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Newly synthesized proteins that leave the endoplasmic reticulum (ER) are funnelled through the Golgi complex before being sorted for transport to their different final destinations. Traditional approaches have elucidated the biochemical requirements for such transport and have established a role for transport intermediates. New techniques for tagging(More)
The flow of material from peripheral, early endosomes to late endosomes requires microtubules and is thought to be facilitated by the minus end-directed motor cytoplasmic dynein and its activator dynactin. The microtubule-binding protein CLIP-170 may also play a role by providing an early link to endosomes. Here, we show that perturbation of dynactin(More)
The multiprotein complex, dynactin, is an integral part of the cytoplasmic dynein motor and is required for dynein-based motility in vitro and in vivo. In living cells, perturbation of the dynein-dynactin interaction profoundly blocks mitotic spindle assembly, and inhibition or depletion of dynein or dynactin from meiotic or mitotic cell extracts prevents(More)
Although cytoplasmic dynein is known to attach to microtubules and translocate toward their minus ends, dynein's ability to serve in vitro as a minus end-directed transporter of membranous organelles depends on additional soluble factors. We show here that a approximately 20S polypeptide complex (referred to as Activator I; Schroer, T. A., and M.P. Sheetz.(More)
We use both in vitro and in vivo approaches to examine the roles of Eg5 (kinesin-related protein), cytoplasmic dynein, and dynactin in the organization of the microtubules and the localization of NuMA (Nu-clear protein that associates with the Mitotic Apparatus) at the polar ends of the mammalian mitotic spindle. Perturbation of the function of Eg5 through(More)
What is the origin of the forces generating chromosome and spindle movements in mitosis? Both microtubule dynamics and microtubule-dependent motors have been proposed as the source of these motor forces. Cytoplasmic dynein and kinesin are two soluble proteins that power membranous organelle movements on microtubules. Kinesin directs movement of organelles(More)
Mammalian cells typically contain hundreds of peroxisomes but can increase peroxisome abundance further in response to extracellular stimuli. We report here the identification and characterization of two novel human peroxisomal membrane proteins, PEX11alpha and PEX11beta. Overexpression of the human PEX11beta gene alone was sufficient to induce peroxisome(More)
The dynactin complex visualized by deepetch electron microscopy appears as a short filament 37-nm in length, which resembles F-actin, plus a thinner, laterally oriented filament that terminates in two globular heads. The locations of several of the constituent polypeptides were identified on this structure by applying antibodies to decorate the dynactin(More)
The role of cytoplasmic dynein in microtubule-based organelle transport was examined using a reconstituted assay developed from chick embryo fibroblasts. Factors present in a high-speed cytosol caused the movement of purified organelles on microtubules predominantly in the minus end direction. Inactivation of cytoplasmic dynein in the high-speed cytosol by(More)
The multisubunit protein, dynactin, is a critical component of the cytoplasmic dynein motor machinery. Dynactin contains two distinct structural domains: a projecting sidearm that interacts with dynein and an actin-like minifilament backbone that is thought to bind cargo. Here, we use biochemical, ultrastructural, and molecular cloning techniques to obtain(More)