IDENTIFICATION OF DROSOPHILA CYTOSKELETAL PROTEINS BY INDUCTION OF ABNORMAL-CELL SHAPE IN FISSION YEAST

To clone metazoan genes encoding regulators of cell shape, we have dev eloped a functional assay for proteins that affect the morphology of a simple organism, the fission yeast Schizosaccharomyces pombe. A Droso phila melanogaster cDNA library was constructed in an inducible expres sion vector and transformed into S. pombe. When expression of the Dros ophila sequences was induced, aberrant cell shapes were found in 0.2% of the transformed colonies. Four severe phenotypes representing defec ts in cytokinesis and/or cell shape maintenance were examined further. Each displayed drastic and specific reorganizations of the actin cyto skeleton. Three of the cDNAs responsible for these defects appear to e ncode cytoskeletal components: the actin binding proteins profilin and cofilin/actin depolymerizing factor and a membrane-cytoskeleton linke r of the ezrin/merlin family. These results demonstrate that a yeast p henotypic screen efficiently identifies conserved genes from more comp lex organisms and sheds light on their potential in vivo functions.