The APC-associated protein EB1 associates with components of the dynactin complex and cytoplasmic dynein intermediate chain

Human EB1 is a highly conserved protein that binds to the carboxyl terminus of the human adenomatous polyposis coli (APC) tumor suppressor protein [1] , a domain of APC that is commonly deleted in colorectal neoplasia [2]. EB1 belongs to a family of microtubule-associated proteins that includes Schiz osaccharomyces pombe Mal3 [3] and Saccharomyces cerevisiae Bim1p [4], Bim1p appears to regulate the timing of cytokinesis as demonstrated by a genetic interaction with Act5, a component of the yeast dynactin complex [5], Wher eas the predominant function of the dynactin complex in yeast appears to be in positioning the mitotic spindle [6], in animal cells, dynactin has been shown to function in diverse processes, including organelle transport, for mation of the mitotic spindle, and perhaps cytokinesis [7-10], Here, we dem onstrate that human EB1 can be coprecipitated with p150(Glued), a member of the dynactin protein complex. EB1 was also found associated with the inter mediate chain of cytoplasmic dynein (CDIC) and with dynamitin (p50), anothe r component of the dynactin complex, but not with dynein heavy chain, in a complex that sedimented at approximately 5S in a sucrose density gradient. The association of EB1 with members of the dynactin complex was independent of APC and was preserved in the absence of an intact microtubule cytoskele ton, The molecular interaction of EB1 with members of the dynactin complex and with CDIC may be important for microtubule-based processes.