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BioMed Research International
Volume 2013 (2013), Article ID 910941, 9 pages
http://dx.doi.org/10.1155/2013/910941
Research Article

Robust Cell Size Checkpoint from Spatiotemporal Positive Feedback Loop in Fission Yeast

Jie Yan,1 Xin Ni,2 and Ling Yang1,2

1School of Mathematical Sciences, Soochow University, Suzhou 215006, China
2Center for Systems Biology, Soochow University, Suzhou 215006, China

Received 29 April 2013; Accepted 7 June 2013

Academic Editor: Tao Huang

Copyright © 2013 Jie Yan et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Cells must maintain appropriate cell size during proliferation. Size control may be regulated by a size checkpoint that couples cell size to cell division. Biological experimental data suggests that the cell size is coupled to the cell cycle in two ways: the rates of protein synthesis and the cell polarity protein kinase Pom1 provide spatial information that is used to regulate mitosis inhibitor Wee1. Here a mathematical model involving these spatiotemporal regulations was developed and used to explore the mechanisms underlying the size checkpoint in fission yeast. Bifurcation analysis shows that when the spatiotemporal regulation is coupled to the positive feedback loops (active Cdc2 promotes its activator, Cdc25, and suppress its inhibitor, Wee1), the mitosis-promoting factor (MPF) exhibits a bistable steady-state relationship with the cell size. The switch-like response from the positive feedback loops naturally generates the cell size checkpoint. Further analysis indicated that the spatial regulation provided by Pom1 enhances the robustness of the size checkpoint in fission yeast. This was consistent with experimental data.