Impaired Cell Fate by Gain-of-function Mutations in a Chromatin Reader

We previously identified the YEATS domain-containing protein ENL as a reader of histone acetylation. Recently, hotspot mutations in ENL were frequently found in Wilms’ tumor, the most common type of pediatric kidney cancer. Here, we report that these cancer-associated mutations in the ENL YEATS domain confer gain of functions in transcriptional control and impair kidney differentiation by driving self-reinforced chromatin targeting. Ectopic expression of ENL mutants in kidney cell lines resulted in transcriptional changes of genes enriched in embryonic nephron progenitors and Wilms’ tumor. When tested in a nephrogenesis assay, ENL mutant expression led to undifferentiated structures resembling those observed in human Wilms’ tumor. Genome-wide analyses revealed that while mutant ENL bound to largely similar genomic loci as wild-type ENL, they exhibited increased occupancy at a subset of targets, including developmentally critical genes such as the HOXA cluster. The cancer-associated mutations enabled self-reinforced recruitment of ENL on chromatin by promoting self-association, resulting in the formation of discrete nuclear puncta that are characteristic of phase-separated biomolecular condensates. Enhanced occupancy of ENL mutants led to a marked increase in the recruitment and activity of transcription elongation machinery that enforces active transcription from target loci­­­­. Collectively, our studies represent, to our knowledge, the first discovery that cancer-associated mutations in a chromatin reader drive self-reinforced chromatin targeting, which in turns, perturbs developmental programs and derails normal cell fate control during mammalian development towards an oncogenic path. Established stable cell lines to ectopic express either wild type or mutant human ENL in HEK293 and HK2 cell lines, and used these cell lines for Flag, CDK9 and Pol II S2P ChIP-seq and RNA-seq analysis.