Phosphorylation of the human respiratory syncytial virus N protein provokes a decrease in viral RNA synthesis

When HEp-2 cells are infected by human respiratory syncytial virus (HRSV) its N protein becomes phosphorylated at tyrosine (Y) Y38, in a strictly regulated way. To determine how this phosphorylation affects nucleocapsid (NC) template activity during viral RNA synthesis, N protein variants were analysed in which Y38 and nearby Y residues were substituted by phenylalanine (F; Y23F, Y38F and Y69F) or aspartic acid (D; Y23D and Y38D). While the capacity of these proteins to form the NC and to interact with the P protein was maintained, their NC template activity was altered affecting distinctly viral transcription and replication of HRSV based minigenomes. Thus, Y38 phosphorylation of the HRSV N protein modulates NC template activity probably by altering the interactions of the monomeric components of the NC.