THE CLUA(-) MUTANT OF DICTYOSTELIUM IDENTIFIES A NOVEL CLASS OF PROTEINS REQUIRED FOR DISPERSION OF MITOCHONDRIA

The cluA gene of Dictyostelium discoideum encodes a novel 150-kDa prot ein. Disruption of cluA results in clustering of mitochondria near the cell center. This is a striking difference from normal cells, whose m itochondria are dispersed uniformly throughout the cytoplasm. The muta nt cell populations also exhibit an increased frequency of multinuclea ted cells, suggesting an impairment in cytokinesis. Both phenotypes ar e reversed by transformation of cluA(-) cells with a plasmid carrying a constitutively expressed cluA gene. The predicted sequence of the cl uA gene product is homologous to sequences encoded by open reading fra mes in the genomes of Saccharomyces cerevisiae and Caenorhabditis eleg ans, but not to any known protein. The only exception is a short regio n with some homology to the 42-residue imperfect repeats present in th e kinesin light chain, which probably function in protein-protein inte raction. These studies identify a new class of proteins that appear to be required for the proper distribution of mitochondria.