Critical role of DNA checkpoints in mediating genotoxic-stress-induced filamentous growth in Candida albicans.
The polymorphic fungus Candida albicans switches from yeast to filamentous growth in response to a range of genotoxic insults, including inhibition of DNA synthesis by hydroxyurea (HU) or aphidicolin (AC), depletion of the ribonucleotide-reductase subunit Rnr2p, and DNA damage induced by methylmethane sulfonate (MMS) or UV light (UV). Deleting RAD53, which encodes a downstream effector kinase for both the DNA-replication and DNA-damage checkpoint pathways, completely abolished the filamentous growth caused by all the genotoxins tested. Deleting RAD9, which encodes a signal transducer of the DNA-damage checkpoint, specifically blocked the filamentous growth induced by MMS or UV but not that induced by HU or AC. Deleting MRC1, the counterpart of RAD9 in the DNA-replication checkpoint, impaired DNA synthesis and caused cell elongation even in the absence of external genotoxic insults. Together, the results indicate that the DNA-replication/damage checkpoints are critically required for the induction of filamentous growth by genotoxic stress. In addition, either of two mutations in the FHA1 domain of Rad53p, G65A, and N104A, nearly completely blocked the filamentous-growth response but had no significant deleterious effect on cell-cycle arrest. These results suggest that the FHA domain, known for its ability to bind phosphopeptides, has an important role in mediating genotoxic-stress-induced filamentous growth and that such growth is a specific, Rad53p-regulated cellular response in C. albicans.
Shi
Qing-Mei
QM
Institute of Molecular and Cell Biology, Agency for Science, Technology and Research Biological Sciences Institutes, Singapore 138673.
Wang
Yan-Ming
YM
Zheng
Xin-De
XD
Lee
Raymond Teck Ho
RT
Wang
Yue
Y
D000483:Alleles; D000595:Amino Acid Sequence; D016590:Aphidicolin / Q000633:toxicity; D002176:Candida albicans / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development* / Q000528:radiation effects; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D004249:DNA Damage / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D004261:DNA Replication / Q000187:drug effects / Q000528:radiation effects; D004271:DNA, Fungal / Q000378:metabolism*; D005656:Fungal Proteins / Q000737:chemistry; D005800:Genes, Fungal; D006918:Hydroxyurea / Q000633:toxicity; D008741:Methyl Methanesulfonate / Q000633:toxicity; D008969:Molecular Sequence Data; D009154:Mutation / Q000187:drug effects / Q000528:radiation effects; D017434:Protein Structure, Tertiary / Q000187:drug effects / Q000528:radiation effects; D012264:Ribonucleotide Reductases / Q000172:deficiency; D014466:Ultraviolet Rays
D004271:DNA, Fungal; D005656:Fungal Proteins; D016590:Aphidicolin; D008741:Methyl Methanesulfonate; D012264:Ribonucleotide Reductases; D006918:Hydroxyurea