The 5'-terminal sequence of VSV(NJ) (Ogden): is the interaction of the NS protein with the NS binding site responsible for heterotypic interference activity?

Abstract

The 5'-terminal sequence of VSV(NJ) (Ogden) and VSV(NJ) (Hazelhurst) was compared in an attempt to understand why the defective interfering particle, DI-LT, heterotypically interferes with VSV(NJ) (Ogden) but not with VSV(NJ) (Hazelhurst). The 5'-terminal sequence of VSV(NJ) (Ogden) genomic RNA was determined by direct RNA sequencing and by DNA sequencing of cDNA clones of the 3'-terminal sequence of VSV(NJ) (Ogden) DI particle genome. Primer extension analysis of the 5'-terminus of VSV(NJ) (Ogden) standard genomic RNA confirmed these data. Within the last 47 nucleotides, equivalent to the negative-strand leader RNA, the only nucleotide changes between VSV(NJ) (Ogden) and VSV(NJ) (Hazelhurst) occur between nucleotides 19 and 26, representing part of the putative NS binding region described by Isaac and Keene (J. Virol. 43, 241-249 (1982] for VSV(IND) DI particles. The spacer (S) region, located between the polyadenylation signal of the L gene and the 47th nucleotide of the leader RNA, contains more differences. The polyadenylation signal of the L gene is fully conserved, but the remainder of the L gene region (177 nucleotides) has highly diverged between VSV(NJ) (Ogden) and VSV(NJ) (Hazelhurst). The changes in the NS binding region of the negative-strand leader RNA provide further evidence for the divergent evolution of VSV(NJ) (Ogden) and VSV(NJ) (Hazelhurst). The NS binding region has been implicated as a crucial site for the initiation of RNA transcription and replication. The interaction of the NS protein with this site may determine the ability of DI particles to interfere heterotypically.