Interaction of oligoribocytidylates with T7 DNA in neutral and acid media.

Oligoribocytidylates of chain length 4 to 12 were found to interact with native T7 DNA at neutral and slightly acid pH. The results suggest that binding occurred at deoxycytosine clusters which may be displaced by the oligomers at neutral pH, while a local triple-stranded structure would be formed at acid pH. Transcription of DNA-(Cp)n complexes by Escherichia coli RNA polymerase showed a decrease in level without affecting the specificity of the transcription, suggesting that oligocytidylate binding did not occur on the promoters.