Coordination of initiation of nuclear division and initiation of cell division in Schizosaccharomyces pombe:: Genetic interactions of mutations

sep1(+) encodes a Schizosaccharomyces pombe homolog of the HNF-3/forkhead family of the tissue-specific and developmental gene regulators identified in higher eukaryotes, Its mutant allele sep1-1 causes a defect in cytokinesis and confers a mycelial morphology. Here we report on genetic interactions of sep1-1 with the M-phase initiation mutations wee1(-), cdc2-1w, and cdc25-22, The double mutants sep1-1 wee1(-) and sep1-1 cdc2-1w form dikaryon cells at high frequency, which is due to nuclear division in the absence of cell division, The dikaryosis is reversible and suppressible by cdc25-22, We propose that the genes wee1(+), cdc2(+), cdc25(+), and sep1(+) form a regulatory link between the initiation of mitosis and the initiation of cell division.