Molecular characterization suggests kinetic modulation of expression of accessory viral protein, W, in Newcastle disease virus infected DF1 cells.

Viruses adopt strategies to efficiently utilize their compact genome. Members of the family Paramyxoviridae, exhibit a cotranscriptional RNA editing mechanism wherein polymerase stuttering generates accessory proteins from Phosphoprotein (P) gene. Newcastle disease virus (NDV), an avian paramyxovirus, expresses two accessory proteins, V and W, by RNA editing. While P and V proteins are well studied, very little is known about W protein. Recent studies confirmed W protein expression in NDV and the unique subcellular localization of W proteins of virulent and avirulent NDV. We characterized the W protein of NDV strain Komarov, a moderately virulent vaccine strain. W mRNA expression ranged between 7 and 9% of total P gene transcripts similar to virulent NDV. However, W protein expression, detectable by 6 h, peaked at 24 h and dropped by 48 h post infection in DF1 cells indicating a kinetically regulated expression by the virus. The W protein localized in the nucleus and by mutations, a strong nuclear localization signal was identified in the C-terminal region of W protein. The viral growth kinetics study suggested neither supplementation of W protein nor subcellular localization pattern of the supplemented W protein influenced viral replication in vitro similar to that noticed in avirulent NDV. A cytoplasmic mutant of W protein localized in cytoplasm unlike specific mitochondrial colocalization as recorded in velogenic NDV strain SG10 indicating a possible role of W protein in determining the viral pathogenicity. This study describes for the first time, the distinct features of W protein of moderately virulent NDV.

Supplementary information: The online version contains supplementary material available at 10.1007/s13337-023-00813-2.