Sites of copy choice replication involved in generation of vesicular stomatitis virus defective-interfering particle RNAs.

The copy choice model for the generation of defective interfering (DI) particles of vesicular stomatitis virus suggests that during replication the polymerase prematurely terminates, moves with the nascent daughter strand to another site on the same or a different template molecule, and resumes elongation of the nascent chain. We have analyzed the sites where premature termination or resumption of replication has occurred during the generation of the deletion DI particle LT, the snapback DI particle 011, and the panhandle DI particles T, T(L), and 611. The recombination sites were identified by comparing the nucleotide sequences of the relevant regions of these DI particle RNAs to those of the vesicular stomatitis virus L gene (Schubert et al., J. Virol. 51:505-514, 1984). Sequence homology was not detected between these sites, which rules out the existence of a general terminator or promoter sequence involved in copy choice replication. In several cases, however, premature termination or resumption of RNA replication may be favored by specific signal sequences. The sequences immediately before the start and at the end of the deletion in DI LT contain two hexanucleotides, ATCTGA and GATTGG, in a similar spacing. In these case of DI T and 611, but not of DI T(L), the end of the 5'-terminal region bears the hexanucleotide CCUCUU. This sequence is also repeated in the stem region in all three DI particle genomes. In addition, we present data that the added 3'-terminal regions of the panhandle DI particle RNAs may differ by only one base and are 46 [DI T(L) and 611] or 45 (DI T) bases long. We suggest that each site of the vesicular stomatitis virus genome has the potential to give rise to DI particle RNAs. Specific sequences, however, may modulate this process in a quantitative way, and they favor the generation of certain types of DI particle genomes like those of the panhandle type.