A functional interaction between DNA helicase E and DNA polymerase E from calf thymus has been detected which results in the extension of an upstream 3'OH through a downstream primer to the end of a synthetic template. DNA synthesis resulting in full-length extension products was dependent on the addition of DNA helicase E and hydrolysis of ATP, suggesting that displacement of the downstream primer was required. Identical reactions using DNA polymerases α and γ in place of DNA polymerase ϵshowed no full-length products dependent on helicase E, indicating that polymerases α and γ were incapable of functionally interacting with the helicase. The reaction leading to full-length extension products was time dependent and dependent on the concentration of added polymerase ϵ and helicase E. Exonucleolytic degradation of the downstream primer, or ligation of the downstream primer to the upstream 3'OH, were not responsible for the full-length products observed. Displacement of the downstream primer by DNA helicase E was not affected by the addition of polymerase ϵ to the reactions. Template dilution experiments demonstrated that DNA polymerase ϵ and helicase E were acting in concert to perform displacement synthesis. Additional evidence for functional coordination was obtained by demonstration that DNA helicase E stimulated DNA polymerase ϵin a standard DNA synthetic assay using dA3000dT16 as the templateprimer. The results presented are consistent with the hypothesis that DNA helicase E and DNA polymerase ϵ are capable of coordinated activities that result in displacement synthesis. A functional interaction of this sort may be involved at the eukaryotic replication fork or in DNA repair.
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