Effect of uORFs on RFLAT-1 translation efficiency. (a) Sequence alignment of the 5′-UTR of human and mouse RFLAT-1. The positions of the uAUGs and the first methionine are depicted (shaded box). Underlined are the stop codons for each of the three uORFs. Clear boxes indicate identical nucleotides; dashed lines, missing nucleotides. (b) RFLAT-1 5′-UTR uORF’s, designated 1, 2, and 3, are schematically represented. (c and d) The 5′-UTR Luc (wild-type or mutant) was subjected to in vitro translation (c) or transiently transfected into Jurkat T cells (d) as in Figure 1.