Identification of a mutation in editing of defective Newcastle disease virus recombinants that modulates P-gene mRNA editing and restores virus replication and pathogenicity in chicken embryos.
Editing of P-gene mRNA of Newcastle disease virus (NDV) enables the formation of two additional proteins (V and W) by inserting one or two nontemplated G residues at a conserved editing site (5'-AAAAAGGG). The V protein of NDV plays an important role in virus replication and is also a virulence factor presumably due to its ability to counteract the antiviral effects of interferon. A recombinant virus possessing a nucleotide substitution within the A-stretch (5'-AAgAAGGG) produced 20-fold-less V protein and, in consequence, was impaired in replication capacity and completely attenuated in pathogenicity for chicken embryos. However, in a total of seven serial passages, restoration of replication and pathogenic capacity in 9- to 11-day-old chicken embryos was noticed. Determining the sequence around the editing site of the virus at passage 7 revealed a C-to-U mutation at the second nucleotide immediately upstream of the 5'-A(5) stretch (5'-GuUAAgAAGGG). The V mRNA increased from an undetectable level at passage 5 to ca. 1 and 5% at passages 6 and 7, respectively. In addition, similar defects in another mutant possessing a different substitution mutation (5'-AAAcAGGG) were restored in an identical manner within a total of seven serial passages. Introduction of the above C-to-U mutation into the parent virus (5'-GuUAAAAAGGG) altered the frequency of P, V, and W mRNAs from 68, 28, and 4% to 15, 44, and 41%, respectively, demonstrating that the U at this position is a key determinant in modulating P-gene mRNA editing. The results indicate that this second-site mutation is required to compensate for the drop in edited mRNAs and consequently to restore the replication capacity, as well as the pathogenic potential, of editing-defective NDV recombinants.
Mebatsion
Teshome
T
Department of Virology, Intervet International B.V., 5830 AA Boxmeer, The Netherlands. teshome.mebatsion@intervet.com
de Vaan
Leonie T C
LT
de Haas
Niels
N
Römer-Oberdörfer
Angela
A
Braber
Marian
M
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002642:Chick Embryo; D005814:Genes, Viral; D009154:Mutation; D009522:Newcastle disease virus / Q000235:genetics* / Q000472:pathogenicity / Q000502:physiology; D010750:Phosphoproteins / Q000235:genetics*; D017393:RNA Editing / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic; D014764:Viral Proteins / Q000235:genetics*; D014774:Virulence / Q000235:genetics; D014779:Virus Replication / Q000235:genetics
C055691:P phosphoprotein, Newcastle disease virus; D010750:Phosphoproteins; D012333:RNA, Messenger; D012367:RNA, Viral; D014764:Viral Proteins