EFFECTS OF NANOMOLAR TAXOL ON CRANE-FLY SPERMATOCYTE SPINDLES INDICATE THAT ACETYLATION OF KINETOCHORE MICROTUBULES CAN BE USED AS A MARKEROF POLEWARD TUBULIN FLUX

Kinetochore microtubules (kMTs) in meiosis-I crane-fly spermatocytes l abel strongly with antibodies to acetylated alpha-tubulin, except near the kinetochore, where there is a ''gap'' in labelling [Wilson and Fo rer, 1989: Cell Motil. Cytoskeleton 14:237-250]. Previously we measure d the length of gaps in metaphase and anaphase cells, and from these d ata deduced that during anaphase kMTs disassemble primarily at the pol e [Wilson et al., 1994: J. Cell Sci. 107:3015-3027]. However, the stud y rested on our assumption that the gap is due to a time lag between p olymerisation at the kinetochore and acetylation of the polymerised MT s: the subunits enter kMTs at the kinetochore and do not become acetyl ated until they have moved poleward. In the present study we tested ou r interpretation of the gap by treating spermatocytes with paclitaxel (taxol) to reduce microtubule dynamics [e.g. Jordan et al., 1993: Proc . Natl. Acad. Sci. U.S.A. 90:9552-9556]. We expected that if our assum ptions were correct, taxol would slow tubulin addition at the kinetoch ore but acetylation would continue, and the gap in acetylation would g et smaller. We found that 5 to 50 nM taxol results in increased acetyl ation of kMTs at the kinetochore, supporting our interpretation of the gap. Nanomolar taxol also increases the level of acetylation in other microtubule populations and causes changes in spindle morphology. (C) 1997 Wiley-Liss, Inc.