THE SACCHAROMYCES-CEREVISIAE CLU1 AND D-DISCOIDEUM CLUA GENES ARE FUNCTIONAL HOMOLOGS THAT INFLUENCE MITOCHONDRIAL MORPHOLOGY AND DISTRIBUTION

The cluA gene, encoding a novel 150 kDa protein, was recently characte rized in Dictyostelilum discoideum; disruption of cluA impaired cytoki nesis and caused mitochondria to cluster at the cell center. The genom e of Saccharomyces cerevisiae contains an open reading frame (CLU1) th at encodes a protein that is 27% identical, 50% similar, to this Dicty ostelium protein. Deletion of CLU1 from S. cerevisiae did not affect c ell viability, growth properties, sporulation efficiency, or frequency of occurrence of cells lacking functional mitochondria. However, in c lu1 Delta cells the mitochondrial reticulum, which is normally highly branched, was condensed to one side of the cell. Transformation of clu A(-) Dictyostelium mutants with the yeast CLU1 gene yielded amoebae th at divided normally and had dispersed mitochondria. The mitochondria i n cluA(-) Dictyostelium cells complemented with CLU1 were not as widel y scattered as in cluA(+) Dictyostelium cells, but formed loose cluste rs throughout the cytoplasm. These results indicate that the products of the CLU1 and cluA genes, in spite of their limited homology, are fu nctional homologues.