Alternate promoters and developmental modulation of expression of the chicken GATA-2 gene in hematopoietic progenitor cells

We have isolated and characterized the chicken GATA-2 (cGATA-2) gene. We show that, as in the case of some other members of the GATA gene family, the gene is expressed from alternative first exons. One of the resulting mRNAs represents only a minor form of the GATA-2 mRNA in the cells and tissues we analyzed; the other is ubiquitously expressed. We have defined the minimal promoter that controls expression of this most abundant mRNA and that is necessary for full activity in hematopoietic progenitor cells. The activity of this promoter in transient assays is consistent with developmental differences of expression levels in these cells. We identify within the promoter a previously unrecognized extended CCAAT motif essential for its activity. The organization of the cGATA-2 gene, with alternative first exons and a CCAAT box in the proximal promoter, is similar to that recently described for mouse GATA-2, and the proximal promoter also resembles the only promoter so far described in Xenopus. Nonetheless, the roles of the promoters in development and tissue-specific expression are quite different in these organisms, most strikingly in the mouse, which assigns developmental roles to its proximal and distal promoters that are quite different from those in the chicken. We suggest that although the overall organization may remain the same, the role assigned to each promoter varies among organisms. We identify distant upstream regulatory elements in the cGATA-2 gene that modulate expression from the proximal promoter and that may be responsible for this variation.