Sam68ΔC inhibits the association of unspliced pgTat RNAs with PABP1. 293T cells were transfected with pgTat and Rev in the absence (pcDNA) or presence of the various Sam68ΔC mutants. Cell lysates were prepared 48 h post-transfection and used in the assays below. a) PABP1 western blot showing the input and immunoprecipitated (IP) protein using either rabbit IgG (R-IgG) or anti-PABP1 (PABP). b) RNase protection assays showing input and immunoprecipitated (IP) pgTat RNAs. RNA was extracted from either rabbit IgG (R-IgG) or anti-PABP1 (PABP) precipitated samples and analyzed by RPA. c) Quantitation of RPA shown in (b). The ratio of US-C to S-C pgTat mRNA immunoprecipitated with anti-PABP1 was standardized to the input. The amount of US-C precipitated in the presence of pcDNA was set to 1.0. Error bars represent one standard deviation. Data was quantitated from 3 independent experiments. Asterisk indicates a value significantly different (p-value < 0.05) from samples transfected with pcDNA.