The purpose of this project is to examine the interaction of trans regulators of globin gene transcription with the globin gene promoters, and potentially to clone the genes responsible for the developmental regulation of globin genes. To this end we have made recombinant DNA constructs in which an antibiotic resistance gene, neo, is transcribed from different globin gene promoters. By transfection of these constructs into different cell types we have shown that they are transcribed in a tissue specific and developmental stage specific manner. Since expression of the neo gene can be selected for using antibiotic G418, these recombinant genes can be used to study globin gene regulation by genetic selection experiments. In particular by linking these genes to other selectable markers (TK, prt) we have been able to stably introduce them into non-expressing cell lines. We intend to study whether these non-expressed genes can be reactivated in trans (i) by promoter competition, (ii) by transfection of activated oncogenes, (iii) by cell fusion with erythroid cells, or (iv) by transfection with normal human DNA sequences including the putative trans regulatory genes.