Related Experiment Video
Updated: Jul 31, 2026

Two- and Three-Dimensional Live Cell Imaging of DNA Damage Response Proteins
Published on: September 28, 2012
A p53-dependent S-phase checkpoint helps to protect cells from DNA damage in response to starvation for pyrimidine
M L Agarwal1, A Agarwal, W R Taylor
1Department of Molecular Biology, Lerner Research Institute, The Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
Abstract:
Normal mammalian cells arrest primarily in G1 in response to N-(phosphonacetyl)-L-aspartate (PALA), which starves them for pyrimidine nucleotides, and do not generate or tolerate amplification of the CAD gene, which confers resistance to PALA. Loss of p53, accompanied by loss of G1 arrest, permits CAD gene amplification and the consequent formation of PALA-resistant colonies. We have found rat and human cell lines that retain wild-type p53 but have lost the ability to arrest in G1 in response to PALA. However, these cells still fail to give PALA-resistant colonies and are protected from DNA damage through the operation of a second checkpoint that arrests them reversibly within S-phase. This S-phase arrest, unmasked in the absence of the G1 checkpoint, is dependent on p53 and independent of p21/waf1.
Related Concept Videos
Negative Regulator Molecules
DNA Damage can Stall the Cell Cycle
Restarting Stalled Replication Forks
Inhibition of Cdk Activity
Abnormal Proliferation
DNA Damage Can Stall the Cell Cycle

