Fission yeast Rad26 responds to DNA damage independently of Rad3.
BACKGROUND
The Rad26/Rad3 complex in fission yeast detects genotoxic insults and initiates the cell cycle arrest and recovery activities of the DNA damage checkpoint. To investigate how the Rad26/Rad3 complex performs these functions, we constructed and characterized Rad26-GFP.


RESULTS
Rad26-GFP localized to approximately six nuclear dots in cycling cells. Following treatment with a DNA damaging agent, Rad26-GFP localization changed. Damaged cells contained one or two bright Rad26-GFP spots, in addition to smaller, more numerous Rad26-GFP speckles. Genetic analyses demonstrated that these Rad26-GFP patterns (dots, spots and speckles) were unaffected by null mutations in other DNA damage checkpoint genes, including rad3+. Data obtained with our Rad26.T12-GFP fusion protein correlate spots with cell cycle arrest activities and speckles with DNA repair activities. In addition, physiological experiments demonstrated that rad26Delta and rad3Delta alleles confer sensitivity to a microtubule-depolymerizing drug.


CONCLUSIONS
We have discovered three distinct Rad26-GFP cellular structures. Formation of these structures did not require other checkpoint proteins. These data demonstrate that Rad26 can respond to genotoxic insult in the absence of Rad3 and the other checkpoint Rad proteins.
Wolkow
Tom D
TD
Department of Genetics, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA. wolkow@rascal.med.harvard.edu
Enoch
Tamar
T
D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D002467:Cell Nucleus / Q000737:chemistry; D064447:Checkpoint Kinase 2; D004249:DNA Damage; D004260:DNA Repair; D008870:Microtubules / Q000187:drug effects; D009154:Mutation; D011494:Protein Kinases / Q000235:genetics / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000032:analysis; D012568:Schizosaccharomyces / Q000737:chemistry / Q000166:cytology / Q000187:drug effects; D029702:Schizosaccharomyces pombe Proteins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D013827:Thiabendazole / Q000494:pharmacology
D018797:Cell Cycle Proteins; D011993:Recombinant Fusion Proteins; D029702:Schizosaccharomyces pombe Proteins; C088086:rad26 protein, S pombe; D011494:Protein Kinases; D064447:Checkpoint Kinase 2; C456840:rad3 protein, S pombe; D013827:Thiabendazole