Fig 1.

Phospho-RXXS-specific antibodies can recognize HPV8 E2 proteins phosphorylated at S253. Proteins extracted from CV-1 cell lines carrying control vector pMEP4 or plasmids expressing truncated E2 proteins were immunoprecipitated with M2 anti-FLAG antibody beads. Two versions of wild-type (WT) and mutated E2 proteins were used; one contained a 16-amino-acid region of the hinge fused to the C-terminal domain (240-255-CTD) and the other contained a 40-amino-acid region of the hinge fused to CTD (216-255-CTD). The mutated E2 protein in the 240-255-CTD background has an alanine substitution at residue 253 (S253A). The mutated E2 protein in the 216-255-CTD background has alanine substitutions at residues S253 and S254 (S253A/S254A). Phosphorylated E2 proteins were detected by phospho-RXXS (RRX-pS) and phospho-RRXS motif-specific antibodies. Total E2 protein was detected using rabbit anti-FLAG antibody.