Purification and Identification of Proteins That Bind to the Hereditary Persistence of Fetal Hemoglobin –198 Mutation in the γ-Globin Gene Promoter

Expression of the γ-globin gene is silenced in adult humans. However, certain point mutations in the γ-globin gene promoter are capable of maintaining expression of this gene during adult erythropoiesis, a condition called non-deletion hereditary persistence of fetal hemoglobin (HPFH). Among these, the British form of HPFH carrying a T →C point mutation at position –198 of the Aγ-globin gene promoter results in 4–10% fetal hemoglobin in heterozygotes. In this study, we used nuclear extracts from murine erythroleukemia cells to purify a protein complex that binds the HPFH –198 γ-globin gene promoter. Members of this protein complex were identified by mass spectrometry and include DNMT1, the transcriptional coactivator p52, the protein SNEV, and RAP74 (the largest subunit of the general transcription factor IIF). Sp1, which was previously considered responsible for HPFH –198 γ-globin gene activation, was not identified. The potential role of these proteins in the reactivation and/or maintenance of γ-globin gene expression in the adult transcriptional environment is discussed.