Figure 6. Ribosomes Are Scanning Specifically for the CUG/Leucine Start.

(A, C, and E) Lmtk^– cells were transfected with the indicated constructs and K^b cDNA. After 2 d they were tested for MYL8/K^b or LYL8/K^b expression using the BCZ103 T cell hybridoma. Error bars represent the standard deviation of three replicate wells. (ATG)₃ATG (solid circles, A) denotes the ATG-initiated peptide preceded by three ATGs upstream of and out of frame with the peptide; (CAG)₃ATG (open circles, A) is the identical DNA construct but the upstream ATGs were replaced with CAG. (ATG)₃CTG (solid circles, C) denotes the CTG-initiated peptide preceded by three ATGs upstream of and out of frame with the peptide; (CAG)₃CTG (open circles, C) is the identical DNA construct but the upstream ATGs were replaced with CAG. (CTG)₃CTG (solid circles, E) denotes the CTG-initiated peptide preceded by three CTGs upstream of and out of frame with the peptide; (CAG)₃CTG (open circles, E) is the identical DNA construct but the upstream CTGs were replaced with CAG.

(B, D, and F) Extracts from COS-7 cells transfected with cDNA encoding K^b and the indicated constructs were separated by RP-HPLC. Fractions were tested for BCZ103 T cell-stimulating activity with K^b+B7.2⁺ L cells as APCs. Arrows indicate the peak elution positions of the MYL8 and the LYL8 peptides. Points on graphs correspond to those in (A), (C), and (E).