A CYTOPLASMIC DYNEIN MOTOR IN DROSOPHILA - IDENTIFICATION AND LOCALIZATION DURING EMBRYOGENESIS

We have characterized a cytoplasmic dynein motor isoform that is prese nt in extracts of Drosophila embryos. A prominent high molecular weigh t (HMW) polypeptide (>400 kDa) is enriched in microtubules prepared fr om nucleotide-depleted embryonic extracts. Based on its ATP-sensitive microtubule binding activity, 20 S sedimentation coefficient, sensitiv ity to UV-vanadate and nucleotide specificity, the HMW polypeptide res embles cytoplasmic dyneins prepared from other organisms. The Drosophi la cytoplasmic dynein acts as a minus-end motor that promotes microtub ule translocation in vitro. A polyclonal antibody raised against the d ynein heavy chain polypeptide was used to localize the dynein antigen in whole-mount preparations of embryos by immunofluorescence microscop y. These studies show that the dynein motor is associated with microtu bules throughout embryogenesis, including mitotic spindle microtubules and microtubules of the embryonic nervous system.