FIG. 7.
An La deletion mutant defective in leRNA binding does not support RSV growth. A549 cells were transfected with anti-La siRNA (10 nM or 50 nM) or no siRNA (0) and, where indicated (+), also with pCAGGS plasmids expressing full-length La encoded by an siRNA-resistant (siRNAR) gene (lanes 5 to 10) or the deletion mutant La1-187 (lanes 2 to 4 and 7), each containing a His tag. (A) The proteins were detected by Western analysis with anti-La or anti-His antibody. (B) RSV growth was monitored by immunoblotting detecting viral N protein and by extracellular RSV titers at 40 h p.i., as indicated below the lanes. Underlined titers were substantially lower than those of the no-siRNA control. Note that the siRNA targets La mRNA sequence encoding amino acids 243 to 250 and hence does not silence the recombinant at residues 1 to 187. By design, the siRNA-resistant La was also unaffected by the siRNA (see Materials and Methods).