Transcription factor OTF-1 interacts with two distinct DNA elements in the A gamma-globin gene promoter

A DNA region (site II) in the promoter of the human A gamma-globin gene (-182 to -168) is involved in transcriptional regulation. At least two nuclear proteins bind to this region: the erythroid-specific factor NF-E1/GF-1 and another factor present in many cell lines. In the present study, we demonstrate that the ubiquitous factor binding to site II has immunological identity with the octamer transcription factor OTF-1, which has been implicated in the regulation of expression of genes such as histone H2b and small nuclear RNA. In addition, we show that OTF-1 binds to site I (-291 to -267), a purine-rich region upstream of site II. Interestingly, OTF-1 binds to sites I and II with equal affinity. This was unexpected since the 14 bp site I binding site AAGAATAAATTAGA (-291 to -278), determined by methylation interference, does not show obvious similarities to the canonical octamer binding site for OTF-1 in site II (ATGCAAAT). Interaction of OTF-1 with functionally active binding sites in the gamma-globin promoter suggests that this factor has a role in gamma-globin transcription.