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Magnesium Concentration Modulates Replication Slippage of Mesophilic and Thermophilic DNA Polymerases In Vitro

Melissa Castillo-Lizardo1, Enrique Viguera2

  • 1German Center for Neurodegenerative Diseases (DZNE), 72076 Tübingen, Germany.

International Journal of Molecular Sciences
|August 13, 2026
PubMed

Insights

Magnesium ions (Mg2+) affect DNA polymerase slippage fidelity, reducing errors at low concentrations for some polymerases. This suggests physiological Mg2+ levels may suppress genomic instability in vivo.

Area of Science:

  • Molecular Biology
  • Genetics
  • Biochemistry

Background:

  • Replication slippage at repetitive DNA sequences causes insertions and deletions, contributing to genomic instability.
  • Magnesium ions (Mg2+) are crucial cofactors for DNA polymerase activity, but their influence on slippage fidelity is not well understood.

Purpose of the Study:

  • To investigate the effect of Mg2+ concentration on DNA polymerase slippage fidelity.
  • To determine how Mg2+ modulates slippage across different mesophilic and thermophilic DNA polymerases.

Main Methods:

  • Utilized an in vitro primer extension assay with a single-stranded DNA template containing direct repeats and a hairpin-forming inverted repeat.
  • Assessed slippage frequency across various DNA polymerases (T4 Pol, T7 Pol, E. coli pol I Klenow fragment, pol I KF exo-, pol III holoenzyme, Taq pol, Pfu pol) at different Mg2+ concentrations.

Main Results:

  • Mg2+ concentration modulates slippage frequency in a polymerase-dependent manner.
  • Low Mg2+ concentrations suppress slippage in T7 Pol, pol I KF, pol III HE, and Taq Pol, while T4 Pol and Pfu Pol exhibit consistent slippage.
  • Mg2+ modulates strand displacement activity, with reduced slippage observed in polymerases showing enhanced strand displacement at intermediate Mg2+ levels. Proofreading activity did not affect slippage.

Conclusions:

  • There is an inverse correlation between DNA polymerase strand displacement activity and slippage propensity.
  • Physiological free Mg2+ levels may play a role in suppressing DNA replication slippage and maintaining genomic stability in vivo.
Keywords:
DNA polymerase fidelitydirect repeatshairpin structuremagnesium effectreplication slippagestrand displacement activity

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