RNA polymerase of influenza virus. II. Influence of oligonucleotide chain length on the priming activity of RNA synthesis by virion-associated RNA polymerase.

The virion-associated RNA-dependent RNA polymerase of influenza virus PR8 was activated by treatment with specific non-ionic detergents, and was remarkably stimulated by exogenously added oligonucleotide primers. Among synthetic oligonucleotides of various chain lengths, the dinucleotide ApG and the trinucleotide ApGpC were the best primers, exhibiting at least 15-fold stimulation; the Km values for these primers were within the range of 0.024-0.10 mM. In spite of the potentially high affinity to the 3' terminal sequence of viral RNAs, two species of heptanucleotides, ApGpCpApApApA and ApGpCpGpApApA, complementary to the 3' termini of RNA segments no. 4, 5, and 8, and of segments no. 1, 2, 3, 6, and 7, respectively, stimulated the RNA polymerase activity by less than 3-fold, if at all, and thus were less efficient primers than di- and trinucleotides. It appears that the selective utilization of specific oligonucleotides as primers for transcription initiation is not a linear function of increased duplex stability between template RNA and complementary oligonucleotides but rather a reflection of the primer-binding properties of RNA polymerase at its product site.