Fig. 1.
The TCV RBSE. (A) Model for cap-independent translation initiation in TCV. The model suggests that the RBSE functions to recruit or recycle 60S ribosomal subunits to the template that then accesses the 5′ end possibly through interaction with prebound 40S subunits. (B) Schematic drawing of the genome organization of TCV and the secondary structure of the RBSE. The secondary structure of RBSE was verified by imino-NOE walks of this construct and a number of mutants (see SI Text). The hairpins are labeled as H1, H2 and H3, which consists of H3a, H3b and an internal loop (the nomenclature is simplified from previous nomenclature [(7) for this report]. The pseudoknot formed between the residues in the H2 loop and the residues at the 3′ end was previously determined (10). The cis-acting sequences, external to the RBSE on both the 5′ and 3′ ends of the TCV 3′ UTR are also shown. The italic numbers are those of the genome and smaller numbers are those for RBSE starting from position 1. (C) RBSE ribosome binding competition experiments. Deacylated tRNAphe can compete with binding of RBSE to the P site of yeast ribosomes (Left), and RBSE does not compete with acylated Phe-tRNAphe for binding to the A site of ribosomes (Right).