Figure 1.

DNA replication stress. A, Replication fork during normal DNA replication process. Topoisomerases, helicases, DNA polymerases, and dNTP are necessary components for the accurate progression of DNA replication. B‐E, Multiple causes of DNA replication stress. B, dNTP starvation: eg, hydroxyurea induces dNTP starvation by inhibition of ribonucleotide reductase activity. C, Polymerase inhibition: eg, aphidicolin inhibits DNA polymerase activity. D, Inhibition of DNA unwinding by DNA cross‐links, DNA intercalators, or topoisomerase inhibitors. DNA lesions caused by the inhibitors in this category are often converted to DNA strand breaks. E, Inhibition of DNA polymerase progression by DNA adducts: eg, cyclobutane pyrimidine dimer produced by UV light exposure