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ATRX regulates binding of Polycomb repressive complex 2 to Xist RNA and Polycomb targets

ABSTRACT: In mammals, dosage compensation entails inactivation of an entire X chromosome in female cells. X-chromosome inactivation (XCI) depends on the long noncoding RNA Xist and its recruitment of Polycomb Repressive Complex 2 (PRC2). How PRC2 specifically interacts with Xist and other Polycomb targets remains unclear. Using XCI as a model, we take an unbiased proteomics approach to search for new Xist and PRC2 regulators. We identify ATRX, a chromatin remodeler associated with mental retardation, alpha thalassemia, and cancer in humans. We show that ATRX is a high-affinity RNA-binding protein. ATRX directly interacts with RepA/Xist RNA and is required for loading of PRC2 onto the RNA in vivo. The Xist gene is a hotspot of ATRX occupancy. Without ATRX, PRC2 cannot load onto Xist RNA nor spread in cis along the X-chromosome. Epigenomic profiling reveals a dependency of PRC2 on ATRX that extends beyond XCI. Depleting ATRX results in genome-wide disruptions to PRC2 localization and trimethylation of histone H3-lysine 27 (H3K27me3). PRC2 is displaced from genes and relocalized to intergenic space, causing reduced H3K27me3 and concomitant changes in expression of Polycomb targets. We conclude that ATRX is a required specificity determinant for PRC2 targeting and function.

ORGANISM(S): Mus musculus

PROVIDER: GSE56981 | GEO | 2014/11/07

SECONDARY ACCESSION(S): PRJNA245107

REPOSITORIES: GEO

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