Distinct mechanism of STAT inhibition by different paramyxoviruses. (A) Sequence alignment of the highly conserved C-terminal domain (CTD) from various paramyxovirus V proteins mentioned in text. Histidine and 7 cysteine residues and zinc fingers 1 and 2 are indicated. (B) Schematic diagram of PIV5, measles, and Nipah V proteins drawn to scale showing the key features, including the CTD (pink box) and important regions and residues for STAT interaction. (Top) PIV5 V protein. A single region for STAT interaction has not been described, but residue N100 in the N-terminal domain shared between P and V has been shown to provide species-specific interaction with human STAT2. (Middle) Measles V protein. The measles V CTD has a unique extension (green) of unknown significance. The CTD alone is necessary and sufficient for STAT2 interaction. Within the CTD D248 has been found to be important in measles V protein STAT2 interaction. The STAT1 interaction in measles V protein is mediated by residues 110–130 (red box) that includes tyrosine 110 (Y110). (Bottom) Nipah V protein. The Henipavirus CTD is dispensable for STAT interaction. Residues 100–160 (red box) are necessary and sufficient for STAT1 binding, whereas STAT2 association requires STAT1 and a larger region involving residues 100–300. The STAT1-binding domain is also an interaction site for Polo-like kinase 1 (PLK1).