Mechanism of strand displacement synthesis by DNA replicative polymerases

Maria Manosas, Michelle M. Spiering, Fangyuan Ding, David Bensimon, Jean François Allemand, Stephen J. Benkovic, Vincent Croquette

Research output: Contribution to journalArticlepeer-review

62 Scopus citations


Replicative holoenzymes exhibit rapid and processive primer extension DNA synthesis, but inefficient strand displacement DNA synthesis. We investigated the bacteriophage T4 and T7 holoenzymes primer extension activity and strand displacement activity on a DNA hairpin substrate manipulated by a magnetic trap. Holoenzyme primer extension activity is moderately hindered by the applied force. In contrast, the strand displacement activity is strongly stimulated by the applied force; DNA polymerization is favoured at high force, while a processive exonuclease activity is triggered at low force. We propose that the DNA fork upstream of the holoenzyme generates a regression pressure which inhibits the polymerization-driven forward motion of the holoenzyme. The inhibition is generated by the distortion of the template strand within the polymerization active site thereby shifting the equilibrium to a DNA-protein exonuclease conformation. We conclude that stalling of the holoenzyme induced by the fork regression pressure is the basis for the inefficient strand displacement synthesis characteristic of replicative polymerases. The resulting processive exonuclease activity may be relevant in replisome disassembly to reset a stalled replication fork to a symmetrical situation. Our findings offer interesting applications for single-molecule DNA sequencing.

Original languageEnglish (US)
Pages (from-to)6174-6186
Number of pages13
JournalNucleic acids research
Issue number13
StatePublished - Jul 2012

All Science Journal Classification (ASJC) codes

  • Genetics


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