Action of DNA Polymerase I of Escherich with DNA-RNA Hybrids as Templates (B. megateriurn DNA/optimal conditions/high specific aci

Experiments indicating the ability of the ribo strand of a DNA-RNA template to guide polydeoxy- nucleotide synthesis by highly purified DNA polymnerase I of E. coli (EC 2.7.7.7) are presented. With poly(rA) poly- (dT) as template, poly(dT) is formed with a high efficienicy, but almost no poly(dA). The specific activity of the enzyme, when tested with this template under suitable conditions, is eight times greater than that fountd for the poly(dA-dT) template. Single-stranded DNA fractions, with no tem- plate activity for DNA polymerase, are converted to effi- cient templates after their transcription by RNA poly- merase. A concerted polymerization reaction, in which the action of DNA polymerase is dependent on that of RNA polymerase, can also be demonstrated with synthetic polydeoxynucleotides and single-stratnded fractions of de- natured DNA as templates.