Assignment of the temperature-sensitive lesion in the replication mutant A1 of vesicular stomatitis virus to the N gene

Temperature-sensitive phenotype of the human parainfluenza virus type 3 candidate vaccine strain (cp45) correlates with a defect in the L gene

We have previously demonstrated that the temperature sensitivity of a human parainfluenza virus type 3 (HPIV-3) candidate vaccine strain (cp45), which is currently under evaluation in humans, is associated with poor transcriptional activity of the virus at the nonpermissive temperature (R. Ray, K. Meyer, F. Newman, and R. B. Belshe, J. Virol. 69:1959-1963, 1995). In this study, the temperature sensitivity of cp45 virus was further investigated by the complementation of a specific gene function. CV-1 cells were transfected with cloned genes from wild-type HPIV-3 encoding the large protein (L), phosphoprotein (P), and nucleocapsid protein (NP), alone or together, for the expression of biologically active proteins. Only cells expressing the L gene were able to rescue cp45 replication when incubated at the nonpermissive temperature (39.5 degrees C), whereas cells transiently expressing NP or P were incapable of rescuing the virus. The virus titers obtained following complementation of the L protein were 190 to 2,300 PFU/ml of culture medium, compared with the undetectable growth of the cp45 temperature-sensitive mutant at the nonpermissive temperature. Rescued progeny virus still maintained the temperature-sensitive phenotype. Results from this study suggest that the temperature sensitivity of the cp45 candidate vaccine strain is associated primarily with L-protein function and that the defect can be complemented by transient expression of the wild-type protein. This study underscores the importance of the L protein in RNA polymerase activity and its critical role in virus replication.

Nucleotide sequence of the L gene of vesicular stomatitis virus (New Jersey): identification of conserved domains in the New Jersey and Indiana L proteins

The nucleotide sequence of the L gene of vesicular stomatitis virus, New Jersey serotype (Hazelhurst subtype), was determined. Primer extension dideoxy sequencing of genomic RNA using reverse transcriptase initiated within the adjacent G gene provided a consensus sequence of 6522 nucleotides. The G/L intergenic junction spanned 21 nucleotides and contained a pseudo transcription start signal as well as two sequences (10 and 6 nucleotides in length) which are reiterated within the L coding region. The predicted L mRNA was 6398 nucleotides long and contained a single open reading frame corresponding to an L protein encompassing 2109 amino acids with a MW of 241,546. Comparison of the amino acid sequence of this New Jersey serotype L protein to that previously reported for the L protein of the serologically and genetically distinct Indiana serotype (M. Schubert, G. G. Harmison, and E. Meier (1984). J. Virol. 51, 505-514.) revealed a high degree of functional homology. In addition, six regions (43 to 103 amino acids in length) which displayed a high percentage of identical amino acids (85 to 96%) were identified. Five of these regions were clustered within the amino-terminal half of the L protein. Two of these regions contained sequences, 41 amino acids in length, which were significantly similar to corresponding regions of the L proteins of the paramyxoviruses Sendai and Newcastle disease virus. These structurally conserved regions may correspond to functional domains of the multifunctional L protein.

The fates of undermethylated mRNA cap structures of vesicular stomatitis virus (New Jersey) during in vitro transcription

A dual label pulse-chase analysis employing S-adenosyl-L-[methyl-3H]methionine and [beta-32P]GTP has been devised to identify precursors to the cap structure 7mG(5')ppp(5')Am present on the 5'-termini of vesicular stomatitis virus mRNAs. Both monomethylated cap structures, 7mG(5')ppp(5')A and G(5')ppp(5')Am, have been detected in vitro in New Jersey serotype reactions containing suboptimal concentrations of S-adenosyl-L-methionine. The simultaneous chasing of both radiolabeled substrates allowed the determination of the transcriptive fate of each pulse-labeled cap structure in the total RNA population. Ten percent of the 7mG(5')ppp(5')A cap structure and 27% of the G(5')ppp(5')Am cap structure generated during the pulse were chased into 7mG(5')ppp(5')Am. These results suggested that while there may have been a preferred order of 5'-cap methylation, the order was not compulsory. The dual label analysis also revealed that only 34% of the pulse-labeled G(5')ppp(5')A cap structure could be chased into methylated cap structures. A nascent RNA chain length-dependent "methylation window" is proposed.