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. 2020 Apr 14;9:e54575. doi: 10.7554/eLife.54575

Figure 3. The 5'-UTR-IRES domain II is formed by a dual hairpin that mediates eIF3 recruitment.

Figure 3.

(A) Overview of the 40S–5'-UTR-IRES–eIF3 cryo-EM map with 40S colored gray, eIF3 red and 5'-UTR-IRES blue. On the right, a zoomed view centers around 5'-UTR-IRES domain II. (B) Detailed view of the cryo-EM map for the region occupied by 5'-UTR-IRES domain II, with 40S components colored gold, eIF3 red and 5'-UTR-IRES blue. Domain II is sandwiched between ribosomal protein uS17 (located at the back of the 40S body) and eIF3 core subunits a and c. (C) 5'-UTR-IRES domain II is formed by a dual hairpin that establishes interactions with α-helices 8 and 10 from eIF3a. These contacts are mediated mainly by basic residues of eIF3 and the phosphate backbone of the IRES. (D) superposition of the 40S–5'-UTR-IRES–eIF3 complex with the canonical 48S complex (left, PDB ID 6FEC) and with the CSFV-IRES–40S complex (right, PDB ID 4c4q). The 5'-UTR-IRES binds to the 40S with a conformation that is compatible with the canonical position described for eIF3 in the 48S complex.