(A and B) A reporter expressing HIV-1 Gag-Pol (A) or the MMTV −1PRF signal RNA (B) was transiently transfected into 293T cells, with or without a plasmid expressing SFL-Myc or SFLS-Myc. Cell lysates were immunoprecipitated with anti-Myc antibody. Association of the RNA with SFL or SFLS was indicated by relative enrichment, which was calculated as the amount of RNA in the precipitates divided by that in the cell lysates (upper). The relative enrichment in the cells expressing the wild-type reporter and SFL was set as 100. Data presented are means ± SD of two independent measurements, representative of three independent experiments. That comparable amounts of proteins were immunoprecipitated was confirmed by western blotting (middle). The reporter RNA expression levels in the cells were measured (lower).
(C) EMSA of radio-labeled RNA with increasing amounts of SFL (left) or GST (right) protein. CAA, RNA probe of repeated CAA; PRF, RNA probe containing the −1PRF signal of HIV-1.