR, Salas-Pino S. Nuclear Mechanics in the Fission Yeast. Cells. 2019;8(10):1285. doi: 10.3390/cells8101285

3. Mori R, Oliferenko S. Cell Biology: An Open Solution for Closed Mitosis. Curr Biol. 2020;30(16):R942-R944. doi: 10.1016/j.cub.2020.06.067

4. Rezig IM, Yaduma WG, McInerny CJ. Processes Controlling the Contractile Ring during Cytokinesis in Fission Yeast, Including the Role of ESCRT Proteins. J Fungi (Basel). 2024;10(2):154. doi: 10.3390/jof10020154

The fission yeast cell cycle progresses through G1, S, G2, and M phases, guided by a cell cycle clock that precisely times each step. Checkpoints act as “guards,” ensuring DNA is accurately replicated and chromosomes are properly segregated. During S phase, DNA is duplicated, and in M phase, mitosis and cytokinesis produce two genetically identical daughter cells, maintaining proper growth and division.

Figure 2: This Cell Cycle Clock figure illustrates the transitions through the four phases: the red pointer indicates the current phase, while the black pointer shows the previous phase.

1. Peng X, Karuturi RK, Miller LD, Lin K, Jia Y, Kondu P, Wang L, Wong LS, Liu ET, Balasubramanian MK, Liu J. Identification of cell cycle-regulated genes in fission yeast. Mol Biol Cell. 2005;16(3):1026-42. doi: 10.1091/mbc.e04-04-0299.

2. Kaykov A, Nurse P. The spatial and temporal organization of origin firing during the S-phase of fission yeast. Genome Res. 2015;25(3):391-401. doi: 10.1101/gr.180372.114

3. Swaffer MP, Jones AW, Flynn HR, Snijders AP, Nurse P. CDK Substrate Phosphorylation and Ordering the Cell Cycle. Cell. 2016;167(7):1750-1761.e16. doi: 10.1016/j.cell.2016.11.034

4. Miller KE, Vargas-Garcia C, Singh A, Moseley JB. The fission yeast cell size control system integrates pathways measuring cell surface area, volume, and time. Curr Biol. 2023;33(16):3312-3324.e7. doi: 10.1016/j.cub.2023.06.054

5. Kapadia N, Nurse P. Spatiotemporal orchestration of mitosis by cyclin-dependent kinase. Nature. 2025;643(8074):1391-1399. doi: 10.1038/s41586-025-09172-y