FIG 4.

Translational control by eIF1A is predominantly determined by the 5′ UTR length. (A) Analysis of the nucleotide context, using the MEME program, of the translation start site of the CDS unaffected, downregulated (DOWN), and upregulated (UP) gene sets. (B) Box plot showing the relation between the 5′ UTR length and the translation efficiency of the CDS genes whose expression was unaffected, downregulated, and upregulated as well as the cell cycle gene subset of downregulated genes, as indicated. (C) Schematic diagram of the reporter gene constructs used to examine the role of eIF1A on 5′ UTR length. The Renilla luciferase is preceded by a 5′ UTR with a length of 311 nucleotides (nt), and the 5′ UTR length of firefly luciferase is 111 nucleotides. (D) MEFs were transfected with control or eIF1AX plus eIF1A(18) siRNA, and 48 h later, the cells were cotransfected again with the siRNA pool with the reporter genes described in panel C. Cells were harvested 24 h after the second transfection and analyzed for Renilla and firefly luciferase activities. The graph presents the Renilla and firefly luciferase ratios from 6 independent experiments (average ± standard error). *, statistically significant differences (P < 0.05). (E) Effect of eIF1A KD on the mRNA levels of cotransfected reporter genes described in panel C analyzed by RT-quantitative PCR. RL, Renilla luciferase; FF, firefly luciferase.