Newcastle disease virus phosphoprotein gene analysis and transcriptional editing in avian cells

Nucleotide sequence was determined for the phosphoprotein (P) gene from 23 Newcastle disease virus (NDV) isolates representing all defined pathotypes with different chronological and geographic origins. Sequence variation, with synonymous substitutions dominating, occurred throughout the P gene. An exception was a conserved central region containing the transcriptional editing site. Four G nucleotide additions were detected in NDV P gene mRNA potentially creating alternative open reading frames. However, only one in-frame stop codon exists with a single G addition among all isolates that would allow for a potential V protein. A second potential stop codon does not exist in the P gene consensus sequence among all isolates with more than one G nucleotide addition at the editing site. This precludes a possible W protein in these isolates. A second potential alternative in-frame start site exists among all isolates that could encode a predicted X protein for NDV. Comparison of the P gene editing sites among the Paramyxovirinae and predicted P gene usage demonstrates that NDV more closely resembles the respiroviruses and morbilliviruses. Phylogenetic analysis of P gene sequences among NDV isolates demonstrates there are two clades of these viruses. One group includes viruses isolated in the US prior to 1970, while a second cluster includes virulent viruses circulating worldwide.