High frequency of single-base transitions and extreme frequency of precise multiple-base reversion mutations in poliovirus.

Abstract

We employed independent clones of a temperature-sensitive mutant of type 1 poliovirus, to quantitate the frequency of specific U -+ C transitions at nucleotide 5310, within the genomic region encoding polypeptide 3AB, which is involved in the initiation ofRNA replication.Only this U --C base substitution restores the wild-type phenotypic ability to form plaques at 39C; the other two base substitutions at this site are lethal. The observed frequency of this specific transition averaged 2 x i0S, and all revertant viruses forming plaques at39°C contained the expected cytidine at nucleotide 5310. Incredibly, only 3 of 10 revertants exhibited this one specific U --C transition whereas 7 of 10 exhibited this same transition plus four additional base substitutions that precisely reverted temperature-sensitive 3AB-310/4 to wildtype poliovirus sequence (these latter four mutations had been introduced into 3AB-310/4 as silent third base mutations to provide new restriction sites in infectious cDNAs). No other mutations were detected in this polypeptide 3AB domain in either the single-base or the precise 5-base revertants. No intermediates were seen; all revertants exhibited either the single U --C transition at nucleotide 5310 or the same transition plus four precise reversions to the wild-type sequence at sites 8, 11, 43, and 46 bases distant from nucleotide 5310. Similar results were obtained after transfection of cDNAderived transcripts. We discuss possible mechaniss for our data. These include (but may not be limited to) error-prone polymerase activity, sequential RNA recombination events joining independent mutations, or some unusual RNA editing process.Considerable data now document the extensive genetic variability and potential for rapid evolution of RNA viruses (1-19). The molecular basis for this variation is extremely high mutation frequencies per average site in RNA virus genomes (ranging between 10-3 and 10-6 and usually of the order of 10' to 10-5). Such high mutation frequencies dictate that even clones of RNA viruses are not homogeneous populations but consist of complex "mutant swarms" or "quasispecies" populations (20)(21)(22)(23)(24)(25)(26). By virtue of their extreme heterogeneity, quasispecies populations can adapt rapidly to new environments by selection of variants preexisting within the population. Some very low polymerase error values have been reported for poliovirus. Thus, Parvin et al. (27) have estimated a poliovirus mutation rate of <10-6 per site for viable neutral or quasineutral mutants of poliovirus.A similar low error frequency of 2.5 x 10-6 was estimated for the reversion of a poliovirus amber mutant (28). In contrast, frequencies of resistance to monoclonal antibody neutralization for poliovirus are in the range 10-3 to 10-5 base substitutions per site (29,30). In vitro measurements of poliovirus polymerase error frequencies (31) and the mutation frequency of poliovirus type 1 to a high degree of resistance to guanidine indicated specific single-site mutation frequencies...

RNA virus error catastrophe: Direct molecular test by using ribavirin

“…However, it has been argued that the available data do not accurately establish the mutation frequencies of animal RNA viruses, and the true mutation frequencies may be as low as 10 Ϫ6 (25,26). Most estimates of high RNA virus mutation frequencies have been based on genetic assays (1,6,(27)(28)(29)(30)(31)(32)(33)(34), which could give inaccurate estimates if the phenotypes are not completely tight. For example, the mutation frequency of poliovirus has been estimated at 2.1 ϫ 10 Ϫ4 by scoring for the presence of a single nucleotide mutation that confers a loss of dependence on guanidine (1).…”

RNA editing in the Wilms' tumor susceptibility gene, WT1.

“…The polymerase activity of viral RTs exihibits no proofread ing function and is notoriously error prone, misincorporating inappropriate nucleotides at frequencies in the range of 1 in lO""^ to 10~^ (Goff 1990;De La Torre et al 1992). However, WTl cDNAs generated using either AMV or MMLV enzymes showed a U or a C nucleotide at position 839 of WTl at nearly equal frequencies from at least some RNA sources.…”

Characterization of pharmacologically active compounds that inhibit poliovirus and enterovirus 71 infectivity

“…PV mutants resistant to anti-PV inhibitors or anti-PV antibodies could emerge rapidly, because a mutant exists in a population of virus (10 3 to 10 5 ), if a single mutation was sufficient for resistance (Blondel et al, 1986;Crotty et al, 2001;de la Torre et al, 1992;Diamond et al, 1985;Pincus et al, 1986Pincus et al, , 1987. Actually, PV isolates from an immunodeficient case chronically infected with PV showed resistance to pleconaril, which is an anti-PV drug that targets the viral capsid proteins to prevent uncoating (Abdel-Rahman & Kearns, 1998), despite the absence of pleconaril treatment (MacLennan et al, 2004).…”