Erythroid differentiation depends on the establishment of specific patterns of gene expression. Hypersensitive site 2 (HS2, serving as a major enhancer of globin genes)-binding proteins may be involved in its natural open chromosomal environment formation. Previously we prepared monoclonal antibodies against HS2-binding nuclear proteins of terminal differentiated erythroid cells. By utilizing the monoclonal antibodies, we screened λ-gt11 human fetal liver cDNA expression library and obtained one cDNA clone, which was named erythroid differentiation related gene (EDRF1, Genbank accession number AF040247) , encompassing an entire open reading frame. We investigated the expression pattern of EDRF1 by RT-PCR technique. And a clue to the function of EDRF1 has been found from confirmation of high levels of EDRF1 mRNA in differentiated K562 and human fetal liver tissue. To illuminate the function of EDRF1 in K562 cells, sense and antisense EDRF1 constructs were prepared and transfected into K562 cells, α-glob