Globin genes exhibit tissue, developmental and maturational specificity. It is our purpose to understand the molecular basis of globin gene regulation. Our efforts have focused on the beta-globin gene cluster that contains the epsilon, gamma and beta genes expressed during the embryonic, fetal and adult developmental periods, respectively. Within this cluster are several cis-acting regulatory elements that interact with trans-acting factors (proteins) to modulate globin gene expression. The locus control region (LCR) located upstream from the cluster contains four regulatory elements (5' HS1-4). 5'HS4 has been dissected functionally and shown to be composed of binding motifs for 3 proteins, NF-E2/AP1, GATA-1 and an Sp1-like protein. An enhancer within 5'HS-2 augments hemoglobin synthesis during differentiation by virtue of its interaction with an erythroid specific nuclear protein, NF-E2. We have partially purified NF-E2, separating it from members of the AP1 families (JUN and FOS) and have shown that the purified protein retains it nucleotide binding specificity. Interaction between the gamma promoter and the 5'HS-2 enhancer appears to be mediated by a protein that binds to sequences within the gamma promoter near the start site for initiation of transcription. Proteins that interact with the enhancer 3' to the gamma globin gene have also ben characterized. These include the erythroid specific protein, GATA-1 and a protein identified in our laboratory that interacts with both the enhancer and gamma promoter called PEF-1. PEF-1 has been purified and shown to be a 110kd protein; amino acid sequence data has been obtained and will form the basis for molecularly cloning its coding sequences.
