Figure 4. G-1 disrupts microtubule assembly in vitro.

A) High-resolution laser scanning confocal images showing effect of G-1 on microtubule assembly in vitro. Paclitaxel was used as a positive control. Addition of DMSO (≤ 0.05%, CTRL) had no effect on microtubule assembly, which is indicated by appearance of many microtubules formed by polymerization of X-rhodamine-labelled tubulin in the in vitro reaction system. Addition of paclitaxel greatly increased microtubule assembly, whereas addition of G-1 to the reaction drastically disrupted microtubule assembly. B) Effects of G-1 on microtubule assembly evaluated through a microtubule sedimentation assay. The left panel showed the representative gels loaded with pellet or supernatant after incubation with paclitaxel, control (0.05% DMSO) or G-1. The graphs show quantitative results. Each bar represents mean ± SEM (n = 3). *: P < 0.05; **: P < 0.01; ***: P < 0.001 compared to control. Taxol: with 20μM paclitaxel; CTRL: with DMSO vehicle treatment; G-1: with G-1 treatment.