Frequent intragenic transcription termination within the N gene of vesicular stomatitis virus

In addition to the five capped and polyadenylated mRNAs and the 47 nucleotide leader RNA synthesized by purified vesicular stomatitis virus (VSV), we have isolated an additional RNA species that is synthesized in large amounts in vitro. The RNA molecules are capped, heterogeneous at the 3′-end, and sediment in a velocity gradient at 9 S. Fingerprint analyses and competition hybridization experiments indicate that the 9 S RNA corresponds to the 5′-terminal transcription product of the N gene. The termination of transcription occurs randomly around 400 nucleotides from the initiation site. The RNA product is synthesized in vivo and also when the transcriptase activity in vitro is reconstituted by the addition of the L and NS proteins to the N-protein RNA complex, indicating that it is probably a normal product of transcription. Photoreaction of VSV with 4′-substituted psoralen failed to inhibit synthesis of the 9 S RNA product under conditions when full-length mRNA synthesis is diminished by more than 90%. Thus, it appears that the psoralen binding site on the genome RNA is located beyond the termination region of the 9 S RNA. The RNA is synthesized at both early and late times during transcription in approximately equal molar amounts relative to the N-mRNA. The role of this frequent intragenic transcription termination product of the N gene in the virus life cycle is discussed.