Berlin 2008 – scientific programme

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BP: Fachverband Biologische Physik

BP 8: Active Filament Networks

BP 8.2: Invited Talk

Tuesday, February 26, 2008, 10:00–10:30, C 243

Regulation of microtubule sliding by antagonizing microtubule motors and crosslinkers — •Marcel Janson — Wageningen University, Wageningen, The Netherlands

Polarized microtubule networks, like the mitotic spindle, are organized in part by molecular motors that actively slide microtubules along each other. Proteins like ase1, on the other hand, create static crosslinks between these biofilaments. How cells tune both antagonizing activities to make sure that microtubules attain their correct position and polarity is largely unknown. We quantified the relative sliding of microtubules in live fission yeast cells. Here, motor proteins bind to the ends of microtubules while ase1-crosslinks are established between overlapping microtubules. The corresponding distribution of forces generates a length-dependent sliding velocity. Computer simulations were used to demonstrate that the resulting velocities are sufficient to organize randomly nucleated microtubules into an array of antiparallel microtubules that is morphological similar to arrays in yeast. The localization of ase1 in these arrays is of special interest. Ase1 selectively binds to pairs of antiparallel microtubules and in doing so sets up spatial signals in cells. Single molecule fluorescence imaging and controlled in vitro assays demonstrated that dimers of ase1 diffuse along the lattice of microtubules. These dimers multimerized into higher-order structures that were stably docked to microtubules. Multimerization preferentially occurred between overlapping microtubules showing that cells exploit the local geometry and abundance of ase1 binding sites to achieve selective ase1 localization.