Protein phosphatases pph3, ptc2, and ptc3 play redundant roles in DNA double-strand break repair by homologous recombination.
In response to a DNA double-strand break (DSB), cells undergo a transient cell cycle arrest prior to mitosis until the break is repaired. In budding yeast (Saccharomyces cerevisiae), the DNA damage checkpoint is regulated by a signaling cascade of protein kinases, including Mec1 and Rad53. When DSB repair is complete, cells resume cell cycle progression (a process called "recovery") by turning off the checkpoint. Recovery involves two members of the protein phosphatase 2C (PP2C) family, Ptc2 and Ptc3, as well as the protein phosphatase 4 (PP4) enzyme, Pph3. Here, we demonstrate a new function of these three phosphatases in DSB repair. Cells lacking all three phosphatases Pph3, Ptc2, and Ptc3 exhibit synergistic sensitivities to the DNA-damaging agents camptothecin and methyl methanesulfonate, as well as hydroxyurea but not to UV light. Moreover, the simultaneous absence of Pph3, Ptc2, and Ptc3 results in defects in completing DSB repair, whereas neither single nor double deletion of the phosphatases causes a repair defect. Specifically, cells lacking all three phosphatases are defective in the repair-mediated DNA synthesis. Interestingly, the repair defect caused by the triple deletion of Pph3, Ptc2, and Ptc3 is most prominent when a DSB is slowly repaired and the DNA damage checkpoint is fully activated.
Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02454-9110, USA.
Jung-Ae
JA
Kim
Wade M
WM
Hicks
Jin
J
Li
Sue Yen
SY
Tay
James E
JE
Haber
D015825:Chromosomes, Fungal / Q000235:genetics; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004261:DNA Replication / Q000235:genetics; D005785:Gene Conversion / Q000235:genetics; D017353:Gene Deletion; D049770:Genes, Mating Type, Fungal; D050296:Microbial Viability; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D000071636:Protein Phosphatase 2C; D011995:Recombination, Genetic / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000201:enzymology* / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
D029701:Saccharomyces cerevisiae Proteins; C502440:PPH3 protein, S cerevisiae; C491716:PTC2 protein, S cerevisiae; C000607464:PTC3 protein, S cerevisiae; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D000071636:Protein Phosphatase 2C