FIG. 2.

Effect of a short uORF A in the linear and structured leader context on the formation of translation initiation complexes. Labeled transcripts were incubated briefly in wheat germ extract in the presence of translation elongation inhibitors (cycloheximide [100 μg/ml] and sparsomycin [200 μM]). Initiation complexes formed with full-length mRNAs were assayed by density centrifugation in 10 to 30% sucrose gradients. Sedimentation was from right to left. Positions of unbound RNA, 40S subunits, and 80S and high-molecular-weight polysomal complexes are indicated. (A) Migration of the L-A, L, and S-A transcripts; (B) migration of the S-A, S, and ΔS transcripts.