Nuclear transport and spindle microtubule formation in fission yeast: Ran GTPase and microtubule-associated protein TACC/Alp7 Center for Developmental Biology

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Category	Seminar
Date and Time	2007-08-03 16:00 - 17:00
Venue	Seminar Room A7F
Speaker	Masamitsu Sato
Affiliation	Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo
Title	Nuclear transport and spindle microtubule formation in fission yeast: Ran GTPase and microtubule-associated protein TACC/Alp7
Host	Asako Sugimoto
Summary	Microtubule is an essential cellular structure for establishment of cell polarity, material transport and chromosome segregation. During mitosis, microtubule is re-organised into the spindle structure, which pulls chromosomes towards each spindle pole. Many microtubule-associated proteins (MAPs) are known to regulate spindle formation. Spindle microtubules can be formed not only at the spindle poles, but also in the vicinity of chromosomes in higher eukaryotes. Interestingly, the general nuclear transport regulator, Ran GTPase, regulates this process by targeting several MAPs. It is enigmatic, however, why the nuclear transport system is coupled with spindle formation. We focused on Ran-dependent spindle formation in fission yeast. This organism undergoes "closed-mitosis" in which the nuclear envelope does not break down and therefore the mitotic spindle needs to be formed in the compartmentalised nucleus. We found that Ran in fission yeast targets Alp7/TACC (transforming acidic coiled-coil protein), which is distinct from known targets in higher organisms. Biological significance and evolutional conservation of the regulatory circuit of Alp7/TACC as a cargo of Ran for the microtubule formation will be discussed. Reference: Sato M, Toda T. Nature, 447:334-7 (2007)