Fig. 7. Staurosporine inhibits the dynamic exchange of NuMA on microtubule asters. (A) Indirect immunofluorescence images of microtubule asters using a human NuMA-specific monoclonal antibody (Human NuMA) and a rabbit polyclonal antibody that recognizes both human and hamster NuMA (Total NuMA) immediately (0') or 40 minutes (40') after mixing with either buffer alone (KHMM+STR) or hamster mitotic extract (BHK Extract+STR). (B) Extracts were separated into 10,000 g soluble (S) or insoluble (P) fractions and immunoblotted with a human NuMA-specific monoclonal antibody and a tubulin-specific antibody at various times (indicated in minutes) following dilution with either buffer alone (KHMM+STR) or hamster mitotic extract (BHK Extract+STR). (C) The proportion of human NuMA in the pellet fraction was determined using densitometry of immunoblots from three independent trials and is normalized to 100% using the 0-minute time point in following dilution in KHMM buffer alone. Values represent the average and standard deviation. (D) Fluorescent images from the 40-minute time point were scanned with a horizontal line 1 pixel wide. Pixel intensities for both human NuMA (green) and total NuMA (red) are shown. Scale bar, 2 µm.