MAMMALIAN-CELLS EXPRESS 3 DISTINCT DYNEIN HEAVY-CHAINS THAT ARE LOCALIZED TO DIFFERENT CYTOPLASMIC ORGANELLES

We describe two dynein heavy chain (DHC)-like polypeptides (DHCs 2 and 3) that are distinct from the heavy chain of conventional cytoplasmic dynein (DHC1) but are expressed in a variety of mammalian cells that lack axonemes. DHC2 is a distant member of the ''cytoplasmic'' branch of the dynein phylogenetic tree, while DHC3 shares more sequence simil arity with dynein-like polypeptides that have been thought to be axone mal. Each cytoplasmic dynein is associated with distinct cellular orga nelles, DHC2 is localized predominantly to the Golgi apparatus. Moreov er, the Golgi disperses upon microinjection of antibodies to DHC2, sug gesting that this motor is involved in establishing proper Golgi organ ization. DHC3 is associated with as yet unidentified structures that m ay represent transport intermediates between two or more cytoplasmic c ompartments, Apparently, specific cytoplasmic dyneins, like individual members of the kinesin superfamily, play unique roles in the traffic of cytomembranes.