Nonreplicative RNA Recombination in Poliovirus

Abstract

Current models of recombination between viral RNAs are based on replicative template-switch mechanisms. The existence of nonreplicative RNA recombination in poliovirus is demonstrated in the present study by the rescue of viable viruses after cotransfections with different pairs of genomic RNA fragments with suppressed translatable and replicating capacities. Approximately 100 distinct recombinant genomes have been identified. The majority of crossovers occurred between nonhomologous segments of the partners and might have resulted from transesterification reactions, not necessarily involving an enzymatic activity. Some of the crossover loci are clustered. The origin of some of these “hot spots” could be explained by invoking structures similar to known ribozymes. A significant proportion of recombinant RNAs contained the entire 5′ partner, if its 3′ end was oxidized or phosphorylated prior to being mixed with the 3′ partner. All of these observations are consistent with a mechanism that involves intermediary formation of the 2′,3′-cyclic phosphate and 5′-hydroxyl termini. It is proposed that nonreplicative RNA recombination may contribute to evolutionarily significant RNA rearrangements.

Emergency Services of Viral RNAs: Repair and Remodeling

“…Nonreplicative RNA recombination implicates joining of fragments originating from distinct viral (or cellular) RNA molecules without involvement of the viral RdRP, though this enzyme is of course required for further copying of chimeric molecules generated thusly. This kind of recombination was first demonstrated to occur in experiments with pairs of segments originating from poliovirus genomes disrupted in either the 5= UTR or the RdRP-encoding region (189,190). Subsequently, it was observed in other picornaviruses (191,192) as well as in flaviviruses (193)(194)(195)(196).…”

Why do RNA viruses recombine?

“…Non-replicative RNA recombination has also been demonstrated experimentally [18][19][20] , albeit at a much lower frequency than copy choice recombination. During this process, recombining RNAs are cleaved at specific points and ligated to form hybrid molecules.…”

Genetic Instability of RNA Viruses

“…This mechanism was documented by recovery of viable viruses (or replicative templates) following cotransfection of cells with two viral RNA fragments, each of which was unable to function in replication independently. The fragments recombined to form functional RNAs [49][50][51][52]. This mechanism of nonreplicative recombination might not involve a viral enzyme activity.…”

“…This mechanism of nonreplicative recombination might not involve a viral enzyme activity. Instead, it seems that the two RNA strands are joined together either by a transesterification reaction [49], or by ligation, presumably by cellular ligases [51][52][53]. Thus, RNA genome fragments created by physical shearing, nuclease cleavage, or cryptic ribozyme activity have the potential to be joined to form a novel viral genome, which can be further refined by homologous recombination to remove duplicated sequence [54].…”