An important problem in cell and developmental biology is to understand how coordination between the actin and microtubule cytoskeletons is achieved. This proposal aims to address this by exploring the interaction between an actin motor, myosin VI, and a microtubule binding protein, D-CLIP-190. Biochemical assays will be performed to determine how the association between these two proteins is regulated. Furthermore, the interacting domains of these proteins will be mapped. Finally, using reagents developed in the course of this work, the in vivo functional relevance of this interaction will be explored. This work will utilize the fruit fly Drosophila melanogaster as a model system. This system is ideally suited both for biochemical experiments as well as enabling one to address the functions of molecules of interest in many different cell and tissue types in vivo. Because of the molecular and functional conservation of proteins across species, this work should expand our understanding of the interaction between the actin and microtubule cytoskeletons in all organisms. These two cytoskeletal systems are vital to nearly all aspects of cellular function, including those functions that go awry in cancerous states. Thus, learning more about how they function in a coordinated way in normal cells will aid us in understanding the causes and mechanisms of cancer.