Functional analysis of theDrosophila CDC2 Dm gene in fission yeast

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Abstract
Thecdc2 + gene product (p34cdc2) is a protein kinase that regulates entry into mitosis in all eukaryotic cells. The role that p34cdc2 plays in the cell cycle has been extensively investigated in a number of organisms, including the fission yeastSchizosaccharomyces pombe. To study the degree of functional conservation among evolutionarily distant p34cdc2 proteins, we have constructed aS. pombe strain in which the yeastcdc2 + gene has been replaced by itsDrosophila homologue CDC2Dm (theCDC2Dm strain). ThisCDC2Dm S. pombe strain is viable, capable of mating and producing four viable meiotic products, indicating that the fly p34CDC2Dm recognizes all the essentialS. pombe cdc2 + substrates, and that it is recognized by cyclin partners and other elements required for its activity. The p34CDC2Dm protein yields a lethal phenotype in combination with the mutant B-type cyclin p56cdc13-117, suggesting that thisS. pombe cyclin might interact less efficiently with theDrosophila protein than with its native p34cdc2 counterpart. ThisCDC2Dm strain also responds to nutritional starvation and to incomplete DNA synthesis, indicating that proteins involved in these signal transduction pathways, interact properly with p34CDC2Dm (and/or that p34cdc2-independent pathways are used). TheCDC2Dm gene produces a ‘wee’ phenotype, and it is largely insensitive to the action of theS. pombe weel + mitotic inhibitor, suggesting thatDrosophila weel + homologue might not be functionally conserved. ThisCDC2Dm strain is hypersensitive to UV irradiation, to the same degree asweel-deficient mutants. A strain which co-expresses theDrosophila and yeastcdc2+ genes shows a dominantwee phenotype, but displays a wild-type sensitivity to UV irradiation, suggesting that p34cdc2 triggers mitosis and influences the UV sensitivity by independent mechanisms.