Identification of promoter-proximal oligonucleotides and a unique dinucleotide, pppGpC, from in vitro transcription products of vesicular stomatitis virus.

The oligonucleotides synthesized by purified vesicular stomatitis virus in vitro in the absence of one or more ribonucleoside triphosphate precursors have been studied. The oligonucleotides contained the 5'-terminal sequences of the leader RNA and one or more mRNA's. The promoter-proximal oligonucleotides lacked 5'-terminal cap structure and contained triphosphate A. These results suggest that the RNA polymerase is located at multiple promoter sites on the genome RNA from where it initiates transcription. The capping reaction appears to occur subsequently during RNA chain elongation. We have also demonstrated that a unique dinucleotide, pppGpC, of presently unknown function is synthesized in vitro in large amounts during RNA synthesis or in the presence of GTP and CTP only.