Figure 7. NF45 and NF90 complex alone is not sufficient for SP-10 promoter activation in the context of native chromatin. (A) Spleen cells from the SP-10 promoter GFP transgenic mouse (Reddi et al, 1999) were stimulated with PMA and ionomycin. Secreted IL-2, measured by ELISA, confirmed the presence of transcriptionally active NF45-NF90 complex. Unstimulated spleen cells did not have detectable level of IL2 (not shown). (B) To determine whether this activated NF45-NF90 complex was sufficient to activate the integrated –408/+28 SP-10-GFP transgene in spleen cells, we measured GFP reporter gene expression by flow cytometry. The straight and dotted lines represent the –408/+28 transgenic and wild-type mice, respectively. No difference in fluorescence intensity was observed between the sorted CD3⁺ T-cells from the transgenic or wild-type mice, indicating lack of SP-10 promoter activation. This experiment shows that additional factors must act on the chromatin prior to NF45 and NF90 in order to activate the SP-10 promoter.