Cytokinesis is the most fundamental process in the development of all living organisms. The mechanisms that control cytokinesis are unknown, yet we know that membrane-cytoskeletal events are crucial for the cellular dynamics that occur. The process is not only of considerable intellectual interest but also of relevance to a number of physiological and pathological conditions. Members of the dynamin protein family have been shown to play essential roles in cell division in both plant and animal systems. Yet outstanding questions remain as to how dynamin is regulated during mitosis and what role dynamin plays during furrow ingression and completion. We would like to identify proteins that regulate dynamin/DYN-1 function during mitosis. We have initially characterized DIP-1 (Dynamin Interacting Protein-1), a protein identified to interact with DYN-1 from a genome-wide yeast two-hybrid screen (Li et al. 2004). DIP-1 is an uncharacterized transmembrane, ankryin, and BRCT domain-containing protein similar to BARD1 in its C-terminus. BRCT domain-containing proteins are commonly involved in cell cycle control, and BRCT domains are found in proteins such as BRCA1 and ECT2, both of which are also involved in cytokinesis (Bae et al. 2005; Saito et al. 2003). Preliminary data suggests that DIP-1 functions in cleavage furrow completion, similar to what we observe with
dyn-1 fRNAi treated embryos. Defects in cell cycle progression, microtubule organization, and chromatin bridging are also observed. DIP-1 protein may exist in several isoforms as
dip-1 is alternatively spliced. We are also currently testing whether DYN-1 and DIP-1 biochemically interact. Determining the mitotic role of DIP-1 may provide us with a unique approach by which we can investigate the role and regulation of dynamin/DYN-1 during mitosis.