Targeting Translation Activity at the Ribosome Interface with UV-Active Small Molecules

[Image: see text] Puromycin is a well-known antibiotic that is used to study the mechanism of protein synthesis and to monitor ribosome activity due to its incorporation into nascent peptide chains. However, puromycin effects outside the ribosome catalytic core remain unexplored. Here, we developed two analogues (3PB and 3PC) of the 3′-end of tyrosylated-tRNA that can efficiently interact with several proteins associated with ribosomes. We biochemically characterized the binding of these analogues and globally mapped the direct small molecule–protein interactions in living cells using clickable and photoreactive puromycin-like probes in combination with in-depth mass spectrometry. We identified a list of proteins targeted by the molecules during ribosome activity (e.g., GRP78), and we addressed possible uses of the probes to sense the activity of protein synthesis and to capture associated RNA. By coupling genome-wide RNA sequencing methods with these molecules, the characterization of unexplored translational control mechanisms will be feasible.