THE MYOSIN ATPASE INHIBITOR 2,3-BUTANEDIONE-2-MONOXIME (BDM) INHIBITSTIP GROWTH AND CYTOKINESIS IN THE FISSION YEAST, SCHIZOSACCHAROMYCES-POMBE

The growth of fission yeast cultures was reversibly inhibited by expos ure to the myosin-ATPase inhibitor 2,3-butanedione-2-monoxime (BDM). W ild-type cells treated with 20 mM BDM for approximately two generation times were smaller than untreated controls and had a septation index approximately twice that seen in the absence of the inhibitor. The org anization of actin at the cell poles was somewhat disorganized in the presence of BDM; however, cells formed a cytokinetic actin ring. When nitrogen-starved stationary-phase cells were reinoculated into fresh m edium in the presence of BDM, the time taken to repolarize the actin c ytoskeleton and to resume the characteristic vegetative cell shape bef ore initiation of the first cell division were both substantially dela yed. BDM significantly inhibited the increase in cell length of cdc25. 22 cells arrested for cell cycle progress by incubation at the restric tive temperature and substantially delayed the initiation of both mito sis and cytokinesis in arrested cclc25.22 cells after release of the t emperature block. These results suggest that tip growth and cytokinesi s-processes in fission yeast that involve the actin cytoskeleton-also require myosin activity. Cell Motil. Cytoskeleton 41:117-125: 1998. (C ) 1998 Wiley-Liss, Inc.