Ablation of RSV P protein by anti-P dsRNA. Transfection of A549 cells with 0 (no dsRNA), 10, 100, or 300 nM dsRNA and infection with RSV were carried out as described under Materials and Methods. Lane 'U' indicates control, uninfected cells. Top: Immunoblot (Western) of total cell extracts was performed with either rabbit anti-P or monoclonal anti-actin antibody (Boehringer-Mannheim), as indicated. Bottom: Viral protein synthesis in dsRNA-treated cells was measured by standard immunoprecipitation procedures as described previously . Infected A549 cells (or uninfected control, lane 'U') were metabolically labeled with 35S-(methionine plus cysteine) at 18 h post-infection, followed by lysis of the cells, precipitation with anti-RSV antibody, and analysis of the labeled proteins by SDS-PAGE and autoradiography. 'La' represents treatment with 100 nM anti-lamin A/C dsRNA. The different viral protein bands are so indicated.