DNA polymerase, DNA primase, and ribonucleotide reductase

DNA polymerase, DNA primase, and ribonucleotide reductase (RNR) constitute a fundamental enzymatic network required for genomic stability and cellular proliferation (Source: UniProt, P09884, P23921). DNA polymerase is responsible for the high-fidelity synthesis of DNA strands, while DNA primase initiates this process by synthesizing short RNA primers (Source: PubMed, 16544971). Ribonucleotide reductase acts as the rate-limiting enzyme that converts ribonucleotides into deoxyribonucleotides, providing the essential building blocks for DNA synthesis (Source: StatPearls, NBK557443). This collective pathway is a major therapeutic target in oncology, particularly for purine nucleoside analogs like fludarabine and clofarabine, which inhibit all three components to halt cancer cell growth. By simultaneously depleting dNTP pools and blocking the polymerization machinery, these drugs induce DNA strand breaks and trigger apoptosis. These enzymes are frequently overexpressed in malignant cells to support rapid division, making them effective targets for chemotherapy. However, because these enzymes are also active in healthy rapidly dividing cells, treatment often results in significant side effects such as myelosuppression and immunosuppression. The coordinated inhibition of these three enzymes provides a synergistic effect that is more potent than targeting any single enzyme alone.

Other names

DNA replication machineryNucleoside analog target triadDNA synthesis enzymesDNA replication enzyme complex

Inhibition of DNA synthesis through the depletion of deoxyribonucleotide pools via ribonucleotide reductase inhibition and the direct blockade of DNA strand initiation and elongation via DNA primase and DNA polymerase inhibition (Source: StatPearls, NBK557443; PubMed, 16544971).