Régulation de l'épissage alternatif par citrullination à l'arginine. – ACT

Arginine citrullination is the post-translational modification of arginine to the citrulline catalyzed by a family of enzymes called peptidyl arginine deiminases (PADIs). Among the five PADI family members, PADI2 is the most conserved and widely expressed. An elevated level of PADI2 is known to associate with several pathological disorders, including autoimmune diseases, neurological disorders, prion disease, and several cancers. However, the molecular mechanisms by which PADI2-mediated citrullination affects transcriptional processes and contributes to pathological conditions at multiple levels remain poorly understood. Our work spotlights that PADI2 specifically citrullinates the master regulator of the transcription machinery, which is RNA polymerase II in cancer cells. We discovered that the citrullination of RNA polymerase 2 is essential to facilitate the transcription of key genes required for cell proliferation and cell signaling regulation. This work revealed a new function of PADI2 that potentially explains the transcriptional link with disease conditions.

Given the functional link between transcription and RNA processing, we set out to examine the possibility that PADI2 affects alternative splicing (AS) regulation in mammalian cells. Indeed, our unpublished data show that PADI2 broadly affects the AS events without affecting the gene expression of key splicing factors (SFs), suggesting PADI2 had a potential impact on splicing machinery. Based on strong preliminary data, the main objective of our proposed ACT project is to understand the molecular basis of the regulatory role of PADI2 in AS regulation. Therefore, in the ACT project, we will illuminate an unknown function of PADI2 in the field of splicing regulation.

We aim to map the PADI2-directed AS events on the global functional AS network. Here, the generation of the first PADI2 splicing regulatory network will potentially lead to the identification of pivotal splicing factors that mediate PADI2 effects on AS regulation. To dissect the molecular mechanisms by which PADI2 modulates the AS regulation, we will perform a systematic characterization of PADI2 substrates in the splicing machinery. We proposed to provide the functional consequence of the citrullination of essential splicing factors by identifying the impact on functional protein complexes. Hence, this part of the project will bring important implications in the context of PADI2 linked cellular processes to disturb protein-protein interactions that are commonly observed in pathological conditions. We expect this will also open more promising avenues to develop therapeutic strategies to develop novel approaches through the use of splicing switching antisense oligonucleotides or small molecule splicing regulators. Overall, the ACT proposed project holds great promise for improving human health and the quality of life and therefore fits perfectly with the overall objectives of the ANR and its scientific priorities associated with the "Défi 4 Vie, Santé et Bien être"