Sequential synthesis of 5'-proximal vesicular stomatitis virus mRNA sequences.

We examined the kinetics of synthesis in vitro of the 5' ends of the vesicular stomatitis virus mRNAs by analysis of specific RNase T1 oligonucleotides located near the 5' ends of the mRNAs. Our results indicate that, like synthesis of full-length mRNAs, the 5' ends of the mRNAs are synthesized sequentially, following the gene order N, NS, and M. Additional experiments with UV-irradiated virus demonstrated that synthesis of the mRNA regions containing these oligonucleotides is dependent on synthesis of the mRNA from the preceding gene. These results are inconsistent with a model of vesicular stomatitis virus transcription involving simultaneous initiation and presynthesis of leader RNAs 30 to 70 nucleotides long for each mRNA. We also characterized two small RNA species whose synthesis is highly resistant to UV irradiation. Partial sequence analysis indicates that these RNAs are a 5'-capped fragment of the N mRNA and a 5' fragment of the leader RNA.