Phosphorylation of measles virus phosphoprotein at S86 and/or S151 downregulates viral transcriptional activity

► We report the significance of phosphorylation of measles virus P protein. ► Mutations at N phosphorylation sites enhance phosphorylation of P at S86 and/or S151. ► Phosphorylation of P at S86/S151 downregulates viral transcription. ► Enhanced phosphorylation of P causes exponential attenuation of viral transcription.