CHARACTERIZATION OF YEAST DYANCTIN COMPLEX

这个子项目是众多研究子项目之一

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Dynactin is a multi-subunit protein complex required for most dynein activities, proposed to serve either as a cargo adaptor or to enhance dynein motor processivity. Dynactin consists of two parts with eleven different polypeptides. 1) The actin-like Arp1 filament has conventional actin and capping protein at its barbed end and Arp11, p25, p27, and p62 at its pointed end. 2) The arm consists of p150Glued, dynamitin, and p24/22. In Saccharomyces cerevisae, homologues of several dynactin subunits have been identified, and deletion of their genes produces phenotypes identical to those of dynein null mutations. On the other hand, homologues for p24/22, p25, p27 and p62 have not been identified, and the composition of yeast dynactin has not been defined biochemically. Here, we report the discovery of an apparent p24/22 homolog in budding yeast, based on the following: 1) The null mutant has a dynein-like phenotype for spindle movement. 2) The predicted polypeptide has an appropriate size and secondary structure. 3) The null mutant is synthetic with kar9∆but not dyn1∆. 4) The protein localizes to microtubule plus ends and the spindle pole body, as seen for Nip100 / p150Glued. 5) Dynein accumulates of dynein at the plus end of microtubules in the null mutant, as seen withknown dynactin mutants. Biochemical fractionations of intact dynactin complex are underway, which may identify other subunits of yeast dynactin. Based on our current understanding, dynactin is needed to offload dynein from the plus ends to the cortex.