Priming of deoxyribonucleic acid synthesis on phage fd and phiX174 templates by oligoribonucleotides contaminating nucleoside 5'-triphosphates.

Commercial preparations of guanosine 5'-triphosphate and deoxyguanosine 5'-triphosphate are contaminated with oligoribonucleotides 4 to 6 residues in length. The oligoribonucleotides can be separated from the nucleoside 5'-triphosphates by chromatography on DEAE-Sephadex A-25 or by gel filtration through Sephadex G-25. The oligoribonucleotides are effective primers for the DNA polymerase of bacteriophage T7 on the single-stranded circular DNAs of phage fd and phiX174; they are covalently attached to the 5' terminus of the newly synthesized DNA. The priming activity is specific; the oligoribonucleotides do not serve as primers for DNA polymerase I of Escherichia coli or for the DNA polymerase induced by phage T4.