Abstract B009: The RNA binding activity of the BRAF Kinase

Abstract Multiprotein complexes are key molecular switches of oncogenic signal transduction pathways that relay the flux of information coming from transmembrane receptors and distribute signals to a myriad of effectors. As such the regulation of protein-protein interactions is crucial in signal transduction pathways. For instance, activation of the mitogen-activated protein kinases pathway (MAPK) occurs through a cascade of phosphorylation and protein-protein interactions (PPIs) and is often deregulated in cancer. RNA-protein interactions play key roles in biological processes. More than a thousand RNA binding proteins (RBPs) influence the fate of mRNAs and non-coding RNAs in different ways. It is however less described how RNAs can in turn influence the functions of proteins to which they bind. Here we propose that RNAs scaffold PPIs in the MAPK pathway, thereby fine-tuning oncogenic signaling. We focused our study on cutaneous melanoma for which the MAPK is activated in more than 70% of the cases due to activating mutations in BRAF and NRAS. Using UV-CrossLinking ImmunoPrecipitation (CLIP) experiments, we found that several proteins of the MAPK pathway, including BRAF (but not MEK and ERK) interact with RNAs in RAS-activated melanoma cells. In addition, using a PLA- based imaging technique that allows the visualisation of the proximity of two given proteins, we showed that RNAs promote the stabilisation of BRAF-PPIs, suggesting a scaffolding role of RNAs in the MAPK pathway. Loss of BRAF RNA binding activity (achieved with a single point mutation) is associated with decreased BRAF dimerization and signaling. The oncogenic mutant protein BRAF (V600E) also interacts with RNA in a variety of melanoma cell lines including a BRAF inhibitor-resistant melanoma cell line in which the dimerization of BRAF and CRAF is partly dependent on RNA. Identifying BRAF-bound RNAs will open new therapeutic strategies targeting RNA-protein interactions. We also envision that the level of BRAF-RNA interactions could serve as a predictive marker of response to BRAF (V600E) inhibitors. Citation Format: Alexia Le Barch, Sabrina Mennour, Patricia Uguen, Stephan Vagner. The RNA binding activity of the BRAF Kinase [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: RNAs as Drivers, Targets, and Therapeutics in Cancer; 2024 Nov 14-17; Bellevue, Washington. Philadelphia (PA): AACR; Mol Cancer Ther 2024;23(11_Suppl):Abstract nr B009.