DNA synthesis from unbalanced nucleotide pools causes limited DNA damage that triggers ATR-CHK1-dependent p53 activation.
p53-dependent G(1) and G(2) cell cycle checkpoints are activated in response DNA damage that help to maintain genomic stability. p53 also helps to protect cells from damage that occurs during S phase, for example, when the cells are starved for DNA precursors or irradiated with a low dose of UV. p53 is activated in normal cells starved for pyrimidine nucleotides by treatment with N-(phosphonacetyl)-l-aspartate (PALA). The treated cells progress through a first S phase with kinetics similar to those of untreated cells. However, the DNA of the treated cells begins to become damaged rapidly, within 12 h, as revealed by a comet assay, which detects broken DNA, and by staining for phosphorylated histone H2AX, which accumulates at sites of DNA damage. Because the cells survive, the damage must be reversible, suggesting single-strand breaks or gaps as the most likely possibility. The transiently damaged DNA stimulates activation of ATR and CHK1, which in turn catalyze the phosphorylation and accumulation of p53. Although PALA-induced DNA damage occurs only in dividing cells, the p53 that is activated is only competent to transcribe genes such as p21 and macrophage inhibitory cytokine 1 (whose products regulate G(2) and G(1) or S phase checkpoints, respectively) after the cells have exited the S phase during which damage occurs. We propose that p53 is activated by stimulation of mismatch repair in response to the misincorporation of deoxynucleotides into newly synthesized DNA, long before the lack of pyrimidine nucleoside triphosphates causes the rate of DNA synthesis to slow appreciably.
Hastak
Kedar
K
Department of Genetics and Case Comprehensive Cancer Center, Case Western Reserve University, Cleveland, OH 44106, USA.
Paul
Rajib K
RK
Agarwal
Mukesh K
MK
Thakur
Vijay S
VS
Amin
A R M Ruhul
AR
Agrawal
Sudesh
S
Sramkoski
R Michael
RM
Jacobberger
James W
JW
Jackson
Mark W
MW
Stark
George R
GR
Agarwal
Munna L
ML
D001224:Aspartic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism*; D002460:Cell Line; D000071877:Checkpoint Kinase 1; D004247:DNA / Q000096:biosynthesis*; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D008954:Models, Biological; D009711:Nucleotides / Q000378:metabolism*; D010746:Phosphonoacetic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011743:Pyrimidines / Q000378:metabolism; D016196:S Phase / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000378:metabolism
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D009711:Nucleotides; D011743:Pyrimidines; D016159:Tumor Suppressor Protein p53; D025521:Tumor Suppressor Proteins; D001224:Aspartic Acid; C013195:sparfosic acid; D004247:DNA; D011494:Protein Kinases; C576324:ATM protein, human; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; D017346:Protein Serine-Threonine Kinases; C030986:pyrimidine; D010746:Phosphonoacetic Acid