Initiation of synthesis of messenger RNA of deoxynucleotide kinase by oligoribonucleotides.

The effects of nucleoside triphosphates and oligoribonucleotides on the initiation of synthesis of messenger RNA of the T4 phage-specific enzyme, deoxynucleotide kinase, have been studied. The procedure involved incubation of T4 DNA, purified RNA polymerase from Escherichia coli, and selected nucleotide compounds during a brief period to permit initiation of RNA synthesis. Further initiation was arrested by the addition of ribampicin, and completion of the transcription of the newly initiated RNA was permitted to take place in the presence of the full complement of nucleoside triphosphates. After translation of the messenger RNA into phage-specific enzymes, the measured activities of the latter whe first incubation period. The effectiveness of individual nucleoside triphosphates, when present singly or in combination during the initiation period, was compared to that when all four nucleoside triphosphates were available. ATP alone was extremely effective as an initiator of the synthesis of the messenger RNA for deoxynucleotide kinase. The addition of UTP to ATP not only enhanced the magnitude of initiation but also affected the kinetics of ATP interaction with T4 DNA and RNA polymerase during the initiation period. Several oligoribonucleotides including a series ApA to ApApApA, UpU to UpUpUpU, and the heteropolymers, Ap1pU and ApApApU, were tested as initiators of kinase mRNA synthesis. A sequence of nucleotides in the promoter region of T4 DNA for the deoxynucleotide kinase gene has been proposed as a result of these experiments.