Fig. 4.

Soluble (non-MT) tubulin promotes the ability of HSET to drive aster self-organization of GMPCPP-MTs independent of MT polymerization. a EGFP-HSET-driven self-organization of GMPCPP-stabilized MTs with increasing tubulin concentration. Alexa594-labeled GMPCPP-MTs (10% labeled, 1 µM tubulin in polymer form, magenta) were mixed in assay buffer with EGFP-HSET (100 nM, green) and monitored by time-lapse microscopy at 37 °C. Unlabeled tubulin was added to the reaction at the indicated concentration. Technical replicates were repeated N ≥ 3 times for each condition, and representative images are shown. Scale bar, 50 µm. b EGFP-HSET-driven self-organization of GMPCPP-stabilized MTs in the absence of MT polymerization. Experiments were performed identically to a but in the absence of taxol and the presence of saturating colchicine and GDP to prevent polymerization. Technical replicates were repeated N ≥ 2 times for each condition, and representative images are shown. Scale bar, 50 µm