Amplification of snap-back DNA synthesis reactions by the uvsX recombinase of bacteriophage T4

J Biol Chem. 1991 Jul 25;266(21):14031-8.


The uvsX protein of bacteriophage T4 is a recA-type recombinase. This protein has previously been shown to help initiate DNA replication on a double-stranded DNA template by catalyzing synapsis between the template and a homologous DNA single strand that serves as primer. Here, we demonstrate that this replication-initiating activity of the uvsX protein greatly amplifies the snap-back (hairpin-primed) DNA synthesis that is catalyzed by the T4 DNA polymerase holoenzyme on linear, single-stranded DNA templates. Amplification requires the presence of uvsX protein, the DNA polymerase holoenzyme, T4 gene 32 protein, and a T4 DNA helicase, in a reaction that is modulated by the T4 uvsY protein (an accessory protein to the uvsX recombinase). The reaction products consist primarily of large networks of double-stranded and single-stranded DNA. With alkali or heat treatment, these networks resolve into dimer-length single-stranded DNA chains that renature instantaneously to reform a monomer-length double helix. A simple model can explain this uvsX protein-dependent amplification of snap-back DNA synthesis; the mechanism proposed makes several predictions that are confirmed by our experiments.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenosine Triphosphatases / metabolism*
  • DNA Helicases / metabolism
  • DNA Replication*
  • DNA, Single-Stranded / metabolism
  • DNA, Viral / genetics
  • DNA, Viral / ultrastructure
  • DNA-Binding Proteins / metabolism*
  • Membrane Proteins / metabolism*
  • Microscopy, Electron
  • Nucleic Acid Renaturation
  • Recombination, Genetic*
  • T-Phages / enzymology*
  • Viral Proteins / metabolism*


  • DNA, Single-Stranded
  • DNA, Viral
  • DNA-Binding Proteins
  • Membrane Proteins
  • UvsX protein, Enterobacteria phage T4
  • UvsY protein, Enterobacteria phage T4
  • Viral Proteins
  • Adenosine Triphosphatases
  • DNA Helicases