Fig. 8. Purified recombinant p43 binds in vitro transcribed E.aediculatus telomerase RNA in vitro. ³²P-labeled telomerase RNA (∼6.6 nM) carrying the photoaffinity chromophore 5-iodo-U at all U positions was incubated on ice with 330 nM p43 (lanes 1 and 3–20), without p43 (lane 2), or with p43 pre-treated with protease (lane 3), followed by UV irradiation to induce cross-linking (except lane 4). Samples were denatured and analyzed on 4–20% acrylamide gels. Samples run in lanes 5, 7, 9, 11 and 6, 8, 10, 12 included 50-fold and 500-fold molar excess, respectively, of the indicated unlabeled competitor RNAs over labeled E.aediculatus telomerase RNA. Samples run in lanes 13, 15, 17, 19 and 14, 16, 18, 20 included 5- and 50-fold excess by mass, respectively, of the indicated homopolymers over labeled E.aediculatus telomerase RNA. Protein molecular weight markers are indicated on the right. XL, cross-linked RNA–protein complexes.