Remodeling of oncogenic transcriptomes by small-molecules targeting the RNA-binding protein NONO

A large swath of the human proteome is dedicated to RNA homeostasis, but most RNA-binding proteins lack chemical probes1,2. Here, phenotypic screening led to the discovery of electrophilic small molecules that swiftly (within 4 h) and stereospecifically decrease transcripts encoding the androgen receptor (AR) and its major V7 splice variant in human prostate cancer cells. We show by chemical proteomics that these compounds covalently engage cysteine-145 on the RNA-binding protein NONO. Transcriptomics and proteomics profiling revealed that covalent NONO ligands suppress a discrete set of transcripts and proteins, including multiple oncogenic transcription factors, and impair the proliferation of cancer cells. These effects were not observed following genetic disruption of NONO, which instead blocked ligand activity. The covalent ligands promote accumulation of NONO in nuclear foci and at the first 5? splice site of immature transcripts, pointing to a trapping mechanism that may prevent compensatory action by the related protein PSPC1, which was found to increase in cancer cells following genetic or chemical perturbation of NONO. These findings, taken together, designate NONO as a druggable RNA-binding protein that can be co-opted by covalent small molecules to suppress pro-tumorigenic transcriptional networks. Overall design: Examination of RNA-seq and eCLIP-seq in 22Rv1 human prostate cancer cell line with 3 ligand treatmetns: SKBG-1(R), SKBG-1(S), DMSO under the context of WT and NONO-KO