Complete sequences of the intergenic and mRNA start signals in the Sendai virus genome: homologies with the genome of vesicular stomatitis virus.

All of the consensus intergenic and transcription initiation sequences of the genome of Sendai virus, a paramyxovirus, have been determined. The boundary between the intergenic sequence, 3'-GAA, and the mRNA start signal, 3'- UCCCANUUUC , was identified by sequencing the 5' termini of specific viral mRNA molecules. One of the five intergenic trinucleotides differed from the rest, consisting of 3'- GGG , and single base substitutions were observed in two of the mRNA start signals. The Sendai virus intergenic sequence was similar to the analogous sequence (3'-GA) of vesicular stomatitis virus (VSV), a member of another family of negative-strand RNA viruses, the rhabdoviruses , but there was no sequence homology between the mRNA start signals of the two viruses. Nevertheless, these mRNA start signals were organized in the same way, being ten bases long and possessing two consensus regions, divided by one (Sendai virus) or two (VSV) variable internal nucleotides. These findings extend the evidence that both families of negative-strand RNA viruses descended from a common ancestor and that an archetypal mechanism of transcriptional regulation has been conserved in their evolution.