title: Diffusion and formation of microtubule asters: physical processes versus biochemical regulation.
abstract: Microtubule asters forming the mitotic spindle are assembled around two centrosomes through the process of dynamic instability in which microtubules alternate between growing and shrinking states. By modifying the dynamics of this assembly process, cell cycle enzymes, such as cdc2 cyclin kinases, regulate length distributions in the asters. It is believed that the same enzymes control the number of assembled microtubules by changing the "nucleating activity" of the centrosomes. Here we show that assembly of microtubule asters may be strongly altered by effects connected with diffusion of tubulin monomers. Theoretical analysis of a simple model describing assembly of microtubule asters clearly shows the existence of a region surrounding the centrosome depleted in GTP tubulin. The number of assembled microtubules may in some cases be limited by this depletion effect rather than by the number of available nucleation sites on the centrosome.
authors.affiliation: Department of Physics, Princeton University, NJ 08544, USA.
authors.forename: M
authors.initials: M
authors.lastname: Dogterom
authors.forename: A C
authors.initials: AC
authors.lastname: Maggs
authors.forename: S
authors.initials: S
authors.lastname: Leibler
mesh_terms: D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism; D018385:Centrosome / Q000502:physiology* / Q000648:ultrastructure; D004058:Diffusion; D006160:Guanosine Triphosphate / Q000378:metabolism; D008870:Microtubules / Q000502:physiology* / Q000648:ultrastructure; D008938:Mitosis / Q000502:physiology*; D008954:Models, Biological; D009010:Monte Carlo Method; D008941:Spindle Apparatus / Q000502:physiology* / Q000648:ultrastructure; D014404:Tubulin / Q000378:metabolism; D014981:Xenopus
chemical_list: D014404:Tubulin; D006160:Guanosine Triphosphate; D016203:CDC2 Protein Kinase