UNC0621, a novel small-molecule modulator of Ewing sarcoma chromatin accessibility, interacts with an RNA-associated macromolecular complex and influences RNA splicing

ABSTRACT: Cancer genotyping projects have identified frequent mutations in epigenetic regulators. Ewing sarcoma is a pediatric tumor characterized by the critical translocation-associated fusion oncoprotein EWS::FLI and a low mutational burden. EWS::FLI targets characteristic genetic loci where it mediates aberrant chromatin and the establishment of de novo enhancers. Ewing sarcoma thus provides a model to interrogate mechanisms underlying chromatin dysregulation in tumorigenesis. Previously, we developed a high-throughput chromatin-based screening platform and demonstrated its utility in identifying small molecules capable of altering chromatin accessibility at EWS::FLI-bound loci. Here, we report the identification of UNC0621, a molecule with previously uncharacterized mechanism of action, as a small molecule modulator of chromatin state at sites of aberrant chromatin accessibility at EWS::FLI-bound loci. UNC0621 suppresses cellular proliferation of Ewing sarcoma cell lines by cell cycle arrest. Proteomic studies demonstrate that UNC0621 associates with RNA binding and splicing proteins as well as chromatin regulatory proteins. Surprisingly, interactions with chromatin and many RNA-binding proteins, including EWS::FLI fusion protein and its known interactors, were RNA-independent. Our findings suggest that UNC0621 affects EWS::FLI-mediated chromatin activity by interacting with and altering the activity of RNA splicing machinery and chromatin modulating factors. Genetic modulation of these proteins similarly inhibits proliferation and alters chromatin in Ewing sarcoma cells. The use of an oncogene-associated chromatin signature as a target represents a novel strategy to directly screen for modulators of epigenetic machinery and provides a framework for using chromatin-based assays for future therapeutic discovery efforts.

ORGANISM(S): Homo sapiens

PROVIDER: GSE213545 | GEO | 2023/03/13

REPOSITORIES: GEO