Two distinct cytokinesis pathways drive trypanosome cell division initiation from opposite cell ends.
Cytokinesis in Trypanosoma brucei, an early branching protozoan, occurs along its longitudinal axis uni-directionally from the anterior tip of the new flagellum attachment zone filament toward the cell's posterior end. However, the underlying mechanisms remain elusive. Here we report that cytokinesis in T. brucei is regulated by a concerted action of Polo-like kinase, Aurora B kinase, and a trypanosome-specific protein CIF1. Phosphorylation of CIF1 by Polo-like kinase targets it to the anterior tip of the new flagellum attachment zone filament, where it subsequently recruits Aurora B kinase to initiate cytokinesis. Consistent with its role, CIF1 depletion inhibits cytokinesis initiation from the anterior end of the cell, but, surprisingly, triggers cytokinesis initiation from the posterior end of the cell, suggesting the activation of an alternative cytokinesis from the opposite cell end. Our results reveal the mechanistic roles of CIF1 and Polo-like kinase in cytokinesis initiation and elucidate the mechanism underlying the recruitment of Aurora B kinase to the cytokinesis initiation site at late anaphase. These findings also delineate a signaling cascade controlling cytokinesis initiation from the anterior end of the cell and uncover a backup cytokinesis that is initiated from the posterior end of the cell when the typical anterior-to-posterior cytokinesis is compromised.
Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, TX 77030 Electron Microscopy Core, Houston Methodist Hospital Research Institute, Houston, TX 77030 State Key Laboratory of Biocontrol, School of Life Sciences, and Key Laboratory of Tropical Diseases and Control of the Ministry of Education, Zhongshan Medical School, Sun Yat-Sen University, Guangzhou 510275, China; fjayala@uci.edu lsslzr@mail.sysu.edu.cn ziyin.li@uth.tmc.edu. Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697 fjayala@uci.edu lsslzr@mail.sysu.edu.cn ziyin.li@uth.tmc.edu. Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, TX 77030; fjayala@uci.edu lsslzr@mail.sysu.edu.cn ziyin.li@uth.tmc.edu.
