In vitro transcribed RNA with heparin (5000 U/ml, Sigma) and 160 U of RNAse inhibitor (RNase OUT, Invitrogen) was incubated on ice for 15 min in cross-link buffer (20 mM Tris, pH 7.9, 2.5 mM MgCl 2 ) with 0.5 mg of recombinant Hax-1 protein, BSA (Sigma) or thioredoxin (recombinant thioredoxin purified from bacteria using pET201 vector in the same conditions as Hax-1 protein). Cross-linking was performed on ice for 30 min in the UV Stratalinker 1800 (Stratagene). After cross-linking, the reaction was incubated in the presence of RNase A (final concentration 0.6 mg/ml) for 20 min. in room temperature. Laemmli loading buffer was added and the samples were heated to 958C for 5 min. Samples were analyzed on SDS-PAGE, with Prestained SDS-PAGE Standards, Kaleidoscope (Bio-Rad).