FOG-1–mediated down-regulation of GATA-2 expression correlates with GATA factor switching at the −2.8-kb GATA-2 enhancer element in mast cells. (A) Quantitative RT-PCR analysis of GATA-2 mRNA transcript levels in GFP⁺ GMPs infected with retroviruses expressing either the empty vector (IRES-GFP) or FOG-1–IRES-GFP, sorted after 2 d, and analyzed immediately. Error bars represent SEM (n = 3). (B) ChIP assay examining occupancy of the GATA-2 −2.8-kb enhancer or the Necdin promoter by GATA-1, GATA-2, and/or FOG-1 in 4-wk-old BMMCs retrovirally transduced with either the empty vector (IRES-GFP) or FOG-1–IRES-GFP and sorted for GFP⁺ cells after 2 d. A schematic drawing of the mouse GATA-2 locus with the −2.8-kb enhancer element is indicated. 1S and 1G refer to different transcriptional start sites. Normal pooled rat IgG was used as the control for GATA-1 ChIP, and FOG-1 preimmune rabbit serum served as the control for FOG-1 and GATA-2 ChIPs. The level of detected amplicon was normalized to a standard curve of input chromatin and is indicated as relative units. Error bars represent the SEM (n = 2).