Pyrimidine-rich region mutations compensate for a stem-loop V lesion in the 5' noncoding region of poliovirus genomic RNA.
Five revertants of a linker-scanning mutation adjacent to the stem-loop V attenuation determinant (X472) in the 5' noncoding region of poliovirus RNA were independently isolated from neuroblastoma cells and contained RNAs with seven nucleotide changes in the pyrimidine-rich region. Generation of the identical rare second-site mutations suggests the existence of a replicase-dependent mutagenesis mechanism during poliovirus replication. Enzymatic structure probing of the mutated pyrimidine-rich domain identified secondary structure changes between stem-loops V and VI. A consensus secondary structure model is presented for wild-type stem-loops V and VI and the pyrimidine-rich region located in the 5' noncoding region of poliovirus RNA. A pyrimidine-rich region mutant (X472-R4N) produced large plaques in neuroblastoma cells and small plaques in HeLa cells, but the plaque size differences were not due to cell-type differences in viral translation or RNA replication. Release of X472-R4N from HeLa cells was 10-fold lower than release from neuroblastoma cells, which may explain the small plaque phenotype of X472-R4N in HeLa cells. Wild-type poliovirus was also released more efficiently from neuroblastoma cells (approximately 4-fold increase compared with release from HeLa cells), indicating that poliovirus neurotropism may be influenced by the cell-type efficiency of virus release. Thermal treatment increased the levels of infectious X472-R4N virions but not wild-type virus particles; thus RNA sequence and structural changes in the mutated 5' noncoding region of X472-R4N may have altered RNA-protein interactions necessary for virus infectivity.
Stewart
S R
SR
College of Medicine, University of California, Irvine, California, 92697, USA.
Semler
B L
BL
D020121:5' Untranslated Regions; D001483:Base Sequence; D002213:Capsid / Q000235:genetics; D002675:Child, Preschool; D005260:Female; D016679:Genome, Viral; D006367:HeLa Cells; D006361:Heating; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D009447:Neuroblastoma; D009690:Nucleic Acid Conformation; D017955:Poliovirus / Q000235:genetics* / Q000254:growth & development; D014176:Protein Biosynthesis; D011743:Pyrimidines; D012367:RNA, Viral / Q000096:biosynthesis / Q000737:chemistry; D014407:Tumor Cells, Cultured; D010948:Viral Plaque Assay; D014771:Virion
D020121:5' Untranslated Regions; D011743:Pyrimidines; D012367:RNA, Viral; C030986:pyrimidine