Checkpoint defects leading to premature mitosis also cause endoreplication of DNA in Aspergillus nidulans.
The G2 DNA damage and slowing of S-phase checkpoints over mitosis function through tyrosine phosphorylation of NIMX(cdc2) in Aspergillus nidulans. We demonstrate that breaking these checkpoints leads to a defective premature mitosis followed by dramatic rereplication of genomic DNA. Two additional checkpoint functions, uvsB and uvsD, also cause the rereplication phenotype after their mutation allows premature mitosis in the presence of low concentrations of hydroxyurea. uvsB is shown to encode a rad3/ATR homologue, whereas uvsD displays homology to rad26, which has only previously been identified in Schizosaccharomyces pombe. uvsB(rad3) and uvsD(rad26) have G2 checkpoint functions over mitosis and another function essential for surviving DNA damage. The rereplication phenotype is accompanied by lack of NIME(cyclinB), but ectopic expression of active nondegradable NIME(cyclinB) does not arrest DNA rereplication. DNA rereplication can also be induced in cells that enter mitosis prematurely because of lack of tyrosine phosphorylation of NIMX(cdc2) and impaired anaphase-promoting complex function. The data demonstrate that lack of checkpoint control over mitosis can secondarily cause defects in the checkpoint system that prevents DNA rereplication in the absence of mitosis. This defines a new mechanism by which endoreplication of DNA can be triggered and maintained in eukaryotic cells.
De Souza
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Henry Hood Research Program, Weis Center for Research, Pennsylvania State University College of Medicine, Danville, Pennsylvania 17822, USA.
Ye
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XS
Osmani
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SA
D000251:Adenosine Triphosphatases / Q000235:genetics; D001233:Aspergillus nidulans / Q000235:genetics*; D016203:CDC2 Protein Kinase / Q000235:genetics; D018797:Cell Cycle Proteins; D004249:DNA Damage / Q000235:genetics; D004265:DNA Helicases / Q000235:genetics; D004261:DNA Replication / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics; D015966:Gene Expression Regulation, Fungal; D006918:Hydroxyurea / Q000494:pharmacology; D008938:Mitosis / Q000235:genetics*; D009154:Mutation; D010766:Phosphorylation; D016196:S Phase / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D014466:Ultraviolet Rays
D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C088086:rad26 protein, S pombe; D016203:CDC2 Protein Kinase; D000251:Adenosine Triphosphatases; C061897:Rad3 protein, S cerevisiae; D004265:DNA Helicases; D006918:Hydroxyurea