Chromatin run-on reveals the transcriptional etiology of glioblastoma multiforme

The human genome encodes a variety of poorly understood RNA species that remain challenging to identify using existing genomic tools. We developed chromatin run-on and sequencing (ChRO-seq) to map the location of RNA polymerase using virtually any input sample, including samples with degraded RNA that are intractable to conventional RNA-seq. We used ChRO-seq to develop the first maps of nascent transcription in primary human glioblastoma (GBM) brain tumors. Whereas enhancers discovered in primary GBMs resemble open chromatin in the normal human brain, rare enhancers activated in malignant tissue drive regulatory programs similar to the developing nervous system. We identified enhancers that regulate genes characteristic of each known GBM subtype, identified transcription factors that drive them, and discovered a core group of transcription factors that control the expression of genes associated with clinical outcomes. This study uncovers new insights into the molecular etiology of GBM and introduces ChRO-seq which can now be used to map regulatory programs contributing to a variety of complex diseases.