2.3. TIA-1 and TIAR interact with the first stem-loop of viral RNA 5′-UTR
EV71 5′-UTR contains cloverleaf and IRES structure.
Fig. 2F illustrates the potential secondary structure of EV71 5′-UTR as predicted by M-FOLD [7]. In order to determine the binding sites of TIA-1 and TIAR, we generated two sequences recognized by endonuclease KpnI (105) and PstI (568) in complementary DNA of viral 5′-UTR from 5′-end and used them for mapping analysis. After transcribing DNA to biotin-labeled truncated RNAs (nt1-105 and nt1-568) using T7 RNA polymerase, we performed aforementioned RNA pull-down assay to examine the specific binding regions for TIA1 or TIAR and showed that these two proteins bound both truncated viral RNA fragments (Fig. 2G), suggesting that both TIA-1 and TIAR interact with nt 1–105 (stem-loop I). As a control for nonspecific binding of these two proteins to other sites of 5′-UTR and polyclonal sites of empty T vector, we also performed RNA pull-down assay using biotin-labeled 5′-UTR (105–745) and biotin-labeled RNA polyclonal sites of empty T-vector. As a result, we failed to detect interaction of these two proteins with viral RNA nt105-745 and empty T-vector RNA (Fig. 2H), suggesting that RNA nt1-105 at the 5′-UTR specifically mediated interaction with TIA-1 and TIAR.