Spatiotemporal dynamics of condensins I and II: evolutionary insights from the primitive red alga Cyanidioschyzon merolae |
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Authors: | Takayuki Fujiwara Kan Tanaka Tsuneyoshi Kuroiwa Tatsuya Hirano |
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Affiliation: | National Institutes of Health;aChromosome Dynamics Laboratory, RIKEN, Wako, Saitama 351-0198, Japan;bChemical Resources Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan;cCore Research for Evolutional Science and Technology, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076, Japan;dFaculty of Science, Rikkyo University, Toshima-ku, Tokyo 171-8501, Japan |
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Abstract: | Condensins are multisubunit complexes that play central roles in chromosome organization and segregation in eukaryotes. Many eukaryotic species have two different condensin complexes (condensins I and II), although some species, such as fungi, have condensin I only. Here we use the red alga Cyanidioschyzon merolae as a model organism because it represents the smallest and simplest organism that is predicted to possess both condensins I and II. We demonstrate that, despite the great evolutionary distance, spatiotemporal dynamics of condensins in C. merolae is strikingly similar to that observed in mammalian cells: condensin II is nuclear throughout the cell cycle, whereas condensin I appears on chromosomes only after the nuclear envelope partially dissolves at prometaphase. Unlike in mammalian cells, however, condensin II is confined to centromeres in metaphase, whereas condensin I distributes more broadly along arms. We firmly establish a targeted gene disruption technique in this organism and find, to our surprise, that condensin II is not essential for mitosis under laboratory growth conditions, although it plays a crucial role in facilitating sister centromere resolution in the presence of a microtubule drug. The results provide fundamental insights into the evolution of condensin-based chromosome architecture and dynamics. |
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