Figure 6.

Model of STAT5-regulated transcription of Cis in response to IL-3. In unstimulated Ba/F3 cells, the level of histone H3 and H4 acetylation along the Cis gene is high, probably through the action of HAT complexes. The absence of effect of TSA suggests that the gene is not targeted by HDACs. Upon IL-3 stimulation, STAT5 (ST5) is recruited to its binding sites (gray boxes). STAT5 binding results in a local decrease in histone H3/H4 acetylation, and in chromatin remodeling at position –184, possibly through nucleosome sliding (dashed oval). STAT5 also allows, directly or indirectly, an as yet uncharacterized TSA-sensitive factor (gray diamond) to participate in the recruitment of the basal transcription machinery (PIC, pre-initiation complex), in turn permitting transcriptional initiation to occur (22).