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. Author manuscript; available in PMC: 2016 Aug 13.
Published in final edited form as: Cell. 2015 Aug 13;162(4):872–884. doi: 10.1016/j.cell.2015.07.041

Figure 6. Mass spectrometry of immunoprecipitated Myc13-tagged 3′UTR translation products.

Figure 6

(A) Tagged 3′UTR translation products were immunopurified and resolved by SDS-PAGE, and peptide products of trypsin (SED1, YDR524C-B, CWP2, HOR7, HSP150 and YMR122W-A) or GluC (YDR524C-B) digestion were identified by LC-MS/MS analysis. Peptide sequences (underlined) were determined by peptide fragmentation-MS, highlighted in brick red for canonical tryptic peptides ending in Lys/Arg, respectively, and preceded by the corresponding codons (Lys/Arg). Shown in blue and cyan are “semi-tryptic” peptides lacking either a C-terminal Lys/Arg or the preceding Lys/Arg codons, and “semi-GluC” peptides lacking either a C-terminal Glu or a preceding Glu codon, respectively. (B) A portion of the main ORF and 3′UTR sequence of YMR122W-A translated in all 3 frames, showing the MS-identified tryptic peptide (in gold) translated in the +1 frame of the 3′UTR. The first upstream stop codon in the +1 frame of the ORF (unfilled black box), main ORF stop codon (grey), 3′UTR termination codon in the +1 frame (red), and window encompassing the deduced reinitiation site are indicated.