DNA polymerase and ribonucleoside-diphosphate reductase (DNA pol / RNR)

DNA polymerase and ribonucleoside-diphosphate reductase (RNR) are two distinct enzymes that work in tandem to ensure the fidelity and availability of precursors for DNA synthesis. RNR catalyzes the conversion of ribonucleoside diphosphates into deoxyribonucleoside diphosphates, which is the rate-limiting step in the production of DNA building blocks (Source: NIH, PMC3157070). DNA polymerase then utilizes these deoxyribonucleotides to synthesize new DNA strands during replication and repair (Source: UniProt, P12023). In clinical practice, these enzymes are often targeted together by antimetabolite drugs, particularly nucleoside analogs like gemcitabine and clofarabine. These agents are unique because they inhibit both enzymes: their diphosphate form reduces the pool of natural nucleotides by inhibiting RNR, while their triphosphate form is incorporated into DNA by DNA polymerase, leading to strand termination and apoptosis (Source: PubChem, CID 60750). This dual-action mechanism is highly effective in treating various cancers, including pancreatic cancer and certain leukemias, though it also leads to significant side effects like myelosuppression due to the inhibition of DNA synthesis in healthy hematopoietic cells.

Other names

DNA-directed DNA polymeraseRibonucleotide reductaseRNRRibonucleoside-diphosphate reductase large subunitRibonucleoside-diphosphate reductase small subunitDNA pol alphaDNA pol deltaDNA pol epsilon

Nucleoside analogs act as prodrugs that, once phosphorylated, inhibit ribonucleoside-diphosphate reductase to deplete natural deoxyribonucleotide pools and are subsequently incorporated into DNA by DNA polymerase to cause chain termination (Source: PubMed, PMID: 15153611).