FIG. 1.

Immunoprecipitation and microtubule cosedimentation assays reveal that signal transducer and activator of transcription 3 (STAT3) interacts with both tubulin and microtubules. (A) 293T cells transfected with GFP or GFP-tubulin were lyzed and the cell lysates were incubated with anti-GFP agarose beads. The immunoprecipitate was analyzed by immunoblotting with the anti-STAT3 antibody, and cell lysates were analyzed with anti-STAT3 and anti-GFP antibodies. (B) HeLa cells were lyzed, and the lysates were incubated at 37°C for 30 min in the presence or absence of paclitaxel and GTP (P/G indicates paclitaxel and GTP). The microtubules and microtubule-associated proteins were pelleted by ultracentrifugation, and proteins in the pellet fraction (P) and the supernatant fraction (S) were examined by immunoblotting.