The DNA damage checkpoint regulates a transition between yeast and hyphal growth in Schizosaccharomyces japonicus Molecular and Cellular Biology 30 (20) : 2909-2917. 2010. Niki Laboratory, Microbial Genetics Laboratory The DNA damage checkpoint regulates a transition between yeast and hyphal growth in Schizosaccharomyces japonicus. Kanji Furuya and Hironori Niki Molecular and Cellular Biology , 30 (20) : 2909-2917. 2010. 　doi:10.1128/MCB.01613-09 　Dimorphic yeasts change between unicellular growth and filamentous growth. Many dimorphic yeasts species are pathogenic for humans and plants, being infectious as invasive hypha. We have studied the determinants of the dimorphic switch in the non-pathogenic fission yeast Schizosaccharomyces japonicus, which is evolutionarily close to the well-characterised fission yeast Sz. pombe. We report that camptothecin, an inhibitor of Topoisomerase I, reversibly induced the unicellular to hyphal transition in Sz. japonicus at low concentrations of camptothecin that did not induce checkpoint arrest and the transition required the DNA checkpoint kinase Chk1. Furthermore, a mutation of chk1 induced hyphal transition without camptothecin. Thus we identify a second function for Chk1 distinct from its role in checkpoint arrest. Activation of the switch from single cell bipolar growth to monopolar filamentous growth may assist cells to evade the source of DNA damage. 　 Some yeast species show two types of growing phases, yeast growth or hyphal growth, dependent on stresses in the living environment. It had been known that only nutrient stress causes change of dimorphic growth. Furthermore, DNA stresses can also induce hyphal transition in Schizosaccharomyces japonicus . The hyphal differentiation is dependent on the Rad9-Chk1 pathway, which is involved in cell cycle checkpoint. Photo images show yeast cells with nuclei labeled by GFP or mCherry-HistoneH3. ←Back