REGULATION OF CYTOPLASMIC DYNEIN FUNCTION IN-VIVO BY THE DROSOPHILA GLUED COMPLEX

The Drosophila Glued gene product shares sequence homology with the p1 50 component of vertebrate dynactin. Dynactin is a multiprotein comple x that stimulates cytoplasmic dynein-mediated vesicle motility in vitr o. In this report, we present biochemical, cytological, and genetic ev idence that demonstrates a functional similarity between the Drosophil a Glued complex and vertebrate dynactin. We show that, similar to the vertebrate homologues in dynactin, the Glued polypeptides are componen ts of a 20S complex. Our biochemical studies further reveal differenti al expression of the Glued polypeptides, all of which copurify as micr otubule-associated proteins. In our analysis of the Glued polypeptides encoded by the dominant mutation, Glued(1), we identify a truncated p olypeptide that fails to assemble into the wild-type 20S complex, but retains the ability to copurify with microtubules. The spatial and tem poral distribution of the Glued complex during oogenesis is shown by i mmunocytochemistry methods to be identical to the pattern previously d escribed for cytoplasmic dynein. Significantly, the pattern of Glued d istribution in oogenesis is dependent on dynein function, as well as s everal other gene products known to be required for proper dynein loca lization. In genetic complementation studies, we find that certain mut ations in the cytoplasmic dynein heavy chain gene Dhc64C act as domina nt suppressors or enhancers of the rough eye phenotype of the dominant Glued(1) mutation. Furthermore, we show that a mutation that was prev iously isolated as a suppressor of the Glued(1) mutation is an allele of Dhc64C. Together with the observed dependency of Glued localization on dynein function, these genetic interactions demonstrate a function al association between the Drosophila dynein motor and Glued complexes .