Pyruvate Kinase M (PKM) binds ribosomes in a poly-ADP ribosylation dependent manner to induce translational stalling

In light of the numerous studies identifying post-transcriptional regulators on the surface of the endoplasmic reticulum (ER), we ask whether there are factors that regulate compartment specific mRNA translation in human cells. Using a proteomic survey of spatially regulated polysome interacting proteins, we identified the glycolytic enzyme Pyruvate Kinase M (PKM) as a cytosolic (i.e., ER-excluded) polyribosome interactor and investigate how it influences mRNA translation. We discovered that the PKM-polysome interaction is directly regulated by ADP levels–providing a link between carbohydrate metabolism and mRNA translation. By performing enhanced crosslinking immunoprecipitation-sequencing (eCLIP-seq), we found that PKM crosslinks to mRNA sequences that are immediately downstream of regions that encode for lysine and glutamate enriched tracts. Additionally, PKM binding to ribosomes causes translational stalling near these lysine and glutamate encoding sequences. Lastly, we find that PKM recruitment to polysomes is dependent on poly-ADP ribosylation. Overall, our study uncovers a novel role for PKM in posttranscriptional gene regulation, linking cellular metabolism and mRNA translation, and provides the first reported evidence of nascent chains being co-translationally modified with poly-ADP ribose. Ribosome profiling analysis of HEK293T depleted of PKM by RNAi