Localisation of the temperature-sensitive defect in the nucleoprotein of an influenza A/FPV/Rostock/34 virus.

The nucleotide sequences of the nucleoprotein (NP) genes of fowl plague virus (FPV) and of a temperature-sensitive (ts) mutant (ts81) derived therefrom have been determined. The ts81-NP nucleotide sequence possesses a single nucleotide substitution in comparison to the wild type. This causes an amino acid exchange at position 332 of the NP. An alanine in the wild type-NP is substituted by a threonine in ts81-NP. This substitution leads to a significant difference in the secondary structure prediction. Although this mutation is located within the karyophilic region of the NP, the accumulation of the NP in ts81-infected cells is not significantly affected at 40 degrees C. Therefore, we assume that the cooperation with one of the polymerase proteins (P) is interfered with at 40 degrees C, leading to the loss of viral vRNA or replicative cRNA synthesis. The comparison of the FPV-NP nucleotide sequence to a previously published sequence of the same strain (Tomley and Roditi, 1984) highlights ten nucleotide differences, four of them leading to amino acid substitutions.