The influence of a double-stranded hindrance on DNA synthesis performed by DNA polymerase alpha, T4 DNA polymerase, DNA polymerase I (Klenow fragment) and AMV reverse transcriptase.

The influence of a double-stranded region on DNA synthesis performed by a series of DNA polymerases on a single-stranded template was studied. Two types of double-stranded hindrances were employed: a stable hairpin formed by the template alone and a region formed by the template and an extraneous oligonucleotide complementary to the template. While T4 and calf thymus alpha DNA polymerases are strongly arrested at the beginning of either of the two double-stranded hindrances, the Klenow fragment of E. coli DNA polymerase I and avian myeloblastosis virus reverse transcriptase can pass through the double-stranded regions. The DNA chain-elongation rate seems to be undisturbed in the case of reverse transcriptase but greatly reduced for DNA polymerase I.