Abstract 401: The Lineage-specific Transcription Factor PU.1 Prevents Heterochromatinization of Macrophage-specific Genes During Hematopoietic Differentiation
We are using a quantitative approach to determine the fractional occupancy of nucleosomes at gene regulatory regions (i.e. enhancers and promoters) in primary mouse macrophages. This has allowed us to determine the dynamics of nucleosome removal at regulatory regions upon pro-inflammatory gene induction (Gjidoda, A. et al. 2014 Nucleosomes are stably evicted from enhancers but not promoters upon induction of certain pro-inflammatory genes in mouse macrophages. PLoS ONE 9(4): e93971). Moreover, we are interested in understanding how an accessible chromatin architecture is established at regulatory regions during macrophage differentiation, so that the transcriptional machinery can be recruited to these sites in mature cells. These studies have shown that the lineage-specific transcription factor PU.1 has to be present in hematopoietic progenitors to mark macrophage-specific genes for later induction. Using a previously established macrophage differentiation system from a PU.1-/- mouse as well as primary macrophages, we find that in the absence of PU.1 binding to the enhancer of a macrophage-specific gene, the enhancer is bound by PRC2 as cells are differentiated into mature macrophages. This leads to wrapping of the whole gene locus into heterochromatin, which is associated with tri-methylation of H3K27 and increased nucleosome occupancy. Our results show that one role of lineage-specific transcription factors is to prevent heterochromatinization of cell-type specific genes during differentiation to allow their expression in mature cells.
Author Disclosures: M. Floer: None. M. Tagore: None. M.J. McAndrew: None. A. Gjidoda: None.
This research has received full or partial funding support from the American Heart Association.
- © 2015 by American Heart Association, Inc.