The repressive and alleviating nature of FACT shapes the transcriptional landscape in ES cells
The conserved and essential histone chaperone FACT (Facilitates Chromatin Transcription) reorganizes nucleosomes during DNA transcription, replication and repair and ensures both, efficient elongation of RNA Pol II and nucleosome integrity. In mammalian cells, FACT is a heterodimer, consisting of SSRP1 and SUPT16. Here, we show that in contrast to yeast, FACT accumulates at the transcription start site of genes reminiscent of RNA Polymerase II profile. Depletion of FACT in mouse embryonic stem cells leads to up-regulation of pro-proliferative genes and key pluripotency factors concomitant with hyper-proliferation of mES cells. Using MNase-, ATAC-, and Nascent Elongating Transcript Sequencing (NET-seq) we show that up-regulation of genes coincides with loss of nucleosomes upstream of the TSS and concomitant increase in antisense transcription, indicating that FACT impacts the promoter architecture to regulate expression of these genes. Finally, we demonstrate a role for FACT in cell fate determination and show that FACT depletion primes ES cells for the neuronal lineage.