User:WikiES/sandbox

Actomyosin ring is a prominent structure during cell division or cytokinesis (i.e., splitting from the parent cell after duplication and segregation of the genetic material has been completed). The ring forms perpendicular to the axis of the spindle apparatus. It is composed of actin and myosin II bundles, commonly called actomyosin, that operates in contractile motion although the mechanism on how or what triggers the constriction is still an evolving topic. Other cytoskeletal proteins are also involved in maintaining stability of the ring. Apart from cytokinesis in which the the ring constricts as the cells divide, actomyosin ring constriction has also been found to activate during wound closure. During the process actin filaments are degraded, preserving the thickness of the ring. After cytokinesis is complete, one of the two daughter cells inherits a remnant, called the midbody ring.

---copied from original article: subsection Variation between Kingdoms
In animals the ring forms along the cleavage furrow on the inside of the plasma membrane. In fungi it forms at the mother-bud neck before mitosis. Septin is heavily involved in the formation of the fungal AMR. In most bacteria and many archea a homologous structure called the z-ring forms out of FtsZ, a homolog of tubulin. Chloroplasts form an analogous structure out of FtsZ. These structures are not made out of actomyosin but serve a similar role in constricting and permitting cytokinesis. In plant cells, there is no actomyosin ring. Instead a cell plate grows centrifugally outwards from the center of the plane of division until it fuses with the existing cell wall.

---Edits on the subsection: Variation between Kingdoms

Variation between Kingdoms

In animals, the ring forms along the cleavage furrow on the inside of the plasma membrane then splits by abscission. In fungi, it forms at the mother-bud neck before mitosis. Septin is heavily involved in the formation of the fungal AMR. In most bacteria and many archea, a homologous structure called the z-ring forms out of FtsZ, a homolog of tubulin. Chloroplasts form an analogous structure out of FtsZ. These structures are not made out of actomyosin but serve a similar role in constricting and permitting cytokinesis. In plant cells, there is no actomyosin ring. Instead a cell plate grows centrifugally outwards from the center of the plane of division until it fuses with the existing cell wall.

added info to expand 1st paragraph

The cell cycle is divided into two primary phases: DNA synthesis or S phase and Mitosis or M phase. During the S phase, chromosome duplication occurs whereas M phase is characterized by two processes known as nuclear (mitosis) and cytoplasmic (cytokinesis) divisions. The formation of the actomyosin ring occurs towards the latter stage of mitosis, the telophase, in which sister chromatids are identically separated at the opposite sides of the spindle forming nuclei.

Activation of the cell-cycle kinases (e.g. Rho-kinases) during telophase initiates constriction  of the actomyosin ring by creating a groove that migrates in an inward motion. The actomyosin ring follows an orderly sequence of identification of active division site, formation of the ring, constriction of the ring, and disassembly of the contractile ring [1].

References

[1] Cheffings TH, Burroughs NJ, Balasubramanian MK. Actomyosin Ring Formation and Tension Generation in Eukaryotic Cytokinesis. Curr Biol. 26(15):719-737. doi: 10.1016/j.cub.2016.06.071

[2] Mana-Capelli, S. & McCollum, D. Actomyosin Ring. Encyclopedia of Systems Biology 8-8 (2013). doi:10.1007/978-1-4419-9863-7_779 URL: https://link.springer.com/referenceworkentry/10.1007%2F978-1-4419-9863-7_779

[3] Munjal, Akankshi and Lecuit, Thomas. 2014. Actomyosin networks and tissue morphogenesis. Development. 141(9):1789-1793.

[4] Mendes Pinto, I., Rubinstein, B., & Li, R. (2013). Force to Divide: Structural and Mechanical Requirements for Actomyosin Ring Contraction. Biophysical Journal, 105(3), 547–554. http://doi.org/10.1016/j.bpj.2013.06.033

[5] Martin, Adam. 2016. Embryonic ring closure: Actomyosin rings do the two-step. J. Cell. Biol. 215(3):301-303.

[6] Cornelia Schwayer, Mateusz Sikora, Jana Slováková, Roland Kardos, Carl-Philipp Heisenberg, Actin Rings of Power, In Developmental Cell, Volume 37, Issue 6, 2016, Pages 493-506, ISSN 1534-5807, https://doi.org/10.1016/j.devcel.2016.05.024.

[7] Chen, chun-ting & Hehnly, Heidi & Doxsey, Stephen. (2012). Orchestrating vesicle transport, ESCRTs and kinase surveillance during abscission. Nature reviews. Molecular cell biology. 13. 483-8. 10.1038/nrm3395.

[8] Fededa, J. P., & Gerlich, D. W. (2012). Molecular control of animal cell cytokinesis. Nature Cell Biology, 14(5), 440-7. doi: http://dx.doi.org.portal.lib.fit.edu/10.1038/ncb2482

[9] Meitinger, F. & Palani, S. Actomyosin ring driven cytokinesis in budding yeast. Seminars in Cell & Developmental Biology 53, 19-27 (2016).

[10] Alberts, B. et al. The Molecular Biology of the Cell. 896 (Garland Science, 2015).

[11] Bi, E., Maddox, P., Lew, D., Salmon, E., McMillan, J., Yeh, E., & Pringle, J. (1998). Involvement of an Actomyosin Contractile Ring in Saccharomyces cerevisiae Cytokinesis. Journal of Cell Biology, 142(5), 1301–1312. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2149343/