TAF1,the largest subunit of TFIID, is dispensable for adult hematopoiesis [Pro-seq]

While many sequence-specific transcription factors (TFs) have been identified as key regulators of hematopoietic stem cell (HSC) lineage determination, the function of general TFs in HSC behavior is poorly understood. To evaluate the function of the TFIID subunit TAF1 in normal hematopoiesis, we generated Taf1 conditional knockout mice and identified an essential role of TAF1 in fetal erythropoiesis. Surprisingly, TAF1 deletion in adult mice was not lethal to hematopoiesis; rather, we observed a marked expansion of the hematopoietic stem and progenitor cell (HSPC) compartment, with increased self-renewal and impaired differentiation capacity in these cells. TAF1-null HSPCs failed to produce mature blood cells in chimeric mice; these cells also failed to up-regulate key differentiation genes when induced to differentiate in vitro. TAF1 loss not only disrupted TFIID assembly and chromatin recruitment, but also reduced RNAPII promoter-proximal pausing. Thus, HSPCs utilize distinct transcriptional regulatory mechanisms to undergo differentiation versus maintaining self-renewal. Overall design: To determine how Taf1 loss affects RNAPII activity in mouse HSPCs , we generated Taf1 conditional KO mouse models, and isolated HSPCs from 3 control and 2 KO mice 2 weeks post poly (I:C) induced Taf1 deletion. Nuclear run-on assays (Pro-seq) were performed with one million purified nuclei.