DNA synthesis from unbalanced nucleotide pools causes limited DNA damage that triggers ATR-CHK1-dependent p53 activation

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 105; no. 17; pp. 6314 - 6319
• Main Authors: Hastak, Kedar, Paul, Rajib K, Agarwal, Mukesh K, Thakur, Vijay S, Amin, A.R.M. Ruhul, Agrawal, Sudesh, Sramkoski, R. Michael, Jacobberger, James W, Jackson, Mark W, Stark, George R, Agarwal, Munna L
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 29.04.2008; National Acad Sciences
• Subjects: Aspartic Acid - analogs & derivatives; Aspartic Acid - pharmacology; Ataxia Telangiectasia Mutated Proteins; Biological Sciences; Cell cycle; Cell Cycle Proteins - metabolism; Cell growth; Cell Line; Cell lines; Cells; Checkpoint Kinase 1; Cytokines; Deoxyribonucleic acid; DNA; DNA - biosynthesis; DNA Damage; DNA-Binding Proteins - metabolism; Fibroblasts; Genomics; Humans; Interphase; Kinetics; Models, Biological; Nucleotides - metabolism; Phosphonoacetic Acid - analogs & derivatives; Phosphonoacetic Acid - pharmacology; Phosphorylation; Phosphorylation - drug effects; Protein Kinases - metabolism; Protein-Serine-Threonine Kinases - metabolism; Pyrimidine nucleotides; Pyrimidines - metabolism; S Phase - drug effects; Tumor Suppressor Protein p53 - metabolism; Tumor Suppressor Proteins - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0802080105

p53-dependent G₁ and G₂ 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 G₂ and G₁ 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.