PU.1 gene expression is not affected during GER-mediated down-regulation of myeloid markers.

(A) Expression of myeloid-specific (MHCII) and eosinophil-specific (EOS47) antigens was monitored after β-estradiol stimulation of GER-expressing myeloblasts by indirect immunofluorescence staining and flow cytometry. The time point shown represents 2 days of induction, but significant changes were observed after 18 hours (not shown). (B) PU.1 gene expression was analyzed in the same cells as in (A) by Northern blotting as described in Figure 1. RNA was isolated after 1 and 2 days of induction and compared to the level in uninduced cells (0 days of induction) (panel a). Two species of PU.1 mRNA are found in avian cells.2 To normalize RNA levels, the blot was probed for GAPDH as an internal standard (panel b).