DNA polymerase (gemcitabine target context)

Gemcitabine does not bind DNA polymerase directly but acts as a deoxycytidine analog that, after intracellular activation, produces cytotoxic metabolites. The most active form, gemcitabine triphosphate (dFdCTP), competes with deoxycytidine triphosphate for incorporation into DNA by DNA polymerase during S-phase. Once incorporated, gemcitabine causes "masked" chain termination—DNA polymerase adds only one more nucleotide after gemcitabine, after which elongation stops and the repair machinery cannot excise the incorporated drug, leading to persistent DNA damage and apoptotic cell death in cancer cells[1][3][4][5]. Additionally, gemcitabine metabolites inhibit the 3′–5′ exonuclease activity of DNA polymerase, making removal of the drug from the nascent DNA strand inefficient, and deplete cellular dCTP pools by inhibiting ribonucleotide reductase[1][5]. DNA polymerases themselves are established therapeutic targets in oncology via this mechanism; however, "gemcitabine on DNA polymerase" is an incomplete or ambiguous target name—gemcitabine acts on the process catalyzed by cellular DNA polymerases, not the enzyme directly.

Other names

DNA-directed DNA polymerasefamily A polymerasepol α (polymerase alpha)pol ε (polymerase epsilon)DNA polymerase I (in bacteria)

Chain termination during DNA synthesis following incorporation of gemcitabine triphosphate (dFdCTP); "Masked" DNA chain termination: after incorporation, DNA polymerase adds only one additional nucleotide before elongation is blocked; repair enzymes cannot efficiently remove gemcitabine, locking the lesion in DNA[3][1][4]; Inhibition of DNA polymerase editing (exonuclease) function: dFdC phosphates inhibit the 3′–5′ exonuclease activity, preventing removal of incorporated gemcitabine residues[5]; Depletion of endogenous nucleotides (e.g., by inhibiting ribonucleotide reductase and CTP synthetase), increasing likelihood of gemcitabine incorporation[1][4]