Histone H3 E50K mutation confers oncogenic activity and supports an EMT phenotype

Sequencing of human patient tumors has identified recurrent missense mutations in genes encoding core histones. We report that mutations that convert histone H3 amino acid 50 from a glutamate to a lysine (H3E50K) supports an oncogenic phenotype in human cells. Expression of H3E50K is sufficient to transform human cells as evidenced by a dramatic increase in cell migration and invasion, and a statistically significant increase in proliferation and clonogenicity. H3E50K also increases the invasive phenotype in the context of co-occurring BRAF mutations, which are present in patient tumors characterized by H3E50K. E50 lies on the globular domain surface in a region that contacts H4 within the nucleosome. We find that H3E50K perturbs global proximal H3 posttranslational modifications and dysregulates gene expression, activating the epithelial to mesenchymal transition. Functional studies using S. cerevisiae reveal that, while yeast cells that express H3E50K as the sole copy of histone H3 show sensitivity to cellular stressors including caffeine, H3E50K cells display growth properties that are distinct from the characterized H3K36M oncohistone yeast model. Taken together, these data suggest that additional histone H3 mutations have the potential to be oncogenic drivers and function through distinct mechanisms that dysregulate gene expression Overall design: To investigate whether the histone H3.3 E50K mutant differentially regulates the global transcriptome compared to H3.3 WT. We are using immortalized but untransformed HMEC DD cells with dominant negative p53 cells that stably overexpressed a C-terminal TY1 epitope-tagged H3.3 WT and E50K.