Figure 3. Interaction of SLRef RNA with Cellular Proteins. (A). ³²P-labeled HCV IRES RNA was UV cross-linked to Huh7 S10 extract in absence (lane C) or presence of 100 fold molar excess of SLRef and SLRf RNA (as indicated), digested with RNase A and resolved by SDS-10% PAGE followed by phosphor imaging. (B). ³²P-labeled HCV IRES RNA in absence (lane 2) or presence (lane 3) of SLRef RNA was UV-cross linked with Huh 7 S10 extracts and the complexes were immunoprecipitated using La antiserum (lane 2, 3) or using pre-immune serum (Lane 1) as indicated. (C). α ³²P-labeled HCV IRES RNA was UV cross-linked to recombinant purified La protein, with 100 and 200 fold molar excess of either unlabeled SLRef or SLRf RNA (as described in the panel) as competitor RNAs.(D) γ ³²P-labeled small RNAs were incubated with increasing concentration of La protein and then analyzed by filter binding assay.(E) α ³²P-labeled HCV IRES RNA was UV cross-linked to recombinant purified S5 protein, with 100 and 200 fold molar excess of either unlabeled HCV IRES RNA, SLRef, mSLRef, SLRf RNA (as described in the panel) as competitor RNAs.(F) γ ³²P-labeled small RNAs were incubated with increasing concentration of S5 ribosomal protein and then analyzed by filter binding assay.