DNA Synthesis at a Fork in the Presence of DNA Helicases

Abstract

In a mixture of Escherichia coli DNA polymerase III holoenzyme, single-strand-binding protein, artificially forked phage .lambda. DNA with primer annealed to the leading side of the fork, dNTP [deoxyribonucleoside triphosphates] and ATP, DNA synthesis is enhanced by helicase II and less so by helicases I, III or rep protein of E. coli or phage T4 helicase. The effect of helicase II depends on ATP, is enhanced by helicase III, and is not observed using DNA polymerase I or phage T4 DNA polymerase. In the absence of dNTP helicase II is less active than helicase I or T4 helicase in unwinding the forked DNA. Helicase II apparently shifts the forks and stimulates DNA polymerase III. Helicase II is probably a part of the DNA-synthesizing system of E. coli.