"We then tested whether SUP-26 binds directly to the
tra-2 3' UTR in vitro. We found that a purified SUP-26 GST fusion (GST::SUP-26 RRM), which contains the SUP-26a RRM domain (amino acids 81-259), formed a complex with a 32P-labeled TGE RNA oligonucleotide, displaying retarded mobility in a gel shift assay (Fig. 4E, lanes 1 and 2). Unlabeled TGE oligonucleotide competed effectively for binding to GST::SUP-26 RRM in a concentration-dependent manner, blocking the complex formation (Fig. 4E, lanes 3-6). In contrast, an RNA oligonucleotide with the identical nucleotide composition but a scrambled sequence was much less effective in doing so, showing an approximately ninefold lower binding affinity (Fig. 4E, lanes 7-10). These results suggest that SUP-26 binds specifically to the 3'UTR of the
tra-2 mRNA through the 28-nt TGEs."