p53-induced apoptosis is specified by a translation program regulated by PCBP2 and DHX30.

Activation of p53 by the small molecule Nutlin can result in a combination of cell cycle arrest and apoptosis. The relative strength of these events is difficult to predict, leaving uncertainty as to the therapeutic benefits of Nutlin. Here, we report a new translation control mechanism shaping p53-dependent apoptosis. We performed polysomal profiling in the cell lines SJSA1 and HCT116, of which only the first undergoes robust cell death in response to p53 activation by Nutlin. We establish Nutlin-induced apoptosis in SJSA1 cells to be associated with a set of translationally enhanced mRNAs carrying a newly identified 3'UTR motif which we labeled CG-motif. We identified PCBP2 and DHX30 as interactor proteins of the CG-motif that are more abundant in HCT116 cells compared to SJSA1. The binding of DHX30 to the CG-motif detected in HCT116 cells was shown to be dependent on PCBP2. Interestingly, DHX30 depletion enhances polysome association of CG-motif mRNAs in HCT116 cells, shifting their outcome towards apoptosis. In U2OS, an osteosarcoma-derived cell line that unlike SJSA1 undergoes persistent cell cycle arrest in response to Nutlin, DHX30 is highly expressed and its depletion enhances the expression of CG-motif mRNAs. Overall design: 4 biological samples per condition are used. A total of 24 samples were used: 12 polysomal DMSO (scramble, DHX30 silencing and PCBP2 silencing) and 12 polysomal Nutlin (scramble, DHX30 silencing and PCBP2 silencing).